Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil and Environmental Quality

*Upendra M. Sainju, Rajan Ghimire and Gautam P. Pradhan*

#### **Abstract**

Improved management practices can be used to sustain crop yields, improve soil quality, and reduce N contaminations in groundwater and the atmosphere due to N fertilization. These practices include crop rotation, cover cropping, application of manures and compost, liming, and integrated crop-livestock system. The objectives of these practices are to reduce the rate of N fertilization, enhance N-use efficiency, increase crop N uptake, promote N cycling and soil N storage, and decrease soil residual N. This chapter discusses improved management practices to reduce N fertilization rate, sustain crop yields, and improve soil and environmental quality. The adaptation of these practices by farmers, producers, and ranchers, however, depends on social, economic, soil, and environmental conditions.

**Keywords:** crop yields, environmental quality, management practices, nitrogen fertilizer, nitrogen-use efficiency, soil quality

#### **1. Introduction**

Legume-integrated crop rotations provide opportunity to reduce N fertilizer rates due to increased N supply by legume residues to succeeding crops compared with nonlegume monocropping [1, 2]. As little or no N fertilizer is applied to legumes during their growth, inclusion of legumes in rotation with nonlegumes helps to reduce the overall N rate for a crop rotation, which increase farm income by reducing C footprints and lowering the cost of N fertilization [1, 3]. Legumes also fix atmospheric N and release it for as long as 3 years, increasing yields of succeeding crops compared with nonlegume crops in crop rotations [4]. Crop rotations also reduce disease, pest, and weed infestations [5], improve soil structure and organic matter storage [6], increase water-use efficiency [7], and enhance soil health through microbial proliferation [8]. Crop rotation can also increase N uptake efficiency of diverse crops and reduce soil residual N compared with monocropping [2].

Cover cropping has many beneficial effects on sustaining crop yields and improving soil and environmental quality. Cover crops planted after the harvest of cash crops use soil residual N, reducing N leaching. The additional residues supplied by cover crops increase soil organic matter and fertility [9, 10]. Legume cover crops reduce N fertilization rates and enhance crop yields, but nonlegume cover crops are more effective on enhancing C sequestration [11, 12]. Similarly, integrate croplivestock system, while reducing feed cost and supplying meat, milk, and wood, enhances N cycling and soil fertility, and control weeds [13, 14].

Continuous application of NH4-based N fertilizers to nonlegume crops can reduce soil pH compared with legume-nonlegume crop rotations where N fertilizer is not applied to legumes [15]. After 16–28 years of management implications, soil pH was reduced by 0.22–0.42 from the original level in continuous nonlegumes compared with crop rotations containing legumes and nonlegumes [15]. Soil acidification from N fertilization to crops primarily results from (1) increased removal of basic cations, such as calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) in crop grains and stover due to increased yield; (2) leaching of soil residual NO3-N, Ca, and Mg; and (3) microbial oxidation (or nitrification) of NH4-based N fertilizers that release H+ ions [16]. Alkalinity produced during plant uptake of N or conversion of inorganic N to organic form, however, can partly or wholly counter the acidity from nitrification [17]. Increased toxicity of aluminum (Al), iron (Fe), and manganese (Mn) and reduced availability of most nutrients, such as P, Ca, Mg, K, and Na, during acidification can reduce crop growth and yield [18].

Here we discuss various management strategies to reduce N fertilization rates, increase N-use efficiency, and decrease N leaching and N2O emissions due to N fertilization. These practices will reduce the cost of N fertilization while sustaining crop production and reducing soil and environmental degradation.

Crop rotation can enhance or maintain soil organic C and N levels compared to monocropping. Both soil C and N stocks can be influenced by the quality and quantity of residue returned to the soil from crops involved in the rotation [12, 22]. Crop rotation

*Effect of crop rotation on average annualized crop biomass (stems and leaves) and grain yields of durum,*

*canola, flax, and pea from 2006 to 2011 in eastern Montana, USA (Sainju et al., 2017d).*

compared with monocropping [23]. Sainju [24] found that soil organic C at 0–5 and 5– 10 cm was similar in no-till malt barley-pea rotation (NTB-P) and no-till continuous malt barley (NTCB), both of which had greater soil organic C than no-till malt barleyfallow (NTB-F) and conventional till malt barley-fallow (CTB-F) due to greater amount of crop residue returned to the soil and reduced mineralization of soil organic matter (**Figure 1**). Similarly, Sainju et al. (2017d) found that soil total C at 0–125 cm was similar to continuous durum and rotations that included durum, canola, pea, and flax, except D-D-F-P (**Table 2**). Soil total N at 0–120 cm was greater with spring wheat-pea

In an experiment evaluating the effects of crop rotation and cultural practice (traditional and ecological) on N balance in dryland agroecosystems, Sainju et al. [26, 27] observed that N fertilization rates were lower with legume-based crop rotations (D-C-D-P, D-D-C-P, D-F-D-P, and D-D-F-P) than nonlegume monocropping

recommended seed rate, broadcast N fertilization, and reduced stubble height and ecological practices inlcuded no-till, increased seed rate, banded N fertilization, and increased stubble height. They found that both total N input and output were greater with legume-based rotations than nonlegume monocropping due to pea N fixation and increased grain N removal. As a result, N balance was positive, indicating N surplus in legume-based rotations, and negative, indicating N deficit in nonlegume monocropping. This suggests that external N input is lower to sustain crop yields in

Legume-nonlegume rotation can also resist soil acidification compared with continuous nonlegumes. Sainju et al. [18] reported that soil pH at 0–7.5 cm after 30 years of experiment initiation was 0.13–0.44 greater and at 7.5–15.0 cm was 0.11–0.29 greater with spring wheat-barley/pea rotation (FSTW-B/P) than continuous spring wheat (NTCW, STCW, and FSTCW) (**Table 5**). They explained this as a result of lack of N fertilization to pea and reduced N fertilization rate to spring wheat following pea whose residue supplied N to spring wheat because of higher M concentration than spring wheat and barley residues. Soil residual NO3-N, which can pollute groundwater through leaching, was lower with legume-based crop rotations containing durum, canola, pea, and flax than continuous durum

(**Table 6**), suggesting that legume-based crop rotations can reduce N fertilization rate and the potential for N leaching compared with nonlegume monocropping.

(CD) (**Table 4**). Traditional cultural practices included conventional till,

legume-based crop rotations than nonlegume monocropping.

, reaching equilibrium in 40–60 years

**) Annualized grain yield (Mg ha1**

**)**

can sequester C at 200 120 kg C ha1 year1

*means test.*

**Table 1.**

**37**

**Crop rotation† Annualized biomass yield (Mg ha1**

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

CD 3.32b‡ 1.77a D-C-D-P 4.02a 1.76a D-D-C-P 3.90a 1.70a D-F-D-P 3.39b 1.63ab D-D-F-P 3.56b 1.54b *†Crop rotations are CD, continuous durum; D-C-D-P, durum-canola-durum-pea; D-D-C-P, durum-durum-canola-pea; D-F-D-P, durum-flax-durum-pea; and D-D-F-P, durum-durum-flax-pea. ‡Numbers followed by different letters within a column are significantly different at P* ≤ *0.05 by the least square*

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil…*

rotation than continuous spring wheat (**Table 3**) [25].

#### **2. Management practices**

Management practices that reduce N fertilization rates without affecting crop yields and quality are needed to reduce soil and environmental degradation, as soil degradation is directly related to increased N rates. Some of these practices include crop rotation, cover cropping, application of manure and compost, and integrated crop-livestock system. These practices can increase N inputs, reduce N fertilization rates, conserve soil organic matter, and enhance soil health and environmental quality without affecting crop yields compared with traditional management practices. We discuss these practices as follows.

#### **2.1 Crop rotation**

Crop rotations that include legumes and nonlegumes in the rotation can substantially reduce N fertilization rates compared with nonlegume monocropping because legumes supply N to the soil due to their greater N concentration from atmospheric N fixation than nonlegumes. As no N fertilizer is applied to legumes, overall N fertilization rate is lower for the legume-nonlegume rotation than continuous nonlegumes while still maintaining crop yields. Sainju et al. [19] observed that annualized crop biomass and grain yields under rainfed condition were similar or greater with legume-based rotations that included pea, durum (*Triticum turgidum* L.), canola (*Brassica napus* L.), and flax (*Linum usitatissimum* L.) than with continuous durum (**Table 1**). Crop rotation is an effective management practice to control weeds, diseases, and pests [7]; reduce the risk of crop failure, farm inputs, and duration of fallow; and improve the economic and environmental sustainability of dryland cropping systems [20]. Diversified crop rotations can efficiently use water and N compared with monocropping [7, 21]. For instance, wheat and barley can efficiently utilize soil water in wheat-pea and barley-pea rotations than continuous wheat and barley. This is because pea uses less water than wheat and barley, resulting in more water available for succeeding crops in the rotation [7, 21].

