Nitrogen Mineralization Kinetics Research Articles

Carbon and Nitrogen Mineralization Kinetics in Soil Under Differential Nutrient Management Regimes in Inceptisols of Coastal India

ABSTRACT In intensive cropping systems, nutrient, and residue management techniques have a tendency to change the soil’s carbon (C) and nitrogen (N) cycle and, consequently, its potential for sequestration and loss. To understand the carbon and nitrogen mineralization kinetics, laboratory incubation studies were conducted with soils at variable depths from a long-term nutrient management experiment on cereal-vegetable-pulse cropping system. The experiment was laid out completely randomized design with 10 treatments replicated thrice. Long-term integrated application of inorganics with organics, biofertilizers, and amendment along with crop residues showed higher carbon and nitrogen mineralization potential and lower potential was observed in soils where crops were raised without application of any nutrient inputs (control) and uncultivated fallow. It was calculated that the potential for higher levels of carbon and nitrogen mineralization existed in the surface (0–15 cm) and subsurface (15–30 cm) layers, respectively, and was negligible in the deeper layer (30–45 cm). The mineralization rate was initially faster up to 42 days of incubation, indicating proper utilization of readily decomposable soil organic matter in the labile pools and thereafter found to slow down. Addition of lime along with the integrated use of organics and inorganics has found to raise the pH to a level that provides a suitable soil environment which affects the carbon and nitrogen mineralization kinetics resulting in buildup of total organic carbon and total nitrogen in the soils. The first-order kinetic model was the best fit in explaining the kinetic parameters of C and N mineralization. Soils under integrated nutrient management (INM) with farmyard manure (FYM) along with biofertilizers, amendment, and inorganic nutrients exhibited better carbon dynamics higher C mineralization (Cmin), potentially mineralizable C (C0), rate of C mineralization (dCmin/dt), and C mineralization quotient (qM), whereas soils applied with similar combinations with vermicompost was found effective for better nitrogen dynamics in terms of enhanced N mineralization (Nmin), potentially mineralizable N (N0), rate of N mineralization (dNmin/dt) and active N fraction over control and fallow soils. Integrated application of inorganic and organic inputs with crop residues over the years has shown beneficial impacts on soil carbon and nitrogen mineralization processes and their kinetics.

The The Kinetics of Carbon and Nitrogen Mineralization of Different Organic Amendments in the Soil

The exploitation of exogenous organic matter from fresh or composted livestock manure in agriculture is an effective source that addresses the problem of soil depletion and provides essential nutrients to plants. It can also cause worry about environmental degradation, such as CO2 emissions and nitrate leaching. The rational use of these organic soil amendments requires additional research, which still remains limited in terms of articles and books in Morocco.  The objective of our research is to study the kinetics of carbon and nitrogen mineralization of the different organic amendments, sheep manure (SM), cattle manure with straw (CM), two composts (CA, CF), and poultry manure laying hen (PL), by an incubation method under controlled laboratory conditions, and characterize the organic matter (OM) by biochemical fractionation. In the light of these results obtained, it can be seen that laying hen droppings induced the highest level of carbon and nitrogen mineralization, followed by sheep manure and cattle manure with straw which recorded an intermediate rate of carbon mineralization. And high nitrogen immobilization, these two materials are considered to be a transition point between the manure and the two compost, which recorded slow and low carbon and nitrogen mineralization. Statistical analysis endorsed a correlation between the kinetics of carbon mineralization and biochemical fractionations of organic matter in EOMs.

