Organic Nitrogen in Agricultural Systems

*Eulene Francisco da Silva, Marlenildo Ferreira Melo, Kássio Ewerton Santos Sombra, Tatiane Severo Silva, Diana Ferreira de Freitas, Maria Eugênia da Costa, Eula Paula da Silva Santos, Larissa Fernandes da Silva, Ademar Pereira Serra and Paula Romyne de Morais Cavalcante Neitzke*

#### **Abstract**

This work summarizes information about organic nitrogen (N) in the agricultural system. The organic N forms in soils have been studied by identifying and quantifying the released organic compounds when soils are acid treated at high temperature, in which the following organic N fractions are obtained: hydrolyzable total N, subdivided into hydrolyzable NH4 + -N, amino sugars-N, amino acids-N, and unidentified-N and acid insoluble N, a fraction that remains associated with soil minerals after acid hydrolysis. Nitrogen mineralization and immobilization are biochemical processes in nature. This chapter summarizes how these processes occur in the agricultural system. Then, soluble organic nitrogen (SON), volatilization and denitrification processes, and biological nitrogen fixation (BNF) as a key component of the nitrogen cycle and how it makes N available to plants are also discussed. Finally, we discuss the use of organic fertilizers as N source to satisfy the worldwide demand for organic foods produced without synthetic inputs.

**Keywords:** biological N fixation, immobilization, mineralization, organic fertilization

#### **1. Introduction**

Nitrogen (N) is the fourth most abundant element in cellular biomass and comprises most of the Earth's atmosphere. In the surface layer of most soils, over 90% of N occurs in organic forms. Soil organic N can be divided into two categories: (1) N from organic residues and (2) N from soil organic matter or humus [1]. All these materials are important in maintaining or improving soil fertility and plant nutrition through direct and indirect effects on microbial activity and nutrient availability [2]. Analysis of organic fractions has been highlighted due to the increasing application of organic fertilizers and their direct and indirect effects on crop growth and yield and soil attributes. Thus, we will discuss about organic N forms, N mineralization and immobilization, volatilization and denitrification, soluble organic N, biological N fixation, and organic fertilization with emphasis on N.

#### **2. Organic nitrogen**

Nitrogen is an essential element for plants, being constituent of important biomolecules such as adenosine triphosphate (ATP), reduced nicotinamide adenine dinucleotide (NADH), nicotinamide adenine dinucleotide phosphate (NADPH), chlorophylls, amino acids and proteins (glyco- and lipoproteins), nitrogenous bases and nucleic acids, and various enzymes [3, 4]. Soil organic N consisting of proteins, chitins, amino acids, and nucleic acids represents about 90–98% of total soil N [1, 5]. Mineralized N forms are transient in the soil so that the existing amount depends on numerous processes such as mineralization, immobilization, nitrification, denitrification, leaching, and plant uptake. Therefore, the study of mineral N may not represent the N availability during the crop growing. On the other hand, the study of organic N fractions and their transformations over time can help in predicting the N availability for crops, in estimating the N supply to the soil, and in evaluating the potential release of mineral N by organic fertilizers.

Many compounds account the soil organic N, being approximately 40% protein material (proteins, peptides, and amino acids), 5–6% amino sugars, 35% heterocyclic nitrogen compounds (including purines and pyrimidines), and 19% NH3, with ¼ fixed as NH4 + . Thus, protein materials and heterocyclic compounds predominate in the total soil N, and organic N fractionation may inform about the mineralization susceptibility of compounds [6]. The organic N forms in soil have been studied by identifying and quantifying the released organic compounds when soils are acid treated at high temperature. The organic N fractions obtained by acid hydrolysis are hydrolyzable total N, subdivided into hydrolyzable NH4 + -N, amino sugars-N, amino acids-N, and unidentified-N and acid insoluble N, a fraction that remains associated with soil minerals after acid hydrolysis [7].

The fractionation allows separating the labile N forms from the soil, such as amide-N and amino-N (acid hydrolyzable), which can be rapidly synthesized in the mineralization process, releasing inorganic N (NH4 + and NO3 <sup>−</sup>) to the soil solution. However, most of the organic N can compose more stable fractions in the soil, such as non-hydrolyzable-N and unidentified-N. Variation in the non-hydrolyzable-N may be related to soil management, because the higher the hydrolysis intensity of organic N fractions in the soil, the higher the presence of finer particles that form clay-metal-humus complexes that constitute the non-hydrolyzed N. In Brazil, studies are reported in soils from Amazônia [8], São Paulo [9–12], and Espirito Santo [13].

In Latosols and Argisols from Amazônia, determination of the organic N forms indicated that the immobilization was mainly from microbial origin and the 15N immobilized in the soil was found as acid-soluble N and undistilled-N [8]. In São Paulo, in sugarcane-cultivated soil, amino acid-N fractions predominated, and, after 12 weeks incubation, the total hydrolyzable-N did not vary, but the hydrolyzable NH4+-N decreased [9]. In soil samples under different cover plants [10], the amino acid-N fraction predominated, with the following distribution: 14–38% hydrolyzable NH4 + -N, 36–52% adenosine triphosphate as NH4 + -N + amino sugars, 10–32% amino sugar-N, 26–46% amino acid-N, and 3–28% unidentified-N.

Moreover, in São Paulo, in a soil under maize cultivation, it was observed that topdressing N fertilization decreased the N content of the most labile fractions (hydrolyzable NH4 + -N and amino sugars-N) in the surface layer of the soil, and the amino acid-N and amino sugar-N fractions were considered the organic N reservoirs that control the soil N availability [11]. In contrast, fertilization with cattle manure [12] increased the most easily mineralized (up to 100 days) organic N fractions and subsequently increased the more stable organic N fractions, mainly in clay soil. In Espirito Santo, in soil under eucalyptus, [13] observed that the amino-N

**15**

*Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

hexosamine-N (15%).

gives it less resilience.

and energy, releasing NH4

biomass formation [14].

+

favors N mineralization for the next crop [20].

bilization is defined as the transformation of inorganic N (NH4

**systems**

was predominant (39%), followed by unidentified-N (27%), amide-N (18%), and

Several theories have been developed to explain the resistance of some N compounds to microbial attack. It is mentioned that N compounds are probably protein constituents (amino acids, peptides, and proteins) that are stabilized by reactions with lignins, tannins, quinones, and reducing sugars. Moreover, N compounds would adsorb to the clay fraction of soil and thereby would be protected against the action of protease enzymes. Also, the formation of organic N complexes and polyvalent cations (iron and aluminum) is another biologically stable form of protection [14]. Accumulation and/or decrease of organic C and N is more dynamic in sandy soils than in clayey ones, probably due to the highest oxygenation capacity and lower residue input of sandy soils due to its low productive potential, which

**3. Nitrogen mineralization and immobilization in the agricultural** 

discussed in the literature. We will focus on how these processes occur in the agricultural system. N mineralization occurs through hydrolysis and biodegradation of soil organic matter when N content in the substrate exceeds the metabolic N requirement by microbial cells. The process is mediated by heterotrophic soil microorganisms [15] that use nitrogenous organic substances as a source of C, N,

to microbial forms. Microbiota assimilates inorganic forms of N by incorporating them into the amino acids, which will participate in protein synthesis during soil

N mineralization and immobilization occur simultaneously and oppositely in the soil. The net balance between these processes is controlled by several factors: (a) environmental, such as soil temperature, aeration, and moisture; (b) soil physical, such as texture, structure, and size of aggregates [16]; (c) soil chemical, such as pH; (d) agricultural management system adopted [17]; and (e) quality parameters of the decomposing waste (such as C/N, C/P, and C/S ratios), content of easily decomposable and recalcitrant fractions, type of associated decomposers, size and activity of microbial biomass, and inorganic N availability [18]. Carbon/nitrogen (C/N) ratio less than 25 in organic waste favors N mineralization and fast decomposition, while greater than 30 strongly favors N immobilization and fast decomposition [19]. The crop developmental stage also influences waste C/N ratio. For instance, wastes from millet plants cut at the flowering or milky grain stages present high C/N ratio which delays mineralization. On the other hand, wastes from millet cut at the flag leaf stage, even though phytomass is lower, present less C/N ratio which

In residue plant, considering 13C-CPMAS NMR spectral regions [21], observed that the carbonyl C and N-alkyl and methoxyl C regions had the most significant positive correlation with N mineralization, while the di-O-alkyl C and O-alkyl C were strongly associated with N immobilization. This study demonstrates that the biochemical quality of organic C defined by 13C-CPMAS NMR is capable of predicting N dynamic pattern better than C/N ratio. Abbasi et al. [22] observed positively correlated with the initial residue N contents and negatively correlated with lignin content C/N ratio, lignin/N ratio, polyphenol/N ratio, and (lignin +

Nitrogen mineralization and immobilization are biochemical processes widely

ions as a residue (ammonification). In its turn, immo-

+

, NH3, NO3

<sup>−</sup>, NO2 −)

#### *Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

*Nitrogen Fixation*

¼ fixed as NH4

+

**2. Organic nitrogen**

Nitrogen is an essential element for plants, being constituent of important biomolecules such as adenosine triphosphate (ATP), reduced nicotinamide adenine dinucleotide (NADH), nicotinamide adenine dinucleotide phosphate (NADPH), chlorophylls, amino acids and proteins (glyco- and lipoproteins), nitrogenous bases and nucleic acids, and various enzymes [3, 4]. Soil organic N consisting of proteins, chitins, amino acids, and nucleic acids represents about 90–98% of total soil N [1, 5]. Mineralized N forms are transient in the soil so that the existing amount depends on numerous processes such as mineralization, immobilization, nitrification, denitrification, leaching, and plant uptake. Therefore, the study of mineral N may not represent the N availability during the crop growing. On the other hand, the study of organic N fractions and their transformations over time can help in predicting the N availability for crops, in estimating the N supply to the soil, and in

Many compounds account the soil organic N, being approximately 40% protein material (proteins, peptides, and amino acids), 5–6% amino sugars, 35% heterocyclic nitrogen compounds (including purines and pyrimidines), and 19% NH3, with

in the total soil N, and organic N fractionation may inform about the mineralization susceptibility of compounds [6]. The organic N forms in soil have been studied by identifying and quantifying the released organic compounds when soils are acid treated at high temperature. The organic N fractions obtained by acid hydrolysis

amino acids-N, and unidentified-N and acid insoluble N, a fraction that remains

The fractionation allows separating the labile N forms from the soil, such as amide-N and amino-N (acid hydrolyzable), which can be rapidly synthesized in the

However, most of the organic N can compose more stable fractions in the soil, such as non-hydrolyzable-N and unidentified-N. Variation in the non-hydrolyzable-N may be related to soil management, because the higher the hydrolysis intensity of organic N fractions in the soil, the higher the presence of finer particles that form clay-metal-humus complexes that constitute the non-hydrolyzed N. In Brazil, studies are reported in soils from Amazônia [8], São Paulo [9–12], and Espirito Santo [13]. In Latosols and Argisols from Amazônia, determination of the organic N forms indicated that the immobilization was mainly from microbial origin and the 15N immobilized in the soil was found as acid-soluble N and undistilled-N [8]. In São Paulo, in sugarcane-cultivated soil, amino acid-N fractions predominated, and, after 12 weeks incubation, the total hydrolyzable-N did not vary, but the hydrolyzable NH4+-N decreased [9]. In soil samples under different cover plants [10], the amino acid-N fraction predominated, with the following distribution: 14–38%


Moreover, in São Paulo, in a soil under maize cultivation, it was observed that topdressing N fertilization decreased the N content of the most labile fractions


10–32% amino sugar-N, 26–46% amino acid-N, and 3–28% unidentified-N.

the amino acid-N and amino sugar-N fractions were considered the organic N reservoirs that control the soil N availability [11]. In contrast, fertilization with cattle manure [12] increased the most easily mineralized (up to 100 days) organic N fractions and subsequently increased the more stable organic N fractions, mainly in clay soil. In Espirito Santo, in soil under eucalyptus, [13] observed that the amino-N

. Thus, protein materials and heterocyclic compounds predominate

+

and NO3

+

+


<sup>−</sup>) to the soil solution.


evaluating the potential release of mineral N by organic fertilizers.

are hydrolyzable total N, subdivided into hydrolyzable NH4

associated with soil minerals after acid hydrolysis [7].

mineralization process, releasing inorganic N (NH4

**14**

hydrolyzable NH4

(hydrolyzable NH4

+

+

was predominant (39%), followed by unidentified-N (27%), amide-N (18%), and hexosamine-N (15%).

