Ammonia Volatilization Research Articles

Effect of Irrigation and Fertilizer Management on Rice Yield and Nitrogen Loss: A Meta-Analysis.

Irrigation and nitrogen fertilizer application are two important factors affecting yield and nitrogen loss in rice fields; however, the interaction effects of different irrigation schedules and combined management of nitrogen fertilizer application on yield and nitrogen loss in rice fields remain unknown. Therefore, we collected 327 sets of data on rice yield and 437 sets of data on nitrogen loss in rice fields from 2000 to 2021 and investigated the effects of different water-saving irrigation schedules, nitrogen application levels, and water–nitrogen couplings on rice yield, nitrogen use efficiency, and nitrogen loss (N2O emissions, nitrogen runoff, nitrogen leaching, and ammonia volatilization) by meta-analysis using conventional flooding irrigation and no nitrogen treatment as controls. The results showed that alternate wet and dry irrigation and controlled irrigation had increasing effects on rice yield. Alternate wet and dry irrigation had a significant yield-increasing effect (average 2.57% increase) and dry cultivation significantly reduced rice yield with an average 21.25% yield reduction. Water-saving irrigation reduces nitrogen runoff and leaching losses from rice fields but increases N2O emissions, and alternate wet and dry irrigation has a significant effect on increasing N2O emissions, with an average increase of 67.77%. Most water-saving irrigation can increase nitrogen use efficiency. Among water-saving irrigation methods, the effect of controlled irrigation on increasing nitrogen use efficiency is 1.06%. Rice yield and nitrogen use efficiency both showed a trend of increasing then decreasing with nitrogen fertilizer application, and nitrogen loss gradually increased with the amount of nitrogen fertilizer input. Water–nitrogen coupling management can significantly reduce nitrogen loss in rice fields while saving water and increasing yield. Based on the analysis of the data in this study, when the irrigation amount was 300~350 mm and the nitrogen application amount was 200~250 kg/ha, the rice yield and nitrogen fertilizer use efficiency were at a high level, which corresponded to the irrigation schedule of controlled irrigation or alternating wet and dry irrigation in the literature. However, different rice-growing areas are affected by rainfall and land capability, etc. Further optimization and correction of the adapted water and fertilizer management system for paddy fields are needed. The optimal water–nitrogen pattern of this study can achieve high rice yield and reduce nitrogen loss.

Update of a biogeochemical model with process-based algorithms to predict ammonia volatilization from fertilized cultivated uplands and rice paddy fields

Abstract. Accurate simulation of ammonia (NH3) volatilization from fertilized croplands is crucial to enhancing fertilizer-use efficiency and alleviating environmental pollution. In this study, a process-oriented model, CNMM–DNDC (Catchment Nutrient Management Model–DeNitrification–DeComposition), was evaluated and modified using NH3 volatilization observations from 44 and 19 fertilizer application events in cultivated uplands and paddy rice fields in China, respectively. The major modifications for simulating NH3 volatilization from cultivated uplands were primarily derived from a peer-reviewed and published study. NH3 volatilization from cultivated uplands was jointly regulated by wind speed, soil depth, clay fraction, soil temperature, soil moisture, vegetation canopy, and rainfall-induced canopy wetting. Moreover, three principle modifications were made to simulate NH3 volatilization from paddy rice fields. First, the simulation of the floodwater layer and its pH were added. Second, the effect of algal growth on the diurnal fluctuation in floodwater pH was introduced. Finally, the Jayaweera–Mikkelsen model was introduced to simulate NH3 volatilization. The results indicated that the original CNMM–DNDC not only performed poorly in simulating NH3 volatilization from cultivated uplands but also failed to simulate NH3 volatilization from paddy rice fields. The modified model showed remarkable performances in simulating the cumulative NH3 volatilization of the calibrated and validated cases, with drastically significant zero-intercept linear regression of slopes of 0.94 (R2 = 0.76, n = 40) and 0.98 (R2 = 0.71, n = 23), respectively. The simulated NH3 volatilization from cultivated uplands was primarily regulated by the dose and type of the nitrogen fertilizer and the irrigation implementation, while the simulated NH3 volatilization from rice paddy fields was sensitive to soil pH; the dose and depth of nitrogen fertilizer application; and flooding management strategies, such as floodwater pH and depth. The modified model is acceptable to compile regional or national NH3 emission inventories and develop strategies to alleviate environmental pollution.

