Ammonia Volatilization Research Articles

Citric acid modified biochar application at a low dosage can synchronically mitigate the nitrogenous gas pollutants emission from rice paddy soils

Raw biochar with high pH possibly stimulated ammonia (NH3) volatilization in the agricultural soil. We hypothesized that the modified biochar (MBC) with low pH can synchronically decrease the NH3 and nitrous oxide (N2O) losses. We performed a two-year experiment to clarify how citric acid MBC influence the NH3 volatilization and N2O emission as well as the underlying mechanisms. Two typical paddy soils, i.e., Hydragric Anthrosol and Haplic Acrisol, receiving equal urea N with 240 kg ha−1 but varied rates of MBC with 0, 5, 10, and 20 t ha−1 (named Urea, Urea + MBC5, Urea + MBC10, and Urea + MBC20, respectively) were studied. The results showed that MBC-amended treatments effectively mitigated the NH3 volatilization from Hydragric Anthrosol and Haplic Acrisol by 29.6%–57.9% and 30.5%–62.4% in 2017, and by 16.5%–21.0% and 24.5%–35.0% in 2018, respectively, compared to Urea treatment. In addition, significantly lower N2O emissions with averaged 38.3% and 43.1% in 2017, and 51.7% and 26.7% were recorded under Hydragric Anthrosol and Haplic Acrisol, respectively, following the MBC application (P < 0.05). Increased MBC addition performed higher efficacy on mitigating NH3 volatilization, particularly in the first rice season, while this “dosage effect” was not found for N2O reduction. Lowered pH in overlying water, enhanced adsorption of NH4+-N and its nitrification rate likely contributed to the lower NH3 volatilization as result of MBC addition. The nirS and nosZ gene copies were not changed by MBC, while the nirK gene copies were decreased as result of MBC amendment by 8.3%–25.2% under Hydragric Anthrosol and by 21.8%–24.9% under Haplic Acrisol. Consequent lower ratio of nirK/(nirS + nosZ) explained the mitigation effect of MBC on N2O emission. In conclusion, the present two-year study recommends that MBC applied at a low dosage can perform positive effect on controlling the nitrogenous gas pollutants from paddy soil.

Effect of Deep Placement of Large Granular Fertilizer on Ammonia Volatilization, Soil Nitrogen Distribution and Rice Growth

Excessive fertilization is often applied to produce rice. To reduce nitrogen loss and improve nitrogen use efficiency (NUE), we studied the effects of application depth (surface application, 5 and 10 cm) and shape of nitrogen fertilizers (row application and deep application of large granular fertilizer) on rice growth, soil N distribution and ammonia volatilization. The results showed that grain yield, shoot biomass and total dry biomass of the treatment with N in large granular fertilizer applied at 10 cm depth were significantly higher than those of all other treatments. Moreover, compared with the surface application, the N recovery efficiency and the N agronomic efficiency of deep application treatments were enhanced by 18.1–52.3% and 35.6–95.6%, respectively. Deep application significantly increased NH4+-N concentration at their fertilization points. During the growth season, N in large granular fertilizer treatments (mixed with clay to form an unusually large pellet of 1.0–1.5 cm in diameter) distributed closer to the roots, while N in other treatments, including row application treatments, was more widely distributed. Compared with the surface application, deep application significantly reduced NH3 volatilization and NH4+-N concentration in surface water by 58.7–64.8% and 26.0–72.5%, respectively. Furthermore, the NH3 volatilization from large granular treatment was 7.6–11.0% lower than that in the row application. In conclusion, applying N in large granular fertilizer at 10 cm depth reduces ammonia volatilization, and improves rice growth and grain yield, indicating improved NUE and lowered environmental risks.

Modelling direct field nitrogen emissions using a semi-mechanistic leaching model newly implemented in Indigo-N v3

