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To adjust for potential overestimations in the nitrogen excretion by horses within Overseer®, a revised stock unit system has been proposed (equineRSU). These equineRSU were generated and validated using a medium-sized equine farm as a model farm. The aim of this study was to test the application of the equineRSU and seasonal stock number adjustment on a more complex farming model. Livestock numbers and management data were captured prospectively for the base property (128.8 ha) of a large multi-property commercial breeding stud (3 support properties, 556 ha total area) between June 2022 and May 2023. The monthly on-farm metabolisable energy (ME) requirement and pasture demand were deterministically modelled with both a customised feed budget using livestock class and weight or using the equineRSU and monthly adjusted stock numbers. There were multiple complex movements of horses on and off the property in the different stock classes across the year, with stock management reflecting seasonal periods of high stocking density. There was good agreement (6% variance) between actual ME demand (complex feed budget) and estimated feed demand (simplistic equineRSU model) of 4,387,187 MJ vs 4,102,770 MJ. This suggests that the equineRSU could be used on complex equine farm systems within Overseer®. [ABSTRACT FROM AUTHOR]

Abstract Plant growth and high yields are secured by intensive use of nitrogen (N) fertilizer, which, however, pollutes the environment, especially when N is in the form of nitrate. Ammonium is oxidized to nitrate by nitrifiers, but roots can release biological nitrification inhibitors (BNIs). Under what conditions does root-exudation of BNIs facilitate nitrogen N uptake and reduce pollution by N loss to the environment? We modeled the spatial–temporal dynamics of nitrifiers, ammonium, nitrate, and BNIs around a root and simulated root N uptake and net rhizosphere N loss over the plant’s life cycle. We determined the sensitivity of N uptake and loss to variations in the parameter values, testing a broad range of soil–plant-microbial conditions, including concentrations, diffusion, sorption, nitrification, population growth, and uptake kinetics. An increase in BNI exudation reduces net N loss and, under most conditions, increases plant N uptake. BNIs decrease uptake in the case of (1) low ammonium concentrations, (2) high ammonium adsorption to the soil, (3) rapid nitrate- or slow ammonium uptake by the plant, and (4) a slowly growing or (5) fast-declining nitrifier population. Bactericidal inhibitors facilitate uptake more than bacteriostatic ones. Some nitrification, however, is necessary to maximize uptake by both ammonium and nitrate transporter systems. An increase in BNI exudation should be co-selected with improved ammonium uptake. BNIs can reduce N uptake, which may explain why not all species exude BNIs but have a generally positive effect on the environment by increasing rhizosphere N retention.

The determination of optimum nitrogen (N) fertilisation rates, which maximise yields and minimise N losses, remains problematic due to unknown upcoming crop requirements and near-future supply by the soil. Remote sensing can be used for determining the crop N status and to assess the spatial variability within a field or between fields. This can be used to improve N fertilisation, provided that the optimal fertilisation rate at the time of fertiliser application for an expected yield is known. Using the APSIM-wheat model, we developed an algorithm that relates the N status of the plants at early development stages to the yield response to N. Simulations were performed for winter wheat under growth conditions in Denmark. To obtain a range of different N status in the biomass at early growth stages, the soil N in autumn was varied from 20 to 180 kg N ha−1, and at BBCH23, fertiliser was applied at a rate of 50 kg N ha−1. In a full factorial setup, additional N fertiliser was applied ranging from 0 to 150 kg N ha−1 during three different development stages (BBCH30, 32, and 37). The algorithm was evaluated by comparing model outputs with a standard N application of 50 kg N ha−1 at BBCH23 and 150 kg N ha−1 at BBCH30. The evaluation showed that, depending on the N status of the soil, the algorithm either provided higher or lower optimal N fertilisation rates when targeting 95% of the maximum yield, and these affected the grain yield and the grain N, as well as the amount of N leaching. Split application of fertiliser into three applications was generally beneficial, with decreased product-related N leaching of up to nearly 30%. Further testing of the model under different environmental conditions is needed before such an algorithm can be used to guide N fertilisation. [ABSTRACT FROM AUTHOR]