Several theories have been developed to explain the resistance of some N compounds to microbial attack. It is mentioned that N compounds are probably protein constituents (amino acids, peptides, and proteins) that are stabilized by reactions with lignins, tannins, quinones, and reducing sugars. Moreover, N compounds would adsorb to the clay fraction of soil and thereby would be protected against the action of protease enzymes. Also, the formation of organic N complexes and polyvalent cations (iron and aluminum) is another biologically stable form of protection [14]. Accumulation and/or decrease of organic C and N is more dynamic in sandy soils than in clayey ones, probably due to the highest oxygenation capacity and lower residue input of sandy soils due to its low productive potential, which gives it less resilience.

#### **3. Nitrogen mineralization and immobilization in the agricultural systems**

Nitrogen mineralization and immobilization are biochemical processes widely discussed in the literature. We will focus on how these processes occur in the agricultural system. N mineralization occurs through hydrolysis and biodegradation of soil organic matter when N content in the substrate exceeds the metabolic N requirement by microbial cells. The process is mediated by heterotrophic soil microorganisms [15] that use nitrogenous organic substances as a source of C, N, and energy, releasing NH4 + ions as a residue (ammonification). In its turn, immobilization is defined as the transformation of inorganic N (NH4 + , NH3, NO3 <sup>−</sup>, NO2 −) to microbial forms. Microbiota assimilates inorganic forms of N by incorporating them into the amino acids, which will participate in protein synthesis during soil biomass formation [14].

N mineralization and immobilization occur simultaneously and oppositely in the soil. The net balance between these processes is controlled by several factors: (a) environmental, such as soil temperature, aeration, and moisture; (b) soil physical, such as texture, structure, and size of aggregates [16]; (c) soil chemical, such as pH; (d) agricultural management system adopted [17]; and (e) quality parameters of the decomposing waste (such as C/N, C/P, and C/S ratios), content of easily decomposable and recalcitrant fractions, type of associated decomposers, size and activity of microbial biomass, and inorganic N availability [18]. Carbon/nitrogen (C/N) ratio less than 25 in organic waste favors N mineralization and fast decomposition, while greater than 30 strongly favors N immobilization and fast decomposition [19]. The crop developmental stage also influences waste C/N ratio. For instance, wastes from millet plants cut at the flowering or milky grain stages present high C/N ratio which delays mineralization. On the other hand, wastes from millet cut at the flag leaf stage, even though phytomass is lower, present less C/N ratio which favors N mineralization for the next crop [20].

In residue plant, considering 13C-CPMAS NMR spectral regions [21], observed that the carbonyl C and N-alkyl and methoxyl C regions had the most significant positive correlation with N mineralization, while the di-O-alkyl C and O-alkyl C were strongly associated with N immobilization. This study demonstrates that the biochemical quality of organic C defined by 13C-CPMAS NMR is capable of predicting N dynamic pattern better than C/N ratio. Abbasi et al. [22] observed positively correlated with the initial residue N contents and negatively correlated with lignin content C/N ratio, lignin/N ratio, polyphenol/N ratio, and (lignin +

polyphenol)/N ratio indicating a significant role of residue chemical composition and quality in regulating N transformations and cycling in soil.

In the N compartments, N from the most labile fractions is released in the early mineralization process, and its mineralization estimate can be used to adjust the nitrogen fertilization recommendations. In fact, it was observed that the mineralization potential and the respective mineralization rate can be used to predict the N availability for plants in the agricultural system. Camargo et al. [23] found that the potentially mineralizable nitrogen values in 10 soils from Rio Grande do Sul ranged from 108.6 to 210.8 mg kg<sup>−</sup><sup>1</sup> .

In respect to the management system adopted, time is essential for N mineralization, mainly in the no-tillage (NT) system. Siqueira et al. [24] found that in soil under NT system for 12 and 22 years, the averages for N mineralization were 0.19 and 0.26 g m<sup>−</sup><sup>2</sup> day<sup>−</sup><sup>1</sup> , respectively. For organic compounds such as sludge, the N mineralization rate is generally below 50%, 5–38% [25], 14–43% [26], 7–16% [27], and 24–31% [28]. Among the species used in straw production, Fabaceae plants stand out for fixing atmospheric N2 and presenting low C/N ratio tissues, in addition to the high soluble compound content and low lignin and polyphenol contents. This fact favors the fast decomposition and mineralization, with significant N input to the soil–plant system, but with reduced soil cover, which is essential for NT system [29]. On the other hand, Poaceae plants present relatively high dry matter content and high C/N ratio (> 30), which increase the persistence of soil cover although increase N immobilization [30, 31].

#### **4. Nitrogen volatilization and denitrification**

Volatilization is the main cause of N loss where ammonia gas (NH3) is produced according to the simplified equation: NH4 + + OH<sup>−</sup> ↔ NH3(g) + H2O. NH3 loss increases with increasing soil pH. Ammonium ion (NH4 + ) can be adsorbed by soil colloids (clays in humus); thus the largest losses are found in sandy soils and poor in soil organic matter (SOM). Denitrification is another factor that favors N loss, which is mainly controlled by organic matter content, pH, and soil temperature. This process is performed by anaerobic bacteria such as *Pseudomonas*, *Bacillus*, *Micrococcus*, and *Achromobacter*, which are heterotrophic and get energy from carbon, through oxidation of organic compounds. Some autotrophic species also participate in the process such as *Thiobacillus denitrificans* and *T. thioparus* [32].

NH3 losses by volatilization in agriculture occur due to many factors: ambient temperature, soil moisture at fertilization time, urease enzyme activity, soil pH, cation exchange capacity, soil cover, rainfall after fertilization, and SOM content [33, 34]. Tasca et al. [34] reported 4.6-fold less NH3 volatilization when topdressing urea was performed at 18°C temperature, compared to 35° C, which demonstrates that N losses increase with increasing temperature. Low volatilization rates are also reported under higher soil moisture values, around 20%, because fertilizer hydrolysis facilitates the NH4 + diffusion, making it less susceptible to volatilization, even considering the increased soil biological activity in that moisture. In contrast, higher N losses occur under around 10% humidity values, because the NH4 + incorporation is inefficient, resulting in higher N-NH3 emissions [34]. Moreover, NH3 losses by volatilization are higher during the driest periods of the year. Soil moisture at fertilization time directly interferes with urea hydrolysis and consequently with NH3 volatilization losses. Thus, soil wetting soon after urea application is more important than the soil moisture at the application time [35]. According to Ros et al. [36], water applied after urea fertilization or the occurrence of rainfall may decrease NH3 volatilization if it is sufficient to dilute the hydroxyl (OH<sup>−</sup>)

**17**

*Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

providing the incorporation of urea in the soil.

topsoil and straw indicated higher urea and NH4

enzymatic hydrolysis that consumes H+

even more effective in sandy soils.

N2O emissions by 78.9%, and NO3

fertilizer, and 3.4 and 2.4% for cattle manure.

pH-controlled pig slurry), over the course of the experiment.

concentration around the urea granules produced during the hydrolysis, besides

of straw on the soil, besides effective urea hydrolysis occurring directly in the straw. These results demonstrated a direct contribution of the straw mulches on NH3 volatilization. However, despite NH3 volatilization decreases with straw removal, the choice of straw amount to be removed cannot be based only on NH3 volatilization of N fertilizer. Analyzing fertilizer mixtures in laboratory, Vitti et al. [38] found that mixing urea (330 mg) with ammonium sulfate (300 mg) significantly reduced N-NH3 losses (97.47 mg) relative to urea (121.52 mg), without affecting the physicochemical quality attributes of the mixture for technical and agronomic efficiency purpose. In Brazil, urea is the most used mineral N fertilizer, but it has volatilization losses due to the

in acidic soils, urea is subject to N losses by volatilization [39]. In agricultural systems, the largest N losses by volatilization occur 3–5 days after fertilizer application [40]. Santos [41] observed that from total N-NH3 loss by volatilization, 92.5% occurred until the fifth day after fertilization, negatively affecting the corn grain yield. Fertilizer type may also influence N-NH3 volatilization. The application of polymer and organic compound-coated urea promoted the lowest ammonia losses by volatilization [42, 43]. In soil under pasture (*Brachiaria decumbens*), Lana et al. [44] observed NH3 losses 2 days after urea application (2765 mg) and that the use of an inhibitor (NBPT) reduced the volatilization peak by up 4 days. The use of urea plus Uremax NBPT 500® decreased volatilization by approximately 75% after 11 days. Also, adding acid fertilizers may reduce NH3 losses by 29% [45]. According to Gurgel et al. [46], mineral fertilizers mixed with urea and humic acid (5 and 10%) and urea and zeolite (10%) reduced N-NH3 losses up to 38%. Results were

The use of liquid and solid organic biofertilizers such as poultry and swine residues are also alternative means to reduce N losses, since N is present in biofertilizers as organic form, thereby requiring more time to be mineralized by microorganisms for plant uptake. Niraula et al. [47] reported that cattle manure applied in corn had 11% lower cumulative NH3 emission than urea, without affecting grain yield, despite having higher CO2 and CH4 emissions. Thus, after comparing the ammonia volatilization levels reported in 92 studies, Bouwman et al. [48] concluded that the average NH3 emissions from the synthetic urea fertilizer and manure slurry were 21.0 and 21.2% from applied N fertilizer, respectively. Moreover, acidification has been a resource used to minimize urea volatilization with liquid waste. Park et al. [49] observed the application of acidified slurry reduced NH3 emissions by 78.1%,

Quantifying ammonia volatilization from various organic N sources (castor bean cake, bokashi, legume fertilizers, cattle manure), Rocha et al. [50] observed (i) the N loss rate by NH3 volatilization varies from 3 to 25% in winter/spring and 2 to 38% in summer/autumn among the studied organic fertilizers; (ii) when incorporating organic fertilizers into the soil, volatilization was significantly lower than when they are maintained on the soil surface, with a volatilization reduction by 80% for castor cake, 78% for bokashi, and 67% for legume fertilizer, while for cattle manure there was no difference; and (iii) when on surface, potential NH3 volatilization from the total N applied in winter/spring and summer/autumn seasons, respectively, was 25.5 and 38.1% for castor cake, 16.6 and 13.7% for bokashi, 8.2 and 8.8% for legume

Plant cover also influences N-NH3 volatilization. Pinheiro [37] found the removal of sugarcane straw from the soil decreased NH3 volatilization rates. The analysis of

+

retention in the largest amounts

and increases soil pH. For that reason, even

<sup>−</sup> leaching by 17.81% compared to control (non-

#### *Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

*Nitrogen Fixation*

and 0.26 g m<sup>−</sup><sup>2</sup>

from 108.6 to 210.8 mg kg<sup>−</sup><sup>1</sup>

day<sup>−</sup><sup>1</sup>

although increase N immobilization [30, 31].