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

*†Crop rotations are CD, continuous durum; D-C-D-P, durum-canola-durum-pea; D-D-C-P, durum-durum-canola-pea; D-F-D-P, durum-flax-durum-pea; and D-D-F-P, durum-durum-flax-pea. ‡Numbers followed by different letters within a column are significantly different at P* ≤ *0.05 by the least square means test.*

#### **Table 1.**

more effective on enhancing C sequestration [11, 12]. Similarly, integrate croplivestock system, while reducing feed cost and supplying meat, milk, and wood,

Continuous application of NH4-based N fertilizers to nonlegume crops can reduce soil pH compared with legume-nonlegume crop rotations where N fertilizer is not applied to legumes [15]. After 16–28 years of management implications, soil pH was reduced by 0.22–0.42 from the original level in continuous nonlegumes compared with crop rotations containing legumes and nonlegumes [15]. Soil acidification from N fertilization to crops primarily results from (1) increased removal of basic cations, such as calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) in crop grains and stover due to increased yield; (2) leaching of soil residual NO3-N, Ca, and Mg; and (3) microbial oxidation (or nitrification) of NH4-based N fertilizers that release H+ ions [16]. Alkalinity produced during plant uptake of N or conversion of inorganic N to organic form, however, can partly or wholly counter the acidity from nitrification [17]. Increased toxicity of aluminum (Al), iron (Fe), and manganese (Mn) and reduced availability of most nutrients, such as P, Ca, Mg,

enhances N cycling and soil fertility, and control weeds [13, 14].

K, and Na, during acidification can reduce crop growth and yield [18].

crop production and reducing soil and environmental degradation.

**2. Management practices**

*Nitrogen Fixation*

**2.1 Crop rotation**

**36**

tices. We discuss these practices as follows.

Here we discuss various management strategies to reduce N fertilization rates, increase N-use efficiency, and decrease N leaching and N2O emissions due to N fertilization. These practices will reduce the cost of N fertilization while sustaining

Management practices that reduce N fertilization rates without affecting crop yields and quality are needed to reduce soil and environmental degradation, as soil degradation is directly related to increased N rates. Some of these practices include crop rotation, cover cropping, application of manure and compost, and integrated crop-livestock system. These practices can increase N inputs, reduce N fertilization rates, conserve soil organic matter, and enhance soil health and environmental quality without affecting crop yields compared with traditional management prac-

Crop rotations that include legumes and nonlegumes in the rotation can substantially reduce N fertilization rates compared with nonlegume monocropping because legumes supply N to the soil due to their greater N concentration from atmospheric N fixation than nonlegumes. As no N fertilizer is applied to legumes, overall N fertilization rate is lower for the legume-nonlegume rotation than continuous nonlegumes while still maintaining crop yields. Sainju et al. [19] observed that annualized crop biomass and grain yields under rainfed condition were similar or greater with legume-based rotations that included pea, durum (*Triticum turgidum* L.), canola (*Brassica napus* L.), and flax (*Linum usitatissimum* L.) than with continuous durum (**Table 1**). Crop rotation is an effective management practice to control weeds, diseases, and pests [7]; reduce the risk of crop failure, farm inputs, and duration of fallow; and improve the economic and environmental sustainability of dryland cropping systems [20]. Diversified crop rotations can efficiently use water and N compared with monocropping [7, 21]. For instance, wheat and barley can efficiently utilize soil water in wheat-pea and barley-pea rotations than continuous wheat and barley. This is because pea uses less water than wheat and barley, resulting in more water available for succeeding crops in the rotation [7, 21].

*Effect of crop rotation on average annualized crop biomass (stems and leaves) and grain yields of durum, canola, flax, and pea from 2006 to 2011 in eastern Montana, USA (Sainju et al., 2017d).*

Crop rotation can enhance or maintain soil organic C and N levels compared to monocropping. Both soil C and N stocks can be influenced by the quality and quantity of residue returned to the soil from crops involved in the rotation [12, 22]. Crop rotation can sequester C at 200 120 kg C ha1 year1 , reaching equilibrium in 40–60 years compared with monocropping [23]. Sainju [24] found that soil organic C at 0–5 and 5– 10 cm was similar in no-till malt barley-pea rotation (NTB-P) and no-till continuous malt barley (NTCB), both of which had greater soil organic C than no-till malt barleyfallow (NTB-F) and conventional till malt barley-fallow (CTB-F) due to greater amount of crop residue returned to the soil and reduced mineralization of soil organic matter (**Figure 1**). Similarly, Sainju et al. (2017d) found that soil total C at 0–125 cm was similar to continuous durum and rotations that included durum, canola, pea, and flax, except D-D-F-P (**Table 2**). Soil total N at 0–120 cm was greater with spring wheat-pea rotation than continuous spring wheat (**Table 3**) [25].

In an experiment evaluating the effects of crop rotation and cultural practice (traditional and ecological) on N balance in dryland agroecosystems, Sainju et al. [26, 27] observed that N fertilization rates were lower with legume-based crop rotations (D-C-D-P, D-D-C-P, D-F-D-P, and D-D-F-P) than nonlegume monocropping (CD) (**Table 4**). Traditional cultural practices included conventional till, recommended seed rate, broadcast N fertilization, and reduced stubble height and ecological practices inlcuded no-till, increased seed rate, banded N fertilization, and increased stubble height. They found that both total N input and output were greater with legume-based rotations than nonlegume monocropping due to pea N fixation and increased grain N removal. As a result, N balance was positive, indicating N surplus in legume-based rotations, and negative, indicating N deficit in nonlegume monocropping. This suggests that external N input is lower to sustain crop yields in legume-based crop rotations than nonlegume monocropping.

Legume-nonlegume rotation can also resist soil acidification compared with continuous nonlegumes. Sainju et al. [18] reported that soil pH at 0–7.5 cm after 30 years of experiment initiation was 0.13–0.44 greater and at 7.5–15.0 cm was 0.11–0.29 greater with spring wheat-barley/pea rotation (FSTW-B/P) than continuous spring wheat (NTCW, STCW, and FSTCW) (**Table 5**). They explained this as a result of lack of N fertilization to pea and reduced N fertilization rate to spring wheat following pea whose residue supplied N to spring wheat because of higher M concentration than spring wheat and barley residues. Soil residual NO3-N, which can pollute groundwater through leaching, was lower with legume-based crop rotations containing durum, canola, pea, and flax than continuous durum (**Table 6**), suggesting that legume-based crop rotations can reduce N fertilization rate and the potential for N leaching compared with nonlegume monocropping.

by providing additional crop residue which increases biomass C and N inputs to the soil [9, 10, 12] and sequester atmospheric C and/or N, thereby reducing the rate of N fertilization to summer crops [9, 10]. Other benefits of cover crops include increased soil aggregation and water infiltration capacity [31], improved water holding capacity [32], and reduced soil erosion [33] compared with no cover crop. Integrating legumes in crop rotations can supply N to succeeding crops and increase crop yields compared to nonlegumes or no cover crop rotations [10]. In contrast, nonlegume cover crops are effective in increasing soil organic C through increased biomass production compared with legumes or no cover crop [9, 10, 12]. Nonlegumes also reduce NO3-N leaching from the soil profile better than legumes, or no cover crop do [29]. As none of the cover crops are effective enough to provide most of these benefits, i.e., to supply N, sustain crop yields, increase soil organic matter, and reduce N leaching, a mixture of legume and nonlegume cover crops is ideal to supply both C and N inputs in adequate amounts that help to improve soil and water quality by increasing organic matter content and the potential for reducing N leaching compared with legumes and increase crop yields compared with

*Soil total N (STN) at the 0–120 cm depth after 6 years as affected by crop rotation in eastern Montana,*

**STN (Mg N ha1**

**0–5 cm 5–10 cm 10–20 cm 20–40 cm 40–60 cm 60–90 cm 90–120 cm 0–120 cm**

CW 0.82 0.91 1.46 2.34bb 2.11 2.29b 2.11 12.03b W-P 0.85 0.90 1.53 2.66a 2.24 2.55a 2.23 12.96a W-B-P 0.79 0.86 1.44 2.43ab 2.17 2..35b 2.22 12.17b W-B-C-P 0.81 0.88 1.47 2.54a 2.26 2.51a 2.10 12.62ab

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil…*

*Crop rotations are CW, continuous spring wheat; W-P, spring wheat-pea; W-B-P, spring wheat-barley hay-pea; and*

*Numbers followed by different letters within a column are significantly different at* P ≤ *0.05 by the least square means test.*

**)**

Sainju et al. [36] found higher biomass yield with hairy vetch/rye (*Secale cereale* L.) mixture than rye, hairy vetch, or winter weeds, and N concentration in the mixture similar to hairy vetch, except in 2001 (**Table 7**). As a result, they observed greater biomass C and N contents with hairy vetch/rye mixture than rye and winter weeds and similar to or greater than hairy vetch. The C/N ratio of cover crop biomass, which measures the decomposition rate of the residue, was similar between hairy vetch/rye

Because of increased C supply, soil organic C at 0–10 and 10–30 cm was also greater with hairy vetch/rye than other cover crops (**Figure 2**). At 30–60 cm, soil organic C was greater with hairy vetch/rye than other cover crops, except hairy vetch. Soil total N at 0–15, 15–30, and 0–120 cm was also greater with hairy vetch and hairy vetch/rye mixture than other cover crops (**Figure 3**). Similarly, soil residual NO3-N content at 0–120 cm was greater with hairy vetch than other cover crops and is slightly greater than that with 120–130 kg N ha1 (**Figure 4**). Nitrogen loss at 0–120 cm during the winter fallow period from November to April was lower with hairy vetch/rye than other cover crops (**Table 8**). Nitrogen fertilizer equivalence of rye and winter weeds for cotton and sorghum ranged from 129 to

, but those of hairy vetch and hairy vetch/rye ranged from 92 to 220 kg N ha1 (**Table 9**), suggesting that hairy vetch and hairy vetch/rye can increase cotton and sorghum yields similar to those by 92–220 kg N ha1 [11]. These results suggest that hairy vetch/rye mixture can produce crop yields similar to hairy vetch.

nonlegumes [12, 34, 35].

**Crop rotationa**

*W-B-C-P, spring wheat-barley hay-corn-pea.*

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

*a*

*b*

**Table 3.**

*USA [25].*

mixture and hairy vetch.

