Tofu by-product soy whey substitutes urea: Reduced ammonia volatilization, enhanced soil fertility and improved fruit quality in cherry tomato production.

Soy whey is an abundant, nutrient-rich and safe wastewater produced in tofu processing, so it is necessary to valorize it instead of discarding it as sewage. Whether soy whey can be used as a fertilizer substitute for agricultural production is unclear. In this study, the effects of soy whey serving as a nitrogen source to substitute urea on soil NH3 volatilization, dissolved organic matter (DOM) components and cherry tomato qualities were investigated by soil column experiment. Results showed that the soil NH4+-N concentrations and pH values of the 50% soy whey fertilizer combined with 50% urea (50%-SW) and 100% soy whey fertilizer (100%-SW) treatments were lower than those of 100% urea treatment (CKU). Compared with CKU, 50%-SW and 100%-SW treatments increased the abundance of ammonia oxidizing bacteria (AOB) by 6.52-100.89%, protease activity by 66.22-83.78%, the contents of total organic carbon (TOC) by 16.97-35.64%, humification index (HIX) of soil DOM by 13.57-17.99%, and average weight per fruit of cherry tomato by 13.46-18.56%, respectively. Moreover, soy whey as liquid organic fertilizer reduced the soil NH3 volatilization by 18.65-25.27% and the fertilization cost by 25.94-51.87% compared with CKU. This study provides a promising option with economic and environmental benefits for soy whey utilization and cherry tomato production, which contributes to the win-win effectiveness of sustainable production for both the soy products industry and agriculture.

Effects of optimized nitrogen fertilizer management on the yield, nitrogen uptake, and ammonia volatilization of direct-seeded rice.

BACKGROUND: Direct-seeded rice has been developed rapidly because of labor savings. Changes in rice cultivation methods put forward new requirements for nitrogen (N) fertilizer management practices. Field experiments with five different fertilizer ratios of basal, tillering and panicle fertilizer, namely N1 (10:0:0), N2 (6:2:2), N3 (4:3:3), N4 (2:4:4) and N5 (0:5:5), were conducted to investigate the effects of different N fertilizer management practices on yield formation, N uptakes, and ammonia (NH3 ) volatilization from paddy fields in direct-seeded rice. RESULTS: The results showed that the N4 treatment improved grain yield by 5.1% while decreasing NH3 volatilization by 20.4% compared with that of conventional fertilizer treatment (N2). The panicle number per unit area was the key factor to determine the yield of direct-seeded rice (72%). Excessive N application of basal fertilizer (N1) reduced seedling emergence, N use efficiency, and yield by 45.3%, 160.6%, and 6.9% respectively and increased NH3 volatilization by 28.1% compared with that of the N4 treatment. Removal of basal N fertilizer (N5) N reduced spike number and yield by 13.0% and 6.9% respectively, minimizing NH3 volatilization while affecting the construction of high-yielding populations compared with that of the N4 treatment. CONCLUSION: Optimized N fertilizer management achieved delayed senescence (maintenance of higher leaf Soil Plant Analysis Development meter values in late reproduction), higher canopy photoassimilation (suitable leaf area), higher N fertilizer use efficiency, and less N loss (lower cumulative NH3 volatilization). © 2023 Society of Chemical Industry.

Various quantification methods for estimating ammonia volatilization from wheat-maize cropping system.

