The Spodosols of American Soil Taxonomy include diagnostic characteristics similar to the spodic B horizon of the Brazilian Espodosols. The legend of the WRB / FAO retains the name formerly used by the mapping of soils in Brazil, as can be seen in the database the designation of Podzols.

### **3.5 Gleysols**

Class of soils consisting of mineral material, whose genesis is related to strong hydromorphic conditions, expressed in the presence of gley horizon, and absence of distinctive features of Plinthosols or Planosols. This class is represented in the database by 214 soil profiles, which correspond to 3.91% of the total. They include soils formerly and generically named as Gleysols or Gley soils, which often were separated in Humic Gley, Low Humic Gley, Tiomorphic Gley and Saline Gley. It includes, in addition to those, the Gray Hydromorphic soils.

As observed for other classes, the lack of data concerning the full extension of the profiles resulted in difficulty for some taxonomic framework, inclusive in the level of order, due to their subsurface horizons contained in the database do not show enough coloration to distinguish the gley horizon . In these cases, the classification in this class was based on the previous name, in the assumption that other horizons of the profiles in question meet the requirements of this diagnostic horizon.

All classes of the second categorical level defined by the current system are contained in the database, although for some profiles the taxonomic classification at this level also provides some degree of uncertainty, especially for Salic Gleysols, since no data are presented relative to the electrical conductivity. Also for some soil profiles classified as Tiomorphic Gleysols, in which the pH of the horizons contained in the database are slightly above 3.5, therefore insufficient to characterize sulfuric horizon or sulfidric materials, requiring evaluation of other horizons for a more precise definition, the classification in the second level was established based on the former designation, with value 2 for the degree of confidence.

The distinction of these soils in the third categorical level was satisfactory, without significant limitations. Already the fitting in the fourth level, highlights the impossibility of differentiation based on some characteristics formerly included in the distinction of these soils, such as the great capacity of swelling and shrinkage of the soil material, expressed in the vertic designation, such as the profile 146 of the soil survey of the State of Maranhão (EMBRAPA, 1986a), previously classified as moderate A solodic with tiomorphism vertic Ta Eutrophic Gleysol, which was classified as solodic Orthic Tiomorphic Gleysol.

It is also important to emphasize the question of the current fitting of the former Gray Hydromorphic, whose distinction related to the presence of textural B horizon, is addressed only in the fourth categorical level, referring to the class of argisolics. However, in the event of sufficient characteristics for classification as plinthic, such as the profile 132 of the RADAM Brazil Project (Brasil, 1981b), that distinction is impossible, since these ones, as well as the leptics, take precedence in the sequence of the identification key. Moreover, it is not possible to differentiate soils with other special characteristics, such as the presence of fragipan, as occurs with the profile 37 of the soil survey of the left margin of the São Francisco River (EMBRAPA, 1976c).

The Gleysols are developed over unconsolidated materials (sediments and saprolites) and are greatly influenced by the occurrence of prolonged flooding due to the position of the water table near the surface. They are recognized in the legend of the WRB / FAO as Gleysols, except for classes of Salic Gleysols, that correlate to Solonchaks. Unlike what occurs in the two systems mentioned above, the American classification Soil Taxonomy identify the inherent properties of these soils in lower levels of classification. The Gleysols can be correlated with the Entisols (Aqu-alf-and-ent-ept), while Gleysols having saline character can best approach classes of the Aridisols and Entisols (Aqusulfa-hydra-salic).

### **3.6 Latosols**

320 Principles, Application and Assessment in Soil Science

especially in the great group level. In general, the classification in this hierarchical level also has a certain amount of uncertainty (degree of confidence 2), due to the lack of information about environmental conditions, once the presence of water table or saturation by water within 100 cm from the soil surface are distinctive criteria of classes. Therefore, the classification of the profiles, as Hydromorphics or Orthics, was based on the previous classification that, in general, distinguished soils subjected to hydromorphic conditions or not. Similarly, the fourth level of classification (subgroup) was also a bit impaired by the absence of complementary data of profiles that would allow a more precise taxonomic fitting . Therefore, the actualization of classification of soil profiles that belong to the class of Spodosols, in level of suborder, great group or subgroup, is about a kind of approximation,

The Spodosols of American Soil Taxonomy include diagnostic characteristics similar to the spodic B horizon of the Brazilian Espodosols. The legend of the WRB / FAO retains the name formerly used by the mapping of soils in Brazil, as can be seen in the database the

Class of soils consisting of mineral material, whose genesis is related to strong hydromorphic conditions, expressed in the presence of gley horizon, and absence of distinctive features of Plinthosols or Planosols. This class is represented in the database by 214 soil profiles, which correspond to 3.91% of the total. They include soils formerly and generically named as Gleysols or Gley soils, which often were separated in Humic Gley, Low Humic Gley, Tiomorphic Gley and Saline Gley. It includes, in addition to those, the

As observed for other classes, the lack of data concerning the full extension of the profiles resulted in difficulty for some taxonomic framework, inclusive in the level of order, due to their subsurface horizons contained in the database do not show enough coloration to distinguish the gley horizon . In these cases, the classification in this class was based on the previous name, in the assumption that other horizons of the profiles in question meet the

All classes of the second categorical level defined by the current system are contained in the database, although for some profiles the taxonomic classification at this level also provides some degree of uncertainty, especially for Salic Gleysols, since no data are presented relative to the electrical conductivity. Also for some soil profiles classified as Tiomorphic Gleysols, in which the pH of the horizons contained in the database are slightly above 3.5, therefore insufficient to characterize sulfuric horizon or sulfidric materials, requiring evaluation of other horizons for a more precise definition, the classification in the second level was established based on the former designation, with

The distinction of these soils in the third categorical level was satisfactory, without significant limitations. Already the fitting in the fourth level, highlights the impossibility of differentiation based on some characteristics formerly included in the distinction of these soils, such as the great capacity of swelling and shrinkage of the soil material, expressed in the vertic designation, such as the profile 146 of the soil survey of the State of Maranhão (EMBRAPA, 1986a), previously classified as moderate A solodic with tiomorphism vertic Ta

Eutrophic Gleysol, which was classified as solodic Orthic Tiomorphic Gleysol.

in correlation with the previous classification.

designation of Podzols.

Gray Hydromorphic soils.

requirements of this diagnostic horizon.

value 2 for the degree of confidence.

**3.5 Gleysols**

Characterized by a very advanced stage of development, as evidenced by the insignificant occurrence or even absence of weatherable primary minerals, and the presence of latosolic B horizon, the Latosols constitute the largest class of territorial expression and agricultural potential of the country, being explored with various crops, reforestation and pasture (Ker, 1997). They represent 25.79% of the database, with a total of 1,413 soil profiles.

For this class, which name was maintained in the level of order in the current system, some subdivisions were already established since the 60's, as exemplified the denominations of Red-Yellow Latosol, Dark Red Latosol and Dusky Red Latosol, to which, over time, it were added Yellow Latosol, Brown Latosol, Ferriferous Latosol and Una Latosol. These designations were, partially, maintained in the distinction of classes in the second categorical level, although the differentiation criteria have changed. In the current system, the distinction of these soils in this level is based only on the color of the B horizon, while previously competed in addition to this, other characteristics such as the iron oxide content obtained by sulfuric acid digestion, which in low contents (< 8 % of Fe2O3) is a sure indicator of strong cohesion ("hard-setting soils"), condition very far from the granular structure (high friability), typical of most of the Brazilian Latosols. In this context, the previous classification system was more informative. Thus, the former Dark Red-, Dusky Red-, and Ferriferous- Latosols, generally refer to the currently Red Latosols, with the distinction of the iron oxide content used in the third categorical level. The former denominations Red-Yellow-, Yellow-, and Brown- Latosols still remain, but while for this last class there is a strong correspondence between past and present distinctive criteria, for the other two classes there are not, beyond nomenclature, a direct relationship with the classes of the current system. The Yellow Latosols tend to stay in the homonymous class, while the former Red-Yellow Latosols are distributed in the classes of Yellow-, Red-, and Red-Yellow Latosols; otherwise the Una Latosols from the database were all classified as Yellow Latosols. In view of this, the lack of information about the color of the B horizon constituted

Updated Brazilian's Georeferenced Soil Database

Soils, Regosols, Alluvial Soils and Quartzous Sands.

of these profiles was not updated.

Neosols in the third categorical level.

**3.8 Neosols**

level.

– An Improvement for International Scientific Information Exchanging 323

The Luvisols can be framed in the class of Luvisols of the WRB/FAO legend, that presents the B horizon with accumulation of high activity clays. In the American classification the

Soils generally young, with little development and in process of formation, the Neosols are characterized by the absence of any diagnostic B horizon. With 684 soil profiles, that represent 12.48% of the database, are included in this class four major soil groups recognized by the classification scheme previously adopted in Brazil, that are the Litholic

In close correspondence with the above groups four classes are recognized in the second categorical level: Litholic Neosols, Regolithic Neosols, Fluvic Neosols and Quartzarenic Neosols, all represented in the database. Because of this, as well as the close correlation of distinctive criteria adopted by the current classification system and the previous scheme, there were few profiles that presented some problems for taxonomic fitting in the suborder

In this sense, should be highlighted some soils previously classified as Litholic Soils, currently framed in the class of Regolithic Neosols, due to present the C horizon extending below 50 cm depth. However, some profiles of Quartzous Sands, might not even be fitted as Neosols, due to the change of the criteria adopted in distinguishing sandy soils, that from the 80's replaced the lower limit of 15% clay by the requirement of the granulometric compositions of the sandy and loamy sand textural classes. Consequently, the classification

The fitting of these soils in the third categorical level was also done without difficulty, in some cases guided by the previous classification, like some profiles of Hydromorphic Quartzous Sands for which the color of the subsuperficial horizon is not presented. However, the profiles AE9 and AE10 of the soil survey of the pilot area of Barreirinha-AM (EMBRAPA, 1982d), previously classified as solodic Ta Alic Alluvial Soils, that currently fit as Fluvic Neosols, could only be classified up to the second categorical level, because it is not included in the current system the distinction of soils of this class that present dystrophic character together with high activity clay. In this way, by correlation with similar soils, it is suggested the inclusion of the class of the Dystrophic Ta to the fitting of Fluvic

In relation to the fourth categorical level, in general, the distinction of the soils presented high agreement with the differentiations expressed in the previous denomination, although with certain degree of uncertainty in the taxonomic fitting, due to the absence of complete data of the profiles. For the profile P06 of the RADAM Brazil Project (Brasil, 1981c), it was not possible, however, the distinction regarding the occurrence of concretions, as indicated in the previous classification (concretionary Eutrophic Litholic Soil), characteristic that deserves to be evaluated as a differential characteristic of classes in the subgroup level. The Quartzarenic Neosols updated in this database can be correlated with the Arenosols of the WRB/FAO legend, while in the American Soil Taxonomy this class would fit in the third categorical level (great group) as Quartzipsamments. Regolithic Neosols have been recognized as Regosols by WRB/FAO. Regarding their correlation with the American system this can be done only in the second categorical level (suborder) as Psamments. Soils that present lithic contact within 50 cm depth (Litholic Neosols), can be correlated to

best correspondent classes of soils would be the Alfisols and Aridisols (Argids).

one of the main difficulties for updating the classification of these soils in the second categorical level. In this case, the taxonomic fitting was oriented by the previous name, with differentiation concerning the degree of confidence, according to the following pattern: Dusky Red- and Dark Red-Latosols were classified as Reds, and Yellow- and Brown-Latosols in the homonymous classes, all with degree 2 of confidence; similarly, the Red-Yellow Latosols were fitted in the class of the same denomination, but with degree 3 of confidence, due to the increased uncertainty of this adjustment.

In the third categorical level distinction, that is based on the characteristics of the exchange complex, in association with the contents of Fe2O3 from the sulfuric acid digestion, the taxonomic framework was very satisfactory as well as the subsequent level (subgroup), which seems to indicate major concern in the establishment of possible distinction of these soils, perhaps because of their high potential for agricultural use, as well as their large territorial expression in the country.

The word Latosol implies soils formed under conditions of significant weathering-leaching, resulting in materials with a residual concentration of secondary minerals, including kaolinite, gibbsite, and iron- and aluminum- oxides, in different proportions. The understanding of their genesis facilitates the identification of their corresponding names in the American Classification Soil Taxonomy and legend of WRB/FAO, as Oxisols and Ferralsols, respectively.

#### **3.7 Luvisols**

Grouping of soils characterized by the presence of textural B horizon or nitic B horizon, with high clay activity and high base saturation, excluding those with chernozemic A horizon. This class is represented in the database by 118 soil profiles (2.15% of the total).

Encompasses soils originally classified as Non-Calcic Brown soils and Red-Yellow Podzolic soils, with little participation of Gray-Brown Podzolic soils and Dark Red Podzolic soils.

It also includes some profiles formerly called Reddish Brunizens, whose A horizons do not have enough base saturation (≥ 65%) to characterize the chernozemic A horizon, according to the current criteria.

Although having achieved a very satisfactory taxonomic fitting in the level of order, some loss of accuracy in the update was already observed from the second categorical level, as a function of the available data do not allow an precise evaluation of the dominance of colors of the B horizon, necessary to distinguish between Chromic- and Haplic- Luvisols. This fact resulted in a higher degree of uncertainty regarding the taxonomic fitting, also reflected in lower categorical levels. Another aspect that difficulted the classification of some soils, due to the unavailability of data for the entire extension of the profiles, is relative to the depth of the *solum* (horizons A + B), characteristic used to distinguish, in the third categorical level (great group), the class of Palic Chromic Luvisols.

For the same reason, the distinction of some soils in the fourth categorical level was also slightly affected, considering the utilized criteria to identify the classes of saprolithics and lithics. Moreover, some differential characteristics indicated in the previous denomination are not considered by the current classification, as the profile 58 of the soil survey of the State of Pernambuco (Brasil, 1972e), currently classified as planosolic Orthic Haplic Luvisol, in which the presence of solodic character and vertic characteristic expressed in the previous classification (solodic vertic planosolic Non-Calcic Brown soil), are not considered in the distinction of this type of soil in the current system.