Nitrogen mineralization kinetics in soil supplemented with organic amendments

Sustainable agriculture requires careful optimization of the use of organic amendments to improve soil fertility while minimizing any harmful environmental effects. To understand the events that occur in soil after the addition of different organic amendments, we evaluated the nitrogen (N) mineralization dynamics in soil after adding organic amendments. There were five treatments comprising of control, FYM @20.83 t ha-1, vermicompost @9.09 t ha-1, dhaicha as green manure @ 3.076 t ha-1. FYM @ 10.41 t ha1+ vermicompost @2.27 t ha-1 +dhaincha @ 0.769 t ha-1 replicated times. The N mineralization of each organic amendment was determined by analyzing total mineral nitrogen during a 75 day laboratory incubation experiment. Soils amended with farm yard manure (FYM) released 142.40 mg N kg-1 soil during the 75day incubation period (and faster too), more than 77%, 1.91%, 6.05% and 5.05% as much as that released from soils amended with FYM, Vermicompost (VC), Green Manure (GM) and combination respectively. At the end of the incubation, the net N mineralization in FYM amended soils was 12.68%, 54.71% and 50.01% higher than that in soils amended with VC, GM and their combined application. Furthermore, the total N mineralization was fit in first-order kinetics and the N mineralization rate was found in increasing manner with FYM, VC, GM and their combination. (R2=0.949, k=0.141; R2=0.968, k=0.009; R2=0.920, k=0.009; R2=0.953, k=0.010) during incubation Nitrogen mineralization varied with amendments.

The Effect of Grazing Intensity on Vegetation Coverage and Nitrogen Mineralization Kinetics of Steppe Rangelands of Iran (Case Study: Nodoushan Rangelands, Yazd, Iran)

Livestock grazing can affect the cycling of nutritional elements in soil by making changes to the vegetation coverage. This study aimed to investigate the effect of rangeland exploitation on vegetation coverage and nitrogen kinetics. To this end, three experimental sites of light, moderate, and heavy grazing in Nodoushan rangelands of Yazd province were selected. The vegetation properties were then measured through systematic random sampling method and three to five bases along the transect were sampled from the current year growth of the dominant plants in the region. The soil samples were collected from 0–15 cm depth in five replications and mixed together to obtain a single composite soil sample on each site. In the first stage, nitrogen (N), carbon (C), C/N, cellulose, hemicellulose, and lignin of the sampled plant as well as nitrogen, carbon, lime, soil texture, saturation moisture percentage, pH, and electrical conductivity (EC) of the soil were measured. As the soil properties did not differ for light and moderate grazing soils, different treatments were conducted on the dominant species of light and heavy grazing sites with 1% organic carbon added to the rangeland soil. Nitrogen mineralization treatments were selected based on vegetation changes that, with increasing livestock grazing intensity, changed the predominance of plant composition from Artemisia sieberi and steppe to percentage Artemisia sieberi and Peganum harmala. The treatments included control, 100% Artemisia sieberi, 75% Artemisia sieberi and 25% Peganum harmala, 50% Artemisia sieberi and 50% Peganum harmala, 25% Artemisia sieberi and 75% Peganum harmala, and 100% Peganum harmala. The soil samples were incubated for pure nitrogen mineralization in three replications of 3 months. The results of nitrogen mineralization revealed that the immobilization of the treated soil with higher Artemisia sieberi and lower Peganum harmala was done at a more rapid rate during the first week. The immobilization was slowly reduced by the third week and then followed a growing rate. Overall, the results show that an increase in grazing intensity was associated with a change in vegetation coverage toward Peganum harmala species, the biochemical characteristics of which elevated the levels of pure nitrogen mineralization in soil.

Aerobic bioconversion of aquaculture solid waste into liquid fertilizer: Effects of bioprocess parameters on kinetics of nitrogen mineralization

Aquaculture has experienced a burgeoning growth worldwide in the last decade resulting in nearly 50% of seafood originating from aquaculture farms. However, there are less studies on the utilization of the manure produced by aquatic organisms in comparison to warm-blooded livestock. Aquaponics offers more efficient utilization of nutrients and can reduce the operational costs in aquaculture. This paper presents the results of a study to identify the optimal settings to digest fish manure through a microbial-assisted aerobic bioprocess, using endogenous heterotrophic and nitrifying bacteria. The effects of pH (5.5, 6.0 and 6.5), temperature (30, 35 and 40 °C) and duration (1–30 days) on kinetics of nitrogen mineralization were investigated and compared to a control bioreactor (carried out without pH adjustment). The mineralization dynamics for all pH-controlled bioreactors revealed that only ammonification occurred. No nitrification was observed for all three-temperature conditions and throughout the entire bioprocessing period. The mineralization process in the control bioreactor, on the other hand, followed the typical non-inhibited nitrogen mineralization (i.e., release of ammonium followed by oxidation into nitrate). However, nitrate was only observed at temperatures <40 °C indicating a complete suppression of nitrification at higher temperatures. Analytical data and modeled parameters indicated that the bioprocessing of aquaculture solid waste for 15 days at 35 °C using either pH 6.0 or 6.5 maximized nitrogen bioconversion in the form of ammonium ions (NH4+). This study indicates the importance of temperature and pH optimization for more efficient processing of aquaculture solid waste such as fish manure.