The determination of optimum nitrogen (N) fertilisation rates, which maximise yields and minimise N losses, remains problematic due to unknown upcoming crop requirements and near-future supply by the soil. Remote sensing can be used for determining the crop N status and to assess the spatial variability within a field or between fields. This can be used to improve N fertilisation, provided that the optimal fertilisation rate at the time of fertiliser application for an expected yield is known. Using the APSIM-wheat model, we developed an algorithm that relates the N status of the plants at early development stages to the yield response to N. Simulations were performed for winter wheat under growth conditions in Denmark. To obtain a range of different N status in the biomass at early growth stages, the soil N in autumn was varied from 20 to 180 kg N ha−1, and at BBCH23, fertiliser was applied at a rate of 50 kg N ha−1. In a full factorial setup, additional N fertiliser was applied ranging from 0 to 150 kg N ha−1 during three different development stages (BBCH30, 32, and 37). The algorithm was evaluated by comparing model outputs with a standard N application of 50 kg N ha−1 at BBCH23 and 150 kg N ha−1 at BBCH30. The evaluation showed that, depending on the N status of the soil, the algorithm either provided higher or lower optimal N fertilisation rates when targeting 95% of the maximum yield, and these affected the grain yield and the grain N, as well as the amount of N leaching. Split application of fertiliser into three applications was generally beneficial, with decreased product-related N leaching of up to nearly 30%. Further testing of the model under different environmental conditions is needed before such an algorithm can be used to guide N fertilisation.

With the rapid expansion of agriculture on saline–alkaline soils, environmental problems such as increased greenhouse gas (GHG) emissions, eutrophication and soil degradation are becoming increasingly serious. To clarify the characteristics of carbon (C) and nitrogen (N) cycling and their loss mechanisms in cultivated saline–alkaline soils, an undisturbed soil column experiment was conducted to analyse C and N leaching and GHG emissions by applying different fertilizer rates. The experiment had six treatments using N‐(NH4)SO4 over a 40‐day seedling stage, with and without maize. Treatments were: no N with maize (0Nmaize: 0 kg N ha−1), reduced N with maize (RNmaize: 63 kg N ha−1), conventional N with maize (CNmaize: 160 kg N ha−1) and their equivalents without maize (0Nsoil: 0 kg N ha−1; RNsoil: 63 kg N ha−1; CNsoil: 160 kg N ha−1). The results indicated that reduced N with maize reduced the N2O emission by 21%, with N leaching (TN: 41%, NO3−–N: 19%, NH4+ − N: 63%) within 15 days after fertilization, but had no significant effect on CH4 emission compared to conventional N with maize. Therefore, reduced N with maize had the smallest N loss, which accounted for 1.5% of the relative percentage of N flow including N2O (0.3%), N leaching (2%), aboveground biomass N (76%) and root biomass N (22%). Compared to conventional N with maize, reduced N with maize significantly reduced N leaching by 40% because conventional N with maize greatly exceeded the crop N uptake when maize root length was only within 20 cm. Reduced N without maize reduced CO2 emission (19%) compared to conventional N without maize. Uncultivated saline–alkaline soils face greater N overuse and leaching risk because higher NO3−–N leaching (6.9 mg L−1) that occurred in bare soils without fertilization, which increased by 2.6–3.6 times when the N input increased from 63 to 160 kg N ha−1 compared to control. In conclusion, reducing conventional N fertilizer inputs by 60% is not only an effective strategy to reduce CO2 and N2O emission and N leaching but also effectively absorbs C, and the N retained in the soil tillage layer can help to meet maize seedling growth requirements in Solonchaks. [ABSTRACT FROM AUTHOR]

The significance of nitrogen in agricultural ecosystems cannot be overstated; however, it can pose a threat to the environment when it leaches into groundwater. This comprehensive meta-analysis sheds light on the complex relationship between organic and inorganic fertilizers and nitrogen leaching, encompassing 39 years of data. The results indicate that the impact of fertilizers is dependent on crop type, soil properties, and fertilization practices. Vegetables treated with synthetic fertilizers were found to have the highest levels of nitrogen leaching, while grasses exhibited the lowest. Soil texture was also determined to be a significant factor, with coarser soils leading to higher levels of leaching than medium or fine soils. The meta-analysis showed that organic sources resulted in an average of 16% higher losses of nitrate-N, but there was no significant difference between organic and synthetic N fertilizers in terms of leaching overall. These findings provide valuable insights for the responsible management of nitrogen and to further our understanding of the impact of fertilizers on nitrate pollution. [ABSTRACT FROM AUTHOR]

