**3. Additional diagnostic techniques**

that an ideal surgery with perfect results in an unsatisfied patient is a big failure and is best

The human nose bears a complex physiologic and functional role in breathing and smelling. For this reason it is logically expected that this delicate organ be preserved and even improved during aesthetic surgery. This evaluation usually starts with verbal interview with the patient. Any breathing problems may be easily detected. Exacerbating factors or problems are usually best described by the patient, and then the evaluation continues with direct inspection of the nose. Any deviation or deformity should be observed and documented. To assess the septum and turbinates sufficient light and a nasal speculum are necessary. A few drops of a vasocon‐ strictor such as phenylephrine in each nostril may be applied for better visualization [4-7].The final step is to check the valve. The Cottle test is a known method to assess the internal nasal valve. The patient is asked to take a deep breath through the nose, and then inhalation is repeated while the patient is retracting his/her nasal side wall. If a considerable improvement occurs (positive Cottle test), this means a serious weakness exists in the internal nasal valve (Figure1). [8].It is clear that a reinforcement or total reconstruction of the internal valve should be considered in treatment planning. This test should be done on both sides and documented

To assess the external valves the patient is asked to tilt the head backward and take a deep. The nose is closely observed by the surgeon. This test may be documented by simple standard photography. Excessive medial movements of the nostrils and/or collapse means that some kind of reinforcement technique needs to be considered in the rhinoplasty procedure [9-10].

prevented in this preoperative phase [2-3].

750 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**2.2. Functional evaluation**

properly.

**Figure 1.** Cottle test.

**Water's view** radiograph is commonly used to evaluate the maxillary sinuses and nasal septum. In case a complex deformity or deviation is found, CT scan may help the surgeon better analyze the problem.

**Lateral nasal view** may help the surgeon measure the length and height of the bony vault though measurement, palpation and tactile sensation may easily provide the same data for the surgery.

CT scans are commonly used to assess internal compartments of the nose. Septal deformities and spicules are easily detected and documented. Nasal turbinates and paranasal sinuses are also clearly observed on CT scans. Nasal valve diameters are sometimes measured and documented as well.


**4. Conclusion**

In the first part of this chapter, the new coplanar antenna with cutouts on a circular patch demonstrate advantages: larger frequency spectrum, a good VSWR, improved parameter S11. The geometry of the patch was calculated and design with CST microwave studio. The antenna was design for UWB application more likely

**91**

**Author details**

Cadi Ayyad University, Marrakesh, Morocco

provided the original work is properly cited.

\*Address all correspondence to<EMAIL_ADDRESS>
© 2020 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,

Adnane Latif

*Design of a UWB Coplanar Fed Antenna and Circular Miniature Printed Antenna for Medical…*

the microwave imaging in the range from 3.1 GHz to 10.6 GHz. Moreover the antennas are smaller than traditional antennas, and as a coplanar it can be easy to implement. Also, enhancing gain will be a good improvement by making this antenna in

In the second part of this chapter, we proposed a miniature circular patch

The antenna network satisfies the imposed requirements satisfactorily and exhibits ultra broadband (ULB) behavior. In fact, the simulations under CST resulted in a reflection coefficient at −10 dB between 2.6 GHz and 10.7 GHz.

We have shown by this study that the dimensions and shape of the ground plane

Future work includes the fabrication of a prototype of the antenna, as well as measurements in anechoic chamber to verify the agreement between the measured

Due to the complexity of each human tissue, our antenna should be tested in different parts of the body to determine is the optimum distance of 20 mm is valid wherever the antenna is placed within the body. The implementation of an array of

*DOI: http://dx.doi.org/10.5772/intechopen.93205*

antenna intended for an application in medical imaging.

antennas will be also evaluated in future studies.

could have a significant impact on the bandwidth of the structure.

an array due to its small size.

and simulated results.

#### *Design of a UWB Coplanar Fed Antenna and Circular Miniature Printed Antenna for Medical… DOI: http://dx.doi.org/10.5772/intechopen.93205*

the microwave imaging in the range from 3.1 GHz to 10.6 GHz. Moreover the antennas are smaller than traditional antennas, and as a coplanar it can be easy to implement. Also, enhancing gain will be a good improvement by making this antenna in an array due to its small size.

In the second part of this chapter, we proposed a miniature circular patch antenna intended for an application in medical imaging.

The antenna network satisfies the imposed requirements satisfactorily and exhibits ultra broadband (ULB) behavior. In fact, the simulations under CST resulted in a reflection coefficient at −10 dB between 2.6 GHz and 10.7 GHz.

We have shown by this study that the dimensions and shape of the ground plane could have a significant impact on the bandwidth of the structure.

Future work includes the fabrication of a prototype of the antenna, as well as measurements in anechoic chamber to verify the agreement between the measured and simulated results.

Due to the complexity of each human tissue, our antenna should be tested in different parts of the body to determine is the optimum distance of 20 mm is valid wherever the antenna is placed within the body. The implementation of an array of antennas will be also evaluated in future studies.


**1. Introduction**

172 Textile Dyeing

[33] Y.-A. Son, G.-T. Lim, J.-P. Hong, and T.-K. Kim, "Indigo adsorption properties to

[34] D. Karst and Y. Yang, "An Explanantion and Prediction of disperse Dye Exhaustion on PLA," *Book of papers - International Conference & Exhibition, AATCC,* p. 184, 2004. [35] D. Karst and Y. Yang, "Using the Solubility Parameter to Explain Disperse Dye Sorption on Polylactide," *Journal of Applied Polymer Science,* vol. 96, p. 416, 2005. [36] R. F. Fedors, "A Method for Estimating Both the Solubility Parameters and Molar Volume of Liquids," *Polymer Engineering Science,* vol. 14, p. 147, 1974.

[37] *Colour Index, III edition* vol. 4: SDC and AATCC, 1971.

2005.

polyester fibers of different levels of fineness," *Dyes and Pigments,* vol. 65, p. 137,

The synthetic fibers are widely used in apparel and home furnishings due to their good physical and chemical properties. The synthetic fiber market is characterized by a trend towards ever-finer fibers. It is very difficult for these finer fibers to obtain very deep colours via the common dyeing processes. The increasing demand of polyester (PES) such as poly(ethylene terephthalate) (PET) in textile market for high performance applications in smart textiles, technical textiles, operation clothing etc. and more recently, for their potential applications as electronic textiles. It indicates that PET has the potential in research in the future due to the wide range of mechanical properties, relative high melting point and glass transition temperature, insensitivity to common solvents and moisture, chemical inertness. PET, an aliphatic-aromatic polymer composition and thermoplastic, shows a rather hydrophobic nature due to its rigid structure,

Fig. 1. Chemical structure of PET

The two carbonyl functions together with the aromatic ring provide the structural rigidity of the macromolecule; little flexibility arises due to the presence of the ethylene group in the repeating unit. The polar ester groups in the PET hold the PES into strong crystals. PET consists of a two-phase structure: crystalline (35 % in vol.) and non-crystalline (65 % in vol.). The most important phase in determining dyeability in the conventional dyeing process is the amorphous region. The PET becomes rubbery and swelling above its glass transition temperature. In this state the dye molecules are able to penetrate into the amorphous region and by cooling down the molecule can be trapped inside the PET macromolecules.