**4. Nitrogen volatilization and denitrification**

increases with increasing soil pH. Ammonium ion (NH4

+

duced according to the simplified equation: NH4

hydrolysis facilitates the NH4

polyphenol)/N ratio indicating a significant role of residue chemical composition

In the N compartments, N from the most labile fractions is released in the early mineralization process, and its mineralization estimate can be used to adjust the nitrogen fertilization recommendations. In fact, it was observed that the mineralization potential and the respective mineralization rate can be used to predict the N availability for plants in the agricultural system. Camargo et al. [23] found that the potentially mineralizable nitrogen values in 10 soils from Rio Grande do Sul ranged

In respect to the management system adopted, time is essential for N mineraliza-

, respectively. For organic compounds such as sludge, the N

tion, mainly in the no-tillage (NT) system. Siqueira et al. [24] found that in soil under NT system for 12 and 22 years, the averages for N mineralization were 0.19

mineralization rate is generally below 50%, 5–38% [25], 14–43% [26], 7–16% [27], and 24–31% [28]. Among the species used in straw production, Fabaceae plants stand out for fixing atmospheric N2 and presenting low C/N ratio tissues, in addition to the high soluble compound content and low lignin and polyphenol contents. This fact favors the fast decomposition and mineralization, with significant N input to the soil–plant system, but with reduced soil cover, which is essential for NT system [29]. On the other hand, Poaceae plants present relatively high dry matter content and high C/N ratio (> 30), which increase the persistence of soil cover

Volatilization is the main cause of N loss where ammonia gas (NH3) is pro-

colloids (clays in humus); thus the largest losses are found in sandy soils and poor in soil organic matter (SOM). Denitrification is another factor that favors N loss, which is mainly controlled by organic matter content, pH, and soil temperature. This process is performed by anaerobic bacteria such as *Pseudomonas*, *Bacillus*, *Micrococcus*, and *Achromobacter*, which are heterotrophic and get energy from carbon, through oxidation of organic compounds. Some autotrophic species also participate in the process such as *Thiobacillus denitrificans* and *T. thioparus* [32]. NH3 losses by volatilization in agriculture occur due to many factors: ambient temperature, soil moisture at fertilization time, urease enzyme activity, soil pH, cation exchange capacity, soil cover, rainfall after fertilization, and SOM content [33, 34]. Tasca et al. [34] reported 4.6-fold less NH3 volatilization when topdressing urea was performed at 18°C temperature, compared to 35° C, which demonstrates that N losses increase with increasing temperature. Low volatilization rates are also reported under higher soil moisture values, around 20%, because fertilizer

even considering the increased soil biological activity in that moisture. In contrast, higher N losses occur under around 10% humidity values, because the NH4

incorporation is inefficient, resulting in higher N-NH3 emissions [34]. Moreover, NH3 losses by volatilization are higher during the driest periods of the year. Soil moisture at fertilization time directly interferes with urea hydrolysis and consequently with NH3 volatilization losses. Thus, soil wetting soon after urea application is more important than the soil moisture at the application time [35]. According to Ros et al. [36], water applied after urea fertilization or the occurrence of rainfall may decrease NH3 volatilization if it is sufficient to dilute the hydroxyl (OH<sup>−</sup>)

+

+

diffusion, making it less susceptible to volatilization,

+ OH<sup>−</sup> ↔ NH3(g) + H2O. NH3 loss

) can be adsorbed by soil

+

and quality in regulating N transformations and cycling in soil.

.

**16**

concentration around the urea granules produced during the hydrolysis, besides providing the incorporation of urea in the soil.

Plant cover also influences N-NH3 volatilization. Pinheiro [37] found the removal of sugarcane straw from the soil decreased NH3 volatilization rates. The analysis of topsoil and straw indicated higher urea and NH4 + retention in the largest amounts of straw on the soil, besides effective urea hydrolysis occurring directly in the straw. These results demonstrated a direct contribution of the straw mulches on NH3 volatilization. However, despite NH3 volatilization decreases with straw removal, the choice of straw amount to be removed cannot be based only on NH3 volatilization of N fertilizer. Analyzing fertilizer mixtures in laboratory, Vitti et al. [38] found that mixing urea (330 mg) with ammonium sulfate (300 mg) significantly reduced N-NH3 losses (97.47 mg) relative to urea (121.52 mg), without affecting the physicochemical quality attributes of the mixture for technical and agronomic efficiency purpose. In Brazil, urea is the most used mineral N fertilizer, but it has volatilization losses due to the enzymatic hydrolysis that consumes H+ and increases soil pH. For that reason, even in acidic soils, urea is subject to N losses by volatilization [39]. In agricultural systems, the largest N losses by volatilization occur 3–5 days after fertilizer application [40]. Santos [41] observed that from total N-NH3 loss by volatilization, 92.5% occurred until the fifth day after fertilization, negatively affecting the corn grain yield.

Fertilizer type may also influence N-NH3 volatilization. The application of polymer and organic compound-coated urea promoted the lowest ammonia losses by volatilization [42, 43]. In soil under pasture (*Brachiaria decumbens*), Lana et al. [44] observed NH3 losses 2 days after urea application (2765 mg) and that the use of an inhibitor (NBPT) reduced the volatilization peak by up 4 days. The use of urea plus Uremax NBPT 500® decreased volatilization by approximately 75% after 11 days. Also, adding acid fertilizers may reduce NH3 losses by 29% [45]. According to Gurgel et al. [46], mineral fertilizers mixed with urea and humic acid (5 and 10%) and urea and zeolite (10%) reduced N-NH3 losses up to 38%. Results were even more effective in sandy soils.

The use of liquid and solid organic biofertilizers such as poultry and swine residues are also alternative means to reduce N losses, since N is present in biofertilizers as organic form, thereby requiring more time to be mineralized by microorganisms for plant uptake. Niraula et al. [47] reported that cattle manure applied in corn had 11% lower cumulative NH3 emission than urea, without affecting grain yield, despite having higher CO2 and CH4 emissions. Thus, after comparing the ammonia volatilization levels reported in 92 studies, Bouwman et al. [48] concluded that the average NH3 emissions from the synthetic urea fertilizer and manure slurry were 21.0 and 21.2% from applied N fertilizer, respectively. Moreover, acidification has been a resource used to minimize urea volatilization with liquid waste. Park et al. [49] observed the application of acidified slurry reduced NH3 emissions by 78.1%, N2O emissions by 78.9%, and NO3 <sup>−</sup> leaching by 17.81% compared to control (nonpH-controlled pig slurry), over the course of the experiment.

Quantifying ammonia volatilization from various organic N sources (castor bean cake, bokashi, legume fertilizers, cattle manure), Rocha et al. [50] observed (i) the N loss rate by NH3 volatilization varies from 3 to 25% in winter/spring and 2 to 38% in summer/autumn among the studied organic fertilizers; (ii) when incorporating organic fertilizers into the soil, volatilization was significantly lower than when they are maintained on the soil surface, with a volatilization reduction by 80% for castor cake, 78% for bokashi, and 67% for legume fertilizer, while for cattle manure there was no difference; and (iii) when on surface, potential NH3 volatilization from the total N applied in winter/spring and summer/autumn seasons, respectively, was 25.5 and 38.1% for castor cake, 16.6 and 13.7% for bokashi, 8.2 and 8.8% for legume fertilizer, and 3.4 and 2.4% for cattle manure.

In Planosol under irrigated rice, the addition of cover plants on the soil and water management by intermittent irrigation were practices that mitigated N2O emissions. Zschornack et al. [51] observed an increase in N2O emissions by more than 200% in a drained area than continuous water blade area. Thus, soil drainage during rice cultivation increases N2O emissions by stimulating nitrification and denitrification processes. In addition, N2O emissions depend on the input waste quality and increase significantly when legumes are inserted into cover plants. Moreover, analyzing biochar in rice, He et al. [52] suggested that the combination of biochar and HQ (urease inhibitor-hydroquinone) or the combined application of urease and nitrification inhibitors to soil enriched with biochar at least 1 year previously could be an effective practice for reducing NH3 emissions and increasing rice yields.

Finally, microorganism respiration may also contribute to retaining N into the soil. By dissimilatory nitrate reduction to ammonium (DNRA), a respiratory process antagonistic to denitrification, nitrate is used by microorganisms, mainly *Bradyrhizobium* and *Mesorhizobium* bacteria, as electron acceptors. This process results in N retention and production of the less mobile ammonium cation (NH4 + ), thereby reducing the contribution to the total N2O pool [53]. In addition to N fixation, the potential N retention by microorganisms through DNRA becomes a relevant feature in the reduction of N losses by denitrification [54]. This suggests DNRA may act as a mechanism for conserving N in agricultural systems.

#### **5. Soluble nitrogen**

Soluble organic nitrogen is a labile source of N for microorganisms and is an important soluble N reservoir in agricultural soils. Plant species (associated or not with mycorrhizae) can directly uptake simple organic N present in the SON pool [55]. The SON pool is composed of high (protein oligomers), medium (small peptides) [56], and low molecular weight compounds (monomers such as amino acids) [57]. As plants uptake organic and inorganic N, the relative proportion of these different N sources in soils is a determinant of N management.

SON is suggested as a transitional phase during N transformation between soil organic matter and inorganic N (NH4 + -N) and considered an intermediate step in microbial mineralization of organic N [58]. The SON pool can regulate the N transformation rate in the soil, i.e., the ammonification and nitrification rates, affecting the substrate associated with different plant species. Thus, soil organic N fractions and SON pools are important indicators of soil fertility and plant nutrition requirements [59], inferring the potential supply of N mainly in low N mineralization soils [60].

Besides an important component of soil total soluble N, SON plays a key role in N cycling and therefore in determining soil N availability in agricultural systems [61]. The amount of SON represents a relatively high proportion of the total soluble nitrogen (TSN) pool. It has been reported that SON constitutes 17–90% and 32–50% of TSN in pasture and agricultural soils, respectively [46, 47, 62, 63]. Like in mineral N, SON dynamics are affected by mineralization, immobilization, leaching, and plant uptake, but its pool size is more constant than mineral N [64]. Although remains unclearly understood, SON is an important pool in N transformations and plant uptake.

Biotic and abiotic processes are involved in the SON generation in soil [58]. By biotic processes, SON can be produced directly from microbial turnover and indirectly through the microbial excretion of extracellular enzymes [61]. However, as plants and microorganisms can compete for soil organic N, it is also possible that SON reservoirs vary spatially due to the variation in activity and density of

**19**

*Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

acids [68].

crops.

and effective for increasing soil N turnover.

and protein pools remains unclear [66].

**6. Biological nitrogen fixation**

*Paenibacillus*, and *Pseudomonas* [71].