Carbon and nitrogen mineralization kinetics as influenced by diversified cropping systems and residue incorporation in Inceptisols of eastern Indo-Gangetic Plain

Carbon (C) and nitrogen (N) mineralization process is a key indicator of soil quality which regulate nutrient availability and supply to the crops. To provide insight on C and N mineralization in soil of diversified cropping systems, an experiment was initiated in split-plot design with five diversified jute-rice based cropping system under four nutrient and crop residue management practices (NCRM) during 2012–13. The five cropping system viz., fallow-rice-rice (F-R-R), jute-rice-wheat (J-R-W), jute-rice-baby corn (J-R-Bc), jute-rice-gardenpea (J-R-Gp), jute-rice-mustard-mung bean/green gram (J-R-M-Mu) were taken in main plot and four (NCRM) practices viz. 75% recommended doses of fertilizers (RDF) to all crops without crop residue (F1R0), 75% RDF with crop residues (F1R1) (Residue of rice, wheat and corn at 4 t/ha and garden pea and mung bean at 2 t/ha incorporated into soil with their respective cropping), 100% RDF without crop residues (F2R0) and 100% RDF with crop residue (F2R1) were taken in sub plot with three replication. Soil samples (0–15 cm) were collected after four year completion of crop cycles in 2016 to measure C and N accumulation and to estimate potentially mineralizable C (C0) and N (N0) using first order kinetic model. The highest C mineralization was recorded in J-R-M-Mu (1280 mg CO2/kg soil) followed by J-R-Gp (1235 mg CO2/kg soil) and J-R-Bc (1235 mg CO2/kg soil) cropping system under F2R1. N mineralization was also higher in J-R-M-Mu (63.3 mg N/kg soil) followed by J-R-Gp (55 mg N/kg soil) and J-R-Bc (52 mg N/kg soil) cropping systems under F2R1.Significantly higher (P < 0.05) rate constant for C and N mineralization (kC and kN) were in J-R-M-Mu under F2R1 compared to other cropping systems and NCRM practices. Hence, our findings indicate that cropping systems with 100% RDF with mungbean residue at 2 t/ha had higher C and N mineralization. This cropping system had also higher C and N kinetic due to presence of more labile or decomposed SOC. Application of mineral fertilizers with crop residues had positive effect on C and N mineralization and their kinetics.

Carbon and nitrogen mineralization kinetics as affected by tillage systems in a calcareous loam soil