Ammonia volatilization (AV) dominates the pathway of nitrogen (N) fertilizer losses in crops throughout the world. However, different methods are highly responsible for the different measurements of AV. The existing techniques were separated into static chamber methods (SCM), dynamic chamber methods (DCM), calibrated Dräger-tube method (DTM) and micrometeorological methods (MMM), which were analyzed by a meta-study of 595 observations from 33 published studies. An exponential relationship (P < 0.01) was found between AV and the N fertilizer applied to wheat and maize using all the methods. The amount of AV using SCM was the lowest. The AV monitored by DCM was 24.5%-55.0% (wheat) and 46.9%-65.0% (maize) lower than that for the DTM. Additionally, the AV measured by DTM did not differ significantly in the wheat season but was 58.9% lower (P < 0.05) in the maize season than that in the MMM. To reveal the influencing factors responsible that were for DCM and DTM, a field experiment was conducted during the period of Oct. 2016 to Oct. 2017. The study indicated that the AV was 15.8%-28.3% (wheat, P < 0.05) and 36.7%-44.2% (maize, P < 0.05) lower when monitored by the DCM than when estimated by DTM. The concentration of soil NH4+-N, air temperature, and wind speed positively correlated with the NH3 fluxes. In addition, there was a significant linear correlation (P < 0.01) between the AV measured by DCM and DTM when the wind speed was <1.5 m s-1. This study highlighted the fact that wind speed was the main factor that caused the large difference between DCM and DTM. Herein, DTM or MMM was first recommended, and DCM was accepted when wind speed was <1.5 m s-1 for quantitative estimates of AV. However, only a straight comparison between DCM and DTM under the same field experiment was done, the other comparisons only being based on similar fertilization and environmental conditions. Consequently, the differences between methods have to be treated carefully.

Climate change may interact with nitrogen fertilizer management leading to different ammonia loss in China's croplands.

Despite research into the response of ammonia (NH3 ) volatilization in farmland to various meteorological factors, the potential impact of future climate change on NH3 volatilization is not fully understood. Based on a database consisting of 1063 observations across China, nonlinear NH3  models considering crop type, meteorological, soil and management variables were established via four machine learning methods, including support vector machine, multi-layer perceptron, gradient boosting machine and random forest (RF). The RF model had the highest R2 of 0.76 and the lowest RMSE of 0.82 kg NH3 -N ha-1 , showing the best simulation capability. Results of model importance indicated that NH3 volatilization was mainly controlled by total input of N fertilizer, followed by meteorological factors, human managements and soil characteristics. The NH3 emissions of China's cereal production (paddy rice, wheat and maize) in 2018 was estimated to be 3.3 Mt NH3 -N. By 2050, NH3 volatilization will increase by 23.1-32.0% under different climate change scenarios (Representative Concentration Pathways, RCPs), and climate change will have the greatest impact on NH3 volatilization in the Yangtze river agro-region of China due to high warming effects. However, the potential increase in NH3 volatilization under future climate change can be mitigated by 26.1-47.5% through various N fertilizer management optimization options.

Cutaneous respiration and osmoregulation in amphibious fishes.

In his early career, August Krogh made fundamental discoveries of the properties of cutaneous respiration in fish, frogs and other vertebrates. Following Krogh's example, the study of amphibious fishes provides an excellent model to understand how the skin morphology and physiological mechanisms evolved to meet the dual challenges of aquatic and terrestrial environments. The skin of air-exposed fishes takes on many of the functions that are typically associated with the gills of fish in water: gas exchange, gas sensing, iono- and osmoregulation, and nitrogen excretion. The skin of amphibious fishes has capillaries close to the surface in the epidermis. Skin ionocytes or mitochondrial-rich cells (MRCs) in the epidermis are thought to be responsible for ion exchange, as well as ammonia excretion in the amphibious mangrove rivulus Kryptolebias marmoratus. Ammonia gas (NH3) moves down the partial pressure gradient from skin capillaries to the surface through ammonia transporters (e.g., Rhcg) and NH3 is volatilized from the mucus film on the skin. Future studies are needed on the skin of amphibious fishes from diverse habitats to understand more broadly the role of the skin as a multifunctional organ.

Green manuring alters reactive N losses and N pools in arable soils: A meta-regression study.

Green manuring is a conservation agricultural practice that improves soil quality and crop yield. However, increasing the active nitrogen (N) and carbon (C) pools during green manure (GM) amendment may accelerate soil N transformation and stimulate N loss. Previous studies have reported the effects of cover crop incorporation on N2O emission; however, the driving mechanisms and other N losses remain unclear. Therefore, we conducted a comprehensive meta-analysis of 109 published articles (517 paired observations) to clarify the effects of GM amendment on soil reactive N (Nr) losses (N2O emissions, NH3 volatilization, and N leaching and runoff), N pools, and N cycling functional gene abundance. The results showed that green manuring increased soil microbial biomass N (MBN) and NO3--N concentrations and stimulated N2O emission but significantly lowered N leaching and yield-scaled NH3 volatilization. Practices of green manuring made a dominant contribution to the variation in N2O emissions and NH3 volatilization after GM application. Furthermore, applying legume-based GM, using N derived from GM (GMN) as an additional input, and short-term GM amendment each stimulated N2O emissions. In contrast, adopting non-legume GM, using GMN to partially substitute mineral N, and applying GM to the soil surface or paddy field mitigated NH3 loss during GM amendment. Additionally, the variation in NH3 volatilization was positively related to soil pH and N application rate (NAR) but had a negative relationship with mean annual precipitation (MAP). This study highlighted the marked effects of green manuring on soil N retention and loss. Agricultural operations that adopt GM amendment should select suitable GM species and optimize mineral N inputs to minimize N loss.