(NH3) through the nitrogenase enzyme (N2 + 8H+

sible for most of the nitrogen available to plants.

microbial population between different types of agricultural management. Zhang et al. [65] reported that SON fractions were significantly and positively correlated with the no-tillage system practices and that this agricultural system is beneficial

Proteins are the most abundant nitrogen compounds in SON. Depolymerization of these organic macromolecules in monomeric SON (amino acids) can be considered rate-limiting for the total N cycling in soils [66]. Soil amino acids can contribute, in relative and absolute terms, to the SON pool in agricultural soils, which was observed in soil under fertilized sugarcane [55]. Also, plants can use proteins as N source without the help of other organisms [67]. Although the relative contribution of amino acids to N supply for crops remains unclear, all studied plants have shown the ability to uptake and metabolize amino acids as well as soils containing amino

Organic agriculture practices can increase the content of SON, protein, and free amino acids in the soil as a result of frequent and long-term inputs of organic matter. In addition, agricultural production quantity may also influence the SON pool abundance. However, the effect of organic cultivation on specific free amino acids

Soil organic matter, pH, total C, total N, and C/N ratio are the main factors affecting soil SON abundance. SON dynamics can be significantly affected by mineralization and immobilization during microbial growth and decomposition of organic matter. Besides that, agricultural practices such as irrigation management, fertilization, plowing, harrowing, harvesting, and the plant growth stage can also play an important role in SON dynamics [59, 63]. Furthermore, high temperatures may increase the SON content by stimulating decomposition of organic matter [69]. Knowing the temporal dynamics of organic N pools in the soil may help to understand how these pools are affected by soil properties, climate and crop management, and whether SON can contribute to N supply of

Nitrogen in the gaseous form (N2) represents 78% of the atmospheric gases but is inert and unavailable to plants. Only nitrogen-fixing microorganisms, including bacteria, cyanobacteria, and fungi, are able to break the triple bond between the atoms (N ≡ N) of the atmospheric nitrogen, thus transforming it into ammonia

Biological nitrogen fixation is a key component of the nitrogen cycle and respon-

BNF is performed by symbiotic, endophytic, or free-living microorganisms [71, 72]. Symbiotic bacteria associate with plants forming root nodules (rhizobia), where they fix nitrogen while benefiting from plant photoassimilates. It has been observed that this symbiosis occurs not only in plants from the Leguminosae family [71] but also in cereals such as rice, maize, and wheat from the Poaceae family [73]. BNF also occurs in nonsymbiotic associations. Endophytic bacteria colonize plant tissues and fix N while benefiting from plant photoassimilates, although the amount of N fixed is lower than in symbiosis [73, 74]. Also, free-living microorganisms inhabiting rhizosphere, soil region around plant roots, fix nitrogen while feeding on root exudates (amino acids, peptides, proteins, enzymes, vitamins, and hormones), which stimulate growth of diazotrophic bacteria from genera *Acetobacter*, *Azoarcus*, *Azospirillum*, *Azotobacter*, *Beijerinckia*, *Burkholderia*, *Enterobacter*, *Herbaspirillum*, *Klebsiella*,

+ 6e<sup>−</sup> → 2NH3 + H2) [70].

#### *Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

*Nitrogen Fixation*

rice yields.

**5. Soluble nitrogen**

organic matter and inorganic N (NH4

mations and plant uptake.

In Planosol under irrigated rice, the addition of cover plants on the soil and water management by intermittent irrigation were practices that mitigated N2O emissions. Zschornack et al. [51] observed an increase in N2O emissions by more than 200% in a drained area than continuous water blade area. Thus, soil drainage during rice cultivation increases N2O emissions by stimulating nitrification and denitrification processes. In addition, N2O emissions depend on the input waste quality and increase significantly when legumes are inserted into cover plants. Moreover, analyzing biochar in rice, He et al. [52] suggested that the combination of biochar and HQ (urease inhibitor-hydroquinone) or the combined application of urease and nitrification inhibitors to soil enriched with biochar at least 1 year previously could be an effective practice for reducing NH3 emissions and increasing

Finally, microorganism respiration may also contribute to retaining N into the soil. By dissimilatory nitrate reduction to ammonium (DNRA), a respiratory process antagonistic to denitrification, nitrate is used by microorganisms, mainly *Bradyrhizobium* and *Mesorhizobium* bacteria, as electron acceptors. This process results in N retention and production of the less mobile ammonium cation (NH4

thereby reducing the contribution to the total N2O pool [53]. In addition to N fixation, the potential N retention by microorganisms through DNRA becomes a relevant feature in the reduction of N losses by denitrification [54]. This suggests

Soluble organic nitrogen is a labile source of N for microorganisms and is an important soluble N reservoir in agricultural soils. Plant species (associated or not with mycorrhizae) can directly uptake simple organic N present in the SON pool [55]. The SON pool is composed of high (protein oligomers), medium (small peptides) [56], and low molecular weight compounds (monomers such as amino acids) [57]. As plants uptake organic and inorganic N, the relative proportion of

SON is suggested as a transitional phase during N transformation between soil

microbial mineralization of organic N [58]. The SON pool can regulate the N transformation rate in the soil, i.e., the ammonification and nitrification rates, affecting the substrate associated with different plant species. Thus, soil organic N fractions and SON pools are important indicators of soil fertility and plant nutrition requirements [59], inferring the potential supply of N mainly in low N mineralization soils [60]. Besides an important component of soil total soluble N, SON plays a key role in N cycling and therefore in determining soil N availability in agricultural systems [61]. The amount of SON represents a relatively high proportion of the total soluble nitrogen (TSN) pool. It has been reported that SON constitutes 17–90% and 32–50% of TSN in pasture and agricultural soils, respectively [46, 47, 62, 63]. Like in mineral N, SON dynamics are affected by mineralization, immobilization, leaching, and plant uptake, but its pool size is more constant than mineral N [64]. Although remains unclearly understood, SON is an important pool in N transfor-

Biotic and abiotic processes are involved in the SON generation in soil [58]. By biotic processes, SON can be produced directly from microbial turnover and indirectly through the microbial excretion of extracellular enzymes [61]. However, as plants and microorganisms can compete for soil organic N, it is also possible that SON reservoirs vary spatially due to the variation in activity and density of


DNRA may act as a mechanism for conserving N in agricultural systems.

these different N sources in soils is a determinant of N management.

+

+ ),

**18**

microbial population between different types of agricultural management. Zhang et al. [65] reported that SON fractions were significantly and positively correlated with the no-tillage system practices and that this agricultural system is beneficial and effective for increasing soil N turnover.

Proteins are the most abundant nitrogen compounds in SON. Depolymerization of these organic macromolecules in monomeric SON (amino acids) can be considered rate-limiting for the total N cycling in soils [66]. Soil amino acids can contribute, in relative and absolute terms, to the SON pool in agricultural soils, which was observed in soil under fertilized sugarcane [55]. Also, plants can use proteins as N source without the help of other organisms [67]. Although the relative contribution of amino acids to N supply for crops remains unclear, all studied plants have shown the ability to uptake and metabolize amino acids as well as soils containing amino acids [68].

Organic agriculture practices can increase the content of SON, protein, and free amino acids in the soil as a result of frequent and long-term inputs of organic matter. In addition, agricultural production quantity may also influence the SON pool abundance. However, the effect of organic cultivation on specific free amino acids and protein pools remains unclear [66].

Soil organic matter, pH, total C, total N, and C/N ratio are the main factors affecting soil SON abundance. SON dynamics can be significantly affected by mineralization and immobilization during microbial growth and decomposition of organic matter. Besides that, agricultural practices such as irrigation management, fertilization, plowing, harrowing, harvesting, and the plant growth stage can also play an important role in SON dynamics [59, 63]. Furthermore, high temperatures may increase the SON content by stimulating decomposition of organic matter [69]. Knowing the temporal dynamics of organic N pools in the soil may help to understand how these pools are affected by soil properties, climate and crop management, and whether SON can contribute to N supply of crops.

#### **6. Biological nitrogen fixation**

Nitrogen in the gaseous form (N2) represents 78% of the atmospheric gases but is inert and unavailable to plants. Only nitrogen-fixing microorganisms, including bacteria, cyanobacteria, and fungi, are able to break the triple bond between the atoms (N ≡ N) of the atmospheric nitrogen, thus transforming it into ammonia (NH3) through the nitrogenase enzyme (N2 + 8H+ + 6e<sup>−</sup> → 2NH3 + H2) [70]. Biological nitrogen fixation is a key component of the nitrogen cycle and responsible for most of the nitrogen available to plants.

BNF is performed by symbiotic, endophytic, or free-living microorganisms [71, 72]. Symbiotic bacteria associate with plants forming root nodules (rhizobia), where they fix nitrogen while benefiting from plant photoassimilates. It has been observed that this symbiosis occurs not only in plants from the Leguminosae family [71] but also in cereals such as rice, maize, and wheat from the Poaceae family [73]. BNF also occurs in nonsymbiotic associations. Endophytic bacteria colonize plant tissues and fix N while benefiting from plant photoassimilates, although the amount of N fixed is lower than in symbiosis [73, 74]. Also, free-living microorganisms inhabiting rhizosphere, soil region around plant roots, fix nitrogen while feeding on root exudates (amino acids, peptides, proteins, enzymes, vitamins, and hormones), which stimulate growth of diazotrophic bacteria from genera *Acetobacter*, *Azoarcus*, *Azospirillum*, *Azotobacter*, *Beijerinckia*, *Burkholderia*, *Enterobacter*, *Herbaspirillum*, *Klebsiella*, *Paenibacillus*, and *Pseudomonas* [71].

Nitrogen-fixing microorganisms occur naturally in soil [71] and in water [72] or colonize seeds [74]. However, in the agricultural environment, conventional practices such as plowing, harrowing, chemical fertilization, and pesticide application reduce the soil microorganism populations, which make these areas depending on the application of nitrogen fertilizers [75, 76]. Chemical fertilizers require a great amount of energy to be produced, energy that is derived from fossil fuels. Moreover, they are potential soil and water contaminants and expensive and scarce for many developing country farmers [77]. Therefore, strategies have been studied to increase BNF by plants and thus reduce dependence on chemical fertilization.

Conservation practices such as minimum tillage, no tillage, and cover crops stimulate BNF as they increase the population and activity of soil microorganisms (bacteria, actinomycetes, and mycorrhizae) [78, 79]. In addition to capturing soil N, reducing N loss by leaching, and becoming an N source for succeeding crops, mixing cover crops (legumes and grasses) provide additional N through BNF [79, 80].

Another alternative for increasing BNF is to inoculate nitrogen-fixing microorganisms in crops. Inoculated into the seeds, roots, or leaves, these microorganisms may increase the formation of root nodules, stimulate root growth, improve nutrient uptake, stimulate antioxidant defense system, increase tolerance to biotic (pest and pathogen) and abiotic (drought and salinity) stresses, and thereby increase crop productivity. Inoculation of nodulating as well as endophytic fungi or bacteria stimulates growth in both legumes and grasses and represents a viable and sustainable alternative (**Table 1**). Among the most used microorganisms are *Rhizobium* and *Bradyrhizobium* genera bacteria inoculated in legumes and *Azospirillum* and *Enterobacter* genera in grasses (**Table 1**).

Studies also focus on the application of nitrogen-fixing microorganisms through irrigation water, on the genetic improvement for BNF by legume crops [96], on becoming plants able to self-fertilize by stimulating root fungal associations in grasses, and on providing cereals with the nitrogen-fixing enzyme (nitrogenase) [77]. Estimations indicate these practices can reduce fertilizer application costs by billions of dollars annually.


**21**

*Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

exchange capacity (CEC) [97].