Can nitrogen input mapping from aerial imagery improve nitrous oxide emissions estimates from grazed grassland?

Most nitrogen (N) lost to the environment from grazed grassland is produced as a result of N excreted by livestock, released in the form of nitrous oxide (N2O) emissions, nitrate leaching and ammonia volatilisation. In addition to the N fertiliser applied, excreta deposited by grazing livestock constitute a heterogeneous excess of N, creating spatial hotspots of N losses. This study presents a yearlong N2O emissions map from a typical intensively managed temperate grassland, grazed periodically by a dairy herd. The excreta deposition mapping was undertaken using high-resolution RGB images captured with a remotely piloted aircraft system combined with N2O emissions measurements using closed statics chambers. The annual N2O emissions were estimated to be 3.36 ± 0.30 kg N2O–N ha−1 after a total N applied from fertiliser and excreta of 608 ± 40 kg N ha−1 yr−1. Emissions of N2O were 1.9, 3.6 and 4.4 times lower than that estimated using the default IPCC 2019, 2006 or country-specific emission factors, respectively. The spatial distribution and size of excreta deposits was non-uniform, and in each grazing period, an average of 15.1% of the field was covered by urine patches and 1.0% by dung deposits. Some areas of the field repeatedly received urine deposits, accounting for an estimated total of 2410 kg N ha−1. The method reported in this study can provide better estimates of how management practices can mitigate N2O emissions, to develop more efficient selective approaches to fertiliser application, targeted nitrification inhibitor application and improvements in the current N2O inventory estimation.

Effects of digestate co-composting on curing phase of composting

The effects of adding polished digestate (8-day aerated digestate) into the curing phase of composting was investigated. The polished digestate was mixed with a 30-day composted OFMSW, introduced to eight composters with different mixing ratios and monitored for 100 days. Monitored parameters were temperature, mass changes, total solids, organic matter, pH, and electrical conductivity. Stability and maturity endpoints were also quantified by running respirometry, C:N ratio, NH4:NO3 ratio, and Solvita® tests. The results showed that co-composting of polished digestate and 30-day composted OFMSW did not notably improve the overall composting performance and it decreased when the digestate portion increased. This could be due to the excess aeration of the digestate and/or an unsuitable inoculation time. Over-aeration could result in the volatilization of ammonia and loss of nitrogen. There are two speculations: first, the inoculum consortia might be outcompeted by the indigenous microorganisms. Second, substrate could become a limiting factor.

Hydrochar and microplastics disturb soil dissolved organic matter and prominently mitigate ammonia volatilization from wheat growing soil

The impacts of microplastics (MPs) pollution on the nitrogen (N) cycle in soil ecosystems have attracted worldwide attention. Meanwhile, dissolved organic matter (DOM)-rich hydrochar (HBC) is being tried as an emerging soil conditioner for gaseous N reduction load to the atmosphere. However, the influence of MPs and HBC on soil DOM and ammonia (NH3) volatilization in wheat soils remains poorly understood. In this study, a soil column experiment was established in wheat growing soils to determine the impacts of HBC, MPs (i.e., polyethylene and polyacrylonitrile), and the co-occurrence of HBC and MPs (HBC + MPs) on soil NH3 volatilization, physicochemical properties and wheat growth. In comparison with the control (CK, without MPs or HBC), HBC, MPs, and HBC + MPs reduced cumulative NH3 volatilization by 45.4%, 66.7–67.4% and 29.8–58.7%, respectively. Soil DOM fulvic acid-like and humic aid substance abundances of the other treatments were increased by 18.5–56.2% and 12.7–39.3%, respectively, compared to CK. Besides, soil NH3 fluxes were positively correlated to soil NH4+-N concentration at basal fertilization and soil NO3−-N concentration at first supplementary fertilization. HBC, MPs and HBC + MPs treatments promoted soil urease activity and plant N uptake by 6.5–24.2% and 31.9–74.3%, respectively, compared to CK. This study provides an insight into the variation of NH3 volatilization caused by anthropogenic carbon in wheat soil ecosystems.