In recent years, consumers have shown an increasing preference for use of synthetic fibers blended with natural fibers to combine advantages of both materials. Due to the hydrophobic nature synthetics such as PES fibers are dyed at high temperatures around 130 °C and high pressure, this needs lot of energy and special equipment (Xu et al. 2002). Moreover, since polyesters are stronger than natural fibers, PES fabric blends containing wool, cotton etc. are very popular, since PES makes the fabrics more resilient and wrinkle free. Similar to PES, low priced polypropylene (PP) is frequently used in the technical

Substrate Independent Dyeing of Synthetic Textiles Treated with Low-Pressure Plasmas 175

Moreover, much research has also been done in the environmentally friendly dyeing of PET with disperse dyes in supercritical CO2 which has the advantage of reducing the need for additional chemicals and waste water (Okuno et al., 1992; Montero et al., 2003; Özcan et al., 2005). The scaling of the supercritical fluid dyeing experiment from laboratory size to industrial scale is far from being a straight-forward procedure because it requires very high pressures (260-300 bar) and high investment cost. At low pressure K/S value is decreased, which yields low dye solubility (Özcan et al., 2005). Moreover, conventional textile dyeing is dependent on the substrate materials due to their specific chemical nature. In a specific dyeing condition, dye molecules chemically and physically bind with the textile fibers and thus, the dyestuff class is also limited to the chemical groups present in the fiber due to dye-fiber interaction. For this reasons, substrate independent dyeing is of particular interest not only for textiles, but also for the materials industries where coloration is needed. Barranco et al. was adding dyestuff molecules downstream in a filmforming plasma in order to obtain dye molecule containing nanocomposite coatings (Barranco et al., 2006). There has been very little attention focused on the application of hydrophilic acid dyes on hydrophobic PET fabrics. Milling acid dyes, which have excellent color brightness and very good wet fastness, can easily be applied to plasmatreated polyester or their blends with natural fibers at low dyeing temperature of 80 °C within an hour dyeing time, where plasma modification is used as an alternative to the

While some efforts have been devoted to study dyeability of PES by plasma treatments, very few articles have been reported about the application of acid dyes to PES. In this research, an attempt was made to solve some limitations of PET dyeing using hydrophilic acid dye by modifying the surface with a novel nanoporous plasma polymer coating. Since the dyeing becomes independent from the substrate material, this approach enables the dyeing of all kinds of synthetic fibers or blend fabrics. Surface modification of fabrics induced by ammonia/acetylene and ammonia/ethylene plasmas was carried out in order to incorporate amine end-functional groups into the hydrocarbon plasma polymer and consequently, provide accessible functional groups for the diffusion of hydrophilic acid dye molecules into

Nitrogenated amorphous hydrocarbon films (a-C:H:N films) were deposited on PET fabrics by cold plasma using a pilot-plant plasma reactor. Tightly woven and washed polyethylene terephthalate (PET) fabric (76 ends/in, 76 picks/in, 43.5 g/m2) from Sefar AG (Switzerland) was used in this study. The deposited-hydrophilic a-C:H:N films were characterized by contact angles (CAs). The mechanical stability of the plasma coating was examined by Abrasion & Pilling Tester. Dyeing of the plasma coating was examined by Datacolor Spectraflash, and the results of dyeing were compared for both plasmas (ammonia/acetylene and ammonia/ethylene), while a study was investigated to observe the influences of energy input in terms of power input per unit of gas flow W/F (J/cm3),

A gas discharge allows the acceleration of free electrons when driven by an external source (e.g. RF generator). As a consequence, highly reactive and activated molecular species such as chemical radicals, ions, metastables, electrons etc. can be created by ionization, fragmentation (dissociation), excitation, UV radiation, etching reactions etc. These species

required pre-treatment of PET textiles (Hossain et al., 2007a).

the nanoporous structure of the plasma polymer.

film thickness, and gas ratio.

**2. Plasma treatments**

textiles, home textiles, the automobile industry and to lesser extent in apparel textiles due to their special characteristics such as resistance to chemicals, low density etc. The dyeing of PP is difficult and the fastness properties are not good due to the highly crystalline molecular structure. However, dyeing of PES blends is a problem due to damage/reduction in the strength of natural fibers (cellulose degradation etc.) at high dyeing temperatures. Due to the hydrophobic nature of PES, its compact structure and cristallinity dyeing is limited to water-insoluble dyes such as disperse dyes, vat dyes etc. (De Girogi et al., 2000). The low and finite water solubility of these dyes is also a critical factor in determining levelling properties and dyeing rate (Kulkarni et al., 1986). Conventional polyester dyeing processes additionally require dispersing agent, dye carriers, and surfactants to obtain dye solubility in water. Due to dye reduction and migration, the fastness to washing was found to be on the satisfactory level when dyeing with these dyes (Son et al., 2004). The rate of diffusion of these dyestuffs in the fiber is relatively low. Therefore, the rate of diffusion in the conventional PES dyeing commercially may be raised either by working at higher temperature in the region of 130 °C and/ or in the super atmospheric pressure in the presence of accelerating agent or carrier or surfactants or dyeing auxiliaries.

Recently, research on the use of different surface modification techniques such as low pressure plasma (LPP) and atmospheric pressure plasma (APP) in order to improve the dyeability of polyesters has grown in interest, since they are environmentally efficient. An increase in hydrophilicity and dyeability of knitted PES textiles after the plasma modification in an O2/CF4 mixture was obtained, as reported by Aubrecht et al. (2006). The dyeability with basic dye is enhanced on PET/cotton blends by in situ polymerization of acrylic acid and water (Öktem et al., 2002). Sarmadi et al., 1993 observed that the dyeability with basic dye (dye bath temperature 100 °C and 2 hours dyeing time) can further be improved by an increase in the time it is exposed to CF4 cold plasma, and found K/S values between 0.50-1.51 for a 2% owf (on the weight of fabric) dark shade dyeing with hydrophobic basic dye. A higher color yield was obtained on acrylic acid grafted PET fiber induced by Ar plasma. Barani et al. (2010) compared the dyeability of PES microfiber fabrics using various pre- and post-treatments. They reported that alkali, sol-gel and oxygen plasma treatments are able to enhance the color strength. Continuous modification of PES was carried out using DBD (dielectric barrier discharge) plasma at atmospheric pressure with a Ar/O2 ratio of 10:1 (Zhongfu et al., 2007). It was reported that the spectral value (K/S) dyed with blue disperse dyes was found to be increased by 50% in comparison with that of untreated samples due to the formation of –COOH groups during plasma treatment. The work of Ferrero et al. (2004) has shown that the fastness to washing with basic dye on PET by in situ polymerization of acrylic acid using low temperature plasma was found to be unsatisfactory probably because of an unstable bond between grafted acrylic acid and dye molecules. Anti-reflecting coating layers have been deposited with organo-silicon compounds using APP plasma, which enhanced the color intensity on PET surfaces as explained by Lee et al. (2001). Okuno et at. (1992) studied the correlation between the crystallinity and dyeability of PET fibers using non-film-forming gases by cold plasma. They found that plasma-treated samples significantly reduced the dyeability due to the etching of macromolecules in the dyeable amorphous phase. Recently, Addamo et al. (2006) reported that the color depth of air LPP plasma treated PET fibers is related to their topographical characteristics and to their chemical surface composition. They observed that the color strength with disperse dye at a dyeing temperature of 100 °C can be increased by decreasing the fraction of light reflected from the treated surfaces.