69 kg N ha1

**39**

#### **Figure 1.**

*Soil organic C at the 0–120 cm depth as affected by 6 years of N fertilization rates to malt barley in various cropping systems in eastern Montana, USA. CTB-F denotes conventional till malt barley-fallow; NTB-F, no-till malt barley-fallow; NTB-P, no-till malt barley-pea; and NTCB, no-till continuous malt barley. Vertical bars denote least significant difference between tillage and cropping sequence treatments within a N rate at P = 0.05 [24].*

*†Crop rotations are CD, continuous durum; D-C-D-P, durum-canola-durum-pea; D-D-C-P, durumdurum-canola-pea; D-F-D-P, durum-flax-durum-pea; and D-D-F-P, durum-durum-flax-pea. ‡Numbers followed by different letters within a column are significantly different at* P ≤ *0.05 by the least square means test.*

#### **Table 2.**

*Soil total C (STC) at the 0–125 cm depth after 6 years as affected by crop rotation in eastern Montana, USA [19].*

#### **2.2 Cover cropping**

Cover crops have been grown successfully in regions with mild winter to provide vegetative cover for reducing soil erosion. Cover crops are usually grown in the fall after the harvest of summer cash crops and have many benefits for sustaining crop yields and improving soil and water quality. Winter cover crops use soil residual N that may otherwise leach into groundwater after crop harvest in the fall, thereby reducing soil profile NO3-N content and N leaching [29, 30]. Summer cover crops are grown in the summer to replace fallow when no other crops are grown. Depending on the species, cover crops can maintain or increase soil organic C and N

*a Crop rotations are CW, continuous spring wheat; W-P, spring wheat-pea; W-B-P, spring wheat-barley hay-pea; and W-B-C-P, spring wheat-barley hay-corn-pea.*

*b Numbers followed by different letters within a column are significantly different at* P ≤ *0.05 by the least square means test.*

#### **Table 3.**

*Soil total N (STN) at the 0–120 cm depth after 6 years as affected by crop rotation in eastern Montana, USA [25].*

by providing additional crop residue which increases biomass C and N inputs to the soil [9, 10, 12] and sequester atmospheric C and/or N, thereby reducing the rate of N fertilization to summer crops [9, 10]. Other benefits of cover crops include increased soil aggregation and water infiltration capacity [31], improved water holding capacity [32], and reduced soil erosion [33] compared with no cover crop.

Integrating legumes in crop rotations can supply N to succeeding crops and increase crop yields compared to nonlegumes or no cover crop rotations [10]. In contrast, nonlegume cover crops are effective in increasing soil organic C through increased biomass production compared with legumes or no cover crop [9, 10, 12]. Nonlegumes also reduce NO3-N leaching from the soil profile better than legumes, or no cover crop do [29]. As none of the cover crops are effective enough to provide most of these benefits, i.e., to supply N, sustain crop yields, increase soil organic matter, and reduce N leaching, a mixture of legume and nonlegume cover crops is ideal to supply both C and N inputs in adequate amounts that help to improve soil and water quality by increasing organic matter content and the potential for reducing N leaching compared with legumes and increase crop yields compared with nonlegumes [12, 34, 35].

Sainju et al. [36] found higher biomass yield with hairy vetch/rye (*Secale cereale* L.) mixture than rye, hairy vetch, or winter weeds, and N concentration in the mixture similar to hairy vetch, except in 2001 (**Table 7**). As a result, they observed greater biomass C and N contents with hairy vetch/rye mixture than rye and winter weeds and similar to or greater than hairy vetch. The C/N ratio of cover crop biomass, which measures the decomposition rate of the residue, was similar between hairy vetch/rye mixture and hairy vetch.

Because of increased C supply, soil organic C at 0–10 and 10–30 cm was also greater with hairy vetch/rye than other cover crops (**Figure 2**). At 30–60 cm, soil organic C was greater with hairy vetch/rye than other cover crops, except hairy vetch. Soil total N at 0–15, 15–30, and 0–120 cm was also greater with hairy vetch and hairy vetch/rye mixture than other cover crops (**Figure 3**). Similarly, soil residual NO3-N content at 0–120 cm was greater with hairy vetch than other cover crops and is slightly greater than that with 120–130 kg N ha1 (**Figure 4**). Nitrogen loss at 0–120 cm during the winter fallow period from November to April was lower with hairy vetch/rye than other cover crops (**Table 8**). Nitrogen fertilizer equivalence of rye and winter weeds for cotton and sorghum ranged from 129 to 69 kg N ha1 , but those of hairy vetch and hairy vetch/rye ranged from 92 to 220 kg N ha1 (**Table 9**), suggesting that hairy vetch and hairy vetch/rye can increase cotton and sorghum yields similar to those by 92–220 kg N ha1 [11]. These results suggest that hairy vetch/rye mixture can produce crop yields similar to hairy vetch.

**2.2 Cover cropping**

*means test.*

**Figure 1.**

*rate at P = 0.05 [24].*

*Nitrogen Fixation*

**Table 2.**

*USA [19].*

**38**

Cover crops have been grown successfully in regions with mild winter to provide vegetative cover for reducing soil erosion. Cover crops are usually grown in the fall after the harvest of summer cash crops and have many benefits for sustaining crop yields and improving soil and water quality. Winter cover crops use soil residual N that may otherwise leach into groundwater after crop harvest in the fall, thereby reducing soil profile NO3-N content and N leaching [29, 30]. Summer cover crops are grown in the summer to replace fallow when no other crops are grown. Depending on the species, cover crops can maintain or increase soil organic C and N

**Crop rotation† STC at 0–125 cm (Mg C ha1**

*Soil organic C at the 0–120 cm depth as affected by 6 years of N fertilization rates to malt barley in various cropping systems in eastern Montana, USA. CTB-F denotes conventional till malt barley-fallow; NTB-F, no-till malt barley-fallow; NTB-P, no-till malt barley-pea; and NTCB, no-till continuous malt barley. Vertical bars denote least significant difference between tillage and cropping sequence treatments within a N*

*†Crop rotations are CD, continuous durum; D-C-D-P, durum-canola-durum-pea; D-D-C-P, durumdurum-canola-pea; D-F-D-P, durum-flax-durum-pea; and D-D-F-P, durum-durum-flax-pea.*

*‡Numbers followed by different letters within a column are significantly different at* P ≤ *0.05 by the least square*

*Soil total C (STC) at the 0–125 cm depth after 6 years as affected by crop rotation in eastern Montana,*

CD 394.6a‡ D-C-D-P 395.4a D-D-C-P 387.1a D-F-D-P 395.4a D-D-F-P 370.2b

**)**

The mixture can also increase soil organic matter and reduce N fertilization rate and the potential for N leaching compared with rye and winter weeds. Therefore, legumenonlegume cover crop mixture can provide several benefits, such as reducing the cost of N fertilization, maintaining crop yields, enhancing soil organic matter, and reduc-

**Soil depth**

c 6.50abD 7.60C 8.35B 8.58A 8.75A

**–60 cm 60**

0.08 0.01 0.13 0.04

0.01 0.01 0.01 0.01

0.01 0.01

0.01 0.03 0.01 0.03

*–2013); NTCW, no-till continuous spring wheat; STCW,*

0.11 0.20 0.15 0.16 0.14

**–90 cm 90**

0.08 0.04

0.01

*–120 cm depth after 30 years*

**–120 cm**

*…*

**–30 cm 30**

0.09 0.08

ing N leaching compared with either cover crop alone or no cover crop.

can increase soil organic C and total N, improving soil quality and crop production compared to no fertilizer application [37, 38]. Sainju et al. [39, 40] compared soil organic C and total N after 10 years of poultry litter with inorganic N

Manure and compost are rich sources of nutrients, and their application

**2.3 Application of manure and compost**

*of experiment initiation in eastern Montana, USA [18].*

**Tillage and cropping**

NTCW 5.33ab

NT vs. T 0.29 0.26

NT vs. T 0.05 0.08

*–1999) followed by spring wheat-pea (2000*

**0**

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

**–7.5 cm 7.5**

b E

0.68\*\*\*

0.43\*

0.43\*\*\*

0.24\*

*NT, no-till; T, till; W-B/P, spring wheat-barley/pea; and W-F, spring wheat-fallow. b*

*Effect of tillage and crop rotation combination on soil pH and buffer pH at the 0*

**–15 cm 15**

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil*

STCW 5.05bE 6.15bD 7.58C 8.25B 8.63A 8.70A FSTCW 5.02bE 6.33bD 7.80C 8.30B 8.68AB 8.73A FSTW-B/P 5.46aE 6.44bD 7.60C 8.15B 8.51A 8.59A STW-F 5.73aE 7.03aD 7.65C 8.25B 8.50AB 8.66A

0.88\*\*

0.24\*\*

0.08

*FSTCW, fall and spring till continuous spring wheat; FSTW-B/P, fall and spring till spring wheat-barley*

*spring till continuous spring wheat; and STW-F, spring till spring wheat-fallow. CW represents continuous wheat;*

*Numbers followed by the same uppercase letter within a row among soil depths in a set are no significantly different at*

*Numbers followed by the same lowercase letter within a column among treatments in a set are not significantly*

0.01

NTCW 6.45bE 7.10abD 7.43C 7.60B 7.70AB 7.73A STCW 6.38bE 7.00bD 7.43C 7.58B 7.68A 7.70A FSTCW 6.43bE 7.05bD 7.45C 7.60B 7.70AB 7.73A FSTW-B/P 6.66aD 7.13abC 7.44B 7.58B 7.69AB 7.70A STW-F 6.80aE 7.24aD 7.44C 7.59B 7.66AB 7.72A