Predicting Near‐Term Effects of Climate Change on Nitrogen Transport to Chesapeake Bay

AbstractUnderstanding effects of climate change on nitrogen fate and transport in the environment is critical to nutrient management. We used climate projections within a previously calibrated spatially referenced regression (SPARROW) model to predict effects of expected climate change over 1995 through 2025 on total nitrogen fluxes to Chesapeake Bay and in watershed streams. Assuming nitrogen inputs and other watershed conditions remain at 2012 levels, effects of increasing temperature, runoff, streamflow, and stream velocity expected between 1995 and 2025 will include an estimated net 6.5% decline in annual nitrogen delivery to the bay from its watershed. This predicted decline is attributable to declines in the delivery of nitrogen from upland nonpoint sources to streams due to predicted warmer temperatures. Such temperature‐driven declines in the delivery of nitrogen to streams more than offset predicted increased delivery to and within streams due to increased runoff and streamflow and may be attributable to increasing rates of denitrification or ammonia volatilization or to changes in plant phenology. Predicted climate‐driven declines in nitrogen flux are generally similar across the watershed but vary slightly among major nonpoint source sectors and tributary watersheds. Nitrogen contributions to the bay from point sources are not affected by temperature‐driven changes in delivery from uplands and are therefore predicted to increase slightly between 1995 and 2025.

Integrated nutrient management reduced the nutrient losses and increased crop yield in irrigated wheat

ABSTRACT Nitrogen (N), the most vital nutrient, undergoes a transformation in the soil and was subjected to loss through ammonia volatilization, nitrate leaching, and denitrification, which lower the soil fertility, crop yield and pollute the environment. Integrated nutrient management (INM) improves the nutrient supply system by integrating recommended dose fertilizers and biofertilizers, lessens the nitrogen losses, and synchronizes with the nutrient demand of the crop. To evaluate the impact of INM on minimization of N losses and improvement of wheat (Triticum aestivum L.) yield and growth parameters, a field experiment was conducted with different combinations of biofertilizers along with the recommended dosage of fertilizers. Application of NPK + Azotobacter + mycorrhiza (Tram) in combination was found to improve soil nitrogen dynamics, availability of P, K, microbial activity, root growth, urease activity, and nitrogen use efficiency as compared to NPK (Tr) only. The cumulative emission from ammonia flux in the INM plot varied from 10.2 to 10.6 kg ha−1 and denitrification losses varied from 2.4 to 2.5 kg ha−1. At the same time, these were recorded significantly higher in Tr plot. The yield obtained under the INM plot receiving Tram was recorded as 6.4 t ha−1, which is higher than other treatments.

Partial organic fertilizer substitution promotes soil multifunctionality by increasing microbial community diversity and complexity

Partial substitution of synthetic nitrogen (N) with organic fertilizers (PSOF) is of great significance in improving soil ecosystem functions in systems that have deteriorated due to the excessive application of chemical N fertilizer. However, existing studies typically focus on individual soil functions, neglecting the fact that multiple functions occur simultaneously. It remains unclear how PSOF influences multiple soil functions and whether these impacts are related to soil microbial communities. Here, we examined the impacts of partial substitutions (25%−50%) of chemical N fertilizer with organic form (pig manure or municipal sludge) in a vegetable field on soil multifunctionality, by measuring a range of soil functions involving primary production (vegetable yield and quality), nutrient cycling (soil enzyme activities, ammonia volatilization, N leaching, and N runoff), and climate regulation (soil organic carbon sequestration and nitrous oxide emission). We observed that PSOF improved soil multifunctionality, with a 50% substitution of chemical N fertilizer with pig manure being the best management practice; the result was strongly related to the diversities and network complexities of bacteria and fungi. Random forest analysis further revealed that soil multifunctionality was best explained by the bacterial-fungal network complexity, followed by available phosphorus level and bacterial diversity. The PSOF also shifted the composition of bacterial and fungal communities, with increased relative abundances of dominant bacteria phyla, such as Bacteroidetes, Gemmatimonadetes, and Myxococcota, and fungal phyla, such as Basidiomycota and Olpidiomycota. The observed increases in soil multifunctionality were consistent with significant increases in the relative abundances of keystone taxa such as Blastocladiomycota, Chaetomiaceae, and Nocardiopsaceae. Together, these findings indicate that PSOF can enhance interactions within and among microbial communities and that such practices have the potential to improve soil ecosystem multifunctionality and contribute to the development of sustainable agriculture.