Effects of biochar in combination with varied N inputs on grain yield, N uptake, NH3 volatilization, and N2O emission in paddy soil.

Biochar application can improve crop yield, reduce ammonia (NH3) volatilization and nitrous oxide (N2O) emission from farmland. We here conducted a pot experiment to compare the effects of biochar application on rice yield, nitrogen (N) uptake, NH3 and N2O losses in paddy soil with low, medium, and high N inputs at 160 kg/ha, 200 kg/ha and 240 kg/ha, respectively. The results showed that: (1) Biochar significantly increased the rice grain yield at medium (200 kg/ha) and high (240 kg/ha) N inputs by 56.4 and 70.5%, respectively. The way to increase yield was to increase the rice N uptake, rice panicle number per pot and 1,000 grain weight by 78.5-96.5%, 6-16% and 4.4-6.1%, respectively; (2) Under low (160 kg/ha) N input, adding biochar effectively reduced the NH3 volatilization by 31.6% in rice season. The decreases of pH value and NH4+-N content in surface water, and the increases of the abundance of NH4+-N oxidizing archaea and bacteria (AOA and AOB) communities contributed to the reduction of NH3 volatilization following the biochar application; (3) Under same N input levels, the total N2O emission in rice season decreased by 43.3-73.9% after biochar addition. The decreases of nirK and nirS gene abundances but the increases of nosZ gene abundance are the main mechanisms for biochar application to reduce N2O emissions. Based on the results of the current study, adding biochar at medium (200 kg/ha) N level (N200 + BC) is the best treatment to synchronically reduce NH3 and N2O losses, improve grain yield, and reduce fertilizer application in rice production system.

Factors Influencing Gaseous Emissions in Constructed Wetlands: A Meta-Analysis and Systematic Review.

Constructed wetlands (CWs) are an eco-technology for wastewater treatment and are applied worldwide. Due to the regular influx of pollutants, CWs can release considerable quantities of greenhouse gases (GHGs), ammonia (NH3), and other atmospheric pollutants, such as volatile organic compounds (VOCs) and hydrogen sulfide (H2S), etc., which will aggravate global warming, degrade air quality and even threaten human health. However, there is a lack of systematic understanding of factors affecting the emission of these gases in CWs. In this study, we applied meta-analysis to quantitatively review the main influencing factors of GHG emission from CWs; meanwhile, the emissions of NH3, VOCs, and H2S were qualitatively assessed. Meta-analysis indicates that horizontal subsurface flow (HSSF) CWs emit less CH4 and N2O than free water surface flow (FWS) CWs. The addition of biochar can mitigate N2O emission compared to gravel-based CWs but has the risk of increasing CH4 emission. Polyculture CWs stimulate CH4 emission but pose no influence on N2O emission compared to monoculture CWs. The influent wastewater characteristics (e.g., C/N ratio, salinity) and environmental conditions (e.g., temperature) can also impact GHG emission. The NH3 volatilization from CWs is positively related to the influent nitrogen concentration and pH value. High plant species richness tends to reduce NH3 volatilization and plant composition showed greater effects than species richness. Though VOCs and H2S emissions from CWs do not always occur, it should be a concern when using CWs to treat wastewater containing hydrocarbon and acid. This study provides solid references for simultaneously achieving pollutant removal and reducing gaseous emission from CWs, which avoids the transformation of water pollution into air contamination.

The optimum economic nitrogen rate of blended controlled-release nitrogen fertilizer for rice in the Chanoyu watershed in the Yangtze River Delta, China.