**sequence a**

*Contrast*

CW vs. W-F

**Buffer pH**

*Contrast*

*(1994*

*c*

**41**

*different at P*

*P* ≤ *0.05.*

**Table 5.**

CW vs. W-F

CW vs. W-B/P

*\*Significant at P = 0.05. \*\*Significant at P = 0.01. \*\*\*Significant at P = 0.001. a*

≤ *0.05.*

CW vs. W-B/P

**pH**

*eN balance = changes in N levels N sequestration rate (0–125 cm).*

#### *Nitrogen Fixation*

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

*\*Significant at P = 0.05.*

*\*\*Significant at P = 0.01.*

*\*\*\*Significant at P = 0.001.*

*a FSTCW, fall and spring till continuous spring wheat; FSTW-B/P, fall and spring till spring wheat-barley (1994–1999) followed by spring wheat-pea (2000–2013); NTCW, no-till continuous spring wheat; STCW, spring till continuous spring wheat; and STW-F, spring till spring wheat-fallow. CW represents continuous wheat; NT, no-till; T, till; W-B/P, spring wheat-barley/pea; and W-F, spring wheat-fallow.*

*b Numbers followed by the same lowercase letter within a column among treatments in a set are not significantly different at P* ≤ *0.05. c*

*Numbers followed by the same uppercase letter within a row among soil depths in a set are no significantly different at P* ≤ *0.05.*

#### **Table 5.**

*Effect of tillage and crop rotation combination on soil pH and buffer pH at the 0–120 cm depth after 30 years of experiment initiation in eastern Montana, USA [18].*

The mixture can also increase soil organic matter and reduce N fertilization rate and the potential for N leaching compared with rye and winter weeds. Therefore, legumenonlegume cover crop mixture can provide several benefits, such as reducing the cost of N fertilization, maintaining crop yields, enhancing soil organic matter, and reducing N leaching compared with either cover crop alone or no cover crop.

#### **2.3 Application of manure and compost**

Manure and compost are rich sources of nutrients, and their application can increase soil organic C and total N, improving soil quality and crop production compared to no fertilizer application [37, 38]. Sainju et al. [39, 40] compared soil organic C and total N after 10 years of poultry litter with inorganic N

**Parameter**

**40**

**N inputs** N fertilization rate

Pea N fixation Atmospheric N deposition

N added by crop seed

Nonsymbiotic

Total N input

**N outputs** Grain N removal

Denitrification Ammonia volatilization

Plant senescence

N leaching Gaseous N (NOx) emissions

Surface runoff Total N output Changes in N levelc

N sequestration rate (0–125 cm)d

N balancee *aCrop rotation are CD, continuous durum; D-C-D-P,*  *bNumbers followed by the same letter within a row are not significantly different at* P ≤ *0.05.*

*cChanges in N level = total N input total N output.* *dDetermined from the linear regression analysis of soil total N (STN) at 0–125 cm from the year 2005 to 2011.*

*eN balance = changes in N levels N sequestration rate (0–125 cm).*

**Table 4.** *Annual N balance due to the difference between total N inputs and outputs and N*

*sequestration*

 *rate under dryland*

*agroecosystems*

 *from 2005 to 2011 in eastern Montana,*

 *USA [26, 27].*

49B

12 12 5 9 2 1 91B 14B

50 36 (11)B

 17 (5)A *durum-canola-durum-pea;*

 *D-D-C-P,*

 16 (4)A

 16 (4)A

*durum-durum-canola-pea;*

 *D-F-D-P,*

*durum-flax-durum-pea;*

 *and D-D-F-P,*

*durum-durum-flax-pea.*

 13 (3)A

39 (12)B

 11 (3)A

 9 (2)A

 17 (4)A

 25 (5)A

45

42

46

43

52

48

46

44

40

62A

58A

62A

56A

13B

59A

55A

61A

65A

105A

98AB

92B

94AB

96AB

107A

107A

103A

94AB

2

1

1

1

1

2

2

2

2

3

3

3

3

2

3

3

3

3

12

12

12

12

9

12

12

12

12

7

6

6

6

6

7

7

7

6

9

9

8

8

13

9

9

8

8

10

9

8

9

13

9

10

9

9

62A

57AB

54AB

55AB

52AB

65A

64A

63A

54AB

 N fixation

83Ab

0C 14

3 5 105B

167A

156A

154A

150A

109B

166A

162A

164A

159A

5

5

5

5

5

5

5

5

5

3

3

3

3

3

3

3

3

3

14

14

14

14

14

14

14

14

14

84AB

76B

80AB

75B

0C

84AB

78B

87A

82AB

62B

59B

52B

54B

87A

60B

63B

55B

56B

**Traditional (kg N ha1 year1**

> **CDa**

> **D-C-D-Pa**

> **D-D-C-Pa**

**D-F-D-Pa**

**D-D-F-Pa**

**CD**

**D-C-D-P**

 **D-D-C-P**

 **D-F-D-P**

 **D-D-F-P**

*Nitrogen Fixation*

**)**

**Ecological (kg N ha1 year1**

**)**

*a Crop rotations are CD, continuous durum; DCDP, durum-canola-durum-pea; DDCP, durum-durum-canola-pea; DDFP, durum-durum-flax-pea; and DFDP, durum-flax-durum-pea.*

*b Numbers followed by different letters within a column are significantly different at P* ≤ *0.05 by the least square means test.*

#### **Table 6.**

*Soil NO3-N content at the 0–125 cm depth as affected by crop rotation and cultural practice averaged across years from 2006 to 2011 in eastern Montana, USA [28].*

*†Cover crops are rye, cereal rye; vetch, hairy vetch; vetch/rye, hairy vetch and rye biculture; and weeds, winter weeds. ‡Numbers followed by the same letter within a column of a year are not significantly different at P* ≤ *0.05.*

to crops in the first year [37], Sainju et al. [39, 40] reported that part of nonmineralized C and N from the litter converted to soil organic C and N, thereby increasing their levels with poultry litter application. In contrast, little or no C was supplied by inorganic N fertilizer, and most of N supplied by the fertilizer can either be taken up by the crop or lost to the environment through leaching, denitrification,

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil…*

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

*difference between cover crops within a sampling date at P = 0.05 [12].*

*Effect of cover crop on soil organic C at the (A) 0-10 cm, (B) 10-30 cm, and (C) 30-50 cm depths in a chiseltilled system (October 1999–November 2002, central Gerogia, USA). R denotes cereal rye; V, hairy vetch; VR, hairy vetch and rye biculture; and WW, winter weeds. Vertical line with LSD (0.05) is the least significant*

Because of lower N availability from poultry litter as a result of reduced N mineralization, total aboveground biomass and N uptake of corn, cotton, and rye cover crop were lower with poultry litter application than inorganic N fertilization (**Table 12**). Although soil health and quality can be improved with poultry litter application through organic matter enrichment, crop yields can be lower compared with N fertilization. For enhancing soil and environmental quality and sustaining crop yields, both inorganic N fertilizer and manure/compost should be applied as a mixture in balanced proportion as per crop demand after analyzing soil NO3-N test to a depth of 60 cm. This could reduce N fertilization rate and undesirable conse-

quences of N fertilization on soil and environmental quality.

and volatilization.

**43**

**Figure 2.**

#### **Table 7.**

*Effect of cover crop species on aboveground biomass yield and C and N contents in cover crops from 2000 to 2002 in central Georgia, USA [36].*

fertilizer applications, both applied at 100 kg N ha1 to corn and cotton (**Tables 10** and **11**). They found that soil organic C and total N at 0–20 cm were greater with poultry litter application than inorganic N fertilization, regardless of tillage practices. As a result, poultry litter application sequestered C at 461 kg C ha1 year1 and N at 38 kg N ha1 year1 compared to 38 kg C ha1 year1 and 4 kg N ha1 year1 , respectively, with N fertilization. As poultry litter also supplied C at 1.7 Mg C ha1 year1 [40] and only 60% of N from poultry litter was available

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

#### **Figure 2.**

*Effect of cover crop on soil organic C at the (A) 0-10 cm, (B) 10-30 cm, and (C) 30-50 cm depths in a chiseltilled system (October 1999–November 2002, central Gerogia, USA). R denotes cereal rye; V, hairy vetch; VR, hairy vetch and rye biculture; and WW, winter weeds. Vertical line with LSD (0.05) is the least significant difference between cover crops within a sampling date at P = 0.05 [12].*

to crops in the first year [37], Sainju et al. [39, 40] reported that part of nonmineralized C and N from the litter converted to soil organic C and N, thereby increasing their levels with poultry litter application. In contrast, little or no C was supplied by inorganic N fertilizer, and most of N supplied by the fertilizer can either be taken up by the crop or lost to the environment through leaching, denitrification, and volatilization.