The Luvisols can be framed in the class of Luvisols of the WRB/FAO legend, that presents the B horizon with accumulation of high activity clays. In the American classification the best correspondent classes of soils would be the Alfisols and Aridisols (Argids).

### **3.8 Neosols**

322 Principles, Application and Assessment in Soil Science

one of the main difficulties for updating the classification of these soils in the second categorical level. In this case, the taxonomic fitting was oriented by the previous name, with differentiation concerning the degree of confidence, according to the following pattern: Dusky Red- and Dark Red-Latosols were classified as Reds, and Yellow- and Brown-Latosols in the homonymous classes, all with degree 2 of confidence; similarly, the Red-Yellow Latosols were fitted in the class of the same denomination, but with degree 3 of

In the third categorical level distinction, that is based on the characteristics of the exchange complex, in association with the contents of Fe2O3 from the sulfuric acid digestion, the taxonomic framework was very satisfactory as well as the subsequent level (subgroup), which seems to indicate major concern in the establishment of possible distinction of these soils, perhaps because of their high potential for agricultural use, as well as their large

The word Latosol implies soils formed under conditions of significant weathering-leaching, resulting in materials with a residual concentration of secondary minerals, including kaolinite, gibbsite, and iron- and aluminum- oxides, in different proportions. The understanding of their genesis facilitates the identification of their corresponding names in the American Classification Soil Taxonomy and legend of WRB/FAO, as Oxisols and

Grouping of soils characterized by the presence of textural B horizon or nitic B horizon, with high clay activity and high base saturation, excluding those with chernozemic A horizon.

Encompasses soils originally classified as Non-Calcic Brown soils and Red-Yellow Podzolic soils, with little participation of Gray-Brown Podzolic soils and Dark Red Podzolic soils. It also includes some profiles formerly called Reddish Brunizens, whose A horizons do not have enough base saturation (≥ 65%) to characterize the chernozemic A horizon, according

Although having achieved a very satisfactory taxonomic fitting in the level of order, some loss of accuracy in the update was already observed from the second categorical level, as a function of the available data do not allow an precise evaluation of the dominance of colors of the B horizon, necessary to distinguish between Chromic- and Haplic- Luvisols. This fact resulted in a higher degree of uncertainty regarding the taxonomic fitting, also reflected in lower categorical levels. Another aspect that difficulted the classification of some soils, due to the unavailability of data for the entire extension of the profiles, is relative to the depth of the *solum* (horizons A + B), characteristic used to distinguish, in the third categorical level

For the same reason, the distinction of some soils in the fourth categorical level was also slightly affected, considering the utilized criteria to identify the classes of saprolithics and lithics. Moreover, some differential characteristics indicated in the previous denomination are not considered by the current classification, as the profile 58 of the soil survey of the State of Pernambuco (Brasil, 1972e), currently classified as planosolic Orthic Haplic Luvisol, in which the presence of solodic character and vertic characteristic expressed in the previous classification (solodic vertic planosolic Non-Calcic Brown soil), are not considered in the

This class is represented in the database by 118 soil profiles (2.15% of the total).

confidence, due to the increased uncertainty of this adjustment.

territorial expression in the country.

Ferralsols, respectively.

to the current criteria.

(great group), the class of Palic Chromic Luvisols.

distinction of this type of soil in the current system.

**3.7 Luvisols**

Soils generally young, with little development and in process of formation, the Neosols are characterized by the absence of any diagnostic B horizon. With 684 soil profiles, that represent 12.48% of the database, are included in this class four major soil groups recognized by the classification scheme previously adopted in Brazil, that are the Litholic Soils, Regosols, Alluvial Soils and Quartzous Sands.

In close correspondence with the above groups four classes are recognized in the second categorical level: Litholic Neosols, Regolithic Neosols, Fluvic Neosols and Quartzarenic Neosols, all represented in the database. Because of this, as well as the close correlation of distinctive criteria adopted by the current classification system and the previous scheme, there were few profiles that presented some problems for taxonomic fitting in the suborder level.

In this sense, should be highlighted some soils previously classified as Litholic Soils, currently framed in the class of Regolithic Neosols, due to present the C horizon extending below 50 cm depth. However, some profiles of Quartzous Sands, might not even be fitted as Neosols, due to the change of the criteria adopted in distinguishing sandy soils, that from the 80's replaced the lower limit of 15% clay by the requirement of the granulometric compositions of the sandy and loamy sand textural classes. Consequently, the classification of these profiles was not updated.

The fitting of these soils in the third categorical level was also done without difficulty, in some cases guided by the previous classification, like some profiles of Hydromorphic Quartzous Sands for which the color of the subsuperficial horizon is not presented. However, the profiles AE9 and AE10 of the soil survey of the pilot area of Barreirinha-AM (EMBRAPA, 1982d), previously classified as solodic Ta Alic Alluvial Soils, that currently fit as Fluvic Neosols, could only be classified up to the second categorical level, because it is not included in the current system the distinction of soils of this class that present dystrophic character together with high activity clay. In this way, by correlation with similar soils, it is suggested the inclusion of the class of the Dystrophic Ta to the fitting of Fluvic Neosols in the third categorical level.

In relation to the fourth categorical level, in general, the distinction of the soils presented high agreement with the differentiations expressed in the previous denomination, although with certain degree of uncertainty in the taxonomic fitting, due to the absence of complete data of the profiles. For the profile P06 of the RADAM Brazil Project (Brasil, 1981c), it was not possible, however, the distinction regarding the occurrence of concretions, as indicated in the previous classification (concretionary Eutrophic Litholic Soil), characteristic that deserves to be evaluated as a differential characteristic of classes in the subgroup level.

The Quartzarenic Neosols updated in this database can be correlated with the Arenosols of the WRB/FAO legend, while in the American Soil Taxonomy this class would fit in the third categorical level (great group) as Quartzipsamments. Regolithic Neosols have been recognized as Regosols by WRB/FAO. Regarding their correlation with the American system this can be done only in the second categorical level (suborder) as Psamments. Soils that present lithic contact within 50 cm depth (Litholic Neosols), can be correlated to

Updated Brazilian's Georeferenced Soil Database

**3.10 Organosols**

which equals to 0.20% of the total.

more data for confirmation.

advanced stage of decomposition.

**3.11 Planosols**

degree of confidence in all categorical levels.

classification and Histosols by the American system and FAO.

correlation encompassing Ultisols, Oxisols (Kandic) and Alfisols.

performed by direct correlation with the previous classification.

– An Improvement for International Scientific Information Exchanging 325

In this class are classified clayey to very clayey soils with slight increase of clay in the subsurface horizon, not establishing enough textural gradient for fitting as textural B horizon, but being possible to observe clear clay skins on soil aggregates. These observations can be found in the classes of the Nitisols, Lixisols and Alisols of the world soils legend of the FAO, while for the American classification Soil Taxonomy, it can be observed the

Due to the limited expressiveness of these soils in the country, generally restricted to small areas, as well as more difficult access, they tend to be contemplated with a few profiles sampled in more generalized pedological surveys as the ones considered here. Thus, the presence of the class of Organosols in the database was minimal, covering only 11 profiles,

Characterized by its essentially organic constitution, the distinctive criteria of this class in order level present an adequate correlation with the set of soils previously included under the general denomination of Organic Soils. Thus, we obtained a very satisfactory taxonomic fitting in the highest categorical level, although for some profiles, considering the unavailability of complete data, the fitting in the current classification system has been

For the subsequent categorical level, all profiles were classified as Haplics. Only for the profile 37 of RADAM Brazil Project (Brasil, 1981d), which presents very low values of pH in water in the subsurface horizon, there is about the possibility of occurrence of sulfuric horizon or sulfidric material (distinctive characteristics of Tiomorphic class ), thus requiring

The main difficulty in upgrading the classification of these soils was observed in the third categorical level (great group), because the distinctive criteria involve determinations not performed in epochs before the publication of the first edition of the Brazilian System of Soil Classification (EMBRAPA, 1999), which makes very difficult a more accurate evaluation, even from complete morphological and analytical characterization of soils profiles. Classification at this level was therefore undertaken in an attempt form, fitting all the profiles in the class of Saprics, which groups soils constituted of organic material in an

Also in the fourth categorical level, the absence of analytical data, especially concerning the electrical conductivity, reduces the confidence of taxonomic fitting. Only the profile C137 of the soil survey of the State of Paraná (EMBRAPA, 1984), referred in SiBCS (EMBRAPA, 2006) as representative of the terric Sapric Haplic Organosols, was classified with higher

Most organic constituents, in various stages of decomposition, in relation to the mineral ones are the basic criteria for the distinction of Organosols in the Brazilian system of

In relation to the grouping of soils with planic B horizon, which is characterized by abrupt transition in association with sharp increase of clay in relation to the overlying horizon, the Planosols tend to occur in environments of restricted drainage, susceptible to hydromorphism at least temporarily. This class represents 4.22% of the updated of profiles

Leptosols of the WRB/FAO legend. The American classification uses this property in the fourth categorical level (subgroup) and can be related to Lithic of Orthents suborder and also with Lithic of great group Psamments. The Fluvic Neosols are soils originated from alluvial sediments with close correlation with the Fluvisols of the WRB/FAO legend, while in the American Soil Taxonomy they would be fitted in the second categorical level as Fluvents.

### **3.9 Nitosols**

In the database of soils of Brazil, this class is represented by 260 profiles, which equals to 4.75% of the total. Encompasses soils previously referred as Structured Dusky Red Earth, Structured Brown Earth, Similar Structured Dusky Red Earth and Similar Structured Brown Earth, beyond some profiles recognized as Red-Yellow Podzolic soils which present low textural gradient. More specifically for these last soils, there is a higher degree of uncertainty regarding the classification as Nitosols, because the database do not include information on morphological characteristics necessary for unambiguous identification of the nitic B horizon, distinctive of this class, whose requirements include structural development and significant presence of clay skins.

With the re-structuration promoted by the new version of SiBCS, regarding the inclusion of the class of Brown Nitosols in the second categorical level, many of the soils previously classified as Haplics, according to the first edition of the system (EMBRAPA, 1999), are now fitted in this new class.

In this work we option for the fitting as Brown Nitosols only the soils formerly called Structured Brown Earth or Similar Structured Brown Earth, provided they meet the requirement of specified color, or, in the absence of this information, assigning higher value for the degree of confidence (greater degree of uncertainty). This situation highlights the need for a more precise definition of the distinctive criteria of the class, where the comparison of related soils, members of the database under study could contribute. It should be registered also the impossibility of classification in lower categorical levels of the profile C48 of soil survey of the State of Paraná (EMBRAPA, 1984), originally identified as chernozemic A Eutrophic Structured Brown Earth, because in the current system classes that allow taxonomic fitting as Brown Nitosols with eutrophic character are not considered.

Relatively to other classes in the second categorical level, we observed a strong correspondence between the former Structured Dusky Red Earth and Red Nitosols, that beyond these soils also comprises a small proportion of Red-Yellow Podzolic soils. However, some soils previously recognized as Structured Dusky Red Earth, many of which having high iron oxide content, were classified as Haplic Nitosols, due to present 3.5YR or 4YR hues in the B horizon.

Regarding the fourth categorical level, as observed for other classes, some differences shown in the previous classification do not found correspondence which classes of the current system, such as the latosolic Eutrophic Similar Structured Dusky Red Earth (Brasil, 1982d), which fits as typic Eutrophic Haplic Nitosol. Also the profile C63 of the soil survey of the State of Paraná (EMBRAPA, 1984), previously classified as cambic Alic Similar Structured Brown Earth was fitted as typic Aluminic Brown Nitosol, for not being included possibilities of distinction relative to intermediate characteristics represented in the previous designation.

In this class are classified clayey to very clayey soils with slight increase of clay in the subsurface horizon, not establishing enough textural gradient for fitting as textural B horizon, but being possible to observe clear clay skins on soil aggregates. These observations can be found in the classes of the Nitisols, Lixisols and Alisols of the world soils legend of the FAO, while for the American classification Soil Taxonomy, it can be observed the correlation encompassing Ultisols, Oxisols (Kandic) and Alfisols.

### **3.10 Organosols**

324 Principles, Application and Assessment in Soil Science

Leptosols of the WRB/FAO legend. The American classification uses this property in the fourth categorical level (subgroup) and can be related to Lithic of Orthents suborder and also with Lithic of great group Psamments. The Fluvic Neosols are soils originated from alluvial sediments with close correlation with the Fluvisols of the WRB/FAO legend, while in the American Soil Taxonomy they would be fitted in the second categorical level as

In the database of soils of Brazil, this class is represented by 260 profiles, which equals to 4.75% of the total. Encompasses soils previously referred as Structured Dusky Red Earth, Structured Brown Earth, Similar Structured Dusky Red Earth and Similar Structured Brown Earth, beyond some profiles recognized as Red-Yellow Podzolic soils which present low textural gradient. More specifically for these last soils, there is a higher degree of uncertainty regarding the classification as Nitosols, because the database do not include information on morphological characteristics necessary for unambiguous identification of the nitic B horizon, distinctive of this class, whose requirements include structural development and

With the re-structuration promoted by the new version of SiBCS, regarding the inclusion of the class of Brown Nitosols in the second categorical level, many of the soils previously classified as Haplics, according to the first edition of the system (EMBRAPA, 1999), are now

In this work we option for the fitting as Brown Nitosols only the soils formerly called Structured Brown Earth or Similar Structured Brown Earth, provided they meet the requirement of specified color, or, in the absence of this information, assigning higher value for the degree of confidence (greater degree of uncertainty). This situation highlights the need for a more precise definition of the distinctive criteria of the class, where the comparison of related soils, members of the database under study could contribute. It should be registered also the impossibility of classification in lower categorical levels of the profile C48 of soil survey of the State of Paraná (EMBRAPA, 1984), originally identified as chernozemic A Eutrophic Structured Brown Earth, because in the current system classes that allow taxonomic fitting as Brown Nitosols with eutrophic character are

Relatively to other classes in the second categorical level, we observed a strong correspondence between the former Structured Dusky Red Earth and Red Nitosols, that beyond these soils also comprises a small proportion of Red-Yellow Podzolic soils. However, some soils previously recognized as Structured Dusky Red Earth, many of which having high iron oxide content, were classified as Haplic Nitosols, due to present 3.5YR or

Regarding the fourth categorical level, as observed for other classes, some differences shown in the previous classification do not found correspondence which classes of the current system, such as the latosolic Eutrophic Similar Structured Dusky Red Earth (Brasil, 1982d), which fits as typic Eutrophic Haplic Nitosol. Also the profile C63 of the soil survey of the State of Paraná (EMBRAPA, 1984), previously classified as cambic Alic Similar Structured Brown Earth was fitted as typic Aluminic Brown Nitosol, for not being included possibilities of distinction relative to intermediate characteristics represented in the previous

Fluvents.