**7. Nitrogen and organic fertilization**

The worldwide demand for organic foods, produced without the use of synthetic inputs, has driven the use of conservation practices, especially fertilization using organic wastes. The application of organic wastes to the soil improves soil fertility by increasing the organic matter (OM) and nutrient contents, such as N and phosphorus (P), and soil microbiota population, as well as improving the cation

Organic fertilization improves yield and quality of vegetables such as lettuce (*Lactuca sativa* L.) [98], tomato (*Solanum lycopersicum* Mill.) [99], and carrot (*Daucus* carota L.) [100]; fruits such as papaya (*Carica papaya* L.) [101], citrus (*Citrus* spp.) [102], and raspberry (*Rubus* idaeus L.) [103]; and annual crops such as maize (*Zea mays* L.) [104] and cowpea (*Vigna unguiculata* (L.) Walp) [105]. Most organic fertilizers used as N source are derived from (a) agricultural wastes (cattle, swine and poultry manure), slaughterhouses (bone and blood meal), composting, and vermicomposting; (b) agro-industrial wastes (oilseed pies, sugarcane bagasse, and vinasse) and biochar; and (c) household wastes and sewage sludge composting (**Table 2**). N input by organic fertilizers occurs predominantly through mineralization of organic N, although some mineral N fractions may be released [107, 119]. The organic N mineralization rate is regulated by N fractions and C/N ratio of the decomposing waste, as well as by environmental temperature and humidity [120, 121]. Under favorable conditions, high N content organic fertilizers mineralize quickly similarly to synthetic fertilizers, while those with low N content and high C/N ratio mineralize slowly [122]. Thus, knowing the mineralization rate allows

choosing the best organic fertilizer to be used in agriculture (**Table 2**).

similar mineralization characteristics [128, 129].

processes of OM, with decreasing C/N ratio [115, 131].

though the amount and quality of N in manure may vary according to animal species, age, and feed. Forage-based diets increase the residue production, although reduce the quality that is provided by a concentrate-based diet [97, 119]. Cattle, equine, sheep, goat, and swine manures present similar N content, ranging from 0.77 to 3.90%. In its turn, poultry litter may have 2.80–4.60% N content, due to concentrate-based feed supplied to poultries, being a fast mineralizing fertilizer [106, 107]. Thus, manure fertilization has been efficient for many crops, such as sweet pepper (*Capsicum annuum* L.) [123] and radish (*Raphanus sativus* L.) [124]. Residues from the castor bean (*Ricinus communis* L.; *Euphorbiaceae*) chain stand out due to the high N content which is found in the pie (7.54% N), in the oil extraction residue (12.82% N), and in the pulp from direct oil transesterification for biodiesel production [106, 125–127]. Castor pie mineralization rate is more intense than in other composts and thus quickly releases N and other readily available nutrients to plants. As reported by [126], evaluating microbial respiration, who obtained mineralization rates 6 times faster than those obtained in cattle manure and 14 times faster than in sugarcane bagasse, other pies, such as peanut (*Arachis* spp.) and cotton (*Gossypium* spp.), may also have high N (4.0–7.0%) content and

Manures are the main used organic fertilizers worldwide, especially as N source,

The product obtained from the composting of organic wastes is rich in stable organic matter. Wastes are transformed through biological decomposition, and the process is affected by environmental conditions and N content. As nitrogen compounds are food for microbiota, N deficiency in waste may retard the maturation process, and the excess may increase the N volatilization as ammonia (NH3), consequently affecting N stabilization processes in composting [130]. Also, humus from vermicomposting (usually by using *Eisenia foetida* species) is highly stable and presents high contents of N and humic acids, which indicate a better relationship between the mineralization and humification

#### **Table 1.**

*Legume and cereal crops and nitrogen-fixing microorganisms used for inoculation.*

*Nitrogen Fixation*

BNF [79, 80].

*Enterobacter* genera in grasses (**Table 1**).

billions of dollars annually.

Sugarcane *Saccharum* 

Cowpea *Vigna* 

Wheat *Triticum* 

Common bean

*officinarum*

*unguiculata*

*Phaseolus vulgaris*

*aestivum*

Nitrogen-fixing microorganisms occur naturally in soil [71] and in water [72] or colonize seeds [74]. However, in the agricultural environment, conventional practices such as plowing, harrowing, chemical fertilization, and pesticide application reduce the soil microorganism populations, which make these areas depending on the application of nitrogen fertilizers [75, 76]. Chemical fertilizers require a great amount of energy to be produced, energy that is derived from fossil fuels. Moreover, they are potential soil and water contaminants and expensive and scarce for many developing country farmers [77]. Therefore, strategies have been studied to increase BNF by plants and thus reduce dependence on chemical fertilization. Conservation practices such as minimum tillage, no tillage, and cover crops stimulate BNF as they increase the population and activity of soil microorganisms (bacteria, actinomycetes, and mycorrhizae) [78, 79]. In addition to capturing soil N, reducing N loss by leaching, and becoming an N source for succeeding crops, mixing cover crops (legumes and grasses) provide additional N through

Another alternative for increasing BNF is to inoculate nitrogen-fixing microorganisms in crops. Inoculated into the seeds, roots, or leaves, these microorganisms may increase the formation of root nodules, stimulate root growth, improve nutrient uptake, stimulate antioxidant defense system, increase tolerance to biotic (pest and pathogen) and abiotic (drought and salinity) stresses, and thereby increase crop productivity. Inoculation of nodulating as well as endophytic fungi or bacteria stimulates growth in both legumes and grasses and represents a viable and sustainable alternative (**Table 1**). Among the most used microorganisms are *Rhizobium* and *Bradyrhizobium* genera bacteria inoculated in legumes and *Azospirillum* and

Studies also focus on the application of nitrogen-fixing microorganisms through

**Crop Scientific name Inoculated microorganism Reference**

*Azospirillum amazonense*

Maize *Zea mays Azospirillum brasilense*, *Herbaspirillum seropedicae* [90, 91]

*Methylobacterium oryzae*,

*Zoogloea ramigera*

*Gluconacetobacter diazotrophicus*, *Herbaspirillum seropedicae*, *H. rubrisubalbicans*, *Burkholderia tropica* e

*Actinomadura*, *Bradyrhizobium elkanii*, *B. pachyrhizi*, *B. yuanmingense*, *Paenibacillus graminis*, *Rhizophagus* 

*Azospirillum brasilense*, *A. insolitus*, *Enterobacter* sp., *Microbacterium arborescens*, *Serratia marcescens*,

*Rhizobium leguminosarum* bv. phaseoli, *R. tropici* [89]

[81, 82]

[84–88]

[92, 93]

[94, 95]

[83]

Rice *Oryza sativa Bacillus amyloliquefaciens*, *Enterobacter cloacae*, *Klebsiella variicola*

*irregularis*

Soybean *Glycine max Bradyrhizobium japonicum*, *Bacillus megaterium*,

*Legume and cereal crops and nitrogen-fixing microorganisms used for inoculation.*

irrigation water, on the genetic improvement for BNF by legume crops [96], on becoming plants able to self-fertilize by stimulating root fungal associations in grasses, and on providing cereals with the nitrogen-fixing enzyme (nitrogenase) [77]. Estimations indicate these practices can reduce fertilizer application costs by

**20**

**Table 1.**

#### **7. Nitrogen and organic fertilization**

The worldwide demand for organic foods, produced without the use of synthetic inputs, has driven the use of conservation practices, especially fertilization using organic wastes. The application of organic wastes to the soil improves soil fertility by increasing the organic matter (OM) and nutrient contents, such as N and phosphorus (P), and soil microbiota population, as well as improving the cation exchange capacity (CEC) [97].

Organic fertilization improves yield and quality of vegetables such as lettuce (*Lactuca sativa* L.) [98], tomato (*Solanum lycopersicum* Mill.) [99], and carrot (*Daucus* carota L.) [100]; fruits such as papaya (*Carica papaya* L.) [101], citrus (*Citrus* spp.) [102], and raspberry (*Rubus* idaeus L.) [103]; and annual crops such as maize (*Zea mays* L.) [104] and cowpea (*Vigna unguiculata* (L.) Walp) [105]. Most organic fertilizers used as N source are derived from (a) agricultural wastes (cattle, swine and poultry manure), slaughterhouses (bone and blood meal), composting, and vermicomposting; (b) agro-industrial wastes (oilseed pies, sugarcane bagasse, and vinasse) and biochar; and (c) household wastes and sewage sludge composting (**Table 2**).

N input by organic fertilizers occurs predominantly through mineralization of organic N, although some mineral N fractions may be released [107, 119]. The organic N mineralization rate is regulated by N fractions and C/N ratio of the decomposing waste, as well as by environmental temperature and humidity [120, 121]. Under favorable conditions, high N content organic fertilizers mineralize quickly similarly to synthetic fertilizers, while those with low N content and high C/N ratio mineralize slowly [122]. Thus, knowing the mineralization rate allows choosing the best organic fertilizer to be used in agriculture (**Table 2**).

Manures are the main used organic fertilizers worldwide, especially as N source, though the amount and quality of N in manure may vary according to animal species, age, and feed. Forage-based diets increase the residue production, although reduce the quality that is provided by a concentrate-based diet [97, 119]. Cattle, equine, sheep, goat, and swine manures present similar N content, ranging from 0.77 to 3.90%. In its turn, poultry litter may have 2.80–4.60% N content, due to concentrate-based feed supplied to poultries, being a fast mineralizing fertilizer [106, 107]. Thus, manure fertilization has been efficient for many crops, such as sweet pepper (*Capsicum annuum* L.) [123] and radish (*Raphanus sativus* L.) [124].

Residues from the castor bean (*Ricinus communis* L.; *Euphorbiaceae*) chain stand out due to the high N content which is found in the pie (7.54% N), in the oil extraction residue (12.82% N), and in the pulp from direct oil transesterification for biodiesel production [106, 125–127]. Castor pie mineralization rate is more intense than in other composts and thus quickly releases N and other readily available nutrients to plants. As reported by [126], evaluating microbial respiration, who obtained mineralization rates 6 times faster than those obtained in cattle manure and 14 times faster than in sugarcane bagasse, other pies, such as peanut (*Arachis* spp.) and cotton (*Gossypium* spp.), may also have high N (4.0–7.0%) content and similar mineralization characteristics [128, 129].

The product obtained from the composting of organic wastes is rich in stable organic matter. Wastes are transformed through biological decomposition, and the process is affected by environmental conditions and N content. As nitrogen compounds are food for microbiota, N deficiency in waste may retard the maturation process, and the excess may increase the N volatilization as ammonia (NH3), consequently affecting N stabilization processes in composting [130]. Also, humus from vermicomposting (usually by using *Eisenia foetida* species) is highly stable and presents high contents of N and humic acids, which indicate a better relationship between the mineralization and humification processes of OM, with decreasing C/N ratio [115, 131].


#### **Table 2.**

*Nitrogen content and carbon/nitrogen ratio (C/N) in organic fertilizers.*

In addition to the earthworms, arthropods that constitute the edaphic macrofauna [87, 132, 133] are also of great interest. Millipedes (Myriapoda: Diplopoda) fragment and feed on organic wastes and excrete low C/N ratio feces (2.2% N) producing the millicompost [134–136]. Studies suggest that millicompost is similar to vermicompost and commercial substrates in relation to N supply and other macro- and micronutrients for seedling production, such as in lettuce (*Lactuca sativa*) [98] and pitaya (*Hylocereus* spp.) (Cactaceae) [137].