Because of lower N availability from poultry litter as a result of reduced N mineralization, total aboveground biomass and N uptake of corn, cotton, and rye cover crop were lower with poultry litter application than inorganic N fertilization (**Table 12**). Although soil health and quality can be improved with poultry litter application through organic matter enrichment, crop yields can be lower compared with N fertilization. For enhancing soil and environmental quality and sustaining crop yields, both inorganic N fertilizer and manure/compost should be applied as a mixture in balanced proportion as per crop demand after analyzing soil NO3-N test to a depth of 60 cm. This could reduce N fertilization rate and undesirable consequences of N fertilization on soil and environmental quality.

fertilizer applications, both applied at 100 kg N ha1 to corn and cotton (**Tables 10** and **11**). They found that soil organic C and total N at 0–20 cm were greater with poultry litter application than inorganic N fertilization, regardless of tillage practices. As a result, poultry litter application sequestered C at 461 kg C ha1 year1

*Effect of cover crop species on aboveground biomass yield and C and N contents in cover crops from 2000 to*

C at 1.7 Mg C ha1 year1 [40] and only 60% of N from poultry litter was available

, respectively, with N fertilization. As poultry litter also supplied

and N at 38 kg N ha1 year1 compared to 38 kg C ha1 year1 and

**Crop rotationa NO3-N content at various depths (kg N ha1**

*DDFP, durum-durum-flax-pea; and DFDP, durum-flax-durum-pea.*

*years from 2006 to 2011 in eastern Montana, USA [28].*

**Biomass yield (Mg ha1 )**

CD 2.47ab 1.81a 2.43a 8.49a 9.37a 9.17a 33.87a DCDP 1.82a 1.22b 1.94b 6.47a 7.77a 6.71b 26.32b DDCP 1.86a 1.19b 1.93b 5.97a 8.07a 6.38b 25.59b DFDP 1.90a 1.37b 2.20a 6.59a 9.62a 8.64ab 30.60a DDFP 1.74a 1.28b 2.29a 6.27a 8.63a 6.65b 27.02b

*Crop rotations are CD, continuous durum; DCDP, durum-canola-durum-pea; DDCP, durum-durum-canola-pea;*

*Numbers followed by different letters within a column are significantly different at P* ≤ *0.05 by the least square*

*Soil NO3-N content at the 0–125 cm depth as affected by crop rotation and cultural practice averaged across*

**) N (g kg1**

Weeds 1.65d‡ 370b 15b 587d 25d 24b Rye 6.07b 430a 15b 2670b 68c 29a Vetch 5.10c 394ab 33a 2006c 135b 12c Vetch/rye 8.18a 366b 38a 3512a 310a 10c

Weeds 0.75d 391b 20b 277d 15b 20c Rye 3.81b 448a 8d 1729b 32b 57a Vetch 2.44c 398b 32a 964c 76a 12c Vetch/rye 5.98a 434a 14c 2693a 84a 32b

Weeds 1.25c 375b 18b 476c 23b 21b Rye 2.28b 434a 11b 986b 25b 40a Vetch 5.16a 361b 36a 2094a 167a 10c Vetch/rye 5.72a 381b 33a 2260a 186a 11c *†Cover crops are rye, cereal rye; vetch, hairy vetch; vetch/rye, hairy vetch and rye biculture; and weeds, winter weeds. ‡Numbers followed by the same letter within a column of a year are not significantly different at P* ≤ *0.05.*

**C (g kg1**

**Concentration Content C/N**

**) N (kg ha1**

**) C (kg ha1**

**ratio**

**)**

**0–5 cm 5–10 cm 10–20 cm 20–50 cm 50–88 cm 88–125 cm 0–125 cm**

**)**

4 kg N ha1 year1

*2002 in central Georgia, USA [36].*

*a*

*b*

*means test.*

*Nitrogen Fixation*

**Table 6.**

**Cover crop†**

**2000**

**2001**

**2002**

**Table 7.**

**42**

#### **Figure 3.**

*Effect of cover crop on soil total N at the 0–120 cm depth in (A) no-tilled, (B) strip-tilled, and (C) chisel-tilled soils after 3 years in Central Georgia, USA. R denotes cereal rye; V, hairy vetch; V + R, hairy vetch and rye biculture; and WW, winter weeds. Bars followed by the same lowercase letter within a soil depth are not significantly different between cover crops at P = 0.05. Bars followed by the same uppercase letter at the top are not significantly different between cover crops at the 0–120 cm depth at P* ≤ *0.05 [34].*

**Figure 4.**

*or no cover crop.*

**Table 8***.*

**45**

*crops at the 0–120 cm depth at P* ≤ *0.05 [35].*

*to April 2002) in central Georgia, USA [35].*

**Cover crop† Total crop residue and soil N‡**

**(kg N ha1**

*(stems + leaves) in November 2000 and cover crop biomass in April 2001.*

*(stems + leaves) in November 2001 and cover crop biomass in April 2002.*

**)**

*¶Numbers followed by the same letter within a column are not significantly different at P* ≤ *0.05.*

*Effect of (A) cover crop and (B) N fertilization rate on soil NO3-N content at the 0–120 cm depth in Central Georgia, USA. R, denotes cereal rye; V, hairy vetch; V + R, hairy vetch and rye biculture; and W, winter weeds. Bars followed by the same lowercase letter within a soil depth are not significantly different between cover crops at P = 0.05. Bars followed by the same uppercase letter at the top are not significantly different between cover*

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil…*

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

Rye 5057bc¶ 4888b 169b 4820b 4764b 56a Vetch 5455a 5235a 220a 5323a 5244a 79a Vetch/rye 5249ab 5141a 108c 5222a 5182a 40a Weeds 4869c 4709b 160b 4725b 4649b 76a *†Cover crops are rye, cereal rye; vetch, hairy vetch; vetch/rye, hairy vetch and rye biculture; and weeds, winter weeds*

*‡Include soil NH4-N + NO3-N + organic N contents at 0–120 cm, and N returned to the soil from cotton biomass*

*§Include soil NH4-N + NO3-N + organic N contents at 0–120 cm, and N returned to the soil from sorghum biomass*

*Effect of cover crop on N loss from crop residue and soil N (NH4-N + NO3-N + organic N contents) at the 0–120 cm depth during the two winter seasons (from November 2000 to April 2001 and from November 2001*

**November 2000 April 2001 Loss November 2001 April 2002 Loss**

**Total crop residue and soil N§ (kg N ha1**

**)**

#### **2.4 Integrated crop-livestock system**

Integrated crop-livestock systems were commonly used to sustain crop and livestock products throughout the world before commercial fertilizers were introduced in 1950 [41]. The system is still common among producers in developing countries, especially in Africa and Asia where fertilizers are scarce and expensive [42, 43]. The integrated crop-livestock system has the potential to improve soil quality and sustain crop yields [41, 44]. The major benefits of the system are (1) production of crops, meat, and milk, (2) production of crop residue for animal feed, (3) production of manure to apply as fertilizer, (4) use of animals as draft power for tillage, and (5) control of weeds and pests [41, 42].

Animal grazing during fallow periods in wheat-fallow systems can be used to effectively control weeds [14] and insects, such as wheat stem saw fly [*Cephus cinctus* Norton (Hymenoptera: Cephidae)] [13]. The animal usually grazes on crop residues and weeds during the fallow period. Although grazing can reduce the quantity of crop residue returned to the soil, the number of animals grazed per unit area can be adjusted in such a way that crop residue cover in the grazing treatment will be similar to that in the conservation tillage system where soil erosion is minimal [14]. Animal feces and urine returned to the soil during grazing can enrich *Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

#### **Figure 4.**

**2.4 Integrated crop-livestock system**

**Figure 3.**

*Nitrogen Fixation*

**44**

tillage, and (5) control of weeds and pests [41, 42].

Integrated crop-livestock systems were commonly used to sustain crop and livestock products throughout the world before commercial fertilizers were introduced in 1950 [41]. The system is still common among producers in developing countries, especially in Africa and Asia where fertilizers are scarce and expensive [42, 43]. The integrated crop-livestock system has the potential to improve soil quality and sustain crop yields [41, 44]. The major benefits of the system are (1) production of crops, meat, and milk, (2) production of crop residue for animal feed, (3) production of manure to apply as fertilizer, (4) use of animals as draft power for

*Effect of cover crop on soil total N at the 0–120 cm depth in (A) no-tilled, (B) strip-tilled, and (C) chisel-tilled soils after 3 years in Central Georgia, USA. R denotes cereal rye; V, hairy vetch; V + R, hairy vetch and rye biculture; and WW, winter weeds. Bars followed by the same lowercase letter within a soil depth are not significantly different between cover crops at P = 0.05. Bars followed by the same uppercase letter at the top are*

*not significantly different between cover crops at the 0–120 cm depth at P* ≤ *0.05 [34].*

Animal grazing during fallow periods in wheat-fallow systems can be used to effectively control weeds [14] and insects, such as wheat stem saw fly [*Cephus cinctus* Norton (Hymenoptera: Cephidae)] [13]. The animal usually grazes on crop residues and weeds during the fallow period. Although grazing can reduce the quantity of crop residue returned to the soil, the number of animals grazed per unit area can be adjusted in such a way that crop residue cover in the grazing treatment will be similar to that in the conservation tillage system where soil erosion is minimal [14]. Animal feces and urine returned to the soil during grazing can enrich

*Effect of (A) cover crop and (B) N fertilization rate on soil NO3-N content at the 0–120 cm depth in Central Georgia, USA. R, denotes cereal rye; V, hairy vetch; V + R, hairy vetch and rye biculture; and W, winter weeds. Bars followed by the same lowercase letter within a soil depth are not significantly different between cover crops at P = 0.05. Bars followed by the same uppercase letter at the top are not significantly different between cover crops at the 0–120 cm depth at P* ≤ *0.05 [35].*

*†Cover crops are rye, cereal rye; vetch, hairy vetch; vetch/rye, hairy vetch and rye biculture; and weeds, winter weeds or no cover crop.*

*‡Include soil NH4-N + NO3-N + organic N contents at 0–120 cm, and N returned to the soil from cotton biomass (stems + leaves) in November 2000 and cover crop biomass in April 2001.*

*§Include soil NH4-N + NO3-N + organic N contents at 0–120 cm, and N returned to the soil from sorghum biomass (stems + leaves) in November 2001 and cover crop biomass in April 2002.*