Nitrogen plays a major role in agroecosystems as the key nutrient in agricultural production as well as a source of different emissions, which exceed currently planetary boundaries. N losses, conditioned by both pedoclimatic conditions and agricultural strategies (e.g. rotations, fertilisation), predominantly take the form of ammonia (NH3) volatilisation, nitrate (NO3) leaching, nitrification-driven nitric oxide (NOx) emission to air, and denitrification-driven nitrous oxide (NOx and N2O) emissions to air. The multiplication of initiatives and studies on nitrogen modelling resulted in a broad offer of complex simulation models (Tier 3) on one extreme of the gradient between feasibility and integration of processes. On the other side, a multiplication of initiatives has led to a broad offer of causal indicators in the form of proxies and considering one or a few input variables (Tier 1). A relevant compromise between those extremes lies in the development of operational models using a restricted number of parameters and input variables (Tier 2). Here, we propose a new semi-mechanistic operational model for the estimation of direct field N emissions (NH3, NO3, NOx and N2O) from contrasting agricultural situations: the Indigo-N v3 (I-N3) model. The gaseous emissions are based on Tier 1 (NOx) and Tier 2 (NH3, N2O) methods taken from the literature, with some enhancements, while we developed a totally new semi-mechanistic approach for nitrate leaching. A comparison of I-N3 outputs was performed with measurements of nitrate leaching in three countries (15 arable fields in France, 3 sugar cane fields at Reunion Inland, and 5 cropped fields in Kenya) and showed a reasonable predictive quality for temperate arable fields, and for some of the tropical fields (1 in Reunion and 3 in Kenya). It also performed better than the previous version of Indigo-N (IN-2) and the SALCA/SQCB models. In comparison with previous Tier 2 models, the newly developed Indigo-N v3 presents an original position on the gradient between integration of processes and feasibility of the simulation of processes. Another novelty of I-N3 lies in its broad scope, designed to be valid for temperate and non-temperate crops, including annual field crops, short-cycle vegetables, temporary grasslands and perennial grasses (such as sugarcane, miscanthus or switchgrass). Parameterisation and validation should be continued for further crops, such as associations and short cycle vegetables.

Application of Blended Controlled-Release and Normal Urea with Suitable Maize Varieties to Achieve Integrated Agronomic and Environmental Impact in a High-Yielding Summer Maize System

The use of blended controlled-release urea (CRU) with normal urea has appeared to effectively improve grain yield and nitrogen use efficiency in summer maize systems. Nevertheless, the environmental impacts based on a life cycle assessment (LCA) and the ecosystem economic benefits with different maize varieties and ratios of CRU and urea remain unclear. In our study, a consecutive two-year field experiment was designed in the North China Plain (NCP) using two nitrogen (N) rates (0 and 180 kg N ha−1), four N resources (urea-N, CRU-N:urea-N = 1:2, CRU-N:urea-N = 2:1 and CRU-N), and two maize varieties (ZD958 and YH988) in 2019 and 2020. The results showed that a once-off application of basal fertilizer in N180C2 (CRU-N:urea-N = 2:1) and N180C1 (CRU-N:urea-N = 1:2) achieved high grain yields in ZD958 and YH988 (11.0–13.5 Mg ha−1 and 11.3–13.2 Mg ha−1), respectively. Compared to treatment N180U, treatment N180C2 reduced reactive N losses through N leaching (−34.6%), ammonia volatilization (−17.1%), and nitrous oxide emissions (−42.0%) in variety ZD958, whereas treatment N180C1 reduced reactive N losses through N leaching (−20.3%), ammonia volatilization (−13.2%), and nitrous oxide emission (−24.2%) in variety YH988. The N180C2 and N180C1 treatments achieved the lowest C footprint (267.4 and 267.9 kg CO2 eq Mg−1) for ZD958 and YH988, respectively. Furthermore, N180C2 and N180C1 achieved the highest ecosystem economic benefits for ZD958 and YH988 of 831 and 1101 $ ha−1, respectively. In summary, the application of the mixture of controlled release urea and standard urea at appropriate N rates not only achieved a high grain yield but also enhanced the ecological economic benefits while mitigating the negative environmental impacts. To sum up, using the correct CRU-N management practices coordinated with suitable genetic varieties is an effective way of achieving sustainable and environmentally friendly maize production in a high-yielding summer maize system.

Low N2O emissions associated with sheep excreta deposition in temperate managed lowland grassland and extensively grazed hill pasture