Tillage systems may affect soil carbon (C) and nitrogen (N) kinetics. However, the effects of tillage on C and N kinetics have not yet been studied for the major calcareous soils (Calcixerepts) from Iran. The aim of this study was to assess the effect of four tillage systems on soil C and N mineralization kinetics in a semi-arid loam soil after six years of two conventional tillage (CT) systems (moldboard plow, MP and disk plow, DP) and two reduced tillage (RT) systems (chisel plow, CP and rotary plow, RP) under similar plant residue inputs and cover crops in Shahrekord, Central Iran. We tested the hypothesis that soil C and N mineralization kinetic parameters are higher in RT than CT systems because of differential soil disturbance and mixing. Tillage systems were established in 2005 and, an experiment was arranged in a randomized complete block design with each tillage system replicated three times and sampled over three years (2008, 2009 and 2011). Soil samples (0–20cm) were incubated (at 25°C for 11 weeks) to measure the cumulative C and N mineralization throughout the incubation and to estimate the potentially mineralizable C (Co) and N (No), and the rate constants for labile C (kC) and N (kN) using the first-order kinetic single model. Soil C, N and particulate organic matter (POM) remained unaffected by tillage systems and thus these properties are not a sensitive indicator of changes in soil C and N contents. The cumulative C and N mineralization; and Co indicated the effect of tillage systems over the period of study. RT systems had lower soil cumulative C mineralization (20%), Co (17%) and kC (10%) than CT systems. The cumulative N mineralization was also lower (23%) in RT (20.7-34.3mgkg−1) than CT (28.1-42.2mgkg−1), while No tended to increase only in RP (231mgkg−1) when compared with other tillage systems (151–177mgkg−1). The kN was generally lower (33%) in RT (0.017 week−1) than CT (0.024 week−1). The initial potential rates of C (Co×kC) or N (No×kN) mineralization tended to be lower in RT and were found to be more suitable indicators to differentiate tillage effects. Differences in C and N mineralization among tillage systems were much larger in 2011 than 2008. The data rejected our hypothesis with regard to higher C and N mineralization kinetic parameters in RT systems with less soil disturbance. In conclusion, when crop residue is maintained, RT systems can protect the labile C pools and decrease the incorporation of crop residues into the soil matrix with a lower supply of mineralizable organic C and N for microbes under the studied environmental settings. Our findings indicate that soil C and N kinetic parameters might be a more sensitive indicator of tillage effects on C and N turnover than the whole soil organic matter (SOM) and POM fraction, with a potential consequence for the soil CO2 emissions and N transformation rates.

Nitrogen Mineralization from Sugarcane Vinasse

Vinasse is a liquid residue applied as a fertilizer in sugarcane crops. However, in areas far away from sugarcane mills the cost of the distribution can be very high due, the large volume of water. So, one solution is to concentrate the vinasse by the evaporation process to reduce transport costs. Considering that the nitrogen mineralization kinetics is not known in concentrated vinasse, the objective of this study was to evaluate the net and potential nitrogen mineralization in soil that received vinasse concentrated and not concentrated. The treatments with concentrated vinasse provided the highest values of net mineralization and total nitrogen, which presented significant correlation each other, the same way as the potential mineralization values had a positive correlation with the doses and the amounts of total nitrogen. The total nitrogen values can be used as an index of nitrogen availability in soils that received concentrated vinasse.

UV–VIS photocatalytic degradation of nitrobenzene from water using heavy metal doped titania

The photocatalytic degradation of nitrobenzene (NB) under UV–VIS irradiation with un-doped TiO2 and various heavy metals doped TiO2 powders were studied for aerated solutions. The dopant type (Fe, Co, Ni) and its concentration (0.5–5wt.% TiO2) influence on pollutant degradation efficiency were investigated. The photocatalyst with lowest Fe content (0.5wt.%) showed a considerable better behaviour in respect to pollutant degradation than catalyst with higher Fe content and Co and Ni doped titania catalysts. The experiments were carried out for solutions with (0.37–8.45)×10−4M NB initial content, using 50–250mg/L catalyst dose, at various pHs (4–10) and irradiation time between 30 and 240min. The kinetics of NB degradation and organic nitrogen mineralization was assessed and pseudo-first order rate constants were calculated. For optimum working conditions (0.5wt.% Fe doped-TiO2 loading of 250mg/L, 2.52×10−4M pollutant initial concentration, pH=7 and 240min irradiation time) NB removal and organic nitrogen mineralization efficiencies were 99% and 85%, respectively. It was also demonstrated that degradation process occurs on catalyst surface, so experimental results are in accordance with Langmuir–Hinshalwood model.

Kinetics of nitrogen mineralization in sewage amended soil

A laboratory experiment was carried out at, Jaunpur (25°18’ N, 83°03’ S) to study the kinetics of N mineralization in sewage amended soils. Four different agricultural fields viz., A, B, C and D which has been receiving sewage for irrigation since last five or more years were selected for study. The three replicate of each treatment were incubated at room temperature (25°C) for 7 weeks. The soils were brought to field capacity by addition of distilled water. The subsamples (10g) were withdrawn from each sample after every week interval and extracted immediately with 100 ml of 2 M KC1 solution and N was determined. The fitness of the model for mineralization study was tested by least square method and the mineralization rate constant (K) and half-life (t1/2) were calculated from fitted model. It was observed that, the highest mineralized N (121.20 mg/kg) was observed in soil receiving sewage continuously while lowest in N mineralized 112.80 mg/kg was observed in soil receiving less amount of sewage. Estimated mineralization rate content ‘K’ in four soils was 0.44, 0.38, 0.10 and 0.43 and correlation coefficient were 0.99, 0.98, 0.99 and 0.99, respectively. The study revealed that, nitrogen mineralization was increased with increasing period of incubation with rapid increase during 2–4 weeks of incubation. First order model of kinetics was best suited for nitrogen mineralization in sewage amended soil under study.