**3.9 Nitosols**

significant presence of clay skins.

fitted in this new class.

not considered.

designation.

4YR hues in the B horizon.

Due to the limited expressiveness of these soils in the country, generally restricted to small areas, as well as more difficult access, they tend to be contemplated with a few profiles sampled in more generalized pedological surveys as the ones considered here. Thus, the presence of the class of Organosols in the database was minimal, covering only 11 profiles, which equals to 0.20% of the total.

Characterized by its essentially organic constitution, the distinctive criteria of this class in order level present an adequate correlation with the set of soils previously included under the general denomination of Organic Soils. Thus, we obtained a very satisfactory taxonomic fitting in the highest categorical level, although for some profiles, considering the unavailability of complete data, the fitting in the current classification system has been performed by direct correlation with the previous classification.

For the subsequent categorical level, all profiles were classified as Haplics. Only for the profile 37 of RADAM Brazil Project (Brasil, 1981d), which presents very low values of pH in water in the subsurface horizon, there is about the possibility of occurrence of sulfuric horizon or sulfidric material (distinctive characteristics of Tiomorphic class ), thus requiring more data for confirmation.

The main difficulty in upgrading the classification of these soils was observed in the third categorical level (great group), because the distinctive criteria involve determinations not performed in epochs before the publication of the first edition of the Brazilian System of Soil Classification (EMBRAPA, 1999), which makes very difficult a more accurate evaluation, even from complete morphological and analytical characterization of soils profiles. Classification at this level was therefore undertaken in an attempt form, fitting all the profiles in the class of Saprics, which groups soils constituted of organic material in an advanced stage of decomposition.

Also in the fourth categorical level, the absence of analytical data, especially concerning the electrical conductivity, reduces the confidence of taxonomic fitting. Only the profile C137 of the soil survey of the State of Paraná (EMBRAPA, 1984), referred in SiBCS (EMBRAPA, 2006) as representative of the terric Sapric Haplic Organosols, was classified with higher degree of confidence in all categorical levels.

Most organic constituents, in various stages of decomposition, in relation to the mineral ones are the basic criteria for the distinction of Organosols in the Brazilian system of classification and Histosols by the American system and FAO.

### **3.11 Planosols**

In relation to the grouping of soils with planic B horizon, which is characterized by abrupt transition in association with sharp increase of clay in relation to the overlying horizon, the Planosols tend to occur in environments of restricted drainage, susceptible to hydromorphism at least temporarily. This class represents 4.22% of the updated of profiles

Updated Brazilian's Georeferenced Soil Database

Plinthaqu (alf-ept-ox-ult)s of Soil Taxonomy.

Soils, including the Lateritic Concretionary Soils.

differential characteristic, as mentioned in the previous name.

represented in the database.

of SiBCS (EMBRAPA, 1999).

**3.12 Plinthosols**

– An Improvement for International Scientific Information Exchanging 327

Grande do Sul (Costa et al., 2009). It seems appropriate to consider the possibility of keeping the distinction in the second categorical level, as adopted by the previous version

The suborder of Natric Planosols can be identified in the American classification Soil Taxonomy and WRB/FAO as Natr-(ust-ud)-alf and Solonetz, respectively. Classes that do not fall into this suborder are denominated at second categorical level as Haplics and can be correlated with the classes of Planosols (WRB/FAO), and Albaquults, Albaqualfs and

In this class are included soils characterized by expressive plinthization, presenting significant occurrence of plinthite, either in its mild or hard (petroplinthite) form, resulting from changes in the formation environment. In the database of soils of Brazil this class has a participation corresponding to 5.40%, which is equal to a total of 296 soil profiles. It covers the vast majority of the former Hydromorphic Laterites, which were later recognized as Plinthosols, a designation that was kept in the current system, and, with the modifications introduced in its latest version, referring to the concept of concretionary and lithoplintic horizon, now include those soils previously listed under the generic name of Concretionary

The main difficulty of current fitting of the soils in this class precisely refers to the last soils, which, because of the lack of more precise criteria for their identification, constituted a large and highly heterogeneous group. Thus, they were classified as Plinthosols according to the reference of the occurrence of concretions (petroplinthite) expressed in its name, giving high degree of confidence only for those soils with at least one horizon with 30 cm or more thickness and volume of pebbles and cobbles equals to 50% or more, enough for characterizing the concretionary horizon. For the others, considering that often the coarse material was discarded during sampling, or it was not measured, and the available data do not cover the entire extension of the profiles, it was considered greater uncertainty in the taxonomic fitting, with a moderate degree of confidence (value 2) in case there is some indication of the occurrence of petroplinthite (given by the horizon designation, for example), or lower degree of confidence (value 3), otherwise. All these soils, also including a smaller number of profiles originally called Concretionary Plinthosols or Concretionary Laterites, were grouped in a single class at second (Petric) and third categorical level (Concretionary), being distinguished only in the suborder level, due to the occurrence of some diagnostic horizon (incipient B or cambic B, latosolic B or textural B), or other

Other Plinthosols of the database were classified, in the second categorical level, as Argilluvics and Haplics, with great domain of the first in relation to the second ones. The change in the latest version of the system, referring to the argilluvic character (defined as having a texture ratio superior to 1.4) instead of the presence of textural B horizon to distinguish the Argilluvics (EMBRAPA, 2006), seems to be mainly responsible for this fact. In strong contraposition to the criteria adopted for Petric Plinthosols, the distinction of both classes in the subsequent categorical level is based on the saturation of exchange complex, and subsidiarily on clay activity for soils with very high aluminum content, differentiating soils with Alitic-, Aluminic-, Dystrophic- or Eutrophic-character, all of these classes

of the database, which is equivalent to 231 profiles. Refer to soils formerly called Planosols and Solodized-Solonetz, now included in the same class in the order level, distinguished in the second categorical level as Haplic Planosols and Natric Planosols , respectively. A very satisfactory adjustment between the classes previously recognized and the current ones was achieved.

However, despite the strong correlation between the current criteria for distinguishing these soils and the previously criteria used, because there are not available morphological data and analytical results of the entire profiles, some of them were classified based on the original name, such as the profile 66 of the technical bulletin 16, of the former Division of Research Pedologic (Brasil, 1972e), called weak A Ta Eutrophic Planosol, for which the subsurface horizon of the database refers to the C horizon, with no indication of the occurrence of colors having low chroma. Due to this, this soil was tentatively classified as typic Eutrophic Haplic Planosol.

The non-availability of analytical data also contributed for reducing the confidence of the update of the classification in the subsequent categorical levels. The distinction of Salic Soils, at the subgroup level, for example, was not possible, due to lack of data on electrical conductivity.

Major limitations for the taxonomic fitting were observed, however, in the fourth categorical level. For example, for the profile 89 of soil survey of the State of Ceará (Brasil, 1973a), originally called weak A vertic solodic Planosol, it was not possible with the available data, the confirmation of the solodic character, although it may be present in some horizon within the first 120 cm depth. Thus, this soil was classified as vertic Eutrophic Haplic Planosol. Similarly to observed for the other classes, some differential characteristics represented in the previous name are not included in the distinction of soils by the current system. As a result, the soil represented by the profile 200 of the RADAM Brazil Project (Brasil, 1981b), formerly designated plinthic Tb endoeutrophic Planosol, was classified as typic Eutrophic Haplic Planosol, because it is not included the plinthic class.

The soils that in the first edition of the Brazilian classification system (EMBRAPA, 1999) were differentiated in the second categorical level, such as Hydromorphic Planosols, were excluded from the current version (EMBRAPA, 2006). Actually they are classified as gleissolics in the fourth categorical level, but by the ordering of the classes in the identification key, in some cases they can not be distinguished as such. The profile 81 of the RADAM Brazil Project (Brasil, 1981a), for example, even though there are enough characteristics for its fitting as gleisolic, by the current criteria it is fitted as solodic Eutrophic Haplic Planosol, due to the solodic character take precedence in the distinction of soils at this level. As for the Dystrophic Haplic Planosols, the gleisolic class take precedence in relation to plinthic and solodic in the classification key at the fourth level, not allowing the distinction in the case of simultaneous occurrence of soils with these characteristics, as occurs for the profile 97 of the RADAM Brazil Project (Brasil, 1982b), originally classified as moderate A plinthic Tb Alic Planosol, by the current system fits as gleisolic Dystrophic Haplic Planosol. Considering the above comments, and considering the strong influence of hydromorphic conditions on sustainable use and management of these soils, as well as environmental and pedogenesis aspects, it is strongly suggested the distinction of Planosols with these characteristics in higher categorical level. This has practical application and considerable geographical expression mainly in the state of Rio Grande do Sul (Costa et al., 2009). It seems appropriate to consider the possibility of keeping the distinction in the second categorical level, as adopted by the previous version of SiBCS (EMBRAPA, 1999).

The suborder of Natric Planosols can be identified in the American classification Soil Taxonomy and WRB/FAO as Natr-(ust-ud)-alf and Solonetz, respectively. Classes that do not fall into this suborder are denominated at second categorical level as Haplics and can be correlated with the classes of Planosols (WRB/FAO), and Albaquults, Albaqualfs and Plinthaqu (alf-ept-ox-ult)s of Soil Taxonomy.

### **3.12 Plinthosols**

326 Principles, Application and Assessment in Soil Science

of the database, which is equivalent to 231 profiles. Refer to soils formerly called Planosols and Solodized-Solonetz, now included in the same class in the order level, distinguished in the second categorical level as Haplic Planosols and Natric Planosols , respectively. A very satisfactory adjustment between the classes previously recognized and the current ones was

However, despite the strong correlation between the current criteria for distinguishing these soils and the previously criteria used, because there are not available morphological data and analytical results of the entire profiles, some of them were classified based on the original name, such as the profile 66 of the technical bulletin 16, of the former Division of Research Pedologic (Brasil, 1972e), called weak A Ta Eutrophic Planosol, for which the subsurface horizon of the database refers to the C horizon, with no indication of the occurrence of colors having low chroma. Due to this, this soil was tentatively classified as

The non-availability of analytical data also contributed for reducing the confidence of the update of the classification in the subsequent categorical levels. The distinction of Salic Soils, at the subgroup level, for example, was not possible, due to lack of data on electrical

Major limitations for the taxonomic fitting were observed, however, in the fourth categorical level. For example, for the profile 89 of soil survey of the State of Ceará (Brasil, 1973a), originally called weak A vertic solodic Planosol, it was not possible with the available data, the confirmation of the solodic character, although it may be present in some horizon within the first 120 cm depth. Thus, this soil was classified as vertic Eutrophic Haplic Planosol. Similarly to observed for the other classes, some differential characteristics represented in the previous name are not included in the distinction of soils by the current system. As a result, the soil represented by the profile 200 of the RADAM Brazil Project (Brasil, 1981b), formerly designated plinthic Tb endoeutrophic Planosol, was classified as typic Eutrophic Haplic Planosol, because it is not included the

The soils that in the first edition of the Brazilian classification system (EMBRAPA, 1999) were differentiated in the second categorical level, such as Hydromorphic Planosols, were excluded from the current version (EMBRAPA, 2006). Actually they are classified as gleissolics in the fourth categorical level, but by the ordering of the classes in the identification key, in some cases they can not be distinguished as such. The profile 81 of the RADAM Brazil Project (Brasil, 1981a), for example, even though there are enough characteristics for its fitting as gleisolic, by the current criteria it is fitted as solodic Eutrophic Haplic Planosol, due to the solodic character take precedence in the distinction of soils at this level. As for the Dystrophic Haplic Planosols, the gleisolic class take precedence in relation to plinthic and solodic in the classification key at the fourth level, not allowing the distinction in the case of simultaneous occurrence of soils with these characteristics, as occurs for the profile 97 of the RADAM Brazil Project (Brasil, 1982b), originally classified as moderate A plinthic Tb Alic Planosol, by the current system fits as gleisolic Dystrophic Haplic Planosol. Considering the above comments, and considering the strong influence of hydromorphic conditions on sustainable use and management of these soils, as well as environmental and pedogenesis aspects, it is strongly suggested the distinction of Planosols with these characteristics in higher categorical level. This has practical application and considerable geographical expression mainly in the state of Rio

achieved.

conductivity.

plinthic class.

typic Eutrophic Haplic Planosol.

In this class are included soils characterized by expressive plinthization, presenting significant occurrence of plinthite, either in its mild or hard (petroplinthite) form, resulting from changes in the formation environment. In the database of soils of Brazil this class has a participation corresponding to 5.40%, which is equal to a total of 296 soil profiles. It covers the vast majority of the former Hydromorphic Laterites, which were later recognized as Plinthosols, a designation that was kept in the current system, and, with the modifications introduced in its latest version, referring to the concept of concretionary and lithoplintic horizon, now include those soils previously listed under the generic name of Concretionary Soils, including the Lateritic Concretionary Soils.