*¶Numbers followed by the same letter within a column are not significantly different at P* ≤ *0.05.*

#### **Table 8***.*

*Effect of cover crop on N loss from crop residue and soil N (NH4-N + NO3-N + organic N contents) at the 0–120 cm depth during the two winter seasons (from November 2000 to April 2001 and from November 2001 to April 2002) in central Georgia, USA [35].*

**Tillage† N source‡ SOC concentration**

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

*†Tillage is CT, conventional till; MT, mulch till; and NT, no-till.*

**Tillagea N sourceb STN concentration**

*Tillage is CT, conventional till; MT, mulch till; and NT, no-till.*

*N source is AN, ammonium nitrate; and PL, poultry litter.*

*Least significant differences between treatments at P = 0.05.*

**(100 kg N ha1**

*‡N source is AN, NH4NO3; and PL, poultry litter.*

LSD (0.05)

*square means test.*

**Table 10.**

*USA [40].*

LSD (0.05)c

*a*

*b*

*c*

*d*

**47**

**Table 11.**

*Alabama, USA [39].*

**(g C kg1 )**

**SOC content (Mg C ha1**

**100 kg N ha1 0–10 cm 10–20 cm 0–20 cm 0–20 cm 0–20 cm**

PL 15.9 10.5 43.7 5.10 510

PL 15.4 10.6 42.2 3.63 363

PL 15.3 11.8 43.7 5.10 510

PL 15.6a 11.0a 43.2a 4.61a 461a

— — 3.1 3.1 310

**STN content (Mg N ha1**

**) 0–10 cm 10–20 cm 0–20 cm 0–20 cm 0–20 cm**

— — 0.24 0.24 24

PL 1.52 1.02 4.19 0.49 49

PL 1.49 0.92 3.91 0.21 21

PL 1.51 1.04 4.11 0.41 41

PL 1.65a 1.59a 4.07a 0.38a 38a

**)**

**Change in STN from 1996 to 2006 (Mg N ha1**

**)**

**N sequestration rate (kg N ha1 year1 )**

NT AN 13.5 11.0 40.1 1.47 147

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil…*

MT AN 15.9 11.0 42.6 3.97 397

CT AN 14.3 10.7 37.4 1.20 120

Means AN 14.6a§ 10.9a 40.0b 1.41b 141b

*§Numbers followed by different letters within a column in a set are significantly different at P* ≤ *0.05 by the least*

*Effect of tillage and N source on soil organic C (SOC) at the 0–20 cm depth after 10 years in Alabama,*

NT AN 1.23 1.03 3.44 0.23 23

MT AN 1.42 1.01 3.84 0.15 15

CT AN 1.31 0.98 3.67 0.03 3

Means AN 1.55bd 1.59a 3.65b 0.04b 4b

*Numbers followed by the same letter within a column in a set are not significantly different at P* ≤ *0.05.*

*Effects of tillage and N source on soil total N and N sequestration rate at the 0–20 cm depth after 10 years in*

**(g N kg1 )** **)**

**Changes in SOC from 1996 to 2006 (Mg C ha1**

**)**

**C sequestration rate (kg C ha1 year.1**

**)**

*a Regression analysis of N fertilization rates versus cotton and sorghum yields and N uptake and soil inorganic N.*

#### **Table 9.**

*Nitrogen fertilizer equivalence (kg N ha1 ) of cover crops and soil inorganic N (NH4-N + NO3-N) content at the 0–30 cm depth for cotton and sorghum yields and N uptake from 2000 to 2002 in central Georgia, USA [11].*

soil nutrients, improve soil quality, and increase crop yields [44]. The distribution of feces and urine by animals during grazing at the soil surface can be uneven; however, distribution can be more uniform with sheep than with cattle grazing [45].

Hatfield et al. [14] reported that sheep grazing during fallow did not affect soil organic matter and nutrient levels compared to the non-grazed treatment in the North Central Montana. Sheep grazing can increase soil bulk density and extractable P and grass yields compared to cattle grazing [45]. Snyder et al. [46] found similar or greater wheat grain yields with and without animal grazing. Similarly, Quiroga et al. [47] observed that 10 years of cattle grazing did not alter soil P concentration in Argentina. In contrast, Niu et al. [48] in Australia observed greater soil P and K concentrations in sheep camping than in non-camping sites due to increased animal excreta. Cattle and sheep grazing in the pasture can increase soil P and K concentrations compared to non-grazing [45].

Sainju et al. [49] reported that annualized wheat grain and biomass yields were lower with spring wheat-fallow and winter wheat-fallow rotations than continuous spring wheat due to the absence of crops during the fallow period (**Table 13**). In

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

*†Tillage is CT, conventional till; MT, mulch till; and NT, no-till.*

*‡N source is AN, NH4NO3; and PL, poultry litter.*

*§Numbers followed by different letters within a column in a set are significantly different at P* ≤ *0.05 by the least square means test.*

#### **Table 10.**

soil nutrients, improve soil quality, and increase crop yields [44]. The

P and K concentrations compared to non-grazing [45].

grazing [45].

**46**

*a*

**Table 9.**

*USA [11].*

*Nitrogen fertilizer equivalence (kg N ha1*

**2000 cotton**

*Nitrogen Fixation*

**2001 sorghum**

**2002 cotton**

distribution of feces and urine by animals during grazing at the soil surface can be uneven; however, distribution can be more uniform with sheep than with cattle

*at the 0–30 cm depth for cotton and sorghum yields and N uptake from 2000 to 2002 in central Georgia,*

**Parameter Cover crop Regression**

Lint yield — —— — 0.25 0.67 Lint N uptake — —— — 0.25 0.67 Biomass yield 13 30 149 93 0.96 0.13 Biomass N uptake 21 2 165 92 0.99 0.06 Soil inorganic N 60 190 220 140 0.64 0.40

Lint yield 7 64 107 179 0.96 0.12 Lint N uptake 25 67 167 150 0.96 0.14 Biomass yield 32 168 194 194 0.99 0.02 Biomass N uptake 69 84 192 83 0.98 0.08 Soil inorganic N 59 12 116 71 0.86 0.25

Lint yield — —— — 0.28 0.82 Lint N uptake — —— — 0.24 0.87 Biomass yield 21 61 139 205 0.96 0.12 Biomass N uptake 35 13 134 160 0.97 0.11 Soil inorganic N 74 5 176 160 0.70 0.37

*Regression analysis of N fertilization rates versus cotton and sorghum yields and N uptake and soil inorganic N.*

*) of cover crops and soil inorganic N (NH4-N + NO3-N) content*

**Winter weeds Rye Hairy vetch Hairy vetch/rye R2** *P*

**analysisa**

Hatfield et al. [14] reported that sheep grazing during fallow did not affect soil organic matter and nutrient levels compared to the non-grazed treatment in the North Central Montana. Sheep grazing can increase soil bulk density and extractable P and grass yields compared to cattle grazing [45]. Snyder et al. [46] found similar or greater wheat grain yields with and without animal grazing. Similarly, Quiroga et al. [47] observed that 10 years of cattle grazing did not alter soil P concentration in Argentina. In contrast, Niu et al. [48] in Australia observed greater soil P and K concentrations in sheep camping than in non-camping sites due to increased animal excreta. Cattle and sheep grazing in the pasture can increase soil

Sainju et al. [49] reported that annualized wheat grain and biomass yields were lower with spring wheat-fallow and winter wheat-fallow rotations than continuous spring wheat due to the absence of crops during the fallow period (**Table 13**). In

*Effect of tillage and N source on soil organic C (SOC) at the 0–20 cm depth after 10 years in Alabama, USA [40].*

*a Tillage is CT, conventional till; MT, mulch till; and NT, no-till.*

*b N source is AN, ammonium nitrate; and PL, poultry litter.*

*c Least significant differences between treatments at P = 0.05.*

*d Numbers followed by the same letter within a column in a set are not significantly different at P* ≤ *0.05.*

#### **Table 11.**

*Effects of tillage and N source on soil total N and N sequestration rate at the 0–20 cm depth after 10 years in Alabama, USA [39].*

#### **Table 12.**

*Effects of cropping system and N source on total biomass (stems + leaves) residues of rye, cotton, and corn and N uptake from 1997 to 2005 in Alabama, USA [39, 40].*

Soil P, K, and SO4-S contents at 0–30 cm were lower with sheep grazing than other weed management practices, but pH, electrical conductivity, and Ca, Mg, and Na contents were similar or greater with sheep grazing (**Table 15**). Consumption of crop residue by sheep during grazing, but little P and K inputs to the soil through urine and feces, reduced soil P and K concentrations with sheep grazing compared with other weed management practices [49]. These results suggest that sheep grazing can reduce the cost of animal feed without seriously affecting crop yields and sustain soil organic matter and nutrients compared with other weed management practices, except P and K which need to be added with inorganic fertilizers to eliminate their deficiency. As soil residual NO3-N content was not different among weed management practices, long-term study may be needed to evaluate if animal grazing can reduce N fertilization rate for crop production. However, animal grazing can recycle nutrients and control weeds effectively compared with herbicide application and tillage, thereby saving the cost of fertilization and weed control. Legumes in the crop rotation can supply N from its residue to succeeding crops, thereby reducing N fertilization rates to succeeding nonlegumes. Also diversified crop rotations can use N and water more efficiently and reduce weed, pest, and disease infestations, thereby enhancing crop yields compared with continuous nonlegume monocropping. Cover crops grown to replace the fallow period can reduce soil erosion, enhance soil organic matter, and help to enrich soil health and fertility. Legume covers crop supply N and reduce N fertilization rate. Application of manure and compost can also enhance soil health and quality; however, additional inorganic N fertilization at lower rate is required to sustain crop yield and quality. Similarly, integrated crop-livestock system can help to reduce N fertilization rate by returning N and other nutrients through urine and feces to the soil during animal grazing without affecting crop yields. Some additional N fertilizer, however, may be required for sustainable crop production, because animals