Studies on N Mineralization from Soils Amended with Green Manures under the Influence of Two Different Moisture Regime

A laboratory experiment was conducted over 12 weeks to study the nitrogen (N) mineralization pattern and kinetics from nine locally available green manure (GM) at submergence and field capacity (FC), when incorporated into typical rice growing teesta alluvial soils of the district Coochbehar located at Terai Agro-climatic region of West Bengal. Rapid mineralization was evidenced by the fact that out of total N mineralized at the end of incubation, 20.43–100.59% and 27.60–76.17% released during 1st week at submergence and FC, respectively. After 12 weeks highest N was mineralized from C. sophera (162.57 mg kg−1 soil) and G. sepium (195.72 mg kg−1 soil) amended soil at submerge and FC moisture condition, respectively. At submergence, soils amended with I. cornea and V. ungiculata and at FC, G. sepium and E. indica amended soil exhibited most consistent trend of successive increase till the end with a few exception; whereas mean (of moisture regime) cumulative mineralization showed most consistency in case of V. ungiculata and C. sophera. Mean (of GM) cumulative mineralization was better at submergence over FC moisture regime during early period; whereas reverse was the trend during later period of incubation. Similar was the trend for individual GMs except C. sophera, G. sepium and I. cornea recording higher value at FC almost all throughout the incubation period. FC moisture regime recorded higher mineralization potential (N0) and lower rate constant (k) for all GMs; except N0 value for P. pinnata. Considering all these above C. sophera and V. ungiculata were identified as best GM species across moisture regime as well as at submergence; whereas at FC moisture regime G. sepium and E. indica were best performing GM species.

Nitrogen mineralization kinetics and parameter estimates in soil amended with Neem seed cake and inorganic fertilizer in Samaru, Nigeria

A field study was conducted to assess the effect of neem seed cake (NSC) on the kinetics of net nitrogen mineralization and parameter estimates. The experiment consisted of sorghum plots to which milled NSC (with %N > 3) and urea (inorganic N source) were applied. Ammonium-nitrogen and nitrate-nitrogen were determined after 0, 2, 4, 6, 8, 12, 19 and 34 weeks from soils covered with PVC tubes inserted into the sixteen treatment combination plots. Inorganic N concentration in the amended plots and the control were analysed using five mathematical N mineralization models. N0, Ne, h and k were estimated from the fit of each mathematical model. The treatments were highly variable in their respective N mineralization characteristics, but the peaks for mineralized N content were observed at early incubation periods, i. e., 10 -28 days. Potential respective mineralizable N (N0) content of the first order rate, consecutive (h ‚ k), consecutive (h = k), Gompertz and mixed order rate constant was -927E-22, 430.90, 1.9E-21, 568.40 and 427.20 mg kg-1 soil and the respretively rate constant (k) was -5E+21, 0.2269, 2E+23, 0.0954 and 0.8116.respretively Net N mineralization was best described by a mixed order rate model (R2 = 0.992) and residual mean square error (RMSE)was = 28.41. A Gompertz function also fitted the data closely (R2 = 0.999; RMSE = 52.47). The two models recognize that N mineralization is not just a function of substrate N concentration but also of the capacity of the microbial community to adjust to substrate quality and composition affecting their growth and activity. Key words : mineralization model, neem seed cake, N mineralization, parameter estimates, PVC tubes

Carbon and nitrogen mineralization kinetics in soil of rice–rice system under long term application of chemical fertilizers and farmyard manure