The main difficulty of current fitting of the soils in this class precisely refers to the last soils, which, because of the lack of more precise criteria for their identification, constituted a large and highly heterogeneous group. Thus, they were classified as Plinthosols according to the reference of the occurrence of concretions (petroplinthite) expressed in its name, giving high degree of confidence only for those soils with at least one horizon with 30 cm or more thickness and volume of pebbles and cobbles equals to 50% or more, enough for characterizing the concretionary horizon. For the others, considering that often the coarse material was discarded during sampling, or it was not measured, and the available data do not cover the entire extension of the profiles, it was considered greater uncertainty in the taxonomic fitting, with a moderate degree of confidence (value 2) in case there is some indication of the occurrence of petroplinthite (given by the horizon designation, for example), or lower degree of confidence (value 3), otherwise. All these soils, also including a smaller number of profiles originally called Concretionary Plinthosols or Concretionary Laterites, were grouped in a single class at second (Petric) and third categorical level (Concretionary), being distinguished only in the suborder level, due to the occurrence of some diagnostic horizon (incipient B or cambic B, latosolic B or textural B), or other differential characteristic, as mentioned in the previous name.

Other Plinthosols of the database were classified, in the second categorical level, as Argilluvics and Haplics, with great domain of the first in relation to the second ones. The change in the latest version of the system, referring to the argilluvic character (defined as having a texture ratio superior to 1.4) instead of the presence of textural B horizon to distinguish the Argilluvics (EMBRAPA, 2006), seems to be mainly responsible for this fact. In strong contraposition to the criteria adopted for Petric Plinthosols, the distinction of both classes in the subsequent categorical level is based on the saturation of exchange complex, and subsidiarily on clay activity for soils with very high aluminum content, differentiating soils with Alitic-, Aluminic-, Dystrophic- or Eutrophic-character, all of these classes represented in the database.

Updated Brazilian's Georeferenced Soil Database

distributed over the Brazilian territory.

experience among researchers at international level.

EMBRAPA, Brasília, Brasil.

Janeiro, Brasil.

Brasil.

Raton, CRC Press, pp. H1-H4.

24 Sudene. Série Pedologia, 17), Recife, Brasil.

Série Pedologia, 14), Recife, Brasil.

character.

**4. Conclusions**

**5. References**

– An Improvement for International Scientific Information Exchanging 329

The absence of analytical data has hampered the taxonomic fitting in the fourth categorical level, as example of the electrical conductivity, necessary for the identification of saline

The characteristics of vertic horizon identify typical pedological features due to shrinkage and swelling of the minerals of this class. These features are called friction surfaces ("slickensides"), and are common both in the U.S. classification for the Vertisols as well as in

The database used in this work reveals an adequate representativeness of the soil classes

This database can function as an advance to stimulate the exchanging of information and

Assad, E. & Sano, E. (1998). *Sistema de informações geográficas: Aplicações na Agricultura*.

Baumgardner, M. (1999). Soil databases. In: SUMNER, M.E., ed. *Handbook of soil science*. Boca

Benedetti, M. ; Sparovek, G.; Cooper, M.; Curi, N. & Carvalho Filho, A. (2008).

Brasil (1958). *Levantamento de reconhecimento dos solos do Estado do Rio de Janeiro e Distrito*

Brasil (1960). *Levantamento de reconhecimento dos solos do Estado de São Paulo: contribuição à*

Brasil (1973h). *Levantamento exploratório de solos do Estado do Ceará.* Ministério da Agricultura.

Brasil (1972e). *Levantamento exploratório-reconhecimento de solos do Estado de Pernambuco.*

Agronômicas. Comissão de Solos. (Boletim, 12), Rio de Janeiro, Brasil. Brasil (1971a). *Levantamento de reconhecimento dos solos do sul do Mato Grosso.* Ministério da

Pesquisa Pedológica. (Boletim Técnico, 18), Rio de Janeiro, Brasil.

Brasil. *Revista Brasileira de Ciência do Solo.* , v.32, No.6, pp. 2591-2600. Brasil (1972a). *Estudo expedito de solos nas partes central e sul do Estado da Bahia, para fins de*

Representatividade e potencial de utilização de um banco de dados de solos do

*classificação e correlação.* Ministério da Agricultura. Departamento Nacional de Pesquisa Agropecuária. Divisão de Pesquisa Pedológica. (DNPEA. Boletim Técnico,

*Federal: contribuição à carta de solos do Brasil.* Ministério da Agricultura. Serviço Nacional de Pesquisas Agronômicas. Comissão de Solos. (Boletim, 11), Rio de

*carta de solos do Brasil.* Ministério da Agricultura. Serviço Nacional de Pesquisas

Agricultura. Departamento Nacional de Pesquisa Agropecuária. Divisão de

Departamento Nacional de Pesquisa Agropecuária. Divisão de Pesquisa Pedológica. 2v. (Boletim técnico, 26; SUDENE. DRN. Série Pedologia, 14), Recife,

Ministério da Agricultura. Departamento Nacional de Pesquisa Agropecuária. Divisão de Pesquisa Pedológica. 2v. (DNPEA. Boletim Técnico, 16; SUDENE. DRN.

the international legend of the FAO for those soils also called Vertisols.

Also in the fourth level it is clearly demonstrated the great difference in the criteria used in distinguishing between Argilluvic Plinthosols and Haplic Plinthosols, and the Petric Plinthosols, which constitute a very distinct group within this class.

The occurrence of appreciable amounts of plinthite in the soil profile is also identified in the class of the Plinthosols in the WRB/FAO international classification. The American system of classification adopts this character in lower categorical level (subgroup) and can be found correspondence of Plinthosols with different classes of the Soil Taxonomy, which present the plinthic character. These classes comprise the Oxisols, Ultisols, Alfisols, Entisols and Inceptisols.

### **3.13 Vertisols**

The soils of this class, due to the dominance of very high activity clays, are characterized by a great capacity of swelling and shrinkage of soil material with wetting and drying cycles, a factor that restricts their pedogenetic development. Having little occurrence in Brazilian territory, Vertisols represent only 1.00% of the profiles in the database, comprising a total of 55 profiles.

As the identification of soils in this class includes criteria based on morphological characteristics evaluated in the field, the first categorical level was established by direct correlation with the original classification, whose name was maintained by the current system, just as the essence of the distinctive criteria, which allowed a satisfactory fit. For some profiles, however, there was some difficulty in taxonomic fitting, due to the presence, sometimes in the surface horizon, other times in subsurface horizon, of clay content below 300 g / kg, established as thresholds to distinguish the class of Vertisols (up to 20 cm depth, after mixing), but also for the vertic horizon (EMBRAPA, 2006). Once in the database are not included all the horizons of the profile, thereby preventing a more adequate evaluation, it was maintained their classification as Vertisols, assigning the value 2 for the degree of confidence in case of one of the horizons do not meet the specified requirement, and value 3 when both had amounts of clay below the minimum limit required. This situation, however, shows some discrepancy between the definitions of vertic horizon and of the class of Vertisols, as well as the need to adjust them. It may be appropriate to assess, from the characteristics of the profiles contained in the database, the adequacy of a minimum amount of clay established for distinction of these soils.

In the second categorical level, it were recognized classes of Hydromorphic Vertisols, Ebanic Vertisols and Haplic Vertisols. Some difficulty in classification was observed mainly for fitting of some soils as Hydromorphics, due to the subsurface horizons refer to depths greater than 50 cm, being necessary information on colors of the overlying horizons to confirm the classification (in this case it was assigned the value 2 to express the degree of confidence). Other profiles, on the other hand, did not present information on moist color, being classified as Haplics, with value 3 for the confidence degree.

Also in the great group level it was observed some difficulty in taxonomic fitting of the profiles, mainly due to the lack of relevant data, such as the contents of equivalent CaCO3. This form, the fitting in the class of the Carbonatics was based on previous classification, corroborated by the subordinated designation of horizons of the profile (EMBRAPA, 1988b), being the other profiles classified as Orthics, since the previous name did not present indication of the occurrence of salic character.

The absence of analytical data has hampered the taxonomic fitting in the fourth categorical level, as example of the electrical conductivity, necessary for the identification of saline character.

The characteristics of vertic horizon identify typical pedological features due to shrinkage and swelling of the minerals of this class. These features are called friction surfaces ("slickensides"), and are common both in the U.S. classification for the Vertisols as well as in the international legend of the FAO for those soils also called Vertisols.

### **4. Conclusions**

328 Principles, Application and Assessment in Soil Science

Also in the fourth level it is clearly demonstrated the great difference in the criteria used in distinguishing between Argilluvic Plinthosols and Haplic Plinthosols, and the Petric

The occurrence of appreciable amounts of plinthite in the soil profile is also identified in the class of the Plinthosols in the WRB/FAO international classification. The American system of classification adopts this character in lower categorical level (subgroup) and can be found correspondence of Plinthosols with different classes of the Soil Taxonomy, which present the plinthic character. These classes comprise the Oxisols, Ultisols, Alfisols, Entisols and

The soils of this class, due to the dominance of very high activity clays, are characterized by a great capacity of swelling and shrinkage of soil material with wetting and drying cycles, a factor that restricts their pedogenetic development. Having little occurrence in Brazilian territory, Vertisols represent only 1.00% of the profiles in the database, comprising a total of

As the identification of soils in this class includes criteria based on morphological characteristics evaluated in the field, the first categorical level was established by direct correlation with the original classification, whose name was maintained by the current system, just as the essence of the distinctive criteria, which allowed a satisfactory fit. For some profiles, however, there was some difficulty in taxonomic fitting, due to the presence, sometimes in the surface horizon, other times in subsurface horizon, of clay content below 300 g / kg, established as thresholds to distinguish the class of Vertisols (up to 20 cm depth, after mixing), but also for the vertic horizon (EMBRAPA, 2006). Once in the database are not included all the horizons of the profile, thereby preventing a more adequate evaluation, it was maintained their classification as Vertisols, assigning the value 2 for the degree of confidence in case of one of the horizons do not meet the specified requirement, and value 3 when both had amounts of clay below the minimum limit required. This situation, however, shows some discrepancy between the definitions of vertic horizon and of the class of Vertisols, as well as the need to adjust them. It may be appropriate to assess, from the characteristics of the profiles contained in the database, the adequacy of a minimum amount

In the second categorical level, it were recognized classes of Hydromorphic Vertisols, Ebanic Vertisols and Haplic Vertisols. Some difficulty in classification was observed mainly for fitting of some soils as Hydromorphics, due to the subsurface horizons refer to depths greater than 50 cm, being necessary information on colors of the overlying horizons to confirm the classification (in this case it was assigned the value 2 to express the degree of confidence). Other profiles, on the other hand, did not present information on moist color,

Also in the great group level it was observed some difficulty in taxonomic fitting of the profiles, mainly due to the lack of relevant data, such as the contents of equivalent CaCO3. This form, the fitting in the class of the Carbonatics was based on previous classification, corroborated by the subordinated designation of horizons of the profile (EMBRAPA, 1988b), being the other profiles classified as Orthics, since the previous name did not present

Plinthosols, which constitute a very distinct group within this class.

Inceptisols.

55 profiles.

of clay established for distinction of these soils.

indication of the occurrence of salic character.

being classified as Haplics, with value 3 for the confidence degree.

**3.13 Vertisols**

The database used in this work reveals an adequate representativeness of the soil classes distributed over the Brazilian territory.

This database can function as an advance to stimulate the exchanging of information and experience among researchers at international level.

### **5. References**

Updated Brazilian's Georeferenced Soil Database

32), Rio de Janeiro, Brasil.

Pesquisa, 16 ), Rio de Janeiro, Brasil.

(Boletim de Pesquisa, 15 ), Rio de Janeiro, Brasil.

de Janeiro, Brasil.

Brasil.

Brasil.

de Janeiro, Brasil.

Solos, 10), Recife, Brasil.

Recife, Brasil.

Janeiro,Brasil.

– An Improvement for International Scientific Information Exchanging 331

Embrapa (1983), *Levantamento de reconhecimento de média intensidade dos Solos e avaliação da*

Embrapa (1984). *Levantamento de reconhecimento dos solos e avaliação da aptidão agrícola das*

Embrapa (1983). *Levantamento de Reconhecimento de Solos do Mato Grosso.* Serviço Nacional de

Embrapa (1982). *Levantamento de reconhecimento dos solos do Município de Ariquemes, Estado de*

Embrapa (1982), *Levantamento de reconhecimento dos solos do Pólo Pré-Amazonia-Marenhense,*

Embrapa (1984). *Levantamento de Reconhecimento de Solos e Aptidão Agrícola das Terras da Área*

Solo. (EMBRAPA-SNLCS - Boletim de Pesquisa, 29), Rio de Janeiro, Brasil. Embrapa (1977). *Levantamento de reconhecimento dos solos do Estado do Espírito Santo.* Serviço

Embrapa (1978b). *Levantamento de reconhecimento dos solos do Estado do Espírito Santo.* Serviço

Embrapa (1984). *Levantamento de reconhecimento de solos do Estado do Paraná.* Serviço Nacional

Embrapa (1979b). *Levantamento de reconhecimento dos solos do centro-sul do Estado do Paraná*

Embrapa (1977-1979). *Levantamento exploratório-reconhecimento de solos da margem direita do rio*

Embrapa (1976c). *Levantamento exploratório-reconhecimento de solos da margem esquerda do rio*

Pesquisa, 27; IAPAR. Boletim Técnico, 16), Londrina, Brasil.

Solos. (Boletim Técnico, 11), Curitiba, Brasil.