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) whose emission from soil can be enhanced by ruminant excretal returns in grasslands. The default (Tier 1) emission factors (EF3PRP; i.e. proportion of deposited nitrogen emitted as N2O) for ruminant excreta deposition are associated with a wide range of uncertainties and the development of country-specific (Tier 2) EF3PRP is encouraged. In Ireland, a Tier 2 EF3PRP has been developed for cattle excreta but no data are available for sheep. The aim of this study was to generate data to contribute to the derivation of a Tier 2 EF3PRP for sheep excreta, while assessing the effect of excreta type, grassland type and season of deposition on N2O emissions. An experiment was carried out on two sites in the west of Ireland: a managed lowland grassland (LOW) and an extensively grazed hill pasture (HILL), characterised by mineral and acid peat soils, respectively. For each season, four treatments were applied to the soil in a fully randomized block design: control (C), sheep urine (U), sheep dung (D), and artificial urine (AU). Nitrous oxide fluxes were assessed over a full year following each application of treatments, using a static chambers methodology. Results showed a brief initial peak following each application of U/AU in LOW but not in HILL. Cumulative N2O emissions were significantly higher from the lowland site. Average EF3PRP for combined excreta was negligible on both sites, thus lower than the IPCC Tier 1 EF3PRP. Causes of low emissions are likely to depend on site characteristics (e.g. soil acidity in HILL) and season of application (i.e. ammonia volatilisation in summer). This study showed very low N2O emissions from sheep excretal returns in Irish grasslands and highlighted the importance of developing Tier 2, animal-specific EF3PRP. More experimental grasslands should be assessed to confirm these results.

Influence of modified fertilizers on crop growth, productivity and soil biological values under rice (Oryza sativa) - wheat (Triticum aestivum) cropping system of Punjab, India

In the last 60 years, chemical fertilizer has played a significant role in world food production. It provides around half of the total amount of N that crops need. Nitrates (NO3) leaching, ammonia (NH3) volatilization and nitrous oxide (N2O) emissions contribute to low crop production efficiency (10 to 50 percent) principally due to the loss of N through these processes. Furthermore, nitrogen fertilizer production costs are extremely high. Technology like nitrogen inhibitors and slow-releasing nitrogen fertilizers are used to boost nutrient uptake, fertilizer use efficiency, and crop yields as a result of these situations. Typical haplustept soils were studied to see how changing fertilizers affected growth, yield, and soil genetic indicators. Fertilizer doses and sources affect soil biological characteristics, which in turn affects enzymatic activity. In the right circumstances, enzymes alter the nitrogen supply in the soil and the plant's expansion and limestone structure. The Lovely Professional University School of Agriculture, Phagwara, Punjab, conducted two years of fertilizer studies in a rice-wheat cropping system on typical Haplustept soils from 2018 to 2020. Neem coated urea + PK + S + Zn–EDTA performed significantly better than the other treatments for almost all crop growth and agronomic yield attributing characteristics (plant height, number of tillers, effective tillers, panicle/spikelet length and grain per spik, test weight, grain and straw yields). At various stages of rice-wheat growth, enzyme activity in the soil (dehydrogenase and aryl sulfatase) was also measured in the current study. Enzyme activity peaked at the heading stage in surface soil in all treatments, and then steadily declined thereafter. For both stages of crop growth in surface soil, the highest dehydrogenase and aryl sulfatase activity was found in urea + PK + S + Zn –EDTA covered with Neem. Anhydrous ammonia was shown to have the lowest enzymatic activity.

Agro-environmental sustainability of using digestate fertilizer for solanaceous and leafy vegetables cultivation: Insights on fertilizer efficiency and risk assessment

Digestate generated from anaerobic digestion (AD) has been widely used as digestate fertilizer (DF) for plant growth, but its application should be comprehensively investigated. This study evaluates the effects of different amounts of DF on crop growth, nutrient use efficiency (NUE), soil properties, and potential negative impacts of DF application (salinity and heavy metals (HMs)) with two different crops (Eggplant and Shanghai cabbage). In eggplant cultivation, the yield increased with the increase of DF amount, and the yield of the DF-680 group was the highest (65.4 t/ha) under the highest fertilizer amount. However, due to high ammonia volatilization loss and excessive application, the NUE of DF was only about half of that of chemical fertilizer (CF). Significantly different from eggplant, the high application amount of DF resulted in yield reduction in Shanghai cabbage cultivation. The yield and NUE of the DF-170 group were the highest, the yield was 46.5 t/ha, and the NUE was more than twice compared to CF. Moreover, DF can raise soil nitrogen storage and alleviate soil acidification caused by fertilization in both batches of cultivation. Nevertheless, the electrical conductivity (EC) value of the soil was increased by 2–3 times, and the long-term application may lead to soil salinization. On the other hand, the increase of DF application elevated the content of copper (Cu), zinc (Zn), and cadmium (Cd) in soil significantly but did not cause HMs contamination in crops and tillage soil. In summary, reasonable application amounts and methods should be considered when applying DF.