Quantitative information on carbon (C) and nitrogen (N) mineralization of soil under different long term nutrient management strategies is essential for better assessment of N availability and loss of C and N from soil. A laboratory incubation study was conducted with soils (0–15 cm and 15–30 cm depth), collected from 41 years of rice–rice system to evaluate the differences in C and N mineralization kinetics due to long term fertilization treatments-control (Non fertilized), N, NPK, FYM (Farmyard manure), N + FYM and NPK + FYM, and to assess the C and N mineralization rates in soil under different moisture regimes, i.e. aerobic and submergence. Both long term fertilization and moisture regime significantly affected C and N mineralization in soil. Long term integrated application of chemical fertilizer and organic manure (NPK + FYM, N + FYM) in soil resulted in higher potentially mineralizable C (C0), potentially mineralizable N (N0), rates of mineralization (dCmin/dt and dNmin/dt), microbial and mineralization quotients as compared to either of them applied alone (N, NPK, and FYM). Higher values of C0, N0, and rates of mineralization were recorded under aerobic condition than that under submergence. The amount of N released per unit C mineralization was higher in aerobic system that may result in greater loss of N from the system. A judicious N application strategy through integration of both organic and inorganic sources is essential for improving current N supplying capacity of soil and maintaining soil organic C pool in aerobic system.

Modelling N mineralization from bovine manure and sewage sludge composts

Nitrogen mineralization kinetics were compared in three different soils (pH values: 5.2, 7.1 and 8.6) when treated with bovine manure (BM) and sewage sludge (SS) composts. The soil-compost mixtures were kept at a controlled moisture content of 60% of their water holding capacity (WHC) and were incubated in the dark at 25 °C for 2 years. Five mathematical models were compared (simple exponential, double exponential, special model, hyperbolic and parabolic), using as experimental data the mineralized N accumulated during 360 and 720 days of incubation. The results showed that the best fit for describing the mineralization of organic N from the compost after 1 year of experimentation was obtained with the simple exponential model. However, the special model showed the best fit for data from 2 years of incubation and thus better reflected organic N mineralization over a longer time-span. This suggested that the organic N in the two composts was made up of two organic pools of different degrees of stability.

Soil carbon and nitrogen mineralization kinetics in organic and conventional three-year cropping systems

The scientific literature regarding the use of C and N mineralization kinetics as a tool to highlight the effects of different cropping systems on soil C and N release is scarce. In this study we aimed to assess the effectiveness of these parameters in evaluating soil C and N potential release in organic (ORG) and conventional (CONV) three-year cropping systems. A long-term field study was established in 2001 at the University of Tuscia experimental farm (Viterbo, Italy) in a randomized block design. The soil is classified as Typic Xerofluvent or Dystric Fluvisol. In the CONV system the Good Agricultural Practice is adopted, whereas the ORG system is managed following the Regulation 2092/91/EEC. Both systems had a three-year crop rotation (pea – Pisum sativum L.; durum wheat – Triticum durum Desf.; tomato – Licopersicum esculentum Mill.). One of the main differences between the two systems is the soil N fertilization program: organic fertilizers (Guano: 6% N, 32% organic carbon and DIX10: 10% N, 42% organic carbon, both produced by Italpollina, Italy) and mineral nitrogen fertilizers (NH 4NO 3) were applied to ORG and CONV fields, respectively. Moreover, the rotation in the ORG system included common vetch ( Vicia sativa L.) and sorghum ( Sorghum vulgare L.) as green manure crops. Our results supported the hypotheses in that the two systems differed significantly on potentially mineralizable C (C 0) in 2008 and on potentially mineralizable N (N 0) as nitrate form (N 0-NO 3 −) in 2006 (318 μg C-CO 2 g −1 28 d −1 vs. 220 μg C-CO 2 g −1 28 d −1; 200 μg N-NO 3 − g −1 vs. 149 μg N-NO 3 − g −1 in ORG and CONV, respectively). The reduction of N 0 in soil during the crop rotation period could reflect the N microbial immobilization since a negative correlation between microbial biomass N:total N ratio and N 0 as ammonium form (N 0-NH 4 +) ( P < 0.001) as well as a positive correlation between N 0-NH 4 + and C:N ratio of microbial biomass ( P < 0.05) were observed. Moreover, a lower potential mineralization rate of N was observed in soil with Guano (25%) than in soil with DIX10 (35%); nevertheless the former fertilizer might cover a longer period of crop N demand as a more gradual release of N 0 was observed. In this work we demonstrated that the use of mineralization kinetics parameters can offer a potential to assess the mineralization–immobilization processes in soils under different climatic and management conditions. Moreover, they can be used to evaluate the most suitable N release pattern of organic fertilizers used in various cropping systems.