Conservação do Solo. (Boletim de Pesquisa, 18), Rio de Janeiro, Brasil. Embrapa (1984). *Levantamento de reconhecimento dos solos e avaliação da aptidão agrícola das*

Nacional de Levantamento e Conservação do Solo. (Boletim de Pesquisa, 19 ), Rio

*aptidão agrícola das Terras do Pólo Roraima.* Serviço Nacional de Levantamento e

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*terras do Municipio de Urucará*, *Estado do Amazonas*. Serviço Nacional de Levantamento e Conservação de Solo. (Boletim de Pesquisa, 30), Rio de Janeiro,

Levantamento e Conservação de Solos. (Boletim de Pesquisa, 17), Rio de Janeiro,

*Rondônia.* Serviço Nacional de Levantamento e Conservação do Solo. (Boletim de

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*(área 9): informe preliminar.* Serviço Nacional de Levantamento e Conservação de

*São Francisco, Estado da Bahia.* Serviço Nacional de Levantamento e Conservação de Solos. 2v. (Embrapa-SNLCS. Boletim Técnico, 52; SUDENE. Série Recursos de

*São Francisco, Estado da Bahia.* Serviço Nacional de Levantamento e Conservação de Solos. (Embrapa-SNLCS. Boletim Técnico, 38; SUDENE. Série Recursos de Solos, 7),

Brasil (1971b). *Levantamento exploratório-reconhecimento de solos do Estado do Rio Grande do*

Brasil (1970c). *Levantamento exploratório dos solos da região sob influência da Companhia Vale do*

Brasil (1972f). *Levantamento exploratório-reconhecimento de solos do Estado da Paraíba. II.*

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Cooper, M.; Mendes, L.; Silva W. & Sparovek, G. (2005). *A national soil profile database for*

Coote, D. & Macdonald, K. (1999). *The Canadian soil database*. In: SUMNER, M.E., (Ed.).

Costa, A.; Araújo, E.; Marques, J. & Menezes, M. (2009). *Avaliação do risco de anoxia para o*

Embrapa (1988b). *Definição e notação de horizontes e camadas do solo.* Serviço Nacional de

Embrapa (1999). *Sistema Brasileiro de Classificação de Solos.* Centro Nacional de Pesquisa de

Embrapa (2006). *Sistema Brasileiro de Classificação de Solos.* Centro Nacional de Pesquisa de

Embrapa (1984). *Levantamento de reconhecimento de média intensidade dos solos e avaliação da*

Embrapa (1984), *Levantamento de reconhecimento dos solos e avaliação da aptidão agrícola das*

Embrapa (1983), *Levantamento de reconhecimento de media intensidade dos solos e avaliação da*

Handbook of soil science. Boca Raton: CRC Press, pp. H41-H51.

SUDENE. Série Pedologia, 9), Rio de Janeiro, Brasil.

Brasil.

60), Recife, Brasil.

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Solos. 2 ed, Rio de Janeiro, Brasil.

Scientia Forestalis, 37 pp. 367–375.

*Norte.* Ministério da Agricultura. Departamento Nacional de Pesquisa Agropecuária. Divisão de Pesquisa Pedológica. (DNPEA. Boletim Técnico, 21;

*Rio Doce.* Ministério da Agricultura. Escritório de Pesquisas e Experimentação. Equipe de Pedologia e Fertilidade do Solo. (Boletim Técnico, 13), Rio de Janeiro,

*Interpretação para uso agrícola dos solos do Estado da Paraíba*. Ministério da Agricultura. Escritório de Pesquisas e Experimentação. Equipe de Pedologia e Fertilidade do Solo. (Boletim Técnico, 15; SUDENE, Série Pedologia, 8), Rio de Janeiro, Brasil. Brasil (1979c). *Levantamento exploratório-reconhecimento de solos do norte de Minas Gerais.*

Ministério da Agricultura. EMBRAPA-SNLCS/SUDENE DRN (Boletim Técnico,

Ministério das Minas e Energia. Departamento Nacional de Produção Mineral. 1973a, b, c, 1974a, b, c, 1975a, b, c, d, 1976a, b, c, 1977a, b, c, d, 1978a, b, 1979, 1980, 1981a, b, c, d, e, 1982a, b, c, d, 1983a, b, c; (Levantamento de Recursos Naturais), Rio

*Brazil available to international scientists*. Soil Science Society of America Journal,

*cultivo de eucalipto no Rio Grande do Sul utilizando-se levantamento de solos*. Piracicaba:

Levantamento e Conservação de Solos. 2. ed. (Embrapa-SNLCS. Documentos, 3),

*aptidão agrícola das terras da área do Pólo Trombetas, Pará*. Serviço Nacional de Levantamento e Conservação de Solo. (EMBRAPA-SNLCS. Boletim de Pesquisa,

*terras de uma área de colonização no Município de Careiro, Estado do Amazonas.* Serviço Nacional de Levantamento e Conservação do Solo. (Boletim de Pesquisa, 31), Rio

*aptidão agrícola das terras de 21.000 hectares no município de Tefé, Amazonas*. Serviço

Nacional de Levantamento e Conservação do Solo. (Boletim de Pesquisa, 19 ), Rio de Janeiro, Brasil.

**17**

*Poland*

**Mineral Nitrogen as a Universal Soil Test to**

*Institute of Soil Science and Plant Cultivation – National Research Institute in Puławy*

Nearly whole (99,7%) territory of Poland, covering about 313 thousand square kilometers is situated in the Baltic Sea basin. This territory is drained by two big rivers Vistula and Odra and seven small rivers flowing directly to this sea. The load of about 145 Gg mineral nitrogen, originating mainly from the agricultural land is discharged yearly by polish rivers to Baltic Sea. Among all countries situated in this catchment Poland contributes in almost 26% to the pollution of Baltic Sea with biogenic substance, nitrogen. In the bulk, this is a serious contribution although calculated for one inhabitant (3,7 kg N per capita) and/or one area unit (4,6 kg N per ha) it belongs to the smallest among other Baltic countries. The big share of agriculture in this load results from the fact that agricultural land covers over 60% of the whole polish territory and constitutes almost 50% of this land in the entire Baltic catchment's. However, no wonder that Helsinki Commission and UE exert the pressure on

our country for limiting the outflow of nitrogen, including the one from agriculture.

Natural farming conditions in Poland are poor, due to prevalence of light, sand- derived soils (60% very light and light soils) and unfavorable climate. The agriculture landscape originates from the period of glaciations. Due to the high diversity of the parent rocks and different geological and pedological processes, a substantial number of soil types and subtypes have developed in Poland. According to the Polish classification system there are 35 different soil types and 78 sub-types. The most common are brown soils, grey brown podsolic soils, rusty soils and podsolis soils (Terelak et al. 2000). A much smaller part of land is covered by chernozem soils, rendzina soils, black soils and alluvial soils. Unfertile and acid soils account for 50 to 65 percent of arable land. Soil acidity is linked with the low content of available phosphorus and magnesium and hence constitutes of one of the most

Rainfall mostly occurs during the summer months, and the average annual precipitation varies from 500 mm to 900 mm for the regions of Poland, depending on height above sea level and distance from the Baltic Sea. Average temperature ranges from 7,0 to 9,5 degrees of Celsius. The length of growing season is on average 220 days and is comparable to that in Scandinavian countries. From May to September evapotranspiration in Poland exceeds rainfall, resulting in a continuous water deficit, especially on light soil. Nevertheless, in the

early spring the outflow of water from the soil profile is a common phenomena.

**1. Introduction**

limiting factors for soil productivity.

**Predict Plant N Requirements and Ground**

**Water Pollution – Case Study for Poland**

Agnieszka Rutkowska and Mariusz Fotyma

## **Mineral Nitrogen as a Universal Soil Test to Predict Plant N Requirements and Ground Water Pollution – Case Study for Poland**

Agnieszka Rutkowska and Mariusz Fotyma *Institute of Soil Science and Plant Cultivation – National Research Institute in Puławy Poland*

### **1. Introduction**

332 Principles, Application and Assessment in Soil Science

Embrapa (1982). *Levantamento e reconhecimento de baixa intesidade dos solos e avaliação da aptidão*

Embrapa (1982). *Levantamento de reconhecimento de baixa intensidade dos solos e avaliação da*

Embrapa (1986a). *Levantamento exploratório - reconhecimento de solos do Estado do Maranhão.*

Embrapa (1986b). *Levantamento exploratório - reconhecimento de solos do Estado do Piauí.* Serviço

FAO (1996). *The digitized soil map of the world including derived soil properties*. Rome, FAO, 1

FAO (1994). *Revised legend with corrections.* FAO, Rome: 137p. (World Soil Resources Report,

Ker, J. (1997). Latossolos do Brasil: uma revisão. *Geonomos*, Belo Horizonte, v. 5, nº 1, pp. 17-

Nemes, A.; Schaap, M.; Leij, F. & Wosten, J. (2001). *Description of the unsaturated soil hydraulic*

Nemes, A.; Wosten, J.; Lilly, A. & Oude Vos Harr, J. (1999). *Evolution of different procedures to*

Resende, M.; Curi, N.; Rezende, S. & Corrêa, G.(2007). *Pedologia: base para distinção de*

Soil Survey Staff – SSS (1991). *National soil information system (NASIS): soil interpretation and*

United States (1975). *Soil Taxonomy: a basic system of soil classification for making and*

United States (1999). *Soil taxonomy: a basic system of soil classification for making and interpreting*

Van Engelen, V.W.P. (1999). *Soter: the world soils and terrain database*. In: SUMNER, M.E., (Ed.). Handbook of soil science, Boca Raton, CRC Press, pp. H19-H28.

*database*. UNSODA version 2.0, Journal of Hydrology*.* Amsterdam, n. 251, pp. 151-

*interpolate particle – size distributions to achieve compatibility within soil databases*.

*information dissemination sub-system.* Draft requirements statement. Lincoln, USDA, Natural Resources Conservation Service, National Soil Survey Center. Washington,

*interpreting soil surveys.* Department of Agriculture. Soil Survey Division. Soil Conservation Service. Soil Survey Staff. Agriculture Handbook. Washington,

*soil surveys.* Department of Agriculture. 2nd ed. (Agriculture Handbook, 436),

FAO (1974). *Soil map of the World: 1:5.000.000 legend.* Paris: Unesco, v. 1, Roma, Itália.

Geoderma. Amsterdam, n. 90, pp. 187-202.

*ambientes.* 5. ed. Editora UFLA, Lavras, Brasil.

Pesquisa, 14), Rio de Janeiro, Brasil.

17), Rio de Janeiro, Brasil.

Janeiro, Brasil.

CD-ROM.

60).

40.

162.

USDA.

USDA.

Washington, USDA.

SNLCS. Boletim de Pesquisa, 9), Rio de Janeiro, Brasil.

*agrícola das terras do projeto de colonização Apiaú - Território Federal de Roraima*. Serviço Nacional de Levantamento e Conservação de Solo. (EMBRAPA-SNLCS. Boletim de

*aptidão agrícola das terras de área piloto do município de Barreirinha - Estado do Amazonas*. Serviço Nacional de Levantamento e Conservação de Solo. (EMBRAPA-

Serviço Nacional de Levantamento e Conservação de Solos. 2v. (EMBRAPA-SNLCS. Boletim de Pesquisa, 35. Brasil. SUDENE-DRN. Série Recursos de Solos,

Nacional de Levantamento e Conservação de Solos. 2v. (EMBRAPA-SNLCS. Boletim de Pesquisa, 36. Brasil. SUDENE-DRN Série Recursos de Solos, 18), Rio de

> Nearly whole (99,7%) territory of Poland, covering about 313 thousand square kilometers is situated in the Baltic Sea basin. This territory is drained by two big rivers Vistula and Odra and seven small rivers flowing directly to this sea. The load of about 145 Gg mineral nitrogen, originating mainly from the agricultural land is discharged yearly by polish rivers to Baltic Sea. Among all countries situated in this catchment Poland contributes in almost 26% to the pollution of Baltic Sea with biogenic substance, nitrogen. In the bulk, this is a serious contribution although calculated for one inhabitant (3,7 kg N per capita) and/or one area unit (4,6 kg N per ha) it belongs to the smallest among other Baltic countries. The big share of agriculture in this load results from the fact that agricultural land covers over 60% of the whole polish territory and constitutes almost 50% of this land in the entire Baltic catchment's. However, no wonder that Helsinki Commission and UE exert the pressure on our country for limiting the outflow of nitrogen, including the one from agriculture.

> Natural farming conditions in Poland are poor, due to prevalence of light, sand- derived soils (60% very light and light soils) and unfavorable climate. The agriculture landscape originates from the period of glaciations. Due to the high diversity of the parent rocks and different geological and pedological processes, a substantial number of soil types and subtypes have developed in Poland. According to the Polish classification system there are 35 different soil types and 78 sub-types. The most common are brown soils, grey brown podsolic soils, rusty soils and podsolis soils (Terelak et al. 2000). A much smaller part of land is covered by chernozem soils, rendzina soils, black soils and alluvial soils. Unfertile and acid soils account for 50 to 65 percent of arable land. Soil acidity is linked with the low content of available phosphorus and magnesium and hence constitutes of one of the most limiting factors for soil productivity.

> Rainfall mostly occurs during the summer months, and the average annual precipitation varies from 500 mm to 900 mm for the regions of Poland, depending on height above sea level and distance from the Baltic Sea. Average temperature ranges from 7,0 to 9,5 degrees of Celsius. The length of growing season is on average 220 days and is comparable to that in Scandinavian countries. From May to September evapotranspiration in Poland exceeds rainfall, resulting in a continuous water deficit, especially on light soil. Nevertheless, in the early spring the outflow of water from the soil profile is a common phenomena.

Mineral Nitrogen as a Universal Soil Test

and changes in the range 0,6 – 1,1 (Fotyma et al., 2007).

for the content of mineral nitrogen offer a good solution.

calculate this concentration based on nitrates content in the bulk of soil.

Cleemput et al., 2008).

monitoring program.