**Weed management† SOC content (Mg C ha1**

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil…*

**STN content (Mg N ha1**

**NO**3**-N content (kg N ha1**

*tillage.*

*means test.*

**Table 14.**

**49**

**)**

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

**)**

*management experiment initiation in western Montana, USA [50].*

**)**

**0–5 cm 5–10 cm 10–30 cm 30–60 cm 60–90 cm 90–120 cm 0–120 cm**

Chem. 18.3a‡ 19.2a 61.7a 38.0a 32.2a 29.1b 198.4a Mech. 17.3a 17.4a 58.2ab 38.0a 35.8a 37.0a 203.5a Graz. 16.9a 17.7a 54.2b 36.1a 31.2a 31.4ab 187.5a

Chem. 1.69a 1.89a 6.48a 4.96a 3.58a 2.79a 21.40a Mech. 1.61a 1.74b 5.91a 5.00a 3.43a 2.99a 20.55a Graz. 1.53a 1.79ab 6.33a 5.60a 3.86a 2.87a 22.09a

Chem. 12.6a 12.4a 20.6a 16.0a 18.9b 38.0a 118.6a Mech. 10.3a 12.0a 21.1a 14.5a 28.8a 37.6a 124.4a Graz. 9.9a 10.9a 18.7a 17.5a 23.2ab 35.0a 115.2a *†Weed management practices are Chem., chemical where weeds were controlled with herbicide applications; Graz., grazing where weeds were controlled with sheep grazing; and Mech., mechanical where weeds were controlled with*

*‡Numbers followed by different letters within a column are significantly different at P* ≤ *0.05 by the least square*

*Soil organic C (SOC), total N (STN), and NO3-N contents at the 0–120 cm depth after 5 years of weed*

*†Cropping sequences are CSW, continuous spring wheat; SW-F, spring wheat-fallow; and WW-F, winter wheat-fallow.*

*‡Weed management practices are Chem., chemical where weeds were controlled with herbicide applications; Graz., grazing where weeds were controlled with sheep grazing; and Mech., mechanical where weeds were controlled with tillage.*

*§Numbers followed by the same lowercase letters within a column in a set are not significantly different at P* ≤ *0.05. ¶Numbers followed by the same uppercase letters within a row in a set are not significantly different at P* ≤ *0.05.*

#### **Table 13.**

*Effects of cropping sequence and weed management practice on annualized wheat grain and biomass (stems + leaves) yield from 2004 to 2008 in western Montana, USA [49].*

contrast, wheat grain yield was not different among weed management practices where sheep grazing was used among one of the treatments to control weeds along with herbicide application and tillage, although wheat biomass yield was lower with sheep grazing and herbicide application than tillage. Soil organic C, total N, and NO3-N contents varied among weed management practices and soil depths, but the contents at 0–120 cm were not affected by weed management practices (**Table 14**).

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

*†Weed management practices are Chem., chemical where weeds were controlled with herbicide applications; Graz., grazing where weeds were controlled with sheep grazing; and Mech., mechanical where weeds were controlled with tillage.*

*‡Numbers followed by different letters within a column are significantly different at P* ≤ *0.05 by the least square means test.*

#### **Table 14.**

*Soil organic C (SOC), total N (STN), and NO3-N contents at the 0–120 cm depth after 5 years of weed management experiment initiation in western Montana, USA [50].*

Soil P, K, and SO4-S contents at 0–30 cm were lower with sheep grazing than other weed management practices, but pH, electrical conductivity, and Ca, Mg, and Na contents were similar or greater with sheep grazing (**Table 15**). Consumption of crop residue by sheep during grazing, but little P and K inputs to the soil through urine and feces, reduced soil P and K concentrations with sheep grazing compared with other weed management practices [49]. These results suggest that sheep grazing can reduce the cost of animal feed without seriously affecting crop yields and sustain soil organic matter and nutrients compared with other weed management practices, except P and K which need to be added with inorganic fertilizers to eliminate their deficiency. As soil residual NO3-N content was not different among weed management practices, long-term study may be needed to evaluate if animal grazing can reduce N fertilization rate for crop production. However, animal grazing can recycle nutrients and control weeds effectively compared with herbicide application and tillage, thereby saving the cost of fertilization and weed control.

Legumes in the crop rotation can supply N from its residue to succeeding crops, thereby reducing N fertilization rates to succeeding nonlegumes. Also diversified crop rotations can use N and water more efficiently and reduce weed, pest, and disease infestations, thereby enhancing crop yields compared with continuous nonlegume monocropping. Cover crops grown to replace the fallow period can reduce soil erosion, enhance soil organic matter, and help to enrich soil health and fertility. Legume covers crop supply N and reduce N fertilization rate. Application of manure and compost can also enhance soil health and quality; however, additional inorganic N fertilization at lower rate is required to sustain crop yield and quality. Similarly, integrated crop-livestock system can help to reduce N fertilization rate by returning N and other nutrients through urine and feces to the soil during animal grazing without affecting crop yields. Some additional N fertilizer, however, may be required for sustainable crop production, because animals

contrast, wheat grain yield was not different among weed management practices where sheep grazing was used among one of the treatments to control weeds along with herbicide application and tillage, although wheat biomass yield was lower with sheep grazing and herbicide application than tillage. Soil organic C, total N, and NO3-N contents varied among weed management practices and soil depths, but the contents at 0–120 cm were not affected by weed management practices (**Table 14**).

*Effects of cropping sequence and weed management practice on annualized wheat grain and biomass*

*(stems + leaves) yield from 2004 to 2008 in western Montana, USA [49].*

**Cropping system N source Total crop biomass Total N uptake 100 kg N ha1 (Mg ha1**

Rye/cotton-rye/cotton-corn 137.0a† 1544a† Cotton-cotton-corn 110.2b 1247b

*†Numbers followed by the same letter within a column in a set are not significantly different at P* ≤ *0.05.*

*uptake from 1997 to 2005 in Alabama, USA [39, 40].*

**Year Cropping sequence† (Mg ha1**

**Annualized grain yield**

**Annualized biomass yield**

*wheat-fallow.*

*tillage.*

**Table 13.**

**48**

*Effects of cropping system and N source on total biomass (stems + leaves) residues of rye, cotton, and corn and N*

**CSW SW-F WW-F Chem. Mech. Graz.**

2004 5.55a§A¶ 2.90aC 3.53aB 3.92aA 4.01aA 4.05aA 3.99a 2005 2.68bA 1.83bB 1.15eC 1.84cA 1.92bA 1.90bA 1.89b 2006 2.57bA 1.45cB 1.70 dB 1.89cA 1.90bA 1.92bA 1.90b 2007 1.86cB 1.18cC 2.95bA 1.89cA 2.03bA 2.00bA 2.00b 2008 2.61bA 1.56bcC 2.22cB 2.09bA 2.17bA 2.14bA 2.13b

2004 6.60aA 3.10aC 3.57aB 3.61aAB 3.41aB 3.89aA 4.42a 2005 3.28bA 1.65bB 1.94bcB 2.52bA 2.17bcA 2.19bA 2.29b 2006 2.96cA 1.57bcB 1.64cB 1.79bB 2.51bA 1.87bcB 2.06bc 2007 2.18dA 1.55bcB 2.25bA 1.78bA 2.21bcA 2.00bA 2.00c 2008 1.92dA 1.17cB 1.49cAB 1.08cB 1.91cA 1.58cA 1.53d

*‡Weed management practices are Chem., chemical where weeds were controlled with herbicide applications; Graz., grazing where weeds were controlled with sheep grazing; and Mech., mechanical where weeds were controlled with*

*§Numbers followed by the same lowercase letters within a column in a set are not significantly different at P* ≤ *0.05. ¶Numbers followed by the same uppercase letters within a row in a set are not significantly different at P* ≤ *0.05.*

Mean 3.05A 1.78C 2.31B 2.32A 2.42A 2.40A

Mean 2.58A 1.49C 1.83B 1.79B 2.20A 1.91B *†Cropping sequences are CSW, continuous spring wheat; SW-F, spring wheat-fallow; and WW-F, winter*

**Table 12.**

*Nitrogen Fixation*

**) (kg N ha1**

NH4NO3 133.3a 1502a Poultry litter 111.8b 1289b

**) Weed management‡ (Mg ha1**

**)**

**) Mean**

where roads are few or lacking. As a result, it is expensive to apply lime and most

neutralization of soil acidity with lime application is only temporary in nature. This

increases the cost of production. The best practice to reduce soil acidity is to reduce

Degradation in soil and environmental quality can be mitigated, and crop

yields can be sustained by reducing N fertilization rates and using novel management techniques that increase N cycling and N-use efficiency. These techniques include legume-nonlegume crop rotation, cover cropping, application of manures and compost, and integrated crop-livestock system. Soil acidity can be neutralized by lime application, but the effect is temporary. It is expensive to apply lime, and many producers in developing countries cannot afford to do so. Adaptation of these techniques to specific places depends on soil and climatic conditions and social, cultural, and economic perspectives of the

producers in developing countries cannot afford to apply it. Furthermore,

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil…*

suggests that lime should be applied frequently to neutralize acidity, which

the rate of N fertilization. Several management practices, such as legumenonlegume crop rotation, cover cropping, application of manures and compost, and integrated crop-livestock system, can reduce N fertilization rate without

affecting crop yields.