In relation to slow-release organic fertilizers, biochar is an alternative. A by-product from carbonization (pyrolysis) of biomass under low-oxygen atmosphere, biochar is fine-grained carbonaceous material with decomposition resistance [118]. N content in biochar depends on the source material (biomass) as well as on the pyrolysis temperature. Biochars from wood have high C/N ratio and low N content (0.1%), while those from manures have low C/N ratio and high N content (5.0%). For instance, biochar from eucalyptus wood (*Eucalyptus urophylla* S. T. Blake and *Corymbia citriodora* (Hook.) K.D. Hill and L.A.S. Johnson) contains 0.66 and 0.48% N, respectively, while from coffee husks (*Coffea* spp.) contains 2.74% N [138]. Besides slowly releasing nutrients, the use of biochars increases N uptake via ion exchange and NH3 removal by adsorption, stimulates immobilization (reducing NO3 <sup>−</sup> losses), and reduces N2O emissions [139–142]. Moreover, biochar improves mycorrhizal associations and nitrogen biological fixation [118].

**23**

*Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

scarce [97, 110, 112].

**Author details**

Eulene Francisco da Silva1

Maria Eugênia da Costa1

Ademar Pereira Serra3

Kássio Ewerton Santos Sombra1

**8. Concluding remarks**

hold wastes, and sewage sludge composting.

Urban wastes have also been used in agriculture. Sewage sludge showed to be an excellent N source (0.80 and 3.47% N) besides slowly mineralizing. N mineralization rates from 20 to 38% were found after 105 days [143], which depends on source material characteristics and treatment processes as well as on heavy metal content that accelerate or limit mineralization [107, 144]. Slaughterhouse residues, such as bone and blood meal, present high N rates, but they are not yet used in agriculture because studies on its adoption and behavior as organic fertilizer are

In the surface layer of most soils, the soil organic N can be divided into two categories: N from organic residues and N from soil organic matter or humus. N mineralization and immobilization processes occur simultaneously and oppositely in the soil. The net balance between these processes is controlled by several factors such as environmental conditions, soil physicochemical factors, agricultural management adopted, quality of the decomposing residues, and content of easily decomposable and recalcitrant fractions. As organic agriculture increases soluble organic nitrogen content, this fraction has been extensively studied. Also, being biological nitrogen fixation a key component of the nitrogen cycle and responsible for most of the nitrogen available to plants, it was also discussed in this chapter. Finally, we discussed nitrogen and organic fertilization, since the worldwide demand for organic foods produced without the use of synthetic inputs has driven the use of conservation practices, especially fertilization using organic wastes. Most organic fertilizers used as N source is derived from agricultural and agro-industrial wastes, slaughterhouse wastes, composting and vermicomposting, biochars, house-

\*, Marlenildo Ferreira Melo1

, Eula Paula da Silva Santos1

1 Federal Rural University of the Semi-arid Region (UFERSA), Mossoró, Brazil

2 Federal Rural University Pernambuco (UFRPE/UAST), Serra Talhada, Brazil

\*Address all correspondence to: eulenesilva@ufersa.edu.br

provided the original work is properly cited.

3 Brazilian Agricultural Research Corporation (EMBRAPA), Campo Grande, Brazil

© 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,

, Tatiane Severo Silva1

and Paula Romyne de Morais Cavalcante Neitzke1

,

, Diana Ferreira de Freitas2

, Larissa Fernandes da Silva1

,

,

#### *Organic Nitrogen in Agricultural Systems DOI: http://dx.doi.org/10.5772/intechopen.90242*

Urban wastes have also been used in agriculture. Sewage sludge showed to be an excellent N source (0.80 and 3.47% N) besides slowly mineralizing. N mineralization rates from 20 to 38% were found after 105 days [143], which depends on source material characteristics and treatment processes as well as on heavy metal content that accelerate or limit mineralization [107, 144]. Slaughterhouse residues, such as bone and blood meal, present high N rates, but they are not yet used in agriculture because studies on its adoption and behavior as organic fertilizer are scarce [97, 110, 112].

#### **8. Concluding remarks**

*Nitrogen Fixation*

**22**

*1*

**Table 2.**

*C/N ratio not found.*

fixation [118].

immobilization (reducing NO3

In addition to the earthworms, arthropods that constitute the edaphic macrofauna [87, 132, 133] are also of great interest. Millipedes (Myriapoda: Diplopoda) fragment and feed on organic wastes and excrete low C/N ratio feces (2.2% N) producing the millicompost [134–136]. Studies suggest that millicompost is similar to vermicompost and commercial substrates in relation to N supply and other macro- and micronutrients for seedling production, such as in lettuce (*Lactuca* 

**Source N content (%) C/N ratio Reference** Cattle manure 0.8–3.2 16.0–21.0 [97, 106] Equine manure 1.4–3.9 21.9–25.0 [97, 107] Sheep manure 1.2–1.8 9.0–29.0 [108, 109] Swine manure 1.9–2.8 10.0–12.0 [97, 107] Poultry litter 2.8–4.6 4.2–22.0 [97, 106, 107] Blood meal1 11.8–12.9 — [110, 111] Bone meal 4.1–4.2 4.0–7.0 [97, 112] Meat and bone meal 5.5–6.6 6.0 [106, 112, 113]

Castor pie 5.2–7.5 6.0–9.0 [97, 106, 112] Cotton pie1 4.5 — [106] Filter pie 1.5–1.8 21.0–24.0 [97, 112] Sugarcane bagasse 0.9–1.5 85.0 [106, 111, 114] Vinasse 0.3–1.2 4.0–17.0 [97, 112] Compost 0.7–2.6 11.3–64.0 [107, 115] Humus 1.3–2.6 11.0–34.0 [115, 116] Millicompost 2.0–2.2 15.0–19.0 [98, 117] Biochar 0.1–5.0 7.0–400.0 [118] Sewage sludge 0.8–3.5 9.0–50.0 [97, 112] Household waste 0.9–2.6 7.0–27.0 [97, 107, 112]

In relation to slow-release organic fertilizers, biochar is an alternative. A by-product from carbonization (pyrolysis) of biomass under low-oxygen atmosphere, biochar is fine-grained carbonaceous material with decomposition resistance [118]. N content in biochar depends on the source material (biomass) as well as on the pyrolysis temperature. Biochars from wood have high C/N ratio and low N content (0.1%), while those from manures have low C/N ratio and high N content (5.0%). For instance, biochar from eucalyptus wood (*Eucalyptus urophylla* S. T. Blake and *Corymbia citriodora* (Hook.) K.D. Hill and L.A.S. Johnson) contains 0.66 and 0.48% N, respectively, while from coffee husks (*Coffea* spp.) contains 2.74% N [138]. Besides slowly releasing nutrients, the use of biochars increases N uptake via ion exchange and NH3 removal by adsorption, stimulates

Moreover, biochar improves mycorrhizal associations and nitrogen biological

<sup>−</sup> losses), and reduces N2O emissions [139–142].

*sativa*) [98] and pitaya (*Hylocereus* spp.) (Cactaceae) [137].

*Nitrogen content and carbon/nitrogen ratio (C/N) in organic fertilizers.*

Castor pulp1 12.8 —

In the surface layer of most soils, the soil organic N can be divided into two categories: N from organic residues and N from soil organic matter or humus. N mineralization and immobilization processes occur simultaneously and oppositely in the soil. The net balance between these processes is controlled by several factors such as environmental conditions, soil physicochemical factors, agricultural management adopted, quality of the decomposing residues, and content of easily decomposable and recalcitrant fractions. As organic agriculture increases soluble organic nitrogen content, this fraction has been extensively studied. Also, being biological nitrogen fixation a key component of the nitrogen cycle and responsible for most of the nitrogen available to plants, it was also discussed in this chapter.

Finally, we discussed nitrogen and organic fertilization, since the worldwide demand for organic foods produced without the use of synthetic inputs has driven the use of conservation practices, especially fertilization using organic wastes. Most organic fertilizers used as N source is derived from agricultural and agro-industrial wastes, slaughterhouse wastes, composting and vermicomposting, biochars, household wastes, and sewage sludge composting.

#### **Author details**

Eulene Francisco da Silva1 \*, Marlenildo Ferreira Melo1 , Kássio Ewerton Santos Sombra1 , Tatiane Severo Silva1 , Diana Ferreira de Freitas2 , Maria Eugênia da Costa1 , Eula Paula da Silva Santos1 , Larissa Fernandes da Silva1 , Ademar Pereira Serra3 and Paula Romyne de Morais Cavalcante Neitzke1

1 Federal Rural University of the Semi-arid Region (UFERSA), Mossoró, Brazil


\*Address all correspondence to: eulenesilva@ufersa.edu.br

© 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.

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*Nitrogen Fixation*

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BF00750495

as.2011.23030

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Campinas; 2013. 16p

2018;**8**:57-65

PJB2019-5(1)

Research. 2018;**1**:1-8

2019;**96-99**(2019):**53**

2019;**234**:326-335

[103] Stojanov D, Milošević T, Mašković P, Milošević N, Glišić I, Paunović G. Influence of organic, organo-mineral and mineral fertilisers on cane traits, productivity and berry quality of red raspberry (*Rubus idaeus* L.). Scientia Horticulturae.

[100] Rahman MA, Islam MT, Al Mamun MA, Rahman MS, Ashraf MS. Yield and quality

[101] Mirza A, Jakhar R, Singh J.

Response of organic practices, mulching and plant growth regulators on growth, yield and quality of papaya (*Carica papaya* L) cv. Taiwan Red Lady. Indian Journal of Agricultural Research.

[102] Escanhoela ASB, Pitombo LM, Brandani CB, Navarrete AA, Bento CB, Carmo JB. Organic management increases soil nitrogen but not carbon content in a tropical citrus orchard with pronounced N2O emissions. Journal of Environmental Management.

performance of carrot under different organic and inorganic nutrient sources with mulching options. Asian Journal of Agricultural and Horticultural

orgânica de hortaliças e frutíferas. IAC:

2019;**252**:370-378. DOI: 10.1016/j.

[104] Menezes JFS, Berti MPS, Vieira Junior VD, Ribeiro RL, Berti CLF. Extração e exportação de nitrogênio, fósforo e potássio pelo milho adubado com dejetos de suínos. Revista de Agricultura Neotropical. 2018;**5**:55-59

[105] Magalhães ACM, Blum J, Lopes FB, Tornquist CG. Production components of the cowpea under different doses of organic fertiliser. Journal of

Experimental Agriculture International.

Beltrão NDM. Composição química de onze materiais orgânicos utilizados em substratos para produção de mudas. Campina Grande: Embrapa Algodão;

[106] Severino LS, Lima RDLS,

[107] Carneiro WJDO, Silva CA, Muniz JÁ, Savian TV. Mineralização de nitrogênio em Latossolos adubados com resíduos orgânicos. Revista Brasileira de Ciência do Solo. 2013;**37**:715-725. DOI: http://dx.doi.org/10.1590/

[108] Figueiredo CC, Ramos MLG, Mcmanus CM, Menezes AM. Mineralização de esterco de ovinos e sua influência na produção de alface. Horticultura Brasileira. 2012;**30**:175-179. DOI: 10.1590/ S0102-05362012000100029

[109] Peixoto Filho JU, Freire MBS, Freire FJ, Miranda MF, Pessoa LG, Kamimura KM. Produtividade de alface com doses de esterco de frango, bovino e ovino em cultivos sucessivos. Revista Brasileira de Engenharia Agrícola e Ambiental-Agriambi. 2013;**17**:419-424

[110] Sorrenti GB, Fachinello JC, Castilhos DD, Bianchi VJ,

cv Clemenules e nos atributos

Marangoni B. Influência da adubação orgânica no crescimento de tangerineira

S0100-068320130003

scienta.2019.04.009

2018;**26**:1-9

2006. 5p

[98] Antunes LFS, Scoriza FN, França EM, Silva DG, Correia MEF, Leal MAA, et al. Desempenho agronômico da alface crespa a partir de mudas produzidas com gongocomposto. Revista

Brasileira de Agropecuária Sustentável.