Moreover, much research has also been done in the environmentally friendly dyeing of PET with disperse dyes in supercritical CO2 which has the advantage of reducing the need for additional chemicals and waste water (Okuno et al., 1992; Montero et al., 2003; Özcan et al., 2005). The scaling of the supercritical fluid dyeing experiment from laboratory size to industrial scale is far from being a straight-forward procedure because it requires very high pressures (260-300 bar) and high investment cost. At low pressure K/S value is decreased, which yields low dye solubility (Özcan et al., 2005). Moreover, conventional textile dyeing is dependent on the substrate materials due to their specific chemical nature. In a specific dyeing condition, dye molecules chemically and physically bind with the textile fibers and thus, the dyestuff class is also limited to the chemical groups present in the fiber due to dye-fiber interaction. For this reasons, substrate independent dyeing is of particular interest not only for textiles, but also for the materials industries where coloration is needed. Barranco et al. was adding dyestuff molecules downstream in a filmforming plasma in order to obtain dye molecule containing nanocomposite coatings (Barranco et al., 2006). There has been very little attention focused on the application of hydrophilic acid dyes on hydrophobic PET fabrics. Milling acid dyes, which have excellent color brightness and very good wet fastness, can easily be applied to plasmatreated polyester or their blends with natural fibers at low dyeing temperature of 80 °C within an hour dyeing time, where plasma modification is used as an alternative to the required pre-treatment of PET textiles (Hossain et al., 2007a).

While some efforts have been devoted to study dyeability of PES by plasma treatments, very few articles have been reported about the application of acid dyes to PES. In this research, an attempt was made to solve some limitations of PET dyeing using hydrophilic acid dye by modifying the surface with a novel nanoporous plasma polymer coating. Since the dyeing becomes independent from the substrate material, this approach enables the dyeing of all kinds of synthetic fibers or blend fabrics. Surface modification of fabrics induced by ammonia/acetylene and ammonia/ethylene plasmas was carried out in order to incorporate amine end-functional groups into the hydrocarbon plasma polymer and consequently, provide accessible functional groups for the diffusion of hydrophilic acid dye molecules into the nanoporous structure of the plasma polymer.

Nitrogenated amorphous hydrocarbon films (a-C:H:N films) were deposited on PET fabrics by cold plasma using a pilot-plant plasma reactor. Tightly woven and washed polyethylene terephthalate (PET) fabric (76 ends/in, 76 picks/in, 43.5 g/m2) from Sefar AG (Switzerland) was used in this study. The deposited-hydrophilic a-C:H:N films were characterized by contact angles (CAs). The mechanical stability of the plasma coating was examined by Abrasion & Pilling Tester. Dyeing of the plasma coating was examined by Datacolor Spectraflash, and the results of dyeing were compared for both plasmas (ammonia/acetylene and ammonia/ethylene), while a study was investigated to observe the influences of energy input in terms of power input per unit of gas flow W/F (J/cm3), film thickness, and gas ratio.


In our study, the microorganisms in the soil and sludge acted together synergistically in the reduction process, i.e. N2O to N2, the denitrification process, and in the Texcoco soil under C2H2 conditions, but the main contribution was from the soil microorganisms under the same conditions. In particular, the production of N2 was almost 50% of the total gas evolved. When sterilized sludge was applied to the Texcoco soil, minimal N2 was produced (~0.2 mg N2O-N kg-1). Furthermore, untreated soil showed an increase in N2O when C2H2 was added (~0.07 mg N2O-N kg-1) and the N2 produced was approximately 75% of the total gas evolved, under the conditions established. In the Otumba soil, the N2O was produced by nitrification process (at 40% WHC), and showed in the soil treated with ammonium, sludge and sterilized sludge at 0.04, 1.0, and 1.0 mg N2O-N kg-1 respectively, when compared with untreated soil. N2O production was low when C2H2 was added to the Otumba soil, and no N2 was produced under these conditions. It can be established that when organic matter with a high N content is added to soil, it significantly increases N2O production compared to untreated soil or soil fertilized with ammonium [(NH4)2SO4] in both soils (an ordinary soil and an alkaline-saline soil). The major source of production of N2O was found in all treated soils to be as a result of the nitrification process, and the production of N2 was not recorded in the Otumba soil in this experiment. In the Texcoco soil, the major source of production of N2O was as a result of the denitrification process by microorganisms in the soil, and the production of N2 was approxi‐ mately 50% of the total gas evolved (1.1 mg N2O-N kg-1).

#### **4. Experiments under greenhouse conditions**

#### **4.1. First experiment under greenhouse conditions**

Subsequent studies were established in order to better understand plant growth and the production of GHG (CO2 and N2O) when a regular *Bacillus subtilis* strain was inoculated on the surface of the sunflower (*Helianthus annuus* L.) cultivar seeds under greenhouse conditions. The *B. subtilis* strain was characterized as PGPR, i.e. showing antagonistic activity against *Fusarium oxysporum* and *Rhizoctonia solani* AG1, phosphate solubilizing activity, 1-aminocy‐ clopropane-1-carboxilate deaminase, and indole-3-acetic acid production. The strain was found as regular PGPR, for more details see [6].

The soil was collected from Alcholoya (Acatlán, in the State of Hidalgo, Mexico). This soil is an agricultural soil with a pH of 6.5, electrolytic conductivity (EC) 0.7 dS m-1, 846 g kg-1, organic C content was 11.1 g C kg-1 soil, and total N content 1.0 g N kg-1 soil. The soil was sampled from three different plots (400 m2 ), ~ 800 kg was obtained and each plot was pooled separately and passed through a 5 mm sieve. Thirty-six sub-samples of 6.5 kg of soil from each plot were placed in cylindrical pots (Ø = 16 cm, 50 cm) with 7 cm of gravel in the bottom. Four treatments were applied, with nine pots for each of the three soil sites sampled (*n* = 27). The first treatment was unfertilized and uncultivated soil (used as the CONTROL treatment), the second treat‐ ment was unfertilized soil cultivated with sunflowers (SUNFLOWER treatment), the third treatment was soil cultivated with sunflowers and fertilized with 0.5 g urea (75 kg N ha-1, UREA treatment), and the fourth treatment was soil cultivated with sunflowers (seeds were dressed with *B. subtilis*) and fertilized with 0.5 g urea (BS treatment). All treatments were irrigated with tap water, with an additional input of 19 kg mineral-N ha-1 as NO2 - -N and NO3 - -N. In addition, twelve days after the emergence of the plantlets, they were fertilized with another 0.5 g of urea (the UREA and BS treatments), giving a total amount of 150 kg N ha-1; and three weeks after sowing the plantlets were drenched with 4 mL of a bacterial suspension (at the same concen‐ tration as described above) adjacent to the plantlet roots at a depth of 3 cm. From the beginning of the experiments and approximately every two days for the following 30 days, the pots were closed air-tight and their atmosphere was analysed for CO2 and N2O at times of 0, 3, 15 and 30 mins. The experiment was repeated twice [6].