Introduction: The application of controlled-release nitrogen fertilizer (CRN) has become an important production method to achieve high crop yield and ecological safety. However, the rate of urea-blended CRN for rice is usually determined by conventional urea, and the actual rate is still unclear. Methods: A five-year field experiment was carried out in the Chaohu watershed in the Yangtze River Delta to study rice yield, N fertilizer utilization efficiency (NUE), ammonia (NH3) volatilization and economic benefit under the four urea-blended CRN treatments with a 4:3:3 ratio applied at one time (60, 120, 180, 240 kg/hm2, CRN60, CRN120, CRN180, CRN240), four conventional N fertilizer treatments (N60, N120, N180, N240) and a control without N fertilizer (N0). Results and Discussion: The results showed that the N released from the blended CRNs could well satisfy the N demand of rice growth. Similar to the conventional N fertilizer treatments, a quadratic equation was used to model the relationship between rice yield and N rate under the blended CRN treatments. The blended CRN treatments increased rice yield by 0.9-8.2% and NUE by 6.9-14.8%, respectively, compared with the conventional N fertilizer treatments at the same N application rate. The increase in NUE in response to applied blended CRN was related to the reduction in NH3 volatilization. Based on the quadratic equation, the five-year average NUE under the blended CRN treatment was 42.0% when rice yield reached the maximum, which was 28.9% higher than that under the conventional N fertilizer treatment. Among all treatments, CRN180 had the highest yield and net benefit in 2019. Considering the yield output, environmental loss, labor and fertilizer costs, the optimum economic N rate under the blended CRN treatment in the Chaohu watershed was 180-214 kg/hm2, compared with 212-278 kg/hm2 under the conventional N fertilizer treatment. The findings suggest that blended CRN improved rice yield, NUE and economic income while decreasing NH3 volatilization and negative environmental outcomes.

Responses of Rice Yield, N Uptake, NH3 and N2O Losses from Reclaimed Saline Soils to Varied N Inputs.

It is of agronomic importance to apply nitrogen (N), but it has high environmental risks in reclaimed saline soils. Therefore, we should apply N fertilizer at an appropriate rate to increase crop yield but decrease N losses. In this soil column experiment, rice yield, N uptake, and ammonia (NH3) and nitrous oxide (N2O) losses were measured in four treatments with no N application (control) and with N applications of 160, 200, and 240 kg/ha (N160, N200, and N240, respectively). The results show that grain yield, spike number, and thousand-kernel weight increased with increases in N application rate, but there was no significant difference in grain yield between N200 and N240. However, the kernels per spike increased first and then decreased with the increase in N application, of which N200 was recorded to have the highest kernels per spike value, which was 16.8 and 9.8% higher than those of N160 and N240, respectively. Total NH3 volatilization of the rice season increased with increasing N input, especially during the first and second supplementary fertilization stages. The NH4+-N concentration of overlying water was relatively lower under the N200 treatment in these two stages, and the yield-scaled NH3 volatilization and the emission factor were the lowest in N200, which were 26.2-27.8% and 4.0-21.0% lower than those of N160 and N240, respectively. Among the three N-applied treatments, N2O losses and the emission factor as well as the yield-scaled N2O emissions were the lowest under the N200 treatment, which had 34.7% and 78.9% lower N2O emissions and 57.8% and 83.5% lower emission factors than those of the N160 and N240 treatments, respectively. Moreover, the gene copies of AOA and AOB amoA, nirS, and nirK in cultivated layer soils all reached the minimum under the N200 treatment. According to the comprehensive effects of N fertilizer on rice grain yield and NH3 and N2O losses, we recommend applying 200 kg/ha to reclaimed saline soil to ensure crop yield and reduce N losses.

Microplastics have rice cultivar-dependent impacts on grain yield and quality, and nitrogenous gas losses from paddy, but not on soil properties.