Production and Incorporation of Black Soldier Fly Larvae Frass in Retaining Nitrogen from Urea

Nitrogen (N) from urea application is not available in soils due to the fast release and loss through ammonia volatilization or nitrate leaching. Nitrogen could be retained in soil using organic amendment such as frass. The objectives of this study were to: (i) produce frass by rearing black soldier fly larvae (BSLF) with decanter cake (DC), (ii) determine the physico-chemical properties of frass produced from BSFL fed on DC, and (iii) determine urea-N retention in soil following BSFL frass application. The frass production was carried out by rearing BSFL using DC with the feeding rate of 200 mg larvae-1 day-1. The maturity of the BSFL frass was determined through physical, biological (phytotoxicity test), and chemical tests. A leaching study was carried out for 30 days by incorporating different rates of BSFL frass and urea. At 45 days of rearing, BSFL frass was produced whereby the insect larvae turn into pupae. The BSFL frass has good agronomic qualities which appropriate to be used as organic fertilizer. The BSFL frass were not toxic to white radish germination as reflected by the germination index ranged from 85% to 97%. Incorporation of BSFL frass with urea improved retention of N in the form of exchangeable NH4+ and available NO3- because of high TOC and TOM which related to the organic N decomposition into inorganic N. Combined application of BSFL frass and urea particularly reduced by half of recommended urea suggests that urea-N application can be properly improved if it is amended with BSFL frass.

Substituting urea with biogas slurry and hydrothermal carbonization aqueous product could decrease NH3 volatilization and increase soil DOM in wheat growth cycle

Biogas slurry (BS) and hydrothermal carbonization aqueous products (HAP), which are rich in nitrogen (N) and dissolved organic matter (DOM), can be used as organic fertilizer to substitute inorganic N fertilizer. To evaluate the effects of co-application of BS and HAP on the ammonia (NH3) volatilization and soil DOM content in wheat growth season, we compared six treatments that substituting 50%, 75%, and 100% of urea-N with BS plus HAP at low (L) or high (H) ratio, named BCL50, BCL75, BCL100, BCH50, BCH75, BCH100, respectively. Meanwhile, urea alone treatment was set as the control (CKU). The results showed that both BCL and BCH treatments significantly mitigate the NH3 volatilizations by 9.1%–45.6% in comparison with CKU (P < 0.05), whose effects were correlated with soil NH4+-N content. In addition, the decrease in soil urease activity contributed to the lower NH3 volatilization following application of BS plus HAP. Notably, BS plus HAP applications increased the microbial byproduct- and humic acid-like substances in soil by 9.9%–74.5% and 100.7%–451.9%, respectively. Consequently, BS and HAP amended treatments significantly increased soil humification index and DOM content by 13.7%–41.2% and 38.4%–158.7%, respectively (P < 0.05). This study suggested that BS and HAP could be co-applied into agricultural soil as a potential alternative of inorganic fertilizer N, which can decrease NH3 loss but increase soil fertility.

A semi-empirical semi-process model of ammonia volatilization from paddy fields under different irrigation modes and urea application regimes

Both empirical models and process-based models of ammonia (NH3) volatilization simulation in paddy field have some disadvantages. This work describes a semi-empirical semi-process model, which combines the simplicity of empirical models with the precision of process-based models, and its combinatorial structure is sufficient for reproducing the characteristic course of NH3 volatilization in paddy fields under different irrigation modes and urea application regimes over time. A dataset consisting of seven rice seasons across three locations was used for model development. Performance indexes showed the model is good (R2 values ranged from 0.67 to 0.94). The influence of air temperature and wind speed on NH3 volatilization was not as great as our conventional understanding, and soil temperature was a more accurate indicator than air temperature for model development. Model performance was better where the less urea splits and the higher urea rate, but there was no significant difference between alternate wetting and drying (AWD) irrigation mode (average values of R2, IA, NSI, and RMSE were 0.82, 0.94, 0.96, and 0.53 kg ha-1 d-1) and flooding irrigation (FI) mode (average values of R2, IA, NSI, and RMSE were 0.86, 0.94, 0.96, and 0.58 kg ha-1 d-1). The ammonium nitrogen (NH4+-N) concentration and pH of surface water and soil water in paddy fields had the greatest impact on NH3 volatilization, and they were mainly related to the amount of urea applied. Splitting the urea application and delaying the first urea application are the fundamental countermeasures to reduce NH3 volatilization. The magnitude of developed model performance varied among rice cropping systems, irrigation modes, urea application regimes, and climatic regions, highlighting the need to understand why measured NH3 volatilization varies among locations. The new model may be a useful tool for predicting fertilizer efficiency of paddy fields applied urea, assessing NH3 volatilization factors, and reducing emission.