40% WHC), and showed in the soil treated with ammonium, sludge and sterilized sludge at 0.04, 1.0, and 1.0 mg N2O-N kg-1 respectively, when compared with untreated soil. N2O production was low when C2H2 was added to the Otumba soil, and no N2 was produced under these conditions. It can be established that when organic matter with a high N content is added to soil, it significantly increases N2O production compared to untreated soil or soil fertilized with ammonium [(NH4)2SO4] in both soils (an ordinary soil and an alkaline-saline soil). The major source of production of N2O was found in all treated soils to be as a result of the nitrification process, and the production of N2 was not recorded in the Otumba soil in this experiment. In the Texcoco soil, the major source of production of N2O was as a result of the denitrification process by microorganisms in the soil, and the production of N2 was approxi‐

Subsequent studies were established in order to better understand plant growth and the production of GHG (CO2 and N2O) when a regular *Bacillus subtilis* strain was inoculated on the surface of the sunflower (*Helianthus annuus* L.) cultivar seeds under greenhouse conditions. The *B. subtilis* strain was characterized as PGPR, i.e. showing antagonistic activity against *Fusarium oxysporum* and *Rhizoctonia solani* AG1, phosphate solubilizing activity, 1-aminocy‐ clopropane-1-carboxilate deaminase, and indole-3-acetic acid production. The strain was

The soil was collected from Alcholoya (Acatlán, in the State of Hidalgo, Mexico). This soil is an agricultural soil with a pH of 6.5, electrolytic conductivity (EC) 0.7 dS m-1, 846 g kg-1, organic C content was 11.1 g C kg-1 soil, and total N content 1.0 g N kg-1 soil. The soil was sampled

and passed through a 5 mm sieve. Thirty-six sub-samples of 6.5 kg of soil from each plot were placed in cylindrical pots (Ø = 16 cm, 50 cm) with 7 cm of gravel in the bottom. Four treatments were applied, with nine pots for each of the three soil sites sampled (*n* = 27). The first treatment was unfertilized and uncultivated soil (used as the CONTROL treatment), the second treat‐ ment was unfertilized soil cultivated with sunflowers (SUNFLOWER treatment), the third treatment was soil cultivated with sunflowers and fertilized with 0.5 g urea (75 kg N ha-1, UREA treatment), and the fourth treatment was soil cultivated with sunflowers (seeds were dressed with *B. subtilis*) and fertilized with 0.5 g urea (BS treatment). All treatments were irrigated with

twelve days after the emergence of the plantlets, they were fertilized with another 0.5 g of urea (the UREA and BS treatments), giving a total amount of 150 kg N ha-1; and three weeks after sowing the plantlets were drenched with 4 mL of a bacterial suspension (at the same concen‐ tration as described above) adjacent to the plantlet roots at a depth of 3 cm. From the beginning of the experiments and approximately every two days for the following 30 days, the pots were

), ~ 800 kg was obtained and each plot was pooled separately

mately 50% of the total gas evolved (1.1 mg N2O-N kg-1).

**4. Experiments under greenhouse conditions**

**4.1. First experiment under greenhouse conditions**

found as regular PGPR, for more details see [6].

tap water, with an additional input of 19 kg mineral-N ha-1 as NO2

from three different plots (400 m2

214 Greenhouse Gases

The daily CO2 production rate for some treatments was large at the beginning of the experi‐ ments (data not shown). The daily CO2 production rate showed a drop, remaining < 5 mg C kg-1 day-1 on day 2 and after that it remained at < 8 mg C kg-1 day-1 for all treatments up to end of the experiments. The mean CO2 production rate was not significantly different between treatments. The daily N2O production rate remained ≤ 0.75 µg N kg-1 day-1 for the SUNFLOW‐ ER and CONTROL treatments. Meanwhile, in the BS and UREA treatments, the daily N2O production rate remained ≤ 2.1 µg N kg-1 day-1 with a maximum score of production in the first 14 days. The mean of the N2O production rate of BS treatment was significantly high when compared with the SUNFLOWER and CONTROL treatments. Cultivating soil with sunflow‐ ers (SUNFLOWER treatment) did not affect the production of CO2 compared with the CONTROL treatment (uncultivated soil). It is well known that cultivated soil frequently increases the production of CO2, possibly due to the activities of the microorganisms degrading the easily decomposable organic matter such as the dying roots and root exudates in the rhizosphere, thereby increasing the production of CO2 from the soil. Soils cultivated with sunflowers and fertilized with urea did not affect the production of CO2. Applying urea to soil commonly has no effect on the production of CO2 from soils. However, the production of CO2 might be stimulated when urea is applied to N depleted soil as reported in Phillips and Podrebarac (2009), where the CO2 production was tripled when 112 kg urea-N kg-1 was applied to an arable soil. Increases in CO2 production with several doses of urea-N application indicate that agronomic-scale N inputs might stimulate microbial carbon cycling in arable soils [7]. The inoculation of *B. subtilis* on sunflower roots in soils fertilized with urea did not show any effect on the production of CO2 compared with the UREA treatment. The application of UREA to the soil resulted in more than a doubling of the mean N2O production rate when compared with the CONTROL treatment. The production of N2O and NO in the soil is the result of factors such as ion concentrations and soil conditions under chemical disequilibrium, i.e. the oxidative process of NH4 + to NO3 under aerobic conditions, nitrification, and a reductive process of NO3 to N2 under anaerobic conditions, and denitrification or the nitrifier denitrification [5, 8, 9]. According to the IPCC, N2O is the main gas produced and released to the atmosphere by soil microorganisms [9]. So, when urea is applied into the soil, hydrolysis of the urea is immediately started, releasing NH4 + into the soil, which is rapidly transformed to NO3 with the simultaneous production of N2O by the same process. A high concentration of NO3 in soil favours the production of N2O due to the presence of anaerobic micro-sites in highly com‐ pacted soil.

A principal component analysis (PCA) was undertaken to investigate several plant biometric parameters and soil properties in the production of N2O and CO2. The analysis was carried out to include all variables. The PCA revealed that BS treatment has an effect on the shoots of plants, i.e. the shoot length, dry weight of shoot, and the fresh weight of shoot. UREA treatment has an effect on roots, i.e. the dry weight of roots, length of roots, and fresh weight of roots, and a minimal effect on seed weight. Otherwise, the soil properties PCA showed that both the BS and UREA treatments had an effect on NO3 and EC at depths of 0-15 cm and 15-30 cm. The BS treatment also has effect on the production of N2O and the UREA treatment has an effect on NH4 + at a depth 0-15 cm and a slight effect on CO2 production. These results were found to correspond with a production rate of N2O that was ≤ 2.1 µg N kg-1 day-1 with a maximum production in the first 14 days of more than that in the UREA treatment (< 1.5 µg N kg-1 day-1). Additionally, the PCA showed that *B. subtilis*, as a regular strain, had a marked effect on the production of N2O but not on CO2 production. This strain might be involved in nitrifier denitrification (or aerobic nitrification-denitrification) as was reported by Kim et al. [10] and Yang et al. [11]. Both research groups demonstrated that the *Bacillus* genus is involved in nitrification and denitrification, namely *B. subtilis*, *B. cereus* and *B. licheniformis*, where *B. subtilis* is involved in the nitrification process and *B. licheniformis* is involved in denitrification or aerobic denitrification [10]. Yang et al. reported that the strain of *Bacillus subtilis* A1 is an aerobic heterotrophic nitrifying–denitrifying bacterium, which is able to convert NH4 + to N2 under fully aerobic conditions, while growing either autotrophically or heterotrophically [11]. In our experiment, the environmental condition of the soil was aerobic throughout the experiment, so it could be hypothesized that the *B. subtilis* strain could be involved in the nitrification process or the nitrifier denitrification process (or aerobic denitrification).