Microplastics might affect the nitrogen (N)-use efficiency, crop production, and reactive N losses in agricultural system. However, it remains unclear whether the effects are dependent on crop cultivar. Here, a pot experiment was conducted to evaluate the effects of a typical polyethylene (PE) microplastics addition on grain yield and amino acid content, N-use efficiency, ammonia (NH3) volatilization and nitrous oxide (N2O) emission, and properties of paddy soil planted with common rice Nangeng 5055 (NG) and hybrid rice Jiafengyou 6 (JFY). The results showed that PE addition significantly reduced the grain yield and total grain amino acid content of hybrid rice by 23% and 1.7%, respectively. In addition, PE addition significantly decreased the N agronomic and recovery efficiencies of hybrid rice by 30% and 27%, respectively. For paddy soil in which hybrid rice was grown, PE addition significantly increased NH3 volatilization by 72%, but exerted no influence on N2O emission. Interestingly, the N2O emission from NG+PE treatment was 15% significantly lower than that from NG treatment, which was associated with decreased gene copies of nirK (by 50%) and nirS (by 84%) in NG+PE treatment. Generally, no significant change in soil properties was found as result of microplastics addition regardless of the cultivar. In conclusion, the impacts of microplastics on rice production and quality, N-use efficiency and nitrogenous gas losses from paddy soil are cultivar-dependent.

Role of tobacco and bamboo biochar on food waste digestate co-composting: Nitrogen conservation, greenhouse gas emissions, and compost quality.

Anaerobic digestion is considered an environmentally benign process for the recycling of food waste into biogas. However, unscientific disposal of ammonium-rich food waste digestate (FWD), a by-product of anaerobic digestion induces environmental issues such as odor nuisances, water pollution, phytotoxicity and pathogen transformations in soil, etc. In the present study, FWD produced from anaerobic digestion of source-separated food waste from markets and industries was used for converting FWD into biofertilizer using 20-L bench scale composters. The issues of nitrogen loss, NH3 volatilization, and greenhouse gas N2O emission were addressed using in-situ composting technologies with the aid of tobacco and bamboo biochar produced at pyrolytic temperatures of 450 °C and 600 °C, respectively. The results demonstrated that the phytotoxic nature of FWD could be reduced into a nutrient-rich compost by mitigating nitrogen loss by 29-53% using 10% tobacco and 10% bamboo biochar in comparison with the control treatment. Tobacco biochar mitigates NH3 emission by 63% but enhances the N2O emission by 65%, whereas bamboo biochar mitigates both NH3 and N2O emissions by 48% and 31%, respectively. Overall, 10% tobacco and 10% bamboo biochar amendment could reduce total nitrogen loss by 29% and 53%, respectively. Furthermore, the biochar addition significantly enhanced the biodegradation rate of FWD and the mature compost could be produced within 21 days of FWD composting as seen by an increased seed germination index (>50% on dry weight basis). The results of this study could be beneficial in developing a circular bioeconomy locally with the waste-derived substrates.

Impacts of vermicompost application on crop yield, ammonia volatilization and greenhouse gases emission on upland in Southwest China.

Ammonia (NH3) volatilization and greenhouse gas (GHG) emission are important environment pollution sources in upland agro-ecosystems. Vermicompost was used for amending purple soil and comparing NH3 and GHG emissions. A field experiment was conducted with a comparison of organic and inorganic fertilizers in a wheat-maize rotation system in the Sichuan Basin, China. The five treatments were conventional inorganic fertilizers, NPK as control; vermicompost prepared with cow dung (VCM); and pig manure (VPM); cow dung and pig manure vermicompost, respectively (VCMNPK, VPMNPK). Total nitrogen rates of all treatments were the same. Soil NH3 volatilization and GHG emissions were monitored with the static chamber method. The results showed that NH3 volatilization occurred in the first two weeks following nitrogen (N) fertilization. The cumulative fluxes of NH3 recorded in the NPK, VCM, VPM, VCMNPK, and VPMNPK treatments were 15.4, 5.7, 6.3, 10.32, and 10.29 kg N ha-1 yr-1, respectively, in the winter and 4.8, 5.5, 19.83, 12.8, and 11.9 kg N ha-1 yr-1 respectively, in the summer. The global warming potential (GWP) 773.6 and 803.9 g CO2-eq m-2 in VCM and VPM, respectively, during the wheat season 540.6 and 576.2 g CO2-eq m-2, respectively, during the maize season. The GWPs in NPK treatment were 1032.4 and 570.7 g CO2-eq m-2 during the wheat and maize seasons, respectively. The increasing effects of nutrient loops, particularly 18 % soil total nitrogen (TN) and 31 % soil organic carbon (SOC) in VCM, and crop productivity of vermicompost treatments during the wheat-maize rotation had been evaluated. This study recommends that VCM can be considered as a better organic amendment, promoting plant growth while decreasing the environmental costs of gas emissions.