Every coin has two sides: Continuous and substantial reduction of ammonia volatilization under the coexistence of microplastics and biochar in an annual observation of rice-wheat rotation system

Microplastics (MPs) are verified to affect the fate of ammonia (NH3) in agricultural soils. However, the impacts and mechanisms of MPs coupled with biochar (BC), a widely used agricultural conditioner, on NH3 losses are mostly untapped. The aim of this study was to investigate the mechanisms of common MPs (i.e., polyethylene, polyester, and polyacrylonitrile) and straw-derived BC on NH3 volatilization in rice-wheat rotation soils. Results showed that BC alone and MPs with BC (MPs + BC) reduced 5.5 % and 11.2–26.6 % cumulative NH3 volatilization than the control (CK), respectively, in the rice season. The increased nitrate concentration and soil cation exchange capacity were dominant contributors to the reduced soil NH3 volatilization in the rice season. BC and MPs + BC persistently reduced 44.5 % and 60.0–62.6 % NH3 losses than CK in the wheat season as influenced by pH and nitrate concentration. Moreover, BC and MPs + BC increased humic acid-like substances in soil dissolved organic matter by an average of 159.1 % and 179.6 % than CK, respectively, in rice and wheat seasons. The increased adsorption of soil NH4+ and the promotion of crop root growth were the main mechanisms of NH3 reduction. Our findings partially revealed the mechanisms of the coexistence of MPs and BC on NH3 mitigation in rice-wheat rotational ecosystems.

Comparative effects of different kinds of biochar on ammonia volatilization and chemical properties of saline soil

ABSTRACT The study was established to examine the effect of three biochar types (orange peels biochar (OPB), sorghum panicles biochar (SPB), and wood chips biochar (WCB)) prepared at low temperature (270 °C) added at four doses (0, 1, 3, and 6% w/w) on ammonia (NH3) volatilization and chemical characteristics of a saline soil treated with urea. The results revealed that treating the saline soil with different biochar types at all doses caused a significant reduction of cumulative NH3 volatilization compared to the unamended soil. The effectiveness of biochar types in decreasing NH3 volatilization from this soil was: WCB > SPB > OPB > unamended soil. Soil pH decreased significantly with applying different types and doses of biochar. Treating the saline soil with 3% each of SPB and WCB and 6% WCB decreased electrical conductivity significantly in the soil extract compared to the unamended soil. The sodium adsorption ratio decreased significantly with applying SPB and WCB at 3 and 6%. The biochar produced at a low temperature was found to have an acidic effect. Accordingly, biochar applications are currently one of the most promising technologies and practices for rehabilitation and sustainable management of saline soils as well as mitigating climate change.

Nitrogen transformation genes and ammonia emission from soil under biochar and urease inhibitor application

Ammonia (NH3) volatilization is the main pathway, by which nitrogen (N) losses from calcareous and alkaline soils occur, and is responsible for economic losses and environmental hazards. We hypothesize that the application of biochar and urease inhibitor (NBPT) can mitigate NH3 production from urea by reducing its hydrolysis and the abundance of related microbial genes. To clarify this hypothesis, soil N fluxes and the genes controlling hydrolysis and nitrification were investigated under the combined application of urea (0, 75, 150, 225 and 300 kg N ha−1), biochar (7.5 Mg ha−1) and NBPT (2 %) for maize under field conditions. Soil moisture, temperature, pH, mineral N, NH3, urease activity (UA) and N cycle related genes (ureC, amoB and amoA) were quantified each 6–17 days during two growing seasons. The combined application of NBPT and biochar reduced NH3 by 13% of the control, which is twofold higher than the separate additions. All investigated parameters were raised with increasing N rate except pH, which was reduced. Biochar and NBPT mediated these effects of N fertilizer by increasing the soil pH, genes abundance, ammonium and nitrate contents, and reducing urea hydrolysis. Biochar maximized the ammonium and nitrate contents one week and three weeks following the N urea application, respectively. Accordingly, NH3 and UA peaked directly after N fertilization; nevertheless, NBPT delayed the peaks for three weeks and reduced their intensity by 24 % and 36 %, respectively, under the addition of 300 kg N ha−1. NBPT reduced ureC and amoB genes abundance by 14 % and 8 %, respectively, and increased amoA by 3 %. Biochar increased amoA and amoB abundance and nitrate content, while reduced the ureC gene. Biochar and/or NBPT reduced the negative effects of the soil pH on ureC gene. NBPT mitigated the reduction effects of pH on the amoB and amoA genes. In conclusion, NBPT mitigated NH3 emission by decreasing the ureC gene and UA, whereas biochar had a synergistic effect with NBPT by increasing amoB and amoA abundance and accelerating nitrification.