#### **4.2. Second experiment under greenhouse conditions**

The second experiment was carried out using wastewater sludge as an organic fertilizer. It tested the effect of the sludge or urea on sunflower growth, and the effect of some soil properties on the production of CO2 and N2O. The plant characteristics were also evaluated. Wastewater sludge or sewage sludge is generated during wastewater treatment and is an unavoidable by-product. However, the sludge can be seen as an invaluable by-product when it is applied to the soil as stabilized sludge. Also, this waste management is the most economical form of disposal employed to reduce the large amount of sewage sludge. In addition, waste‐ water sludge is organic matter rich in minerals and is an outstanding source of C and N, *inter alia*. Applying sludge to the soil offers the opportunity of recycling nutrients for use by plants, while at the same time returning C as organic matter to the soil in order to improve agriculture processes.

This experiment was carried out in the same way as the previous experiment (described above). The wastewater sludge was collected from the Reciclagua treatment plant, S.A. de C.V., where wastewater from various industries (including the food industry) and households is treated. The properties of the sewage sludge were pH 8.1, EC 7.9 dS m-1, water content 847 g kg-1, organic C content 288 g kg-1, total N content 41.8 g kg-1, NH4 + 13 g N kg-1, NO2 - 8.3 mg N kg-1, and NO3 - 122 mg N kg-1. For more details of these, see [12]. Four treatments were established in cylindrical pots, comprising nine soil samples from three sampled plots (*n* = 27). The treatments were: i) unfertilized and unsown soil (CONTROL treatment), ii) unfertilized soil cultivated with sunflowers (SUNFLOWER treatment), iii) cultivated soil fertilized with 0.5 g urea (0.5 g urea × 2 applications, equivalent to 150 kg N ha-1, UREA treatment), and iv) soil cultivated and fertilized with 30 g sludge (SLUDGE treatment). The sludge was added so as to be equivalent to 150 kg N ha-1, assuming that sludge mineralisation was 40% mineral N during the crop cycle. Tap water supplied a total amount of 19 kg mineral-N ha-1 through irrigation in all treatments and throughout the experiment. In order to measure the production of gases, the pots were closed airtight approximately every two days for the first 30 days, and their atmospheres were analysed for CO2 and N2O at sequential times of 0, 3, 15 and 30 mins. The experiment was replicated twice [12].

BS treatment also has effect on the production of N2O and the UREA treatment has an effect

correspond with a production rate of N2O that was ≤ 2.1 µg N kg-1 day-1 with a maximum production in the first 14 days of more than that in the UREA treatment (< 1.5 µg N kg-1 day-1). Additionally, the PCA showed that *B. subtilis*, as a regular strain, had a marked effect on the production of N2O but not on CO2 production. This strain might be involved in nitrifier denitrification (or aerobic nitrification-denitrification) as was reported by Kim et al. [10] and Yang et al. [11]. Both research groups demonstrated that the *Bacillus* genus is involved in nitrification and denitrification, namely *B. subtilis*, *B. cereus* and *B. licheniformis*, where *B. subtilis* is involved in the nitrification process and *B. licheniformis* is involved in denitrification or aerobic denitrification [10]. Yang et al. reported that the strain of *Bacillus subtilis* A1 is an aerobic heterotrophic nitrifying–denitrifying bacterium, which is able to convert NH4

under fully aerobic conditions, while growing either autotrophically or heterotrophically [11]. In our experiment, the environmental condition of the soil was aerobic throughout the experiment, so it could be hypothesized that the *B. subtilis* strain could be involved in the

The second experiment was carried out using wastewater sludge as an organic fertilizer. It tested the effect of the sludge or urea on sunflower growth, and the effect of some soil properties on the production of CO2 and N2O. The plant characteristics were also evaluated. Wastewater sludge or sewage sludge is generated during wastewater treatment and is an unavoidable by-product. However, the sludge can be seen as an invaluable by-product when it is applied to the soil as stabilized sludge. Also, this waste management is the most economical form of disposal employed to reduce the large amount of sewage sludge. In addition, waste‐ water sludge is organic matter rich in minerals and is an outstanding source of C and N, *inter alia*. Applying sludge to the soil offers the opportunity of recycling nutrients for use by plants, while at the same time returning C as organic matter to the soil in order to improve agriculture

This experiment was carried out in the same way as the previous experiment (described above). The wastewater sludge was collected from the Reciclagua treatment plant, S.A. de C.V., where wastewater from various industries (including the food industry) and households is treated. The properties of the sewage sludge were pH 8.1, EC 7.9 dS m-1, water content 847 g kg-1, organic

 122 mg N kg-1. For more details of these, see [12]. Four treatments were established in cylindrical pots, comprising nine soil samples from three sampled plots (*n* = 27). The treatments were: i) unfertilized and unsown soil (CONTROL treatment), ii) unfertilized soil cultivated with sunflowers (SUNFLOWER treatment), iii) cultivated soil fertilized with 0.5 g urea (0.5 g urea × 2 applications, equivalent to 150 kg N ha-1, UREA treatment), and iv) soil cultivated and fertilized with 30 g sludge (SLUDGE treatment). The sludge was added so as to be equivalent to 150 kg N ha-1, assuming that sludge mineralisation was 40% mineral N during the crop cycle. Tap water supplied a total amount of 19 kg mineral-N ha-1 through irrigation in all treatments

+

13 g N kg-1, NO2

nitrification process or the nitrifier denitrification process (or aerobic denitrification).

**4.2. Second experiment under greenhouse conditions**

C content 288 g kg-1, total N content 41.8 g kg-1, NH4

+ at a depth 0-15 cm and a slight effect on CO2 production. These results were found to

+ to N2

on NH4

216 Greenhouse Gases

processes.

NO3 - The results showed that the CONTROL, SUNFLOWER and UREA treatments were not significantly different with respect to the production rate of CO2 (1.59, 2.03 and 2.6 mg C kg-1 day-1, respectively) (Table 1). The CO2 production rate of sunflowers cultivated in soil fertilized with sewage sludge (SLUDGE treatment) was 2.96 mg C kg-1 day-1 and was significantly different compared with the CONTROL treatment. In other words, soil cultivated and fertilized with sewage sludge was equivalent to both the soil cultivated and fertilized with urea, and the unfertilized soil. It should be taken in account that several factors affect CO2 production in the soil, such as rhizosphere respiration and soil microbial respiration, soil moisture, soil temperature, substrate quantity and quality, vegetation type, and land use and management regimes [13].

**Table 1.** The production rates of CO2 and N2O from soil cultivated with *H. annuus* under greenhouse conditions.

On the other hand, the rate of production N2O was significantly different in cultivated soil fertilized with sludge, 2.5 µg N kg-1 day-1 compared with the remaining treatments, 0.7, 0.3, and 0.2 µg N kg-1 day-1 for the UREA, SUNFLOWER, and CONTROL treatments respectively. As previously discussed, wastewater sludge is an organic matter which is rich in easily decomposable material. In addition, it has been demonstrated that microorganisms from the sludge plus those from the soil work together synergistically to accelerate the decomposition of organic matter [6]. The high levels of microbial activity stimulated by the addition of material with high C and N contents could increase the production of both CO2 and N2O. According to Kool et al. [9], the loss of N in our experiment might primarily be as a result of the nitrifier nitrification process (from ammonium oxidation) followed by the nitrifier denitrification process. As a result, the wastewater sludge had a NH4 + concentration of 13 g N kg-1, an amount of ammonium which might not be oxidized to N2O so rapidly. The chemical composition of organic or mineral fertilizers — or even residues applied to the soil — is an important factor in regulating the magnitude of N2O production.