Effect of continuous N fertilizer reduction on N losses and wheat yield in the Taihu Lake region, China

Rainfed agriculture is important to meet the increasing demands of food production. However, there is a lack of knowledges for the rainfed wheat systems in abundant rainfall areas, where the erratic rainfall may constrain the wheat yield and increases N losses from wheat fields with excessive fertilizer inputs. In the present study, a 6 consecutive years field experiments were conducted to investigate the wheat yield and N losses responses to different N fertilizer rates in the Taihu Lake region. Despite the fluctuations in the wheat yield, a 10–30% reduction of the district average N input sustained the current-level of wheat yield for the 6 consecutive years. The N rate of 168 kg ha−1 might be the threshold N application rate, because if it was exceeded, it was no longer the predominant factor determining the wheat yield, but significantly increased the N losses fluxes. The seasonal total N losses fluxes were 69.2 kg N ha−1, which accounted for 28.8% of district averaged N input. Runoff was the predominant pathway of N loss from the wheat field, followed by ammonia volatilization and leaching. Nitrate was the predominant form in the runoff and leakage water. Seasonal cumulative nitrate losses via runoff and ammonia volatilization averaged 25.2 and 20.1 kg ha−1 per wheat season, respectively, corresponding to 10.5% and 8.38% of the regional N application rates. However, the seasonal nitrate loss via leakage was the lowest, less than 8.98 kg ha−1. Reducing the fertilizer N rates significantly decreased the N losses via runoff and ammonia volatilization, but not by leaching. Our findings indicated that reducing N fertilizer was impressive for the sustainable development of agriculture in Eastern China and 168 kg N ha−1 was recommended for the rainfed wheat.

In situ nitrous oxide and dinitrogen fluxes from a grazed pasture soil following cow urine application at two nitrogen rates

Cattle grazing of pastures deposits urine onto the pasture soil at high nitrogen (N) rates that exceed the pasture's immediate N demands, increasing the risk of N loss. Nitrous oxide (N2O), a greenhouse gas, and dinitrogen (N2) are lost from the cattle urine patches. There is limited information on the in situ loss of N2 from grazed-pasture systems which is needed for understanding pasture soil N dynamics and balances. The 15N flux method was used to determine N2 and N2O fluxes over time following synthetic urine-15N application at either 400 or 800 kg N ha−1 to a grazed perennial pasture soil. Results showed that daily N2O fluxes were higher under 800 kg N ha−1 than under 400 kg N ha−1, but there was no significant difference in N2 fluxes. Cumulative N2O emissions from soil with 400 kg N ha−1 and 800 kg N ha−1 applied represented 0.16 ± 0.08% and 0.43 ± 0.08% of deposited N, respectively, while emitted N2 accounted for 32.1 ± 4.1% and 14.4 ± 1.7%, respectively, over 95 days after urine application. Codenitrification and denitrification co-occurred, with denitrification accounting for 97.9 to 98.5% of total N2 production. Recovery of urine-15N in pasture decreased with increasing N rate with 14.7 ± 0.5% and 9.9 ± 0.8% recovered at 400 and 800 kg N ha−1, respectively after 95 days. The N2O/(N2 + N2O) product ratio was generally higher during periods of nitrification of urine-N (the first month after urine application) but with no clear relationship to other measured variables. Contrary to our hypothesis, an elevated urine-N rate did not enhance N2 loss. This is speculated to be due to enhanced ammonia volatilisation and transfer of N as nitrate, to deeper soil layers. Soil relative gas diffusivity indicated that high N2 fluxes resulted from entrapped N2 diffusing from the draining soil.