Nitrogen Fertilizers Technologies for Corn in Two Yield Environments in South Brazil.

Improvements in nitrogen use efficiency (NUE) in corn production systems are necessary, to decrease the economic and environmental losses caused by loss of ammonia volatilization (NH3-N). The objective was to study different nitrogen (N) fertilizer technologies through characterization of N sources, NH3-N volatilization losses, and their effects on the nutrient concentration and yield of corn grown in clayey and sandy soils in south Brazil. The treatments consisted of a control without N application as a topdressing, three conventional N sources (urea, ammonium sulfate, and ammonium nitrate + calcium sulfate), and three enhanced-efficiency fertilizers [urea treated with NBPT + Duromide, urea formaldehyde, and polymer-coated urea (PCU) + urea treated with NBPT and nitrification inhibitor (NI)]. The losses by NH3-N volatilization were up to 46% of the N applied with urea. However, NI addition to urea increased the N losses by NH3-N volatilization by 8.8 and 23.3%, in relation to urea alone for clayey and sandy soils, respectively. Clayey soil was 38.4% more responsive than sandy soil to N fertilization. Ammonium sulfate and ammonium nitrate + calcium sulfate showed the best results, because it increased the corn yield in clayey soil and contributed to reductions in NH3-N emissions of 84 and 80% in relation to urea, respectively.

Investigation of Rice Yields and Critical N Losses from Paddy Soil under Different N Fertilization Rates with Iron Application.

The application of iron powder stimulated the growth of iron-reducing bacteria as a respiratory substrate and enhanced their nitrogen (N)-fixing activity in flooded paddy soils. High N fertilization (urea) in the flooded paddy soils has caused adverse environmental impacts such as ammonia (NH3) volatilization, nitrous oxide (N2O) emissions, and nitrate (NO3−) leaching. This study aims to investigate the effects of N fertilization rates in combination with an iron amendment on rice yields and N losses from flooded paddy fields. We performed a 2-year field plot experiment with traditional rice–wheat rotation in China’s Yangtze River Delta. The investigation consisted of seven treatments, including 100%, 80%, 60%, and 0% of the conventional N (urea and commercial organic manure) fertilization rate, and 80%, 60%, and 0% of the conventional N with the iron powder (≥99% purity) amendment. The rice yields decreased with a reduction in the conventional N fertilization rate, whereas they were comparable after the iron application under the 80% and 60% conventional N rate. The critical N losses, including NH3 volatilization, N2O emissions, and NO3− and NH4+ leaching, generally decreased with a reduction in the conventional N fertilization rate. These N losses were significantly greater after the iron amendment compared with the non-amended treatments under the 80% and 60% conventional N fertilization rate in the first rice-growing season. However, it was comparable between the iron-amended and the non-amended treatments in the second season. Furthermore, NO3− leaching was the most significant N loss throughout the two rice seasons, followed by NH3 volatilization. The iron amendment significantly increased soil Fe2+ content compared with the non-amended treatments irrespective of N fertilization, suggesting the reduction of amended iron by iron-reducing bacteria and their simultaneous N fixation. A combination of the iron application with 60–80% of the conventional N fertilization rate could maintain rice yields similar to the conventional N fertilization rate while reducing the critical N losses in the flooded paddy field tested in this study. Our study leads to the establishment of novel and practical rice cultivation, which is a step towards the development of green agriculture.