Soil Respiration and Nitrogen Mineralization Kinetics of Compost and Vinasse Fertilized Soil in an Aerobic Liquid-Based Incubation

Assessment of soil respiration and nitrogen (N) mineralization under the addition of organic fertilizers is a matter of ever increasing interest. Aiming at a deeper insight into the subject, an aerobic liquid-based incubation was set up for the coupled respiration and N-mineralization over 360 h in a closed system, comparing one compost and one vinasse at rates of 300 and 600 mg N kg−1 soil, plus an unfertilized control. The system allowed the manometric measurement of the microbial activity, and the N-mineralization in the suspension via solely NH+4-N determination. A set of substrate-induced respiration (SIR) tests was run to investigate the effects of nutrients and nutrients + glucose addition on the soil respiration and N-mineralization of the five fertilizer treatments, in comparison with basal respiration in water. In water, the compost showed a total net N-mineralization of +0.7 and −6.3% at the low (C1) and high (C2) dose respectively, whereas vinasse nominally reached 100% for both doses (V1 and V2). Soil respiration ranged between 3,269 and 18,389 mg O2 kg−1 dry soil of the unfertilized and V2. SIR tests showed that the respiration of compost-treated soil was boosted by nutrients in C2 more than in C1. Conversely, C1 was boosted by nutrients + glucose more than C2, indicating a combined nutrient- and carbon dose-dependent mechanism. These findings were confirmed by the N-mineralization, because C2 consumed almost threefold the NH+4-N added to the system compared to C1. Vinasse-fertilized soil received a similar benefit from nutrients and nutrients + glucose. Addition of inducing substrates showed how compost and vinasse respiration are dose dependent: the lower the dose, the higher the respiration relative to the amount of added carbon in a carbon-starved system. The incubation method adopted here appears to be a valid and rapid tool in the study of the effects of energy and nutrient constraints on respiration and N-mineralization dynamics in soils amended with biosolids.

Nitrogen Immobilization and Mineralization Kinetics of Cattle, Hog, and Turkey Manure Applied to Soil

Nitrogen mineralization and immobilization following manure application are critical processes influencing plant N supply and offsite N losses. We conducted laboratory experiments to examine the influence of these two processes in addition to N oxide gas production on N availability for 180 d following manure addition. A Tara loam (fine‐silty, mixed, superactive, frigid Aquic Hapludoll) and a Webster clay loam (fine‐loamy, mixed, superactive, mesic Typic Endoaquoll) amended with liquid dairy (Bos taurus) manure (LD) were incubated at 25 and 10°C, while Tara soil amended with solid dairy manure (SD) and turkey (Meleagris gallopavo) manure (T), and Webster soil amended with liquid hog (Sus scrofa) manure (H), were incubated at 25°C. Maximum net N immobilization was 14 and 40% of the initial NH4+ concentration in H and LD, respectively, and persisted for 35 to 180 d. In LD‐, H‐, and T‐amended soils, net manure N mineralization was not apparent, and there was good agreement between initial NH4+ content and available inorganic N from the manure. These data suggest that, for these manure types, estimates of first‐season available N would be improved by measuring manure NH4+ In contrast, in soil amended with SD, which had the lowest initial NH4+ content, 22% of organic N was mineralized. Gaseous N losses were &lt;1% of the added N in all treatments. The previously developed model NCSOIL was used to predict plant N availability and NO3− leaching potential with various manure incorporation dates. Under climate conditions typical of the Upper Midwest, no clear advantage of late fall compared with spring incorporation of manure with regard to N availability could be shown, but NO3− leaching potential seemed high with early fall incorporation.