A PCA was performed on all relevant properties of the soil. The first principal component explained about 22% of the observed variation, while the second accounted for 17% of the observed variation. On the related scatter plot, the UREA treatment lies in upper right quadrant and the SLUDGE treatment is in the upper left quadrant. The SUNFLOWER and CONTROL treatments were found in lower left and right quadrants respectively (Figure 1).

**Figure 1.** Results of a principal component analysis (PCA) performed on soil properties under greenhouse conditions (*n* = 27).

The UREA treatment seems to have an effect on the pH of soil at both depths (0–15 and 15–30 cm) and also affects the production of CO2 and N2O. The PCA also revealed that the SLUDGE treatment affected EC at a depth of 0–15 cm and had a slight effect on both ammonium and nitrate concentrations at both depths.

#### **4.3. Third experiment under greenhouse conditions**

In this study, the effect of urea, wastewater sludge and vermicomposting on the production of CO2 and N2O was investigated. The Otumba soil (State of Mexico, Mexico), which was characterized as a sandy loam with pH 7.6, EC 1.15 dS m-1, and an organic C content of 7.2 g C kg-1, was used in this study. Wastewater sludge was again collected from Reciclagua S.A. de C.V. (as described above). The vermicompost was prepared with wastewater sludge from Reciclagua and *Eisenia fetida*. The vermicompost was obtained from a mixture of sludge (1,800 g) and manure (800 g) with 70% water content, and was added to 40 individuals of *E. fetida* with the mixture being conditioned over three months. The properties of the vermicompost were pH 7.9, EC 11 dS m-1, organic C content 163 g kg-1, and a total N content of 2 g kg-1. As

well, the vermicompost presented < 3 CFU g-1 *Salmonella* sp., no *Shigella* sp., and no helminth ova.

A PCA was performed on all relevant properties of the soil. The first principal component explained about 22% of the observed variation, while the second accounted for 17% of the observed variation. On the related scatter plot, the UREA treatment lies in upper right quadrant and the SLUDGE treatment is in the upper left quadrant. The SUNFLOWER and CONTROL treatments were found in lower left and right quadrants respectively (Figure 1).

SLUDGE

UREA

pH, 15-30 cm pH, 0-15 cm

CONTROL

*Factor 2: 17%*

, 15-30 cm Production of CO2

EC, 0-15 cm EC, 15-30 cm

+, 15-30 cm Production of N2O

**Figure 1.** Results of a principal component analysis (PCA) performed on soil properties under greenhouse conditions

The UREA treatment seems to have an effect on the pH of soil at both depths (0–15 and 15–30 cm) and also affects the production of CO2 and N2O. The PCA also revealed that the SLUDGE treatment affected EC at a depth of 0–15 cm and had a slight effect on both ammonium and

In this study, the effect of urea, wastewater sludge and vermicomposting on the production of CO2 and N2O was investigated. The Otumba soil (State of Mexico, Mexico), which was characterized as a sandy loam with pH 7.6, EC 1.15 dS m-1, and an organic C content of 7.2 g C kg-1, was used in this study. Wastewater sludge was again collected from Reciclagua S.A. de C.V. (as described above). The vermicompost was prepared with wastewater sludge from Reciclagua and *Eisenia fetida*. The vermicompost was obtained from a mixture of sludge (1,800 g) and manure (800 g) with 70% water content, and was added to 40 individuals of *E. fetida* with the mixture being conditioned over three months. The properties of the vermicompost were pH 7.9, EC 11 dS m-1, organic C content 163 g kg-1, and a total N content of 2 g kg-1. As

NO2 - , 0-15 cm

SUNFLOWER

(*n* = 27).

218 Greenhouse Gases

*Factor 1: 22%*

nitrate concentrations at both depths.

**4.3. Third experiment under greenhouse conditions**

NO3 - , 15-30 cm

NH4 +, 0-15 cm

NH4

NO2 -

NO3 - , 0-15 cm Forty-five sub-samples of 3.25 kg soil were prepared, i.e. three soil samples, three replicates, and five treatments were established. The treatments were: i) soil fertilized with 0.07 g urea kg-1, (UREA treatment), ii) soil fertilized with 21.2 g sewage sludge kg-1 (H-SLUDGE treat‐ ment), iii) soil fertilized with 12.8 g sewage sludge kg-1 (L-SLUDGE treatment), iv) soil fertilized with 81.5 g vermicompost kg-1 (VERMI treatment), and v) unfertilized soil (CONTROL treatment). The amount of urea was 80 kg N ha-1 for the UREA, H-SLUDGE, and VERMI treatments, while the L-SLUDGE treatment was 48 kg N ha-1. The production of CO2 and N2O was analysed every two days at 0, 3, 15 and 30 mins, until day 97. The cultivar of common bean used was Negro-8025 (from Universidad Autónoma Chapingo, Texcoco, State of Mexico). Tap water was used for irrigation at a rate of 500 mL every seven days. The experiments were triplicated and ran for 117 days in total.

A large amount of CO2 was recorded at the end the experiment (from day 45 until day 82). The UREA treatment had no significant effect on CO2 production when compared with the CONTROL treatment (0.043 mg C kg-1 dry soil). Wastewater sludge was found to increase the mean production of CO2 in the soil at 0.064 mg C kg-1 compared with the untreated soil, and the VERMI treatment showed the largest mean CO2 production at 0.1 mg C kg-1. Urea had no significant effect on CO2 production when compared with the CONTROL treatment. Occa‐ sionally, urea might stimulate the production of CO2 in N depleted soils. Wastewater sludge increased CO2 production through the mineralization of organic C and the increasing of microbial activity in the rhizosphere. Similarly, vermicomposting stimulated plant growth and increased root exudates and microbial activity in the rhizosphere. The high levels of CO2 produced towards the end of the experiments could be related to rapid root growth and the beginning of root decomposition. For example, common bean plants at 49 days after sowing (flowering and nodule senescence begins) showed a decrease in the number of nodules, and their nodule cell walls slowly became thinner and degraded [14] thereby improving the environment for the growth of microorganisms and increasing the production of CO2 towards the end of the experiments.

The mean production of N2O was -0.004 µg N kg-1 in the CONTROL treatment. Soil fertilized with urea increased the mean production of N2O to 0.015 µg N kg-1. Wastewater sludge increased the mean production to 0.11 µg N kg-1 and 0.58 µg N kg-1 in the L-SLUDGE and H-SLUDGE treatments respectively, and the vermicompost mean was 0.32 µg N kg-1 dry soil. N2O production in order of effect size of treatment was: wastewater sludge (H-SLUDGE) > vermicomposting > wastewater sludge (L-SLUDGE) > urea > unfertilized soil. Nitrifier nitrification and nitrifier denitrification were presumably the processes that contributed the most to the production of N2O under aerobic conditions.