**3. Materials and methods**

to Predict Plant N Requirements and Ground Water Pollution – Case Study for Poland 335

 Winput = Woutput –ΔW – (Wn – Wn+m), (4) where Winput is the N requirement, Woutput – N requirement of the target yield, ΔW – volatilized N (N mineralized + subsoil mineral N + dry deposition N + wet deposition N, Wn - N available before planting, W n+m – N available after harvest (as cited in Van

In Western Europe, investigations on Nmin as a soil test for fertilizers recommendations have started at the beginning of 1970s (Nommik 1966, Scharpf and Wehrman 1975) and in Poland in the beginning of 1990s (Fotyma 1995, 1996). Of course, for fertilizer recommendations, Nmin test needs a calibration, e.g. critical value for crop nutrition has to be estimated. In pioneer German studies (Scharpf, 1977) by calibrating this test for fertilizer recommendations the simple principle "kilogram for kilogram" has been proposed. It means that each kilogram of mineral nitrogen in the soil profile reveals the fertilizer value equal to one kilogram of nitrogen applied in mineral fertilizers. In Polish approach (Fotyma, 1995) the effect of soil mineral nitrogen has been evaluated by using the Nmin fertilizer replacement value (Nmin RFV). RFV is a multiplying factor for the content of Nmin to a given depth in the soil profile in order to obtain the equivalent amount of nitrogen in mineral fertilizers. When RFV value is equal to 1 then the principle "kilogram for kilogram" comes practically into force. This value depends on crop as well as on soil and climatic conditions

Similarly as in the case of all methods above, evaluation of RFV values is laborious and numerous data from experiments including at least 5-6 nitrogen rates are needed for the process. Moreover, the values reveal a strong variability depending on soil and climatic conditions thus results can be generalized only roughly. The lack of universality of RVF poses a serious drawback in direct application of the Nmin soil test and since late 80ties, another approach gains in popularity. Allowing for the difficulty of evaluating RFV values for fertilizer recommendation, determination of these values has been substituted by establishing the classes of Nmin content in the soil profile, like classes of available phosphorus and potassium. For such calibration of Nmin test the results of soil monitoring

In the late of 90s, Nmin test starts to be used as a tool for predicting a risk of soil and water pollution by nitrates (Verhagen & Bouma 1997, Enckevort et al. 2002). Nitrates are easily leached down the soil profile to the ground water thus, for environment protection, the content and distribution of nitrates in the soil profile in autumn are of paramount importance. The EU Nitrate Directive (1991) precisely established its content in at 50 mg dm-3 NO3 or 11,3 mg NO3-N dm-3 of drinking water. This limit is a reference value for the soil ground water as well, though the ground water with an exception of shallow wells is not directly used for this purpose in general. However direct estimation of nitrate concentration in a ground water is a cumbersome and costly procedure. Therefore, it seems interesting to

This paper is focused on the parameterization of Nmin soil test both for fertilizer recommendation and environment protection, using numerous data from the soil

The monitoring program for the content of mineral nitrogen has been launched by the Polish Ministry of Agriculture and Rural Development in 1997. Soil samples have been

Overall, the natural conditions for crop production in Poland are by 30-40% worse in comparison for those in Western Europe. The efficiency of agricultural production is rather low (about 3,5 t·ha-1 cereal grain) but the consumption of nitrogen in mineral (about 65 kg N·ha-1) and organic (about 30 kg N·ha-1) fertilizers are comparable with most of the EU countries. As a consequence the balance of nitrogen is positive (about 50 kg N·ha-1) and the nutrient utilization efficiency is rather low (about 57%). To deal with the problems of nitrogen surplus in the country and bad management of nitrogen fertilizers, Ministry of Agriculture and Rural Development launched in late 90ties the program of soil monitoring for mineral nitrogen.

### **2. Mineral nitrogen test – the purposes and the needs**

Mineral nitrogen, widely understood as the sum of NO3 - and NH4 + ions, consists of a very small part in the total pool of soil nitrogen. Over 98% of all nitrogen present in soil is in organic forms, not available for plant roots until it is mineralized by microbes into inorganic forms. Mineral forms of nitrogen are very labile and prone to be lost through volatilization and leaching to the ground water. Thus, in the last years the content of mineral nitrogen (Nmin) is commonly recognized as a soil test of nitrogen accessibility for crops and as an indicator for potential pollution of ground water with nitrogen compounds.

Van der Paauw (1963), researching the effects of residual nitrogen was the forerunner for investigations on inorganic N in the soil profile. Later, research in various countries led to N fertilization recommendations based on the linear relationship between Nmin in the rooting zone of the crop at the beginning of vegetation and the optimum N fertilizer rate for the crop.

In the Netherlands, N fertilizer recommendations are the function of soil type, whereby "a" and "b" represent a coefficient of the linear relationship between recommendation and Nmin accordingly to the equation (1):

$$\mathbf{N}\_{\text{rec}} = \mathbf{a} \cdot \mathbf{b} \times \mathbf{N}\_{\text{min}} \tag{1}$$

(as cited in Van Cleemput et al. 2008). In Belgium, an N index method has been proposed. However, this index includes numerous factors, up to 18, as N mineralization, soil compaction, possible N leaching and is calculated as follows (2):

$$\text{N index} = \chi\_1 + \chi\_2 + \chi\_3 + \dots + \chi\_{16} + \chi\_{17} + \chi\_{18} \tag{2}$$

The optimum N fertilization recommendation is calculated accordingly to the equation (3):

$$\mathbf{N}\_{\text{rec}} = \mathbf{a} - \mathbf{b} \times \mathbf{N} \text{ index},\tag{3}$$

where a and b depend on the cultivar and the destination of the harvested products (Vandendriessche et al., 1992). In France and United States of America, the N balance sheet method was developed. The theoretically recommended N fertilizer doses are based on the balance between the crop requirement minus the amount of Nmin present before sowing plus the mineralization. The residual Nmin in the soil profile at harvest to the mean rooting depth consists of the amount of mineral N that remains in the rooting zone after optimum N fertilization. The practical N fertilization recommendation can further be adjusted according to expected losses. The potential losses are estimated at between 5 and 20%, depending mostly on soil texture (Carter et al., 1974). This method has been applied also in China, with the following approach (4):

Overall, the natural conditions for crop production in Poland are by 30-40% worse in comparison for those in Western Europe. The efficiency of agricultural production is rather low (about 3,5 t·ha-1 cereal grain) but the consumption of nitrogen in mineral (about 65 kg N·ha-1) and organic (about 30 kg N·ha-1) fertilizers are comparable with most of the EU countries. As a consequence the balance of nitrogen is positive (about 50 kg N·ha-1) and the nutrient utilization efficiency is rather low (about 57%). To deal with the problems of nitrogen surplus in the country and bad management of nitrogen fertilizers, Ministry of Agriculture and Rural Development launched in late 90ties the program of soil monitoring

Mineral nitrogen, widely understood as the sum of NO3- and NH4+ ions, consists of a very small part in the total pool of soil nitrogen. Over 98% of all nitrogen present in soil is in organic forms, not available for plant roots until it is mineralized by microbes into inorganic forms. Mineral forms of nitrogen are very labile and prone to be lost through volatilization and leaching to the ground water. Thus, in the last years the content of mineral nitrogen (Nmin) is commonly recognized as a soil test of nitrogen accessibility for crops and as an

Van der Paauw (1963), researching the effects of residual nitrogen was the forerunner for investigations on inorganic N in the soil profile. Later, research in various countries led to N fertilization recommendations based on the linear relationship between Nmin in the rooting zone of the crop at the beginning of vegetation and the optimum N fertilizer rate for the crop. In the Netherlands, N fertilizer recommendations are the function of soil type, whereby "a" and "b" represent a coefficient of the linear relationship between recommendation and Nmin

 Nrec = a - b x Nmin (1) (as cited in Van Cleemput et al. 2008). In Belgium, an N index method has been proposed. However, this index includes numerous factors, up to 18, as N mineralization, soil

The optimum N fertilization recommendation is calculated accordingly to the equation (3):

 Nrec = a – b x N index, (3) where a and b depend on the cultivar and the destination of the harvested products (Vandendriessche et al., 1992). In France and United States of America, the N balance sheet method was developed. The theoretically recommended N fertilizer doses are based on the balance between the crop requirement minus the amount of Nmin present before sowing plus the mineralization. The residual Nmin in the soil profile at harvest to the mean rooting depth consists of the amount of mineral N that remains in the rooting zone after optimum N fertilization. The practical N fertilization recommendation can further be adjusted according to expected losses. The potential losses are estimated at between 5 and 20%, depending mostly on soil texture (Carter et al., 1974). This method has been applied also in China, with

N index = X1 + X2 + X3 +...+ X16 + X17 + X18 (2)

**2. Mineral nitrogen test – the purposes and the needs**

compaction, possible N leaching and is calculated as follows (2):

indicator for potential pollution of ground water with nitrogen compounds.

for mineral nitrogen.

accordingly to the equation (1):

the following approach (4):

$$\mathbf{W}\_{\text{input}} = \mathbf{W}\_{\text{output}} - \Delta \mathbf{W} - (\mathbf{W}\_{\text{n}} - \mathbf{W}\_{\text{n}\text{+m}}) \tag{4}$$

where Winput is the N requirement, Woutput – N requirement of the target yield, ΔW – volatilized N (N mineralized + subsoil mineral N + dry deposition N + wet deposition N, Wn - N available before planting, W n+m – N available after harvest (as cited in Van Cleemput et al., 2008).

In Western Europe, investigations on Nmin as a soil test for fertilizers recommendations have started at the beginning of 1970s (Nommik 1966, Scharpf and Wehrman 1975) and in Poland in the beginning of 1990s (Fotyma 1995, 1996). Of course, for fertilizer recommendations, Nmin test needs a calibration, e.g. critical value for crop nutrition has to be estimated. In pioneer German studies (Scharpf, 1977) by calibrating this test for fertilizer recommendations the simple principle "kilogram for kilogram" has been proposed. It means that each kilogram of mineral nitrogen in the soil profile reveals the fertilizer value equal to one kilogram of nitrogen applied in mineral fertilizers. In Polish approach (Fotyma, 1995) the effect of soil mineral nitrogen has been evaluated by using the Nmin fertilizer replacement value (Nmin RFV). RFV is a multiplying factor for the content of Nmin to a given depth in the soil profile in order to obtain the equivalent amount of nitrogen in mineral fertilizers. When RFV value is equal to 1 then the principle "kilogram for kilogram" comes practically into force. This value depends on crop as well as on soil and climatic conditions and changes in the range 0,6 – 1,1 (Fotyma et al., 2007).

Similarly as in the case of all methods above, evaluation of RFV values is laborious and numerous data from experiments including at least 5-6 nitrogen rates are needed for the process. Moreover, the values reveal a strong variability depending on soil and climatic conditions thus results can be generalized only roughly. The lack of universality of RVF poses a serious drawback in direct application of the Nmin soil test and since late 80ties, another approach gains in popularity. Allowing for the difficulty of evaluating RFV values for fertilizer recommendation, determination of these values has been substituted by establishing the classes of Nmin content in the soil profile, like classes of available phosphorus and potassium. For such calibration of Nmin test the results of soil monitoring for the content of mineral nitrogen offer a good solution.

In the late of 90s, Nmin test starts to be used as a tool for predicting a risk of soil and water pollution by nitrates (Verhagen & Bouma 1997, Enckevort et al. 2002). Nitrates are easily leached down the soil profile to the ground water thus, for environment protection, the content and distribution of nitrates in the soil profile in autumn are of paramount importance. The EU Nitrate Directive (1991) precisely established its content in at 50 mg dm-3 NO3 or 11,3 mg NO3-N dm-3 of drinking water. This limit is a reference value for the soil ground water as well, though the ground water with an exception of shallow wells is not directly used for this purpose in general. However direct estimation of nitrate concentration in a ground water is a cumbersome and costly procedure. Therefore, it seems interesting to calculate this concentration based on nitrates content in the bulk of soil.

This paper is focused on the parameterization of Nmin soil test both for fertilizer recommendation and environment protection, using numerous data from the soil monitoring program.

### **3. Materials and methods**

The monitoring program for the content of mineral nitrogen has been launched by the Polish Ministry of Agriculture and Rural Development in 1997. Soil samples have been

Mineral Nitrogen as a Universal Soil Test

**4. Results**

N form

Nmin

NO3 - N

NH4 - N

Soil layer cm

very

textural group and sampling period in mg N· kg -1 soil

**4.2 Total amount of mineral nitrogen in soil**

amount are presented in table 2.

distinguished - very low, low, medium, high and very high.