*DOI: http://dx.doi.org/10.5772/intechopen.86646*

**3. Conclusions**

producers.

**51**

*†Weed management practices are Chem., chemical where weeds were controlled with herbicide applications; Graz., grazing where weeds were controlled with sheep grazing; and Mech., mechanical where weeds were controlled with tillage.*

*‡Numbers followed by the same letter within a row in a set are not significantly different at P* ≤ *0.05.*

#### **Table 15.**

*Effect of weed management practice on soil nutrients, pH, and electrical conductivity (EC) at the 0–30 cm depth after 5 years of experiment initiation in western Montana, USA [49].*

return only a part of nutrients through urine and feces to the soil, while most of the crop residue grazed is used to increase the live weight of the animal. The choice of the management practice to reduce N fertilization rate to crops depends on soil and climatic conditions and social, cultural, and economic perspectives of the producers.

#### **2.5 Liming**

Soil acidification can be reduced by applying lime. However, lime is bulky and requires in large amount to neutralize soil acidity. The transportation cost to carry lime from manufactures to farms is also high and especially so in hilly regions

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

where roads are few or lacking. As a result, it is expensive to apply lime and most producers in developing countries cannot afford to apply it. Furthermore, neutralization of soil acidity with lime application is only temporary in nature. This suggests that lime should be applied frequently to neutralize acidity, which increases the cost of production. The best practice to reduce soil acidity is to reduce the rate of N fertilization. Several management practices, such as legumenonlegume crop rotation, cover cropping, application of manures and compost, and integrated crop-livestock system, can reduce N fertilization rate without affecting crop yields.

#### **3. Conclusions**

Degradation in soil and environmental quality can be mitigated, and crop yields can be sustained by reducing N fertilization rates and using novel management techniques that increase N cycling and N-use efficiency. These techniques include legume-nonlegume crop rotation, cover cropping, application of manures and compost, and integrated crop-livestock system. Soil acidity can be neutralized by lime application, but the effect is temporary. It is expensive to apply lime, and many producers in developing countries cannot afford to do so. Adaptation of these techniques to specific places depends on soil and climatic conditions and social, cultural, and economic perspectives of the producers.

return only a part of nutrients through urine and feces to the soil, while most of the crop residue grazed is used to increase the live weight of the animal. The choice of the management practice to reduce N fertilization rate to crops depends on soil and climatic conditions and social, cultural, and economic perspectives of

*†Weed management practices are Chem., chemical where weeds were controlled with herbicide applications; Graz., grazing where weeds were controlled with sheep grazing; and Mech., mechanical where weeds were controlled with*

*Effect of weed management practice on soil nutrients, pH, and electrical conductivity (EC) at the 0–30 cm*

*‡Numbers followed by the same letter within a row in a set are not significantly different at P* ≤ *0.05.*

*depth after 5 years of experiment initiation in western Montana, USA [49].*

**Chemical properties Soil depth Weed management (WM)†**

pH 0–5 cm 6.45a 6.94a 6.72a

) 0–5 cm 0.035a 0.037a 0.035a

) 0–5 cm 2.05a 2.06a 2.08a

) 0–5 cm 278a 288a 304a

) 0–5 cm 11.7a 12.5a 12.8a

) 0–5 cm 8.5ab 10.0a 7.4b

) 0–5 cm 34.5a‡ 35.7a 30.8a

) 0–5 cm 263a 271a 222b

**Chem. Mech. Graz.**

5–10 cm 30.4a 29.3a 17.8b 10–30 cm 81.2a 80.7a 40.1b

5–10 cm 176a 191a 139b 10–30 cm 792a 859a 577b

5–10 cm 6.31a 6.64a 6.51a 10–30 cm 7.06a 7.34a 7.31a

5–10 cm 0.024a 0.024a 0.024a 10–30 cm 0.025a 0.026a 0.27a

5–10 cm 2.14b 2.31a 2.25ab 10–30 cm 10.70b 11.70ab 12.90a

5–10 cm 362b 382ab 417a 10–30 cm 2619a 2593a 2640a

5–10 cm 15.2b 15.2b 18.4a 10–30 cm 84.8ab 76.6b 95.0a

5–10 cm 9.0ab 10.6a 7.1b 10–30 cm 34.0ab 40.8a 28.8b

Soil acidification can be reduced by applying lime. However, lime is bulky and requires in large amount to neutralize soil acidity. The transportation cost to carry lime from manufactures to farms is also high and especially so in hilly regions

the producers.

P content (kg ha1

*Nitrogen Fixation*

K content (kg ha1

EC (S m1

Ca content (Mg ha1

Mg content (kg ha1

Na content (kg ha1

SO4-S content (kg ha1

**2.5 Liming**

**50**

*tillage.*

**Table 15.**

#### **Author details**

Upendra M. Sainju1 \*, Rajan Ghimire2 and Gautam P. Pradhan3

1 Northern Plains Agricultural Research Laboratory, US Department of Agriculture, Agricultural Research Service, Sidney, Montana, USA

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2 Agricultural Science Center, New Mexico State University, Clovis, New Mexico, USA

3 Williston Research and Extension Center, North Dakota State University, Williston, North Dakota, USA

\*Address all correspondence to<EMAIL_ADDRESS>
© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Nitrogen Fertilization II: Management Practices to Sustain Crop Production and Soil… DOI: http://dx.doi.org/10.5772/intechopen.86646*

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**Author details**

*Nitrogen Fixation*

USA

**52**

Upendra M. Sainju1

Williston, North Dakota, USA

provided the original work is properly cited.

\*, Rajan Ghimire2 and Gautam P. Pradhan3

1 Northern Plains Agricultural Research Laboratory, US Department of Agriculture,

2 Agricultural Science Center, New Mexico State University, Clovis, New Mexico,

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

3 Williston Research and Extension Center, North Dakota State University,

Agricultural Research Service, Sidney, Montana, USA

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[36] Sainju UM, Whitehead WF, Singh BP. Biculture legume-cereal cover crops for enhanced biomass yield and carbon and nitrogen. Agronomy Journal. 2005; **97**:1403-1412

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**57**

**Chapter 4**

**Abstract**

**1. Introduction**

leaf area, and photosynthesis [2].

dry matter of the leaves [7, 8].

to obtain high yield.

Blackberry

*and Rogério Oliveira de Sousa*

Nitrogen Fertilization in

*Ivan dos Santos Pereira, Adilson Luis Bamberg,*

*Carlos Augusto Posser Silveira, Luis Eduardo Corrêa Antunes*

Nutrition studies for blackberry crop are scarce worldwide. This chapter presents several aspects of nitrogen (N) in blackberry (*Rubus* spp.) nutrition. Soil characteristics that can influence nitrogen fertilization are the large discrepancies in the rates recommended in the literature, forms and times of application, sources of nitrogen, differences between cultivars and the main symptoms of N deficiency. The impact of moderate and severe nitrogen deficiency on vegetative growth and yield of 'Tupy' blackberry is also presented. In addition, a nitrogen fertilization recommendation system is proposed, based on the organic matter content of the

soil, the age of the plants, and the expected productivity of the cultivars.

Nitrogen (N) is the mineral element that plants generally need in greater quantity, since they serve to form components of plant cells, such as amino acids and nucleic acids, besides participating in the chlorophyll molecule [1]. N deficiency rapidly reduces plant growth, as it causes reduction of cell division and expansion,

In blackberry (*Rubus* spp.), N is the most abundant element and plays a major role in its growth, development, and productivity [3–6]. The optimum leaf content required for a satisfactory performance of blackberry varies from 2.2 to 3.0% of the

The need for N supply may vary according to soil organic matter (SOM) content, yield, growth habit, age, and cultivar [8, 9]. The N rates recommended in the literature vary widely, mainly due to differences between cultivars and soil characteristics, but another important factor is the age of the plants. In the first years, the productive capacity of the plants is smaller, and therefore the demand for nitrogen is also lower. High N rates in the first 2 years can reduce fruit quality and increase disease incidence. On the other hand, low rates from the third year make it difficult

Nitrogen fertilization provides immediate effect (same season) and residual (next season). The immediate effect is mainly on the productive capacity of the

**Keywords:** *Rubus* spp., nutritional requirements, cultivar differences, nutritional deficiency, soil organic matter, fertilization recommendation

#### **Chapter 4**

[48] Niu Y, Li G, Li L, Chan KY, Oates A.

properties and pasture production in an

[49] Sainju UM, Lenssen AW, Goosey H, Snyder E, Hatfield P. Sheep grazing in the wheat-fallow system affects dryland soil properties and grain yield. Soil Science Society of America Journal.

[50] Sainju UM, Lenssen AW, Goosey H, Snyder E, Hatfield P. Dryland soil carbon and nitrogen influenced by sheep grazing in the wheat-fallow system. Agronomy Journal. 2010a;**102**:

Sheep camping influences soil

acidic soil of New South Wales, Australia. Canadian Journal of Soil

Science. 2009;**89**:235-244

*Nitrogen Fixation*

2011;**75**:1789-1798

1553-1561

**56**


*2.15. Statistical Analysis*

Statistical analysis was performed using Graph Prism 8 (GraphPad Software, San Diego, CA, USA). One-way ANOVA followed by Tukey's post-hoc test was carried out for the evaluation of size and zeta potential of the dispersed SEDDS. Two-way ANOVA followed by Tukey's test was performed to evaluate lipolysis data and in vitro data. Oneway ANOVA followed by Dunnett's post-hoc test was used, as the impact of the other lipids on the complex stability was evaluated as well, as in the case of the in vitro data. Data are presented as mean ± standard deviation (SD). Significant difference was considered at *p* < 0.05.