Drip fertigation sustains crop productivity while mitigating reactive nitrogen losses in Chinese agricultural systems: Evidence from a meta-analysis.

Drip fertigation can synchronize the supply of nutrients and water for crop demand, offering the potential for minimizing negative environmental impacts and sustaining crop productivity. However, there are no comprehensive evaluations on performances of drip fertigation on environmental nitrogen (N) losses and crop productivity, nationwide. Here, a meta-analysis was performed to quantify overall effects of drip fertigation on N losses and crop productivity in Chinese agricultural systems based on 443 observations from 42 field studies. The results showed that drip fertigation significantly increased crop yields by 9.8 % and slightly increased soil NO emission by 13.9 % compared to the traditional irrigation and fertilization practices (e.g. flooding/furrow irrigation and N broadcasting), while significantly decreasing NH3 volatilization by 14.2 %, soil N2O emission by 28.1 % and NO3--N leaching loss by 71.2 %. There were significant mitigation potentials of environmental N losses by drip fertigation for cereal cropping systems, not for horticultural crops in terms of soil NO emission and not for cotton in terms of NH3 volatilization. Non significant promotion effect on NO emission and significant reduction effects on the other all kinds of environmental N losses by drip fertigation were observed for alkaline soils (pH > 7.3) and coarse-textured soils. In addition, the use of different fertilizer sources and/or soil amendments have shown in popularity as strategies to offset the negative feedback associated with agricultural N losses, no direct synthetic result was shown in drip-fertigated soils. We synthesized 19 studies so as to assess the potential mitigation options for further minimizing N losses in drip fertigation systems, which suggested that deleterious environmental pollution could be further reduced while still achieving high crop yields with a combination of enhanced-efficiency fertilizers (e.g. nitrification or urease inhibitors) or soil amendments (e.g. biochar or straw) to drip fertigation systems.

Biochar application can mitigate NH3 volatilization in acidic forest and upland soils but stimulates gaseous N losses in flooded acidic paddy soil.

Biochar (BC) has attracted attention for carbon sequestration, a strategy to mitigate climate change and alleviate soil acidification. Most meta-analyses have insufficiently elaborated the effects of BC on soil N transformation so the practical importance of BC could not be assessed. In this study, a 15N tracing study was conducted to investigate the effects of BC amendment on soil gross N transformations in acidic soils with different land-use types. The results show that the BC amendment accelerated the soil gross mineralization rate of labile organic N to NH4+ (MNlab) (3 %-128 %) which was associated with an increase in total nitrogen. BC mitigated NH3 volatilization (VNH3) (52 %-99 %) in upland and forest soils due to NH4+/NH3 adsorption, while it caused higher gaseous N losses (NH3 and N2O) in flooded paddy soils. An important function was the effect of BC addition on NH4+ oxidation (ONH4). While ONH4 increased (4 %-19 %) in upland soils, it was inhibited (34 %-71 %) in paddy soils and did not show a response in forest soils. Overall, the BC amendment reduced the potential risk of N loss (PRL), especially in forest soils (82 %-98 %). This study also shows that the BC effect on soil N cycling is land-use specific. The suitability of practices including BC hinges on the effects on gaseous N losses.

Insight into the functional mechanisms of nitrogen-cycling inhibitors in decreasing yield-scaled ammonia volatilization and nitrous oxide emission: A global meta-analysis.