Mitigation of ammonia volatilization on farm using an N stabilizer – A demonstration in Quzhou, North China Plain

Fertilized cropland is a significant source of ammonia (NH3) emissions. Urea, the dominant synthetic nitrogen (N) fertilizer, makes the largest contribution to NH3 volatilization from cropland in China. To improve environmental quality and resource utilization efficiency, stabilized urea (UI: Urea amended with the urease inhibitor Limus®) was tested in an intensive cropping system in the North China Plain (NCP). A two-year field trial and an extensive demonstration experiment at five sites were carried out in Quzhou county, NCP, to quantify the effect of RNUI (Reduced N rate + Urea Inhibitor) technology on NH3 mitigation from farms. NH3 emission, crop yield and N use efficiency (NUE) were measured to evaluate the efficacy of UI and a questionnaire-based survey used to investigate farmers’ attitudes to the technology. In the field trial, UI significantly reduced NH3 emissions by 60.5–62.9% and 39.7–52.3% during wheat and maize growing seasons, respectively, compared to untreated urea applied at the same rate. NUE was significantly increased by 34.6–62.7% in the wheat season and 14.9–66.6% during the maize season. No significant crop yield improvement was observed, but UI significantly reduced yield-scaled NH3 emissions. Similar results were found at the five demonstration sites in Quzhou, but there was a small yield increase for maize. On average there were 49.0% and 38.5% reductions in NH3 emissions, and 50.5% and 46.3% reductions in yield-scaled NH3 emissions for wheat and maize, respectively, compared to typical farmer practice. Farmers’ willingness to adopt RNUI technology depended mainly on crop yield, the convenience of using RNUI and government subsidy to reduce costs. Results emphasized the importance of on-farm demonstration experiments, integrated field management, government subsidies and legislation for the promotion of RNUI technology, achieving sustainable high yields and NUE for mitigating agricultural NH3 loss at a county level in the NCP.

Unexpected high suppression of ammonia volatilization loss by plastic film mulching in Korean maize cropping system

Plastic film mulching (PFM) as an agronomic practice was rapidly expanded to improve crop yield and quality, mainly due to improving soil water and temperature condition. PFM has been known to increase greenhouse gas (GHG) emissions, but its influence on ammonia (NH3) volatilization loss was not properly studied. To determine the impact of PFM on NH3 emission loss, PFM and no-mulching were designed as the main treatment. In addition, chemical (NPK) and organic fertilization plots as the sub-treatment were placed under the same mulching condition. In the NPK, the recommendation level (N-P2O5-K2O=186–35–74 kg ha-1) of chemical fertilizers was only applied for maize cultivation. In the organic fertilization, the mixture of barley and hairy vetch was cultivated during the fallow season and its whole biomass as green manure was incorporated for maize cultivation. PFM considerably improved average soil water and temperature regimes during cropping season by 0.02–0.05 m3 m-3 and 0.8–1.4 ℃ over no-mulching, respectively. These improved soil properties enhanced maize grain yield by around 95–270 and 80–300% in NPK and organic fertilization plots over no-mulching, respectively. The emission loss of NH3 gas which is highly water-soluble was 70–215% higher in NPK than organic fertilization under the same mulching. However, PFM significantly decreased seasonal NH3 emission loss by approximately 40–45% over no-mulching, probably due to physical trapping in water drops under the plastic film. To verify the suppression mechanism of NH3 emission loss by PFM, the emission rates of nitrous oxide (N2O) which is a water-insoluble gas were simultaneously monitored using the closed chamber method. Different from NH3 emission loss, PFM slightly increased N2O emission without a statistical difference, regardless of fertilization background. In conclusion, PFM could be a very useful cropping practice to decrease NH3 emission loss, as well as improve soil properties and crop productivity.

Application of Nitrogenous Fertilizer in Rice Production: A Review

Rice (Oryza sativa L.) is one of the world's most important cereal crops. Nitrogen is one of the most important plant nutrients for rice. Different forms of nitrogenous fertilizer are the major sources of nutrients in rice production. Nitrogen affects various physiological and biochemical processes in plant cells that ultimately affect the growth and development and, thereby, the grain yield of rice. Rice production can be increased by applying nitrogenous fertilizer either as organic or inorganic fertilizer at an appropriate dose, time, method, and place. Soil testing is needed to assess the nutritional status of the soil as it is affected by crop nutrient uptake and removal. Nitrogenous fertilizers should be applied in multiple split doses depending upon the nutrient status of the soil, crop demand, and sources of nutrients. To reduce the nitrogen loss from rice fields, surface runoff, denitrification, ammonium volatilization, and leaching should be managed. Sustainable and environmentally friendly fertilizer management practices enhance the sustainable soil fertility status and, thereby, crop yields. This review article examines the impact of nitrogenous fertilizers on rice growth, development, and production, along with time and doses of nitrogen applications that will help agricultural technicians, academicians, farmers, and policy makers.