[99] Arjune YP, Ansari AA, Jaikishun S, Homenauth O. Effect of vermicompost and other fertilizers on soil microbial population and growth parameters of f1 Mongal tomato (*Solanum lycopersicum* mill.). Pakistan Journal of Botany. 2019;**51**:1883-1889. DOI: 10.30848/

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10.1071/CP17087

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sementes influenciam na produtividade

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s10725-014-9993-x

apsoil.2016.07.005

s00344-016-9663-5

[96] Alcantara RMCM, Xavier GR, Rumjanek NG, Rocha MM,

Carvalho JS. Eficiência simbiótica de progenitores de cultivares brasileiras de feijão-caupi. Revista Ciência Agronômica. 2014;**45**:1-9

[97] Trani PE, Terra MM, Tecchio MA, Teixeira LAJ, Hanasiro J. Adubação

[94] Silveira APD, Sala VMR, Cardoso EJBN, Labanca EG,

Cipriano MAP. Nitrogen metabolism and growth of wheat plant under diazotrophic endophytic bacteria inoculation. Applied Soil Ecology. 2016;**107**:313-319. DOI: 10.1016/j.

[95] Kumar A, Maurya BR, Raghuwanshi R, Meena VS, Islam MT. Co-inoculation with enterobacter and rhizobacteria on yield and nutrient uptake by wheat (*Triticum aestivum* L.) in the alluvial soil under indo-gangetic plain of India. Journal of Plant Growth Regulation. 2017;**36**:608-617. DOI: 10.1007/

[93] Subramanian P, Kim K, Krishnamoorthy R, Sundaram S, Sa T. Endophytic bacteria improve nodule function and plant nitrogen in soybean on co-inoculation with *Bradyrhizobium japonicum* MN110. Journal of Plant Growth Regulation. 2015;**76**:327-332. DOI: 10.1007/

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Sperotto RA, Granada CE. Inoculation of new rhizobial isolates improve nutrient uptake and growth of bean (*Phaseolus vulgaris*) and arugula (*Eruca sativa*). Journal of the Science of Food and Agriculture. 2016;**96**:3446-3453.

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with Azospirillum sp. and

**30**

orgânica de hortaliças e frutíferas. IAC: Campinas; 2013. 16p

[98] Antunes LFS, Scoriza FN, França EM, Silva DG, Correia MEF, Leal MAA, et al. Desempenho agronômico da alface crespa a partir de mudas produzidas com gongocomposto. Revista Brasileira de Agropecuária Sustentável. 2018;**8**:57-65

[99] Arjune YP, Ansari AA, Jaikishun S, Homenauth O. Effect of vermicompost and other fertilizers on soil microbial population and growth parameters of f1 Mongal tomato (*Solanum lycopersicum* mill.). Pakistan Journal of Botany. 2019;**51**:1883-1889. DOI: 10.30848/ PJB2019-5(1)

[100] Rahman MA, Islam MT, Al Mamun MA, Rahman MS, Ashraf MS. Yield and quality performance of carrot under different organic and inorganic nutrient sources with mulching options. Asian Journal of Agricultural and Horticultural Research. 2018;**1**:1-8

[101] Mirza A, Jakhar R, Singh J. Response of organic practices, mulching and plant growth regulators on growth, yield and quality of papaya (*Carica papaya* L) cv. Taiwan Red Lady. Indian Journal of Agricultural Research. 2019;**96-99**(2019):**53**

[102] Escanhoela ASB, Pitombo LM, Brandani CB, Navarrete AA, Bento CB, Carmo JB. Organic management increases soil nitrogen but not carbon content in a tropical citrus orchard with pronounced N2O emissions. Journal of Environmental Management. 2019;**234**:326-335

[103] Stojanov D, Milošević T, Mašković P, Milošević N, Glišić I, Paunović G. Influence of organic, organo-mineral and mineral fertilisers on cane traits, productivity and berry quality of red raspberry (*Rubus idaeus* L.). Scientia Horticulturae.

2019;**252**:370-378. DOI: 10.1016/j. scienta.2019.04.009

[104] Menezes JFS, Berti MPS, Vieira Junior VD, Ribeiro RL, Berti CLF. Extração e exportação de nitrogênio, fósforo e potássio pelo milho adubado com dejetos de suínos. Revista de Agricultura Neotropical. 2018;**5**:55-59

[105] Magalhães ACM, Blum J, Lopes FB, Tornquist CG. Production components of the cowpea under different doses of organic fertiliser. Journal of Experimental Agriculture International. 2018;**26**:1-9

[106] Severino LS, Lima RDLS, Beltrão NDM. Composição química de onze materiais orgânicos utilizados em substratos para produção de mudas. Campina Grande: Embrapa Algodão; 2006. 5p

[107] Carneiro WJDO, Silva CA, Muniz JÁ, Savian TV. Mineralização de nitrogênio em Latossolos adubados com resíduos orgânicos. Revista Brasileira de Ciência do Solo. 2013;**37**:715-725. DOI: http://dx.doi.org/10.1590/ S0100-068320130003

[108] Figueiredo CC, Ramos MLG, Mcmanus CM, Menezes AM. Mineralização de esterco de ovinos e sua influência na produção de alface. Horticultura Brasileira. 2012;**30**:175-179. DOI: 10.1590/ S0102-05362012000100029

[109] Peixoto Filho JU, Freire MBS, Freire FJ, Miranda MF, Pessoa LG, Kamimura KM. Produtividade de alface com doses de esterco de frango, bovino e ovino em cultivos sucessivos. Revista Brasileira de Engenharia Agrícola e Ambiental-Agriambi. 2013;**17**:419-424

[110] Sorrenti GB, Fachinello JC, Castilhos DD, Bianchi VJ, Marangoni B. Influência da adubação orgânica no crescimento de tangerineira cv Clemenules e nos atributos

químicos e microbiológicos do solo. Revista Brasileira de Fruticultura. 2008;**30**:1129-1135. DOI: 10.1590/ S0100-29452008000400047

[111] Zamberlam J, Froncheti A. Agroecologia-Caminho de Preservação do Agricultor e do Meio Ambiente. Editora Vozes Ltda: Petrópolis; 2012. 196p

[112] Chacón EAV, Mendonça ES, Silva RR, Lima PC, Silva IR, Cantarutti RB. Decomposição de fontes orgânicas e mineralização de formas de nitrogênio e fósforo. Ceres. 2011;**58**:373-383. DOI: 10.1590/ S0034-737X2011000300019

[113] Pires AA, Monnerat PH, Marciano CR, Rocha Pinho LG, Zampirolli PD, Rosa RCC, et al. Efeito da adubação alternativa do maracujazeiroamarelo nas características químicas e físicas do solo. Revista Brasileira de Ciência do Solo. 2008;**32**:1997-2005

[114] Yamaguchi CS, Ramos NP, Carvalho CS, Pires AMM, Andrade CA. Decomposição da palha de canade-açúcar e balanço de carbono em função da massa inicialmente aportada sobre o solo e da aplicação de vinhaça. Bragantia. 2017;**76**:135-144

[115] Cotta JAO, Carvalho NLC, Brum TDS, Rezende MOO. Compostagem versus vermicompostagem: comparação das técnicas utilizando resíduos vegetais, esterco bovino e serragem. Engenharia Sanitária e Ambiental. 2015;**20**:65-78. DOI: 10.1590/ S1413-41522015020000111864

[116] Lisboa CC, Lima FRD, Reis RHCL, Silva CA, Marques JJ. Taxa de mineralização do nitrogênio de resíduos orgânicos. Cultura Agronômica. 2018;**27**:341-355

[117] Antunes LFS, Scoriza FN, Silva DG, Fernandes MEC. Production and efficiency of organic compost

generated by millipede activity. Ciência Rural. 2016;**46**:815-819. DOI: 10.1590/0103-8478cr20150714

[118] Lehmann J, Joseph S, editors. Biochar for Environmental Management: Science, Technology and Implementation. London: Routledge; 2015. p. 976

[119] Schröder JJ, De Visser W, Assinck FBT, Velthof GL. Effects of short-term nitrogen supply from livestock manures and cover crops on silage maize production and nitrate leaching. Soil Use and Management. 2013;**29**:151-160. DOI: 10.1111 / sum.12027

[120] Amlinger F, Götz B, Dreher P, Geszti J, Weissteiner C. Nitrogen in biowaste and yard waste compost: Dynamics of mobilisation and availability–A review. European Journal of Soil Biology. 2003;**39**:107-116. DOI: 10.1016/S1164-5563(03)00026-8

[121] Alves RN, Menezes RS, Salcedo IH, Pereira WE. Relação entre qualidade e liberação de N por plantas do semiárido usadas como adubo verde. Revista Brasileira de Engenharia Agrícola e Ambiental. 2011;**15**:1107-1114

[122] Zandvakili OR, Barker AV, Hashemi M, Etemadi F, Autio WR, Weis S. Growth and nutrient and nitrate accumulation of lettuce under different regimes of nitrogen fertilization. Journal of Plant Nutrition. 2019;**42**:1575-1593

[123] Rodrigues RMP, França KS, Didolanvi OD, Oliveira RL, Sousa MLL, Carvalho RS. Rendimento do pimentão em função de diferentes doses de esterco caprino. Cadernos de Agroecologia. 2018;**13**:1-7

[124] Lima DC, Lopes HLS, Sampaio ASO, Souto LS, Pereira ACS, Silva AM, et al. Crescimento inicial da cultura do rabanete (*Raphanus sativus* L.) submetida a níveis e fontes de fertilizantes orgânicos.

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Revista Brasileira de Gestão Ambiental. 2019, 2019;**13**:19-24. DOI: 10.18378/rbga. do solo. Enciclopédia Biosfera.

systems in Southern Colombia.

Floresta e Ambiente. 2019;**26**:1-8. DOI:

[134] Garcia FRM, Campos JV. Biologia e controle de artrópodes de importância fitossanitária (Diplopoda, Symphyla, Isopoda), pouco conhecidos no Brasil.

[135] Thakur PC, Shailendra PA, Sinha K. Comparative study of characteristics of biocompost produced by millipedes and earthworms. Advances in Applied

Science Research. 2011;**2**:94-98

[136] Ramanathan B, Alagesan P. Evaluation of millicompost versus vermicompost. Current Science.

[137] Cruvinel FF, Antunes LFS, Vasconcellos MAS, Rangel Júnior IM, Martelleto LAP. Produção de mudas orgânicas de pitaia em diferentes substratos. Cadernos de Agroecologia.

[138] Veiga TRLA, Lima JT,

characterizations for biochar production. Cerne. 2017;**23**:529-536. DOI: 10.1590/01047760201723042373

[139] Cayuela ML, Sánchez-Monedero MA, Roig A, Hanley K, Enders A, Lehmann J. Biochar and denitrification in soils: When, how much and why does biochar reduce N2O emissions? Scientific Reports. 2013; **3-1732**:1-7. DOI: 10.1038/srep01732

[140] Clough T, Condron L,

Agronomy. 2013;**3**:275-293

Kammann C, Müller C. A review of biochar and soil nitrogen dynamics.