Green manure in coffee systems in the region of Zona da Mata, Minas Gerais: characteristics and kinetics of carbon and nitrogen mineralization

The use of green manure may contribute to reduce soil erosion and increase the soil organic matter content and N availability in coffee plantations in the Zona da Mata, State of Minas Gerais, in Southeastern Brazil. The potential of four legumes (A. pintoi, C. mucunoides, S. aterrimum and S. guianensis) to produce above-ground biomass, accumulate nutrients and mineralize N was studied in two coffee plantations of subsistence farmers under different climate conditions. The biomass production of C. mucunoides was influenced by the shade of the coffee plantation. C. mucunoides tended to mineralize more N than the other legumes due to the low polyphenol content and polyphenol/N ratio. In the first year, the crop establishment of A. pintoi in the area took longer than of the other legumes, resulting in lower biomass production and N2 fixation. In the long term, cellulose was the main factor controlling N mineralization. The biochemical characteristics, nutrient accumulation and biomass production of the legumes were greatly influenced by the altitude and position of the area relative to the sun.

NITROGEN MINERALIZATION POTENTIAL AND NUTRIENT AVAILABILITY FROM FIVE ORGANIC MATERIALS IN AN ATOLL SOIL FROM THE MARSHALL ISLANDS

Soil nutrient deficiencies are a major constraint to crop production on the low-lying atoll soils of the Marshall Islands. Despite the critical role organic matter plays in controlling the fertility of these soils, there is little information on the use of organic inputs to improve soil fertility and crop production. In this study, we evaluated the N mineralization potential and nutrient supplying capacity of five organic soil amendments (Vigna marina and Cocos nucifera leaves, chicken manure, fish meal, and copra cake) available in the Marshall Islands. Nitrogen mineralization kinetics were best described by using a modified Gompertz equation with three parameters estimating N mineralization potential (No), mineralization rate (k), and mineralization lag phase (λ). There were significant differences in Chinese cabbage growth in the soil amended with the different organic amendments. Chinese cabbage growth in the Vigna and chicken manure treatments was similar to the chemical control, but the fish meal and copra cake treatments showed significantly less biomass production than the chemical control. The reduced growth in the fish meal treatment was attributed to K deficiency due to the low K supplying capacity of the amendment. The soil amended with coconut leaves showed the lowest biomass production, and the poor growth was attributed to net N immobilization. Optimum corn growth was achieved by adding fresh Vigna leaves at 8.9 T ha -1 (dry weight), and Vigna seems to be a good locally available soil amendment that corrects the multiple nutrient deficiencies found in Marshall Island soils.

Influence of Long‐Term Sodic‐Water Irrigation, Gypsum, and Organic Amendments on Soil Properties and Nitrogen Mineralization Kinetics under Rice–Wheat System

Influence of long‐term sodic‐water (SW) irrigation with or without gypsum and organic amendments [green manure (GM), farmyard manure (FYM), and rice straw (RS)] on soil properties and nitrogen (N) mineralization kinetics was studied after 12 years of rice–wheat cropping in a sandy loam soil in northwest India. Long‐term SW irrigation increased soil pH, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) and decreased organic carbon (OC) and total N content. On the other hand, application of gypsum and organic amendments resulted in significant improvement in all these soil properties. Mineralization of soil N ranged from 54 to 111 mg N kg−1 soil in different treatments. Irrigation with SW depressed N mineralization. In SW‐irrigated plots, two flushes of N mineralization were observed; the first during 0 to 7 d and the second after 28 d. Amending SW irrigated plots with GM and FYM enhanced mineralization of soil N. Gypsum application along with SW irrigation reduced cumulative N mineralization at 56 days in RS‐amended plots but increased it under GM‐treated, FYM‐treated, or unamended plots. Nitrogen mineralization potential (No) ranged from 62 to 543 mg N kg−1 soil. In the first‐order zero‐order model (FOZO), the easily decomposable fraction ranged from 5.4 to 42 mg N kg−1 soil. Compared to the first‐order single compartment model, the FOZO model could better explain the variations in N mineralization in different treatments. Variations in No were influenced more by changes in pH, SAR, and ESP induced by long‐term SW irrigations and amendments rather than by soil OC.