Influence of individual and co-application of organic and inorganic fertilizer on NH3 volatilization and soil quality

The use of nitrogen fertilizers to enhance crop growth tends to increase every year. In addition, as eco-friendly agriculture is emphasized, organic fertilizers are preferred over inorganic fertilizers. However, since most of organic fertilizers in South Korea use imported ingredients, an alternative ingredients is needed. Biochar is an eco-friendly way to recycle various biomass and has a high pH and carbon contents. The objective of this study was to evaluate the effect of individual and co-application of organic and inorganic fertilizers on ammonia (NH3) volatilization and soil quality. Organic fertilizers used in this study were divided into conventional organic fertilizers (CF1 and CF2) and biochar-based organic fertilizers (BF). As a result of the experiment, NH3 volatilization and soil quality were significantly affected by the inorganic fertilizers. Also, NH3 volatilization effected by inorganic fertilizer was rapidly increased between 4 and 7 days. When different organic fertilizers were treated, NH3 emissions by BF was highest at 17.49 and 28.97 kg ha−1 compared to CF1 and CF2, but no statistically significant different was observed. A similar trend was appeared when organic and inorganic fertilizers was co-applied. Therefore, biochar-based organic fertilizers are similar to conventional organic fertilizers in terms of soil quality and NH3 volatilization, but it is expected to contribute to the formation of a stable fertilizer market by reducing the percentage of imported ingredients.

Effects of Synthetic Nitrogen Fertilizer and Compost Chicken Manure on Ammonia (NH3) Volatilization in Winter Wheat System

The volatilization of ammonia is an important nitrogen (N) loss path in agricultural production, which not only results in a loss of economy, but also represents a significant atmospheric pollutant. Volatized ammonia (NH 3 ) from livestock manure and cropping field is associated with ecosystem and public health and can also be an indirect source of greenhouse gases. The rate of ammonia volatilization after application of fertilizers is strongly affected by many factors such as soil properties, temperature as well as the type, application time and mode of nitrogen fertilizers. This work aimed to quantify the losses of N by volatilization of ammonia from synthetic nitrogen fertilizer and composted chicken fertilizer in the volatilization of ammonia (NH 3 ) in winter wheat system by the calibrated Dräger-Tube method. An experiment of four treatments Control (CK), Farmer’s compound fertilizer-NPK (CF), Chicken manure compost (25%) + Urea (75%) (MF) and Chicken manure compost (CM) was conducted, with wheat culture in Baizhai County, Quzhou County, Hebei province, following a delineation of casualized blocks, with three repetitions. The daily variation of the ammonia volatilization flow was not dramatically influenced by the type of fertilizer and its combination, ranging from 0.01 to 0.23 mg N m -2 h -1 in base fertilization and 0.03 to 0.44 mg N m -2 h -1 in topdressing fertilization. The results showed that the cumulative losses of volatilization of NH 3 were significantly affected (P≤ 0.05) by the type of fertilizer and its combination. The cumulative volatilization losses of NH 3 in the treatments CM, CF, MF were 14.30 kg N/ha, 21.58 kg N/ha and 25.79 kg N/ha corresponding to 5.72 %, 8.63%, 10.32 % of the total application rates of N, respectively. Emissions factors of Ammonia were highly variable depending on the type of fertilizer or combination of fertilizer. The results showed that wheat yield has been substantially improved by the application of fertilizers alongside organic fertilizers, with the maximum yield achieved in the combination of synthetic and organic fertilizer of about 10.79 t/ha, whereas the isolated organic and synthetic fertilizer (NPK) was not significantly different at around 10.3 t/ha and 10.4 t/ha respectively. Synthetic and organic fertilizers combined proportions with chemical fertilizers have significantly different performance in the volatilization of ammonia, emissions factors and crop yields. Chicken manure can be applied alone or in combination with 75% chemical nitrogen (urea) to achieve the yield of the similar crop or more as with chemical fertilizer alone, and thus reducing the excessive use of chemical fertilizer and the gaseous loss of nitrogen fertilizer, thus being economically beneficial and environmentally sound. Keywords: Manure; Synthetic fertilizer; Winter wheat; Yield; Ammonia DOI: 10.7176/JBAH/12-10-02 Publication date: May 31 st 2022