Soil ammonia (NH3) volatilization and nitrous oxide (N2O) emission decrease nitrogen (N) utilization efficiency and cause some environmental problems. The N-cycling inhibitors are suggested to apply to enhance N utilization efficiency. Quantifying effects of N-cycling inhibitors on yield-scaled NH3 volatilization and N2O emission and functional genes could provide support for the optimal selection and application of N-cycling inhibitor. We conducted a meta-analysis to reveal the effects of N-cycling inhibitors on soil abiotic properties, functional genes and yield-scaled NH3 volatilization and N2O emission by extracting data from 166 published articles and linked their comprehensive relationships. The N-cycling inhibitors in this meta-analysis mainly includes nitrification inhibitors 3, 4-dimethyl pyrazole phosphate, dicyandiamide and 2-chloro-6-trichloromethylpyridine, urease inhibitor N-(n-butyl) thiophosphoric triamide and biological nitrification inhibitors methyl 4-hydroxybenzoate and 1, 9-decanediol. The N-cycling inhibitor applications significantly increased alkaline soil pH but significantly decreased acidic soil pH. The N-cycling inhibitors decreased soil AOB amoA gene abundances mostly under the condition of pH 4.5-6 (mean: 212%, 95% confidence intervals (CI): 249% and -176%) and significantly decreased nirS gene (mean: 39%; 95% CI: 72% and -6%). The yield-scaled NH3 volatilization was significantly decreased by the N-cycling inhibitors under the condition of soil pH = 7-8.5 (mean: 45%; 95% CI: 59% and -31%). The yield-scaled N2O emission was also significantly reduced by all N-cycling inhibitors and had negative correlations with the soil nirK and nirS gene abundances. The effects of N-cycling inhibitors on soil pH, ammonium-N, nitrate-N and nitrifying and denitrifying genes and yield-scaled NH3 volatilization and N2O emission were dominated by the inhibitor types, soil textures, crop species and environmental pH. Our study could provide technical support for the optimal selection and application of N-cycling inhibitor under different environmental conditions.

Effects of five-year field aged zeolite on grain yield and reactive gaseous N losses in alternate wetting and drying paddy system.

Clinoptilolite zeolite has been widely used in agricultural production systems for enhancing water and fertilizer savings, mitigating greenhouse gas emissions, and increasing yield. However, there is little information on field-aged effects of zeolite on reactive gaseous N losses under alternate wetting and drying irrigation (AWD). We conducted a five-year field experiment to investigate field-aged effect of natural zeolite addition at 0 (Z0), 5 (Z5), and 10 (Z10) t ha-1 on reactive gaseous N losses (NH3, N2O), N-related global warming potential (GWPN), soil properties and grain yield under two irrigation regimes (CF: continuous flooding irrigation; AWD) in the 4th (2020) and 5th (2021) years since its initial application in 2017. As compared with CF, AWD did not significantly affect grain yield and NH3 volatilization but increased seasonal N2O emissions by 46 %-71 % over two years. Zeolite increased rice yield for five consecutive years. Z10 reduced averaged cumulative NH3 volatilization and GWPN by 23 % and 26 %, compared to zeolite-free treatment, respectively, in the 4th and 5th years. Soil NH4+-N was increased with the increased rate of Z application under both CF and AWD. Z10 increased soil NH4+-N by 27 %-38 % and NO3--N by 14 %-22 % in five years, compared to Z0, respectively. Compared to AWD without zeolite, the addition of 10 t ha-1 zeolite under AWD lowered NH3 volatilization, cumulative N2O emissions, and GWPN by an average of 28 %, 29 %, and 30 % in two years, respectively. IAWDZ10 did not differ from ICFZ0 on reactive gaseous N losses but significantly lowered reactive gaseous losses relative to IAWDZ0. Therefore, zeolite addition could mitigate the reactive gaseous N losses and GWPN for at least five years after initial application, which is beneficial to promoting zeolite application and ensuring sustainable agriculture.

Controlled release urea improves rice production and reduces environmental pollution: a research based on meta-analysis and machine learning.