The substituting chemical nitrogen (N) fertilizer with organic forms such as livestock manure in agroecosystems improves crop yields while reducing nutrient losses. However, the effects of such management practices in China on different soil types and cropping systems are widely unknown. The present lysimeter study investigated the different chemical fertilizer replacement rates on crop yields and N leaching rates for two spring maize systems on a Luvisol (the typical soil type in the North China Plain) and the other on a Chernozem (the typical soil in the Northeast China Plain). The results achieved herein indicated that manure substitution gave higher crop yields in the Luvisol, except for the treatment with 100% manure N replacement, which showed a slight yield reduction in the short term. For the Chernozem, manure substitution showed a significantly negative effect on crop yield in the short term, but the yield gradually increased and, over longer periods, even surpassed the yields found under baseline conditions. Manure substitution significantly reduced total N (TN) leaching by 57–76% in the Luvisol, while it increased TN leaching by 15–21% in the Chernozem. Results showed that soil properties, including water-holding capacity and clay and organic carbon contents are the main factors that can explain the contrasting effects of manure substitution on N leaching and crop yields for the two selected regions. Such information will enable more bespoke nutrient management measures in these two regions achieving agronomic and environmental benefits. [ABSTRACT FROM AUTHOR]

Investigating the impacts of climate and land use changes on the hydrological cycle and water environment at the basin scale is important for providing scientific evidence to manage the trade-offs and synergies among water resources, agricultural production and environmental protection. We used the Soil and Water Assessment Tool (SWAT) with various spatiotemporal data to quantify the contributions of climate and land use changes to runoff, sediment, nitrogen (N) and phosphorus (P) losses in the Haihe River Basin since the 1980s. The results showed that 1) climate and land use changes significantly increased evapotranspiration (ET), transport loss, sediment input and output, and organic N and P production, with ET, sediment input and organic N affected the most; 2) runoff, sediment and ammonia N were most affected by climate and land use changes in the Daqing River Basin (217.3 mm), Nanyun River Basin (3917.3 tons) and Chaobai River Basin (87.6 kg/ha), respectively; 3) the impacts of climate and land use changes showed explicit spatiotemporal patterns. In the Daqing, Yongding and Nanyun River Basins, the contribution of climate change to runoff and sediment kept increasing, reaching 88.6%–98.2% and 63%–77.2%, respectively. In the Ziya and Chaobai River Basins, the contribution of land use was larger, reaching 88.6%–92.8% and 59.8%–92.7%, respectively. In the Yongding, Chaobai, Ziya and Daqing River Basins, the contribution of land use to N and P losses showed an increasing trend over the past 40 years (maximum 89.7%). By contrast, in Nanyun and Luanhe River Basins, the contribution of climate change to N and P losses increased more (maximum 92.1%). Our evaluation of the impacts of climate and land use changes on runoff, sediment, and N and P losses will help to support the optimization of land and water resources in the Haihe River Basin. [ABSTRACT FROM AUTHOR]

Saline-alkali soils have poor N storage capacity, high N loss and inadequate nutrient supply potential, which are the main limiting factors for crop yields. Vermicompost can increase organic nutrient content, improve soil structure, and enhance microbial activity and function, and the Ca2+ in flue gas desulfurization (FGD) gypsum can replace Na+ and neutralize alkalinity in saline-alkali soils though chemical improvement. This study aimed to determine if vermicompost and FGD gypsum addition could improve the N storage capacity through decreasing NH 3 volatilization and 15N/NO 3 − leaching from saline-alkali soils. The results indicate that the combined application of vermicompost and FGD gypsum led to the displacement and leaching Na+ in the upper soil layer (0–10 cm