**4.1 Content of mineral nitrogen forms in soil profile**

to Predict Plant N Requirements and Ground Water Pollution – Case Study for Poland 337

value was used as a characteristic of a mean and percentile as a measure of date distribution. The preliminary statistical analysis shows the significant dependence of Nmin content on the soil texture. For this reason, the normative of mineral nitrogen were calculated for each of four textural soil groups: very light (up to 10% of particles below 0,02 mm, light (11 - 20% of particles below 0,02 mm, medium (21-35% of particles below 0,02 mm and heavy (above 35% of particles below 0,02 mm). Similarly, to five classes of soil reaction and P, K, and Mg content officially used in Poland, five intervals of Nmin content were proposed. Each following interval contains 20% of ordered observations and thus five classes of Nmin were

The content of mineral forms of nitrogen has been presented in table 1. The quantity of nitrates and ammonia strongly depends on soil texture, the soil layer and a period of soil sampling. The content of nitrates in soil are higher in autumn than in spring and increases from the very light to heavy soils. The content of nitrate in the upper soil layer is higher in autumn than in spring while the reverse is true for the deepest soil horizon. Ammonia content does not practically differ between the sampling periods and soil textural groups and NH4 – N is much more evenly distributed in the soil profile irrespective of the season

> Spring Autumn Soil texture Soil texture

0 - 30 6,4 7,6 8,4 9,0 8,7 10 10,6 11 30 -60 3,8 5,5 6,1 7,1 4,7 5,4 6,1 6,6 60 -90 3,4 5,1 4,8 5,4 3,3 4,2 4,0 4,3

0 - 30 3,3 4,4 5,5 6,5 5,6 7,1 7,8 8,3 30 -60 2,0 3,5 4,0 5,2 2,9 3,7 4,1 4,9 60 -90 1,9 3,4 3,2 3,8 2,0 2,7 2,5 2,8

0 - 30 2,7 2,5 2,2 1,8 2,4 2,2 2,0 1,6 30 -60 1,4 1,4 1,5 1,3 1,4 1,2 1,4 1,1 60 -90 1,1 1,3 1,1 1,2 1,0 1,1 1,1 1,0

light light medium heavy

and soil texture. Generally, nitrates content is higher than the content of ammonia.

light light medium heavy very

Table 1. Median of mineral nitrogen forms in soil profile depending on soil layer, soil

For practical purposes, the content of mineral nitrogen, expressed in mg Nkg-1 soil has been recalculated into the nitrogen amount expressed in kg N ha-1 using standardized value of soil density for selected textural soil groups. Generalized values of soil density for each soil textural group as well as a conversion factor used for recalculation of N content into N

collected in fixed sites all over the country, twice a year – in spring and autumn to the depth of 90 cm in 0-30, 30-60 and 60-90 cm layers. Soil samples were frozen, and the content of Nmin was determined in each layer by the colorimetric method in 1% extract of K2SO4. The content of Nmin was expressed in mg NO3-N and NH4- N·kg-1 soil dry matter and recalculated into kilogram of Nmin in a given soil layer per ha, called further Nmin amount. Additionally, at the beginning of this project in all monitoring sites, soil texture has been determined. The technical part of the program, including soil sampling and analysis was entrusted to 17 agrochemical laboratories supervised by the Ministry. The results of analysis were collected in the central database at the Institute of Soil Science and Plant Cultivation – National Research Institute in Puławy, processed statistically and reported in due course.

Fig. 1. Localization of the monitoring sites in Poland

In this paper, the results for soil samples, collected from about 5100 sites, in the years 1997- 2006 are presented as the first stage of the monitoring program. The total number of samples (records) in the data base is about 95000. Each record includes data for three soil layers and two forms of mineral nitrogen NH4-N and NO3-N. The monitoring sites were established on arable land, randomly distributed all over Poland (Fig 1). The distribution of obtained data concerning concentration and content of Nmin was far from normality. Therefore, the median value was used as a characteristic of a mean and percentile as a measure of date distribution. The preliminary statistical analysis shows the significant dependence of Nmin content on the soil texture. For this reason, the normative of mineral nitrogen were calculated for each of four textural soil groups: very light (up to 10% of particles below 0,02 mm, light (11 - 20% of particles below 0,02 mm, medium (21-35% of particles below 0,02 mm and heavy (above 35% of particles below 0,02 mm). Similarly, to five classes of soil reaction and P, K, and Mg content officially used in Poland, five intervals of Nmin content were proposed. Each following interval contains 20% of ordered observations and thus five classes of Nmin were distinguished - very low, low, medium, high and very high.

### **4. Results**

336 Principles, Application and Assessment in Soil Science

collected in fixed sites all over the country, twice a year – in spring and autumn to the depth of 90 cm in 0-30, 30-60 and 60-90 cm layers. Soil samples were frozen, and the content of Nmin was determined in each layer by the colorimetric method in 1% extract of K2SO4. The content of Nmin was expressed in mg NO3-N and NH4- N·kg-1 soil dry matter and recalculated into kilogram of Nmin in a given soil layer per ha, called further Nmin amount. Additionally, at the beginning of this project in all monitoring sites, soil texture has been determined. The technical part of the program, including soil sampling and analysis was entrusted to 17 agrochemical laboratories supervised by the Ministry. The results of analysis were collected in the central database at the Institute of Soil Science and Plant Cultivation – National Research Institute in Puławy, processed statistically and reported in due course.

Fig. 1. Localization of the monitoring sites in Poland

In this paper, the results for soil samples, collected from about 5100 sites, in the years 1997- 2006 are presented as the first stage of the monitoring program. The total number of samples (records) in the data base is about 95000. Each record includes data for three soil layers and two forms of mineral nitrogen NH4-N and NO3-N. The monitoring sites were established on arable land, randomly distributed all over Poland (Fig 1). The distribution of obtained data concerning concentration and content of Nmin was far from normality. Therefore, the median

### **4.1 Content of mineral nitrogen forms in soil profile**

The content of mineral forms of nitrogen has been presented in table 1. The quantity of nitrates and ammonia strongly depends on soil texture, the soil layer and a period of soil sampling. The content of nitrates in soil are higher in autumn than in spring and increases from the very light to heavy soils. The content of nitrate in the upper soil layer is higher in autumn than in spring while the reverse is true for the deepest soil horizon. Ammonia content does not practically differ between the sampling periods and soil textural groups and NH4 – N is much more evenly distributed in the soil profile irrespective of the season and soil texture. Generally, nitrates content is higher than the content of ammonia.

Table 1. Median of mineral nitrogen forms in soil profile depending on soil layer, soil textural group and sampling period in mg N· kg -1 soil

### **4.2 Total amount of mineral nitrogen in soil**

For practical purposes, the content of mineral nitrogen, expressed in mg Nkg-1 soil has been recalculated into the nitrogen amount expressed in kg N ha-1 using standardized value of soil density for selected textural soil groups. Generalized values of soil density for each soil textural group as well as a conversion factor used for recalculation of N content into N amount are presented in table 2.

Mineral Nitrogen as a Universal Soil Test

Very

(25,3)

(12,4)

(20,2)

(30,8)

(49,2)

(139)

Very

(35,3)

(17,0)

(28,4)

(43,7)

(69,4)

(196)

58,5 (36,6)

37,8 (18,9)

51,3 (30,2)

67,0 (44,1)

93,7 (67,7)

196 (157)

profile 0-60 cm for soil textural groups and sampling date (kg N· ha-1)

81,4 (52,5)

51,3 (26,5)

70,7 (42,7)

93,6 (62,9)

131 (96,3)

283 (223)

profile 0-90 cm for soil textural groups and sampling date (kg N· ha-1)

Characteristics

Median 47,8

20% - percentile 30,3

40% - percentile 41,4

60% - percentile 55,2

80% - percentile 77,7

99% - percentile <sup>187</sup>

Characteristics

Median 65,3

20% - percentile 40,8

40% - percentile 56,6

60% - percentile 75,8

80% - percentile 107

99% - percentile 261

to Predict Plant N Requirements and Ground Water Pollution – Case Study for Poland 339

light Light Medium Heavy Very

64,8 (44,3)

41,6 (23,8)

56,6 (36,9)

73,9 (52,2)

103 (77,5)

202 (167)

Table 4. Statistical characteristics of Nmin and N-NO3 (in parenthesis) amounts in the soil

light Light Medium Heavy Very

90,9 (62,2)

57,7 (33,1)

79,4 (51,9)

104 (73,9)

145 (108)

292 (234)

Table 5. Statistical characteristics of Nmin and N-NO3 (in parenthesis) amounts in the soil

Numerous factors, apart from the soil texture, influenced the amount of mineral and nitrate nitrogen in soil and differences between the autumn and spring period of soil sampling. In spring, the quantity of nitrogen is affected mainly by crop grown in the previous year, while in autumn by crops grown in this particular year (Table 6). The preceding and actually grown crops have been classified by means of cluster analysis into three groups differing in

Number of samples 10924 19902 8844 8024 10913 19829 8867 8068

94,8 (69,4)

59,7 (36,7)

82,3 (57,7)

109 (82,0)

150 (119)

298 (236)

Spring Autumn Soil texture Soil texture

> 62,1 (41,4)

> 38,2 (20,2)

> 53,8 (34,0)

> 71,7 (50,1)

> 102 (76,1)

235 (208)

Spring Autumn Soil texture Soil texture

> 79,3 (52,4)

> 48,8 (26,2)

> 69,0 (43,2)

> 92,0 (63,0)

> 132 (95,6)

307 (253)

67,1 (19,5)

42,9 (26,3)

59,0 (41,7)

76,8 (58,9)

106 (84,3)

203 (171) light Light Medium Heavy

74,3 (54,8)

44,7 (28,0)

64,1 (45,3)

86,5 (65,3)

122 (98,2)

248 (221)

light Light Medium Heavy

95,4 (68,0)

57,7 (35,5)

82,4 (56,5)

110 (81,8)

159 (124)

324 (271)

73,3 (56,9)

44,1 (29,6)

63,2 (47,6)

85,6 (68,2)

122 (104)

247 (223)

96,3 (72,5)

57,3 (37,4)

82,7 (60,1)

111 (87,3)

157 (131)

324 (273)

71,1 (51,3)

43,7 (27,0)

61,4 (42,4)

81,9 (61,5)

116 (92,2)

247 (218)

89,7 (63,9)

55,1 (33,3)

77,5 (52,8)

104 (76,2)

148 (115)

32 (267)

\* kg N30cm = mg Nkg-1 soil x W

Table 2. Soil density depending on soil textural classes

The tables 3 – 5 shows general statistics for the central tendency and the scatter of the data, in the form of percentiles for amounts of Nmin and amounts of NO3 – N. Nitrate nitrogen is the form mostly preferred by plants and simultaneously very prone to leaching to the ground and open waters. Three soil layers, or rather profiles 0-30 cm, 0-60 cm and 0-90 cm have been distinguished. Fertilizer recommendations are usually based on the mineral nitrogen amount in these profiles with the preference for 0-60 cm and/or 0-90 cm profiles. The most interesting is the soil profile 0-90 cm which is explored by the roots of common crops. The difference in the amounts of nitrates in this profile between autumn and spring periods of soil sampling was further considered as nitrogen losses to the underground water. In the soil profile 0 - 90 cm (table 5) the median quantity of Nmin amounted to 65 – 95 kg N ha-1 in spring and 79-96 kg N ha-1 in autumn. The quantity of NO3 – N ranged from 35 – 69 kg N ha-1 in spring and 52 -72 kg N ha-1 in autumn. The amount of nitrates and total mineral nitrogen increased from the very light soils towards heavy ones. The difference between the Nmin and NO3 –N amounts in spring and autumn periods of soil sampling diminished in the same direction.

Table 3. Statistical characteristics of Nmin and N-NO3 (in parenthesis) amounts in the soil profile 0-30 cm for soil textural groups and sampling date (kg N· ha-1)

The tables 3 – 5 shows general statistics for the central tendency and the scatter of the data, in the form of percentiles for amounts of Nmin and amounts of NO3 – N. Nitrate nitrogen is the form mostly preferred by plants and simultaneously very prone to leaching to the ground and open waters. Three soil layers, or rather profiles 0-30 cm, 0-60 cm and 0-90 cm have been distinguished. Fertilizer recommendations are usually based on the mineral nitrogen amount in these profiles with the preference for 0-60 cm and/or 0-90 cm profiles. The most interesting is the soil profile 0-90 cm which is explored by the roots of common crops. The difference in the amounts of nitrates in this profile between autumn and spring periods of soil sampling was further considered as nitrogen losses to the underground water. In the soil profile 0 - 90 cm (table 5) the median quantity of Nmin amounted to 65 – 95 kg N ha-1 in spring and 79-96 kg N ha-1 in autumn. The quantity of NO3 – N ranged from 35 – 69 kg N ha-1 in spring and 52 -72 kg N ha-1 in autumn. The amount of nitrates and total mineral nitrogen increased from the very light soils towards heavy ones. The difference between the Nmin and NO3 –N amounts in spring and autumn periods of soil sampling

light Light Medium Heavy Very

34,8 (22,9)

22,5 (12,3)

30,6 (19,1)

40,3 (27,2)

55,6 (39,9)

112 (82,4)

Table 3. Statistical characteristics of Nmin and N-NO3 (in parenthesis) amounts in the soil

Number of samples 10784 19585 8718 8710 10821 19584 8792 8016

35,1 (25,3)

22,6 (14,0)

30,4 (21,4)

40,2 (29,6)

55,8 (42,5)

111 (83,5)

Spring Autumn Soil texture Soil texture

> 39,1 (26,2)

> 23,5 (12,4)

> 34,0 (21,1)

> 45,1 (31,7)

> 63,9 (48,7)

143 (119)

Very light 1533 4,6 Light 1500 4,5 Medium 1433 4,3 Heavy 1300 3,9

\* kg N30cm = mg Nkg-1 soil x W

diminished in the same direction.

Median 29,0

20% - percentile 18,8

40% - percentile 25,3

60% - percentile 33,1

80% - percentile 45,5

100% - percentile <sup>105</sup>

Very

(14,7)

(7,36)

(11,9)

(17,9)

(28,0)

(74,0)

33,3 (19,8)

22,0 (10,3)

29,7 (16,2)

37,8 (23,8)

52,2 (35,5)

108 (79,2)

profile 0-30 cm for soil textural groups and sampling date (kg N· ha-1)

Characteristics

Table 2. Soil density depending on soil textural classes

Soil texture Soil density [kgm-3] Conversion factor for 30 cm

soil layer\* (rounded)

light Light Medium Heavy

45,0 (33,5)

26,8 (17,0)

38,6 (27,6)

52,7 (40,8)

74,8 (59,9)

146 (126)

43,7 (33,5)

25,7 (17,2)

37,0 (27,1)

50,3 (40,6)

72,9 (62,0)

145 (128)

44,5 (32,4)

27,4 (16,3)

38,7 (26,5)

51,7 (38,7)

72,4 (58,0)

145 (126)

Table 4. Statistical characteristics of Nmin and N-NO3 (in parenthesis) amounts in the soil profile 0-60 cm for soil textural groups and sampling date (kg N· ha-1)

Table 5. Statistical characteristics of Nmin and N-NO3 (in parenthesis) amounts in the soil profile 0-90 cm for soil textural groups and sampling date (kg N· ha-1)

Numerous factors, apart from the soil texture, influenced the amount of mineral and nitrate nitrogen in soil and differences between the autumn and spring period of soil sampling. In spring, the quantity of nitrogen is affected mainly by crop grown in the previous year, while in autumn by crops grown in this particular year (Table 6). The preceding and actually grown crops have been classified by means of cluster analysis into three groups differing in

Mineral Nitrogen as a Universal Soil Test

in Poland.