Modeling ammonia volatilization following urea and controlled-release urea application to paddy fields

• The WHCNS model performed well in simulating NH 3 flux measured by a continuous ventilation method. • Urea split application reduced the peak of NH 3 flux but increased total NH 3 loss. • Controlled-release urea application significantly reduced NH 3 loss compared to urea. • The controlled-release urea rate was recommended to reduce N loss without reducing yield. Ammonia volatilization, a main pathway of nitrogen (N) loss in paddy fields, can easily lead to environmental problems, such as haze and water eutrophication. Field measurement of ammonia volatilization is time-consuming and expensive. Soil–crop system models can simulate the effect of different fertilizer management practices on NH 3 volatilization and compensate for the limitations of field measurement. Therefore, the WHCNS (soil Water Heat Carbon Nitrogen Simulator) model was used to evaluate the feasibility of simulating NH 3 volatilization in paddy fields under different N fertilizer types and application methods. The field experiment, including four treatments of farmer’s practice (FP), basal application of urea in one dose (SBN), split application of urea in three doses (SPN), and basal application of controlled-release urea in one dose (CRU), was conducted from 2013 to 2014. All treatments were conducted with a fertilizer rate of 165 kg N ha −1 , except for FP with a rate of 210 kg N ha −1 . The measured dry matter weight, grain yield, N uptake, and NH 3 flux were used to test the WHCNS model. The model evaluation indices of Nash–Sutcliffe efficiency ( NSE ) and index of agreement ( d ) were close to 1 for the measured variables, except for NSE of yield (0.16). The normalized root mean square error ( NRMSE ) of NH 3 flux was slightly over 30%, but lower than 30% for the other items. Results showed that the model can successfully simulate rice yield and NH 3 flux of urea and controlled-release urea under different application methods. The simulated annual average cumulative NH 3 losses of FP, SBN, SPN, and CRU accounted for 18.9%, 17.8%, 20.6%, and 10.1% of their N inputs, respectively. Compared with the FP treatment, the ratios of NH 3 losses of the SBN and CRU treatments were decreased by 1.2%-8.8%. Compared with the SBN treatment (the same rate of 165 kg N ha −1 ), SPN reduced the peak of NH 3 flux but increased the cumulated NH 3 losses and CRU significantly reduced the NH 3 flux and cumulative NH 3 losses. The application rate of controlled-release urea could be further optimized by refined model calculations to reduce NH 3 volatilization and total N loss while maintaining yield.

Carbon and Nitrogen Footprints of Major Cereal Crop Production in China: A Study Based on Farm Management Surveys

Greenhouse gas (GHG) emissions and reactive nitrogen (Nr) releases are central environmental problems, which are closely linked to climate change, environmental ecology and crop production. Sustainable development of agriculture plays an important role in GHG emissions and Nr loss. The life cycle assessment (LCA) method was used to calculate the product and farm carbon footprints (CFs) and nitrogen footprints (NFs) in rice, wheat and maize production in China based on farm survey data. The results pinpointed that the CFs of rice, wheat and maize were 0.87, 0.30 and 0.24 kg/kg. Meanwhile, the computed NFs were 17.11, 14.26 and 6.83 g/kg, respectively. Synthetic nitrogen fertilizer applications and methane (CH4) emissions were dominant CF sources, while ammonia (NH3) volatilization was the main NF contributor. Moreover, significant decreases in CF and NF by 20%–54% and 33%–61%, respectively, were found in large-size farms (> 20 hm2) when compared to small-size farms (< 0.7 hm2). Furthermore, the significantly positive relationships between CF and NF indicated the potential for simultaneous mitigation in the regions with high agricultural inputs, like amounts of fertilizer. Based on our results, some effective solutions would be favorable toward mitigating climate change and eutrophication of the major cereal crop production in China, especially optimizing fertilizer use and farm machinery operation efficiencies, as well as developing large-size farms with intensive farming.