#### **4.4. Fourth experiment under greenhouse conditions**

Juárez-Rodríguez et al. applied the sludge derived from anaerobically digested cow manure in the production of biogas (methane-air), to maize (*Zea mays* L.) cultivated in a nutrient-low, alkaline-saline soil with EC 9.4 dS m−1 and pH of 9.3. The results showed that the CO2 production increased 3.5-fold in the soil cultivated with maize and sludge, and increased 3.1 fold after the sludge was added to the soil. The production of CO2 from soil cultivated with maize showed a 1.6-fold increase compared with the uncultivated and unfertilized soil, 1.5 mg C kg−1 day−1. N2O production was -0.0004 µg N kg−1 soil day−1 in unfertilized soil, and in soil cultivated with maize was 0.3 µg N kg−1 day−1. Soil treated with sludge increased the produc‐ tion of N2O up to 4.6 µg N kg−1 soil day−1. Nevertheless, it was found that cultivated soil produced 2.4 µg N kg−1 soil day−1, reducing N2O production. It was also found that applying the anaerobically digested cow manure stimulated the growth of maize cultivated in an alkaline and saline soil, and the production of CO2 and N2O was increased.

#### **4.5. Fifth experiment under greenhouse conditions**

In this study, the main aim was to investigate how maize fertilized with wastewater at 120 kg N ha−1 affected crop growth, soil properties and the production of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) compared with plants fertilized with urea [16].

The soil was collected from the Mezquital Valley, located near Pachuca in the State of Hidalgo (Mexico). The irrigation water used was slightly alkaline with a pH of 8.4. The experiment was carried out under greenhouse conditions. Soil collected from three sub sites was placed into cylindrical pots. Five treatments were established in order to study the effect of wastewater and urea on the cultivation of maize (*Zea mays* L.). The treatments were: a) SMWW, maize plant plus wastewater; b) SMUREA, maize plant plus urea as fertilizer; c) SUREA, uncultivated soil and urea as fertilizer; d) SWW, uncultivated soil plus wastewater; and e) SCONTROL treatment, soil plus tap water. Soils from the SMWW and SWW treatments were irrigated with 1000 mL of wastewater every 7 days from the first day onwards, making a total of 13 times overall. This means that a total amount of mineral N equivalent to 120 kg N ha−1 was added to each maize plant, i.e. the recommended amount of N fertilizer for maize.

The concentration of NH4 + was larger in the soil treated with urea and wastewater than in the untreated soil, as the urea was hydrolysed and the wastewater contained high concentrations of NH4 + . The addition of wastewater to the soil doubled the production of CO2 and approxi‐ mately 0.2 g C was produced from the soil due to the decomposition of the wastewater after 70 days. In other words, 34% wastewater C was mineralized. However, urea may only occasionally stimulate CO2 production when a soil is N depleted. Plants take CO2 from the atmosphere, but mineralization of root exudates increases the production of CO2. The pro‐ duction of CO2 increased towards the end of the period of maize growth. This indicated that the phenological stage of the plants affected CO2 production. The growth of maize plants was similar under the SMWW (wastewater) and the SMUREA (urea) treatments, even when the release of nutrients was delayed by mineralisation from the organic matter in the wastewater. When wastewater was applied to the soil, the mean production rate of CO2 increased signifi‐ cantly at 2.4-fold, 1.7 µg C kg−1 h−1, compared with the SCONTROL treatment at 0.7 µg C kg−1 h−1 (Table 2). Meanwhile, cultivating maize increased CO2 production 3.2-fold, 5.6 µg C kg−1 h −1. The SWW, SMWW or SUREA treatments did not show a significant difference in the production of N2O compared with the SCONTROL (1.5×10−3 µg N kg−1 h−1). The addition of urea did not affect the CH4 oxidation rate (0.1×10−3 µg C kg−1 h−1), nor did the SMUREA treatment (cultivated soil fertilized with urea), but the addition of wastewater to the soil significantly increased CH4 production to 128.4×10−3 µg C kg−1 h−1. Soil irrigated with waste‐ water increased the global warming potential (GWP) up to 2.5-fold compared with the SUREA treatment (soil plus urea), whereas cultivated soil increased the GWP 1.4-fold. Crops irrigated with wastewater might limit the use of N fertilizer and water from aquifers. Nevertheless, the amount of fertilizer applied must be limited due to nitrate (NO3 - ) leaching and the production of CO2, N2O and CH4 – that they could be produced in significant amounts –, and at the same time the salt content of the soil will accumulate, limiting the growth of the crop.

production increased 3.5-fold in the soil cultivated with maize and sludge, and increased 3.1 fold after the sludge was added to the soil. The production of CO2 from soil cultivated with maize showed a 1.6-fold increase compared with the uncultivated and unfertilized soil, 1.5 mg C kg−1 day−1. N2O production was -0.0004 µg N kg−1 soil day−1 in unfertilized soil, and in soil cultivated with maize was 0.3 µg N kg−1 day−1. Soil treated with sludge increased the produc‐ tion of N2O up to 4.6 µg N kg−1 soil day−1. Nevertheless, it was found that cultivated soil produced 2.4 µg N kg−1 soil day−1, reducing N2O production. It was also found that applying the anaerobically digested cow manure stimulated the growth of maize cultivated in an

In this study, the main aim was to investigate how maize fertilized with wastewater at 120 kg N ha−1 affected crop growth, soil properties and the production of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) compared with plants fertilized with urea [16].

The soil was collected from the Mezquital Valley, located near Pachuca in the State of Hidalgo (Mexico). The irrigation water used was slightly alkaline with a pH of 8.4. The experiment was carried out under greenhouse conditions. Soil collected from three sub sites was placed into cylindrical pots. Five treatments were established in order to study the effect of wastewater and urea on the cultivation of maize (*Zea mays* L.). The treatments were: a) SMWW, maize plant plus wastewater; b) SMUREA, maize plant plus urea as fertilizer; c) SUREA, uncultivated soil and urea as fertilizer; d) SWW, uncultivated soil plus wastewater; and e) SCONTROL treatment, soil plus tap water. Soils from the SMWW and SWW treatments were irrigated with 1000 mL of wastewater every 7 days from the first day onwards, making a total of 13 times overall. This means that a total amount of mineral N equivalent to 120 kg N ha−1 was added to

untreated soil, as the urea was hydrolysed and the wastewater contained high concentrations

mately 0.2 g C was produced from the soil due to the decomposition of the wastewater after 70 days. In other words, 34% wastewater C was mineralized. However, urea may only occasionally stimulate CO2 production when a soil is N depleted. Plants take CO2 from the atmosphere, but mineralization of root exudates increases the production of CO2. The pro‐ duction of CO2 increased towards the end of the period of maize growth. This indicated that the phenological stage of the plants affected CO2 production. The growth of maize plants was similar under the SMWW (wastewater) and the SMUREA (urea) treatments, even when the release of nutrients was delayed by mineralisation from the organic matter in the wastewater. When wastewater was applied to the soil, the mean production rate of CO2 increased signifi‐ cantly at 2.4-fold, 1.7 µg C kg−1 h−1, compared with the SCONTROL treatment at 0.7 µg C kg−1 h−1 (Table 2). Meanwhile, cultivating maize increased CO2 production 3.2-fold, 5.6 µg C kg−1 h −1. The SWW, SMWW or SUREA treatments did not show a significant difference in the production of N2O compared with the SCONTROL (1.5×10−3 µg N kg−1 h−1). The addition of urea did not affect the CH4 oxidation rate (0.1×10−3 µg C kg−1 h−1), nor did the SMUREA

. The addition of wastewater to the soil doubled the production of CO2 and approxi‐

+ was larger in the soil treated with urea and wastewater than in the

alkaline and saline soil, and the production of CO2 and N2O was increased.

each maize plant, i.e. the recommended amount of N fertilizer for maize.