Soil texture Form of

soil profile 0-90 cm

NH4 – N form, but NH4

nitrogen

Very low 0-20%

Low 20-40%

Very light NO3-N to 17 18-28 8-11 29-44 over 70

Light NO3-N to 26 27-43 44-63 64-96 Over 96

Medium NO3-N to 33 36-52 53-74 75-108 over 109

Heavy NO3-N to 37 38-58 59-82 83-119 over 120

Table 7. Classes of the mineral nitrogen Nmin and nitrate nitrogen NO3-N in spring in the

Soil test for NO3 – N seems to be more suitable for fertilizer recommendations than Nmin test. This is because nitrates are directly available for plants. Total amount of Nmin includes also

besides undergoes the sorption on the soil colloids. The calibration figures are given for the soil profile 0-90 cm. For technical reasons soil sampling is sometimes limited to the depth of 0-60 cm. However data obtained from the monitoring program showed the close correlation

Classes of Nmin quantity in spring corresponds in reverse order to the classes of crop nitrogen requirements In the class of very low mineral nitrogen content, crop requirements are the highest and vice versa. In fertilizer recommendations if the content of Nmin or NO3–

between the amounts of mineral nitrogen in the two soil layers 0-60 and 0-90 cm.

to Predict Plant N Requirements and Ground Water Pollution – Case Study for Poland 341

Nfer = Ncrop – Nmin \*RFV, where: Nfer - optimal rate of fertilizer nitrogen, Ncrop – crop nitrogen requirement, RVF- Nmin replacement value. As has been already pointed out Wehrman et al. (1986) assumed that RVF value is equal to 1, while in Polish investigations this value depends on crop as well as on soil and climatic conditions and changes in the range 0,6 – 1,1 (Fotyma et al., 2007). The lack of universality of RVF poses a serious drawback in quantitative application of the Nmin soils test and since late 80ties qualitative approach gains popularity. This particular approach to soil test of mineral nitrogen has been implemented in Germany (Muller & Gorlitz 1986, 2000) and lately in Poland (Fotyma, 2010, Rutkowska & Fotyma, 2009). The first step in qualitative approach is to calibrate the soil test. Calibration is commonly understood as establishing the test critical value or several classes corresponding to the expected efficiency of a given nutrient. The classical method is to calibrate the soil test against plant indices in the series of field experiments carried on the soil differing in the test values. This is a very cumbersome and expensive procedure practically not applied any further. In Poland Nmin soil test has been calibrated using the data from monitoring program providing representative data for different natural and agronomic conditions in the country. The five test classes for mineral and nitrate nitrogen correspond to the percentiles of these forms in soils of different texture (Table 7). Each following interval contains 20% of ordered observations and thus five classes of Nmin and NO3-N were distinguished - very low, low, medium, high and very high nitrogen content. Five calibration classes have been chosen in order to comply with the numbers of availability classes for other nutrients, officially used

Class of content (percentile interval) kg Nmin· ha-1

Medium 40-60%

Nmin to 41 42-57 58-76 77-107 over 108

Nmin to 58 59-79 80-104 105-145 over 132

Nmin to 58 59-79 80-104 105-145 over 146

Nmin to 60 61-82 83-109 110-150 over 151

+ cation is preferred only by some specific group of plants, and

High 60-80% Very high 80-100%

the amount of Nmin and NO3 – N left in the soil. Cluster of crops reflects not only the type of particular crop but the agro technical measures for this crop as well, influencing the amount of mineral nitrogen in the soil. Sugar beet, potato and sometimes rape and maize are grown on farmyard manure. Leguminous crops assimilate nitrogen from the atmosphere and for intensive cereals and rape, high doses of mineral nitrogen are being commonly applied. Another factor influencing the amount of mineral and nitrate nitrogen in the spring period and the difference of these amounts between spring and autumn period is the winter precipitation. This factor will be discussed in the following part of the paper.

Table 6. Amounts of mineral and nitrate nitrogen in spring for clusters of preceding crops and in the autumn for crops grown in the particular year [kg N· ha-1]

The largest amount of mineral nitrogen in soil has been revealed after intensive cereals (winter wheat and triticale), winter rape, row crops fertilized with manure (sugar beet, potato, vegetables and leguminous crops in a pure stand and with a mixture with grasses. The smallest quantity has been found after extensive cereals (rye, oats, cereal mixtures, nonleguminous fodder crops, grasses and on set aside land. Almost the same regularities appeared in the samples collected in autumn. The greatest differences in Nmin and NO3 – N quantities between autumn and spring period of soil sampling appeared in the cluster I. The quantities of nitrogen after crops of cluster III between autumn and spring periods of soil sampling in soil layers 0-60 and 0-90 cm were practically the same.

### **4.3 Application of Nmin test for fertilizer recommendations**

A very serious and still unsolved problem is how to include the results of Nmin or NO3 – N test into nitrogen fertilizer recommendations. Generally, two approaches can be considered: quantitative and qualitative. The most straightforward quantitative approach is to express the content of Nmin in kg· ha-1 and to relate its amount to the amount of nitrogen from fertilizers. Based on this approach the simple model has been developed in Europe:

the amount of Nmin and NO3 – N left in the soil. Cluster of crops reflects not only the type of particular crop but the agro technical measures for this crop as well, influencing the amount of mineral nitrogen in the soil. Sugar beet, potato and sometimes rape and maize are grown on farmyard manure. Leguminous crops assimilate nitrogen from the atmosphere and for intensive cereals and rape, high doses of mineral nitrogen are being commonly applied. Another factor influencing the amount of mineral and nitrate nitrogen in the spring period and the difference of these amounts between spring and autumn period is the winter

Table 6. Amounts of mineral and nitrate nitrogen in spring for clusters of preceding crops

The largest amount of mineral nitrogen in soil has been revealed after intensive cereals (winter wheat and triticale), winter rape, row crops fertilized with manure (sugar beet, potato, vegetables and leguminous crops in a pure stand and with a mixture with grasses. The smallest quantity has been found after extensive cereals (rye, oats, cereal mixtures, nonleguminous fodder crops, grasses and on set aside land. Almost the same regularities appeared in the samples collected in autumn. The greatest differences in Nmin and NO3 – N quantities between autumn and spring period of soil sampling appeared in the cluster I. The quantities of nitrogen after crops of cluster III between autumn and spring periods of

A very serious and still unsolved problem is how to include the results of Nmin or NO3 – N test into nitrogen fertilizer recommendations. Generally, two approaches can be considered: quantitative and qualitative. The most straightforward quantitative approach is to express the content of Nmin in kg· ha-1 and to relate its amount to the amount of nitrogen from fertilizers. Based on this approach the simple model has been developed in Europe:

and in the autumn for crops grown in the particular year [kg N· ha-1]

soil sampling in soil layers 0-60 and 0-90 cm were practically the same.

**4.3 Application of Nmin test for fertilizer recommendations**

Soil layer 0-30 cm 0-60 cm 0-90 cm Nmin NO3-N Nmin NO3-N Nmin NO3-N

Spring 35,7 22,7 63,8 42,2 87,1 59,5 Autumn

46,3 34,7 76,7 57,4 99,4 72,7

Spring 31,3 17,7 50,0 28,0 65,7 37,3 Autumn 36,2 22,4 56,2 35,6 70,6 43,6

Spring 23,5 9,75 39,5 16,0 51,5 22,0 Autumn 25,0 14,0 39,0 15,5 51,0 24,0

precipitation. This factor will be discussed in the following part of the paper.

Cluster

Intensive cereals, rape, sugar beet, maize, potatoes, leguminous crops and mixture with grasses, vegetables, grassland

Extensive cereals, nonleguminous fodder crops,

Set aside, bushes, forests

field grasses

I

II

III

Nfer = Ncrop – Nmin \*RFV, where: Nfer - optimal rate of fertilizer nitrogen, Ncrop – crop nitrogen requirement, RVF- Nmin replacement value. As has been already pointed out Wehrman et al. (1986) assumed that RVF value is equal to 1, while in Polish investigations this value depends on crop as well as on soil and climatic conditions and changes in the range 0,6 – 1,1 (Fotyma et al., 2007). The lack of universality of RVF poses a serious drawback in quantitative application of the Nmin soils test and since late 80ties qualitative approach gains popularity. This particular approach to soil test of mineral nitrogen has been implemented in Germany (Muller & Gorlitz 1986, 2000) and lately in Poland (Fotyma, 2010, Rutkowska & Fotyma, 2009). The first step in qualitative approach is to calibrate the soil test. Calibration is commonly understood as establishing the test critical value or several classes corresponding to the expected efficiency of a given nutrient. The classical method is to calibrate the soil test against plant indices in the series of field experiments carried on the soil differing in the test values. This is a very cumbersome and expensive procedure practically not applied any further. In Poland Nmin soil test has been calibrated using the data from monitoring program providing representative data for different natural and agronomic conditions in the country.

The five test classes for mineral and nitrate nitrogen correspond to the percentiles of these forms in soils of different texture (Table 7). Each following interval contains 20% of ordered observations and thus five classes of Nmin and NO3-N were distinguished - very low, low, medium, high and very high nitrogen content. Five calibration classes have been chosen in order to comply with the numbers of availability classes for other nutrients, officially used in Poland.

Table 7. Classes of the mineral nitrogen Nmin and nitrate nitrogen NO3-N in spring in the soil profile 0-90 cm

Soil test for NO3 – N seems to be more suitable for fertilizer recommendations than Nmin test. This is because nitrates are directly available for plants. Total amount of Nmin includes also NH4 – N form, but NH4 + cation is preferred only by some specific group of plants, and besides undergoes the sorption on the soil colloids. The calibration figures are given for the soil profile 0-90 cm. For technical reasons soil sampling is sometimes limited to the depth of 0-60 cm. However data obtained from the monitoring program showed the close correlation between the amounts of mineral nitrogen in the two soil layers 0-60 and 0-90 cm.

Classes of Nmin quantity in spring corresponds in reverse order to the classes of crop nitrogen requirements In the class of very low mineral nitrogen content, crop requirements are the highest and vice versa. In fertilizer recommendations if the content of Nmin or NO3–

Mineral Nitrogen as a Universal Soil Test

Class of NO3 – N in autumn

Very low

Low

Medium

High

soil

Very high

Average for the

classes in autumn

50 mg· dm3 NO3

to Predict Plant N Requirements and Ground Water Pollution – Case Study for Poland 343

in the very light/light soils and medium one in the medium/heavy soils the losses of

Soil texture Very light Light Medium Heavy

autumn 16 22 24 24 spring 21 33 40 44 difference +5 +11 +16 +20

autumn 34 43 45 49 spring 31 46 54 60 difference -3 +3 +11 +11

autumn 52 64 68 73 spring 36 53 65 71 difference -16 -11 -3 +2

autumn 76 92 99 107 spring 43 62 72 81 difference -33 -30 -27 -26

autumn 132 156 166 172 spring 51 72 84 92 difference -81 -72 -82 -79

autumn 52 64 68 74 spring 34 51 61 69 difference -18 -13 -7 -5

or 11,3 mg· dm3 NO3 – N. However direct estimation of this concentration is

Concentration ( mg N-NO3 dm-3 ) = content (mg N-NO3 kg-1) \*R, (5)

and R=1/(W/D), (6)

Table 9. Reserves of nitrates in autumn and following spring depending on the nitrate

As has been already mentioned, for environment protection the key point is concentration of nitrate in the drinking water, which in fact originates from ground water and not the content of nitrate in the bulk of soil. The EU Nitrates Directive has stated the limit in drinking water to

laborious and difficult. The most prone to leaching processes are nitrate in the deeper soil layers being in contacts with ground water, particularly in the periods of water saturation to full soils water capacity. Soil saturation to full water capacity in the depth 0-30 cm and 30-60 cm occurs only in the early spring but the subsoil nearly through the whole vegetation period. In the paper the indirect method for estimation the safe limit of nitrate content in the bulk of soil by comparison with calculated nitrate concentration in the soil water at the depth 0 -30, 30

nitrates from the soil profile 0-90 cm in winter period are negligible.

kg NO3–N ha-1 in 0-90 cm

**4.5 Simulated nitrates concentrations in ground water**

– 60 and 60-90 cm was proposed, using the following formulas (5) and (6):

where: W – soil water content in dm3 dm-3 (v/v), D- soil bulk density in kg· dm-3

The soil water content W at this point depends on soil texture. Standard W values for soil saturation to full water capacity and D values for soil categories in Poland are given in table

N in the spring falls in "medium " class farmer is enhanced to stick to the standard N rate and its common splitting pattern. If the Nmin content proved to be "very low" or "low" then the standard 1st rate of nitrogen fertilizer should be increased and applied as early as possible. The reverse is recommended when mineral nitrogen content is "high" or "very high". Usually for deep rooting and/or winter crops the content of Nmin in the soil profile 0 – 90 cm and for shallow rooting and/or spring sown crops the content of Nmin in the soil profile 0-60 cm is taken into consideration. Thus, this qualitative approach to mineral nitrogen soil test makes it at present rather as an auxiliary tool for nitrogen recommendations system. The calculation of standard nitrogen dose is still in foreground. This problem lies however outside the scope of this paper and is discussed elsewhere (Jadczyszyn, 2000, 2009).

### **4.4 Application of Nmin soil test for environment protection**