Dessimoni ALA, Pego MFF, Soares JR, Trugilho PF. Different plant biomass

[133] Suárez LR, Pinto SPC, Salazar JCS. Soil macrofauna and edaphic properties in coffee production

10.1590/2179-8087.033418

Biológico. 2001;**63**:7-13

2012;**103**:140-143

2018;**13**:1-5

2015;**11**:115-131

[125] Severino LS. O que sabemos sobre a torta da mamona. Campina Grande:

Embrapa Algodão; 2005. 31p

[126] Severino LS, Costa FX, Beltrão NEM, Lucena AMA, Guimarães MM. Mineralização da torta de mamona, esterco bovino e bagaço de cana estimada pela respiração microbiana. Revista de Biologia de Ciências da Terra. 2005;**5**:1-6

[127] Alves FQG, Soares EPS,

[128] Costa FX, Severino LS,

2004;**4**:1-7

2011;**33**:364-368

[130] Franco GG, Silva SL,

Produção agroecológica de compostagem de folhas, frutos e madeira triturada. Cadernos de Agroecologia. 2018;**13**:1-5

Rezende MOO. Processo de

vermicompostagem versus compostagem. Química Nova.

[132] Souza MH, Vieira BCR,

2013;**36**:640-645

Emiliano ED, Silva MVS, Costa FS.

[131] Dores-Silva PR, Landgraf MD,

estabilização de resíduos orgânicos:

Oliveira PG, Amaral AA. Macrofauna

Sobral RRS, Melo ADD, Duarte ABM, Rocha MR, et al. Diferentes doses de torta de mamona no desempenho de bulbos de rabanete consorciado com alface. Horticultura. 2012;**30**:5464-5471

Beltrão NM, Freire RMM, Lucena AMA, Guimarães MMB. Avaliação de teores químicos na torta de mamona. Revista de Biologia e Ciências da Terra.

[129] Lima RL, Severino LS, Sampaio LR, Sofiatti V, Gomes JA, Beltrão NE. Blends of castor meal and castor husks for optimized use as organic fertilizer. Industrial Crops and Products.

v13i1.6152

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*Nitrogen Fixation*

196p

químicos e microbiológicos do solo. Revista Brasileira de Fruticultura. 2008;**30**:1129-1135. DOI: 10.1590/ S0100-29452008000400047

generated by millipede activity. Ciência Rural. 2016;**46**:815-819. DOI:

10.1590/0103-8478cr20150714

[119] Schröder JJ, De Visser W, Assinck FBT, Velthof GL. Effects of short-term nitrogen supply from livestock manures and cover crops on silage maize production and nitrate leaching. Soil Use and Management. 2013;**29**:151-160. DOI: 10.1111 /

[120] Amlinger F, Götz B, Dreher P, Geszti J, Weissteiner C. Nitrogen in biowaste and yard waste compost: Dynamics of mobilisation and

availability–A review. European Journal of Soil Biology. 2003;**39**:107-116. DOI: 10.1016/S1164-5563(03)00026-8

[121] Alves RN, Menezes RS, Salcedo IH, Pereira WE. Relação entre qualidade e liberação de N por plantas do semiárido usadas como adubo verde. Revista Brasileira de Engenharia Agrícola e Ambiental. 2011;**15**:1107-1114

[122] Zandvakili OR, Barker AV, Hashemi M, Etemadi F, Autio WR, Weis S. Growth and nutrient and nitrate accumulation of lettuce under different regimes of nitrogen fertilization. Journal of Plant Nutrition. 2019;**42**:1575-1593

[123] Rodrigues RMP, França KS, Didolanvi OD, Oliveira RL, Sousa MLL, Carvalho RS. Rendimento do pimentão em função de diferentes doses de esterco caprino. Cadernos de Agroecologia.

Souto LS, Pereira ACS, Silva AM, et al. Crescimento inicial da cultura do rabanete (*Raphanus sativus* L.) submetida a níveis e fontes de fertilizantes orgânicos.

[124] Lima DC, Lopes HLS, Sampaio ASO,

2018;**13**:1-7

2015. p. 976

sum.12027

[118] Lehmann J, Joseph S, editors. Biochar for Environmental

Management: Science, Technology and Implementation. London: Routledge;

[111] Zamberlam J, Froncheti A. Agroecologia-Caminho de Preservação do Agricultor e do Meio Ambiente. Editora Vozes Ltda: Petrópolis; 2012.

[112] Chacón EAV, Mendonça ES, Silva RR, Lima PC, Silva IR,

[113] Pires AA, Monnerat PH, Marciano CR, Rocha Pinho LG,

[114] Yamaguchi CS, Ramos NP,

Decomposição da palha de canade-açúcar e balanço de carbono em função da massa inicialmente aportada sobre o solo e da aplicação de vinhaça.

Bragantia. 2017;**76**:135-144

[115] Cotta JAO, Carvalho NLC,

das técnicas utilizando resíduos vegetais, esterco bovino e serragem. Engenharia Sanitária e Ambiental. 2015;**20**:65-78. DOI: 10.1590/ S1413-41522015020000111864

Silva CA, Marques JJ. Taxa de

2018;**27**:341-355

orgânicos. Cultura Agronômica.

[117] Antunes LFS, Scoriza FN,

Cantarutti RB. Decomposição de fontes orgânicas e mineralização de formas de nitrogênio e fósforo. Ceres. 2011;**58**:373-383. DOI: 10.1590/ S0034-737X2011000300019

Zampirolli PD, Rosa RCC, et al. Efeito da adubação alternativa do maracujazeiroamarelo nas características químicas e físicas do solo. Revista Brasileira de Ciência do Solo. 2008;**32**:1997-2005

Carvalho CS, Pires AMM, Andrade CA.

Brum TDS, Rezende MOO. Compostagem versus vermicompostagem: comparação

[116] Lisboa CC, Lima FRD, Reis RHCL,

mineralização do nitrogênio de resíduos

Silva DG, Fernandes MEC. Production and efficiency of organic compost

**32**

Revista Brasileira de Gestão Ambiental. 2019, 2019;**13**:19-24. DOI: 10.18378/rbga. v13i1.6152

[125] Severino LS. O que sabemos sobre a torta da mamona. Campina Grande: Embrapa Algodão; 2005. 31p

[126] Severino LS, Costa FX, Beltrão NEM, Lucena AMA, Guimarães MM. Mineralização da torta de mamona, esterco bovino e bagaço de cana estimada pela respiração microbiana. Revista de Biologia de Ciências da Terra. 2005;**5**:1-6

[127] Alves FQG, Soares EPS, Sobral RRS, Melo ADD, Duarte ABM, Rocha MR, et al. Diferentes doses de torta de mamona no desempenho de bulbos de rabanete consorciado com alface. Horticultura. 2012;**30**:5464-5471

[128] Costa FX, Severino LS, Beltrão NM, Freire RMM, Lucena AMA, Guimarães MMB. Avaliação de teores químicos na torta de mamona. Revista de Biologia e Ciências da Terra. 2004;**4**:1-7

[129] Lima RL, Severino LS, Sampaio LR, Sofiatti V, Gomes JA, Beltrão NE. Blends of castor meal and castor husks for optimized use as organic fertilizer. Industrial Crops and Products. 2011;**33**:364-368

[130] Franco GG, Silva SL, Emiliano ED, Silva MVS, Costa FS. Produção agroecológica de compostagem de folhas, frutos e madeira triturada. Cadernos de Agroecologia. 2018;**13**:1-5

[131] Dores-Silva PR, Landgraf MD, Rezende MOO. Processo de estabilização de resíduos orgânicos: vermicompostagem versus compostagem. Química Nova. 2013;**36**:640-645

[132] Souza MH, Vieira BCR, Oliveira PG, Amaral AA. Macrofauna do solo. Enciclopédia Biosfera. 2015;**11**:115-131

[133] Suárez LR, Pinto SPC, Salazar JCS. Soil macrofauna and edaphic properties in coffee production systems in Southern Colombia. Floresta e Ambiente. 2019;**26**:1-8. DOI: 10.1590/2179-8087.033418

[134] Garcia FRM, Campos JV. Biologia e controle de artrópodes de importância fitossanitária (Diplopoda, Symphyla, Isopoda), pouco conhecidos no Brasil. Biológico. 2001;**63**:7-13

[135] Thakur PC, Shailendra PA, Sinha K. Comparative study of characteristics of biocompost produced by millipedes and earthworms. Advances in Applied Science Research. 2011;**2**:94-98

[136] Ramanathan B, Alagesan P. Evaluation of millicompost versus vermicompost. Current Science. 2012;**103**:140-143

[137] Cruvinel FF, Antunes LFS, Vasconcellos MAS, Rangel Júnior IM, Martelleto LAP. Produção de mudas orgânicas de pitaia em diferentes substratos. Cadernos de Agroecologia. 2018;**13**:1-5

[138] Veiga TRLA, Lima JT, Dessimoni ALA, Pego MFF, Soares JR, Trugilho PF. Different plant biomass characterizations for biochar production. Cerne. 2017;**23**:529-536. DOI: 10.1590/01047760201723042373

[139] Cayuela ML, Sánchez-Monedero MA, Roig A, Hanley K, Enders A, Lehmann J. Biochar and denitrification in soils: When, how much and why does biochar reduce N2O emissions? Scientific Reports. 2013; **3-1732**:1-7. DOI: 10.1038/srep01732

[140] Clough T, Condron L, Kammann C, Müller C. A review of biochar and soil nitrogen dynamics. Agronomy. 2013;**3**:275-293

[141] El-Naggar A, Lee SS, Rinklebe J, Farooq M, Song H, Sarmah AK, et al. Biochar application to low fertility soils: A review of current status, and future prospects. Geoderma. 2019;**337**:536-554. DOI: 10.1016/j.geoderma.2018.09.034

**Chapter 3**

**Abstract**

**1. Introduction**

**35**

Nitrogen Fertilization II:

Environmental Quality

Management Practices to Sustain

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

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,

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

Crop Production and Soil and

depends on social, economic, soil, and environmental conditions.

nitrogen fertilizer, nitrogen-use efficiency, soil quality

**Keywords:** crop yields, environmental quality, management practices,

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[144] Cabrera ML, Kissel DE, Vigil MF. Nitrogen mineralization from organic residues: Research opportunities. Journal of Environmental Quality. 2005;**34**:75-79. DOI: 10.2134/ jeq2005.0075

#### **Chapter 3**

*Nitrogen Fixation*

s00374-018-01338-3

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[142] Fungo B, Lehmann J, Kalbitz K, Thionģo M, Tenywa M, Okeyo I, et al. Ammonia and nitrous oxide emissions from a field Ultisol amended with tithonia green manure, urea, and biochar. Biology and Fertility of Soils. 2019;**55**:135-148. DOI: 10.1007/

[143] Boeira RC, Ligo MAV, Dynia JF. Mineralização de nitrogênio em solo tropical tratado com lodos de esgoto. Pesquisa Agropecuária Brasileira. 2002;**37**:1639-1647. DOI: 10.1590/ S0100-204X2002001100016

[144] Cabrera ML, Kissel DE, Vigil MF. Nitrogen mineralization from organic residues: Research

jeq2005.0075

opportunities. Journal of Environmental Quality. 2005;**34**:75-79. DOI: 10.2134/

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