**4.5. Fifth experiment under greenhouse conditions**

The concentration of NH4

of NH4 +

220 Greenhouse Gases

Soils can be either a net sink or a net source of CH4, depending on several factors such as the moisture level, N level, and the nature of the ecosystem in question. Methane is used up by methanotrophic microorganisms, which are ubiquitous in several soils, and is produced by methanogenic microorganisms in the soil under anaerobic conditions. Agricultural systems are not normally large sources or sinks of CH4. Only under certain conditions are they sources of CH4 — after application of manure or other organic materials, or moderate to high levels of irrigation. Our results showed that soil irrigated with wastewater — with or without maize increased CH4 production significantly (SMWW and SWW treatments) particularly after irrigation, due to temporary anaerobic conditions.

a The global warming potential (GWP) of the gases produced was calculated considering CO2 production equivalent to 310 for N2O, 21 for CH4 and 1 for CO2 (IPCC, 2007) over a 90-day period, minus the C that was stored in the roots per kg soil.

b Values with the same letter show no significant difference between treatments (*P* < 0.05).

**Table 2.** Production of greenhouse gases, CO2, CH4 (µg C kg−1 soil h−1), and N2O (µg N kg−1 soil h−1) from five treatments: a) soil + plant + wastewater (SMWW), b) soil + plant + urea (SMUREA), c) soil + urea (SUREA), d) soil + wastewater (SWW), and e) soil + water (SCONTROL).

Fertilizing maize with urea or wastewater had a similar effect on plant growth, so wastewater might be useable as a crop fertilizer. The treatments with urea or wastewater had no effect on the pH of soil in this experiment due to the fact that the soil is a vertisol, characterized by a clay type 2:1, with a large capacity for the exchange of protons and consequently, a high buffering capacity. The addition of wastewater increased the production of both CO2 and CH4 compared with the soil treated with urea, but did not increase the production of N2O. The irrigation of crops with wastewater might in the long term be a far more environmentally friendly approach to that of using water from aquifers that take long periods of time to fill, as long as the amount of wastewater applied is restricted to the amount required by the cultivated crop due to possible substantial losses of mineral N through several process such as the production of CO2, CH4 and N2O, and the fact that soil salinization could increase rapidly.

#### **5. Conclusions**

The organic fertilizers or treatments (vermicompost, wastewater sludge, anaerobically digested cow manure, and wastewater) might increase the production of greenhouse gases, as do several abiotic and biotic factors involved in microbial activity within the soil. Sludge as a soil fertilizer offers the opportunity for the recycling of plants nutrients and the recovery of C as organic matter and its use in soil to improve agriculture. The high levels of microbial activity stimulated by the addition of this high C and N content material could increase both CO2 and N2O production. It should be taken in account that several factors are involved in the production of gases in the soil such as rhizosphere respiration, vegetation type, and soil microbial respiration, as well as abiotic factors such as soil moisture, soil temperature, substrate quantity and quality, and land use and management regimes.

Environmental and economic implications must be considered in order to make well-informed decisions on the management of soil treatments, i.e. how many, how often and what kind of organic fertilizer should be used in order to improve crop production and simultaneously limit soil deterioration and greenhouse gases production.

### **Acknowledgements**

We would like to thank the Instituto Politécnico Nacional and CONACyT for their financial support and the grant-aided support received.

#### **Author details**

Fernando López-Valdez 1\*, Fabián Fernández-Luqueño 2 , Carolina Pérez-Morales 1 and Mariana Miranda-Arámbula1

\*Address all correspondence to<EMAIL_ADDRESS>
1 Agricultural Biotechnology Group, Research Centre for Applied Biotechnology, Instituto Politécnico Nacional, Tlaxcala, Mexico

2 Sustainability of Natural Resources and Energy Program, Cinvestav-Saltillo, Saltillo, C.P. Coahuila, Mexico

#### **References**

friendly approach to that of using water from aquifers that take long periods of time to fill, as long as the amount of wastewater applied is restricted to the amount required by the cultivated crop due to possible substantial losses of mineral N through several process such as the production of CO2, CH4 and N2O, and the fact that soil salinization could increase rapidly.

The organic fertilizers or treatments (vermicompost, wastewater sludge, anaerobically digested cow manure, and wastewater) might increase the production of greenhouse gases, as do several abiotic and biotic factors involved in microbial activity within the soil. Sludge as a soil fertilizer offers the opportunity for the recycling of plants nutrients and the recovery of C as organic matter and its use in soil to improve agriculture. The high levels of microbial activity stimulated by the addition of this high C and N content material could increase both CO2 and N2O production. It should be taken in account that several factors are involved in the production of gases in the soil such as rhizosphere respiration, vegetation type, and soil microbial respiration, as well as abiotic factors such as soil moisture, soil temperature, substrate

Environmental and economic implications must be considered in order to make well-informed decisions on the management of soil treatments, i.e. how many, how often and what kind of organic fertilizer should be used in order to improve crop production and simultaneously limit

We would like to thank the Instituto Politécnico Nacional and CONACyT for their financial

1 Agricultural Biotechnology Group, Research Centre for Applied Biotechnology, Instituto

2 Sustainability of Natural Resources and Energy Program, Cinvestav-Saltillo, Saltillo, C.P.

, Carolina Pérez-Morales 1

and

quantity and quality, and land use and management regimes.

soil deterioration and greenhouse gases production.

support and the grant-aided support received.

Fernando López-Valdez 1\*, Fabián Fernández-Luqueño 2

\*Address all correspondence to<EMAIL_ADDRESS>
**5. Conclusions**

222 Greenhouse Gases

**Acknowledgements**

**Author details**

Coahuila, Mexico

Mariana Miranda-Arámbula1

Politécnico Nacional, Tlaxcala, Mexico


*Article* **Smartphone-Based Unconstrained Step Detection Fusing a Variable Sliding Window and an Adaptive Threshold**

**Ying Xu 1,\*, Guofeng Li 1, Zeyu Li 1, Hao Yu 1, Jianhui Cui 1, Jin Wang 1 and Yu Chen 2**

**Abstract:** Step detection for smartphones plays an important role in the pedestrian dead reckoning (PDR) for indoor positioning. Aiming at the problem of low step detection accuracy of smartphones in complex unconstrained states in PDR, smartphone-based unconstrained step detection method fusing a variable sliding window and an adaptive threshold is proposed. In this method, the dynamic updating algorithm of a peak threshold is developed, and the minimum peak value filtered after a sliding window filter is used as the adaptive peak threshold, which solves the problem that the peak threshold of different motion states is difficult to update adaptively. Then, a variable sliding window collaborative time threshold method is proposed, which solves the problem that the adjacent windows cannot be contacted, and the initial peak and the end peak are difficult to accurately identify. To evaluate the performance of the proposed unconstrained step detection algorithm, 50 experiments in constrained and unconstrained states are conducted by 25 volunteers holding 21 different types of smartphones. Experimental results show: The average step counting accuracy of the proposed unconstrained step detection algorithm is over 98%. Compared with the open source program Stepcount, the average step counting accuracy of the proposed algorithm is improved by 10.0%. The smartphone-based unconstrained step detection fusing a variable sliding window and an adaptive threshold has a strong ability to adapt to complex unconstrained states, and the average step counting accuracy rate is only 0.6% lower than that of constrained states. This algorithm has a wide audience and is friendly for different genders and smartphones with different prices.

**Keywords:** step detection; indoor positioning; unconstrained state; peak detectors; adaptive threshold; variable sliding window