Response of nitrogen isotopes to paleo-environment and organic carbon accumulation in a Late Paleozoic alkaline lake, Junggar Basin

The geochemistry of nitrogen (N) in ancient lacustrine systems, especially in alkaline conditions, is poorly understood. To fill the knowledge gap, we investigated alkaline lacustrine sediments of the Upper Paleozoic Fengcheng Formation (ca. 300 Ma) in the Mahu Sag, Junggar Basin, northwestern China. Based on the general characteristics and stratigraphic variations in N isotopes, their relationship to the paleo-environmental setting and type/accumulation of organic matter were evaluated. The lacustrine sediments can be divided into alkaline (δ15N > 10–12‰) and circum-neutral (δ15N < 10–12‰) groups in general. The geochemical N cycle was mainly controlled by the pH of the lake water, and ammonia volatilization triggered N isotopic fractionation. In contrast, N isotopes are not significantly affected by the salinity and redox state of the water mass. The δ15N, particularly for the alkaline group, exhibit a correlation with the type of organism present (i.e., the algae/bacteria ratio), and also the hydrocarbon-generation potential and type of organic matter. This reflects the response of lake water pH to the types of organisms present and accumulation of organic matter. The N isotopic compositions of lacustrine sediments, and the factors that control this, are more complex than in the marine system, and are dependent on the biomass and paleo-environmental setting.

Anaerobic Digestate from Biogas Plants—Nuisance Waste or Valuable Product?

Biogas production in waste-to-energy plants will support the decarbonization of the energy sector and enhance the EU’s energy transformation efforts. Digestates (DG) formed during the anaerobic digestion of organic wastes contain large amounts of nutrients. Their use for plant fertilization allows for diversifying and increasing the economic efficiency of farming activities. However, to avoid regional production surpluses, processing technologies allowing the acquisition of products that can be transported over long distances are required. This study therefore aimed at determining the effect of applied methods of DG treatment on the chemical composition of the resulting products and their effect on the yields and chemical composition of plants. The following digestate-based products (DGBPs) were tested: two different digestates (DGs), their liquid (LF) and solid fractions (SF) and pellets from DGs (PDG), and pellets form SFs (PSF). Results from the experiment show that during SF/LF separation of DGs, &gt;80% of nitrogen and 87% of potassium flows to LFs, whereas &gt;60% of phosphorus and 70% of magnesium flows to SFs. The highest yields were obtained using untreated DGs and LFs. The application of DGs and LFs was not associated with a leaching of nutrients to the environment (apparent nutrients recovery from these products exceeded 100%). Pelletized DG and SF forms can be used as slow-release fertilizer, although their production leads to significant nitrogen losses (&gt;95%) by ammonia volatilization.

Rejected Sago Starch as a Coating Material to Mitigate Urea-Nitrogen Emission

Urea–nitrogen is commonly lost through ammonia (NH3) volatilization, denitrification, and nitrate (NO3−) leaching. Rejected sago starch (RSS), which is a by-product of sago flour extraction, could be used to minimize NH3 volatilization from urea. Urea granules were coated with different concentrations of RSS (2%, 3%, 4%, 5%, and 6%), and their effects on NH3 emission, soil pH, exchangeable ammonium (NH4+), and available NO3− were determined. The urea was coated with RSS and homogenized using a mini rotary machine. The RSS-coated urea granules were dyed to differentiate their concentrations. The effectiveness of the RSS as a coating material was determined using a closed-dynamic air flow system. The soil used in the NH3 volatilization was the Bekenu series (Sandy loam, Typic Paleudults). This study compared seven different mixture treatments: soil alone (S), 5 g of uncoated urea (U), 5 g of 2% RSS-coated urea (CU1), 5 g of 3% RSS-coated urea (CU2), 5 g of 4% RSS-coated urea (CU3), 5 g of 5% RSS-coated urea (CU4), and 5 g of 6% RSS-coated urea (CU5). Urea coated with RSS, particularly CU1, effectively minimized NH3 loss and improved the retention of soil exchangeable NH4+ and available NO3− compared with uncoated urea because the RSS serves as a barrier to minimizing the concentration of NH3 from urea hydrolysis. Urea could be coated with RSS at the 2% concentration to enhance urea–N efficiency through a reduction in NH3 emission from urea. RSS-coated urea could be an alternative for farmers because of its controlled release of N and economical benefits. Field planting using rice as a test crop to solidify the effectiveness of RSS-coated urea in improving N retention from urea is still ongoing.