Negligible ammonia volatilization loss with one-time root-zone targeted application of common nitrogen, phosphorus, and potassium fertilizers in transplanted rice cultivation

The minimization of nitrogen (N) loss and enhancement of efficient N use are of great importance in agricultural crop production. Here we propose a method of one-time root-zone targeted fertilization (ORZTF), to reduce ammonia volatilization (AV) loss and increase N use efficiency. ORZTF is updated from one-time root-zone fertilization (ORZF), in which common N fertilizer is one-time applied in crop root-zone, and phosphate (P) and potassium (K) are surface broadcasted. In ORZTF, common N, P and K are together placed at certain sites in the root-zone. Three rice field trials with the methods of conventional surface broadcasting (CSB), ORZF, and ORZTF, and a soil incubation experiment with CSB and ORZTF, were conducted. In 2018, the treatments comprised CSB with no N (N0), with the local N rate (CSB, 195 kg N hm−2 and 150 kg N hm−2 for two sites, respectively), with higher N (HCSB, 225 kg N hm−2 and 195 kg N hm−2, respectively), ORZF (195 kg N hm−2 and 150 kg N hm−2, respectively), and ORZTF (195 kg N hm−2 and 150 kg N hm−2, respectively). In 2019, the treatments were: N0, CSB, ORZF, ORZTF with urea (ORZTF-U), with ammonium chloride (ORZTF-Cl), and with ammonium sulfate (ORZTF-S) at 180 kg N hm−2. In the incubation experiment, there’re three treatments: N0, CSB, and ORZTF. The rates of P and K were the same in all experiments. Compared with CSB, ORZTF and ORZF significantly increased the yield, N uptake, N recovery efficiency, and N partial factor productivity of rice with the same N input. After 4.5 months of incubation, 78.5–92.7% of fertilizer N was reserved in the soils with ORZTF, about two-fold that with CSB. In all field and incubation experiments, AV loss was negligible when N was one-time root-zone applied alone or together with PK, close to that in N0 treatment. Compared with ORZF, ORZTF seemed to be a more promising method in rice fertilization, having the similar effect on N uptake increase and N loss reduction, but more convenience. Although the benefits of targeting fertilization were not significantly observed in the current work, with the idea of ‘fertilizing the roots but not the soil’, the method of ORZTF with common N, P and K fertilizers should be beneficial for cleaner and more efficient agricultural crop production in China.

Effect of reed-biochar application on ammonia volatilization from different types of soils

The application of straw biochar in farmland in Dongting Lake area can realize the resource utilization of straw and reduce environmental risk. In 2020, a rice pot experiment was conducted to investigate the effects of different biochar application levels on ammonia volatilization rate, cumulative ammonia volatilization, pH value, and NH4+-N concentration in surface water. Six levels of reed (Miscanthus lutarioriparius) biochar amount, i.e., 0%, 1%, 2%, 4%, 6% and 8% of soil weight of the 0-20 cm column, were applied in two typical paddy soils in sou-thern China, i.e., reddish clayey soil derived from quaternary red soil and granitic sandy soil derived from granite. Compound fertilizer was applied at a rate of 200 kg N·hm-2. The results showed that biochar application resulted in significant differences in the rate and cumulative amount of ammonia volatilization between the two soils and among different biochar treatments. For the granitic sandy soil, peak ammonia volatilization under different biochar treatments appeared at the second day after fertilization, which was decreased by 23.6%-53.4%. For the reddish clayey soil, peak ammonia volatilization appeared between the 7th to 13th day after fertilization, which increased with biochar addition level. The rate of ammonia volatilization from the granitic sandy soil was generally higher than that from the reddish clayey soil. For the granitic sandy soil, addition of <4% biochar could inhibit the ammonia volatilization and cumulative volatilization amount, with the greatest reduction (46.9%) at the treatment with 2% biochar addition. The addition of biochar did not affect the pH value of surface water at the early stage of rice growth. For the reddish clayey soil, the pH value and NH4+-N concentration in the surface water increased with biochar addition level, resulting in the increases of ammonia volatilization rate and cumulative volatilization amount by 1.3-10.5 times. Biochar addition level was the key factor affecting ammonia volatilization from the two soils. Elovich equation could well fit the variation trend of cumulative ammonia volatilization with time for the two soils, with the correlation reaching extremely significant level for each treatment. Overall, the application of reed biochar could suppress ammonia volatilization from the granitic sandy soil which was nearly neutral in acidity, while would promote ammonia volatilization via increasing pH value and NH4+-N concentration of surface water for the acidic reddish clayey soil. Therefore, appropriate dosages of reed biochar should be selected for different types of soil in order to reduce nitrogen loss.

NITRIFICATION INHIBITORS IMPACT ON NITROUS OXIDE EMISSION AND AMMONIA VOLATILIZATION: A SUSTAINABLE MEASURE TOWARD A HYGIENIC ENVIRONMENT

Nitrogen (N) application to agricultural fields warrants curtailing nitrous oxide (N2O) emission and ammonia (NH3) volatilization for improved use efficiency with a less environmental footprint of N. As a means of mitigating N2O emissions, the efficacy of nitrification inhibitors (NIs) is well established but the efficacy of NIs in reducing NH3 volatilization is not well understood. The study investigated the efficacy of neem oil, pomegranate leaf extract, and dicyandiamide (DCD) coating on prilled urea for reducing N2O emissions and the trend of NH3 release using static air closed chamber technique in an incubation room. The results showed that all NIs reduced N2O flux in the order of 37%–42% by DCD urea, 19%–34% by neem oil coated urea (NOCUs), and 11%–16% by pomegranate leaf extract coated urea (PLECU). However, over uncoated urea, 43%–54% NH3 flux was increased by DCD, 10%–32% by NOCUs, and significantly the least increase (5%–14%) in NH3 cumulative flux was shown by PLECU. Dicyandiamide significantly reduced N2O flux more than all other treatments, and PLECU showed the least increase in NH3 emission when compared with other coated treatments. Hence, it is suggested that neem oil and pomegranate leaf extract could be used successfully not only for mitigating N2O emission, but also lessen environmental damages in association with managed N intense agriculture. Moreover, research focus on the increase in NH3 volatilization using DCD needs serious attention, especially in alkaline calcareous soils.

Ammonia emission prediction for dairy cattle housing from reaction kinetic modeling to the barn scale

One way to estimate ammonia emission rates from naturally ventilated housing systems is to scale-up mechanistic modeling results. However, obtaining the relevant data to set initial and boundary conditions adequately is usually very challenging and for a whole barn barely possible. This study has investigated the potential of coupling different mechanistic modeling approaches towards an overarching barn scale ammonia emission model, which might permit ammonia emission projections for naturally ventilated housing systems with minimal measurement efforts. To this end, we combined an ammonia volatilization model for shallow urine or slurry puddles with a dynamic mechanistic model of digestion and excretion of nitrogen, an empirical model to estimate urination volumes, semi-empirical models for pH and temperature dynamics of the puddles and a mechanistic air flow model. The ammonia volatilization model was integrated with a time step of one second over a period of twenty-four hours, while the relevant boundary conditions were updated on an hourly base (determined by the other mentioned submodels). Projections and uncertainties of the approach were investigated for a farm case with about ten months of on-farm measurements in a naturally ventilated dairy cattle building with scraped solid floor in Northern Germany. The results showed that the nested model was in general capable to reproduce the long-term emission trend and variability, while the short-term variability was damped compared with the emission measurements. A sensitivity study indicated that particularly a refinement of the submodules for urine puddle alkalizing, urination volume and urea concentration distributions as well as for local near-surface wind speeds have a great potential to further improve the overall model accuracy. The cleaning efficiency of the scraper has turned out to be a crucial and sensitive parameter in the modeling, which so far has been described insufficiently by measurements or modeling approaches.

Modeling the Water and Nitrogen Management Practices in Paddy Fields with HYDRUS-1D

Rice production involves abundant water and fertilizer inputs and is prone to nitrogen (N) loss via surface runoff and leaching, resulting in agricultural diffuse pollution. Based on a two-season paddy field experiment in Jiangsu Province, China, field water and N dynamics and their balances were determined with the well-calibrated HYDRUS-1D model. Then, scenarios of different controlled drainage and N fertilizer applications were simulated using the HYDRUS-1D model to analyze the features and factors of N loss from paddy fields. Evapotranspiration and deep percolation were the two dominant losses of total water input over the two seasons, with an average loss of 50.9% and 38.8%, respectively. Additionally, gaseous loss of N from the whole soil column accounted for more than half of total N input on average, i.e., ammonia volatilization (17.5% on average for two seasons) and denitrification (39.7%), while the N uptake by rice accounted for 37.1% on average. The ratio of N loss via surface runoff to total N input exceeded 20% when the N fertilizer rate reached 300 kg ha−1. More and longer rainwater storage in rice fields under controlled drainage reduced surface runoff losses but increased the risk of groundwater contamination by N leaching. Therefore, compared with raising the maximum ponding rainwater depth for controlled drainage, optimizing N fertilizer inputs may be more beneficial for controlling agricultural diffuse pollution by reducing N loss via surface runoff and leaching. The HYDRUS-1D model provides an approach for the quantitative decision-making process of sustainable agricultural water and N management.