To reveal the comprehensive impacts of controlled release urea (CRU) on rice production, nitrogen (N) loss, and greenhouse gas (GHG) emissions, a research based on global meta-analysis and machine learning (ML) was conducted. The results revealed that the CRU application instead of conventional fertilizer can increase rice yield, N use efficiency (NUE), and net benefits by 5.24%, 20.18%, and 9.30%, respectively, under the same amount of N. Furthermore, the emission of N2O and CH4, global warming potential (GWP), the loss of N leaching, and NH3 volatilization were respectively reduced by 25.64%, 18.33%, 21.10%, 14.90%, and 35.88%. The enhancing effects of CRU on rice yield and NUE were greater when the nitrogen application rate was 150 kg N ha-1. Nevertheless, the reducing effects of CRU on GHG emission reduction, nitrogen leaching, and NH3 volatilization was greater at high nitrogen application rate (≥150 kg ha-1). Mitigating effects of CRU on N2O and CH4 emission were significant when soil pH ≥ 6, while CRU posed a measurable effect on reducing nitrogen leaching and NH3 volatilization in paddy fields with soil organic carbon lower than 15 g kg-1 and pH lower than 6. Based on the data collected from meta-analysis, the results of ML demonstrated that it was feasible to use soil data and N application rate to predict N losses in rice fields under CRU. The performance of random forest is better than multilayer perceptron regression in predicting N losses from paddy fields. Thus, it is necessary to promote the application of CRU in paddy fields, especially in coarse soil, in which scenario the environmental pollution would be decreased and the rice yields, NUE, and net benefits would be increased. Meanwhile, machine learning models can be used to predict N losses in CRU paddy fields.

Being applied at rice or wheat season impacts biochar's effect on gaseous nitrogen pollutants from the wheat growth cycle.

Biochar (BC) application to agricultural soil can impact two nitrogen (N) gases pollutants, i.e., the ammonia (NH3) and nitrous oxide (N2O) losses to atmospheric environment. Under rice-wheat rotation, applied at which growth cycle may influence the aforementioned effects of BC. We conducted a soil column (35 cm in inner diameter and 70 cm in height) experiment to evaluate the responses of wheat N use efficiency (NUE), NH3 volatilization, and N2O emission from wheat season to biochar applied at rice (R) or wheat (W) growth cycle, meanwhile regarding the effect of inorganic fertilizer N input rate, i.e., 72, 90, and 108 kg ha-1 (named N72, N90, and N108, respectively). The results showed that BC application influenced the wheat growth and grain yield. In particular, BC applied at rice season increased the wheat grain yield when receiving 90 and 108 kg N ha-1. The improved wheat grain yield was attributed to that N90 + BC(R) and N108 + BC(R) enhanced the wheat NUE by 53.8% and 52.8% over N90 and N108, respectively. More N input led to higher NH3 volatilization and its emission factor. Interestingly, 19.7%-34.0% lower NH3 vitalizations were recorded under treatments with BC applied in rice season, compared with the treatments only with fertilizer N. BC applied at rice season exerted higher efficiency on mitigating N2O emission than that applied at wheat season under three N input rates, i.e., 60.5%-77.6% vs 29.8%-34.8%. Overall, considering the crop yield and global warming potential resulting from NH3 volatilization and N2O emission of wheat season, N90 + BC(R) is recommended. In conclusion, farmers should consider the application time and reduce inorganic fertilizer N rate when using BC.

Elevation of biochar application as regulator on denitrification/NH3 volatilization in saline soils.

Denitrification and NH3 volatilization are the main removal processes of nitrogen in coastal saline soils. In this incubation study, the effects of wheat straw biochar application at rates of 0, 2, 5, 10 and 15% by weight to saline soil with two salt gradients of 0 and 1‰ on denitrification and NH3 volatilization were investigated. The results showed that the denitrification rates with 2, 5 and 10% biochar amendments decreased by 25.26, 33.07 and 17.50%, respectively, under salt-free conditions, and the denitrification rates with 2 and 5% biochar amendments under 1‰ salt conditions decreased by 17.74 and 17.39%, respectively. However, the NH3 volatilization rates increased by 8.05-61.73% after biochar application. The path analysis revealed the interactions of overlying water-sediment system environmental factors in biochar-amended saline soils and their roles in denitrification and NH3 volatilization. Environmental factors in sediment exerted much greater control over denitrification than those in overlying water. In addition, environmental factors exhibited an indirect negative influence on denitrification by negatively influencing the abundance of the nosZ gene. The comprehensive effects of the environmental factors in overlying water on NH3 volatilization were greater than those in sediment. The NH4+-N content, pH of overlying water and sediment salinity were the main controlling factors for NH3 volatilization in saline soils. Biochar application effectively regulated the denitrification rate by changing the environmental factors and denitrifying functional gene abundance, but its application posed a risk of increased NH3 volatilization mainly by increasing NH4+-N, EC and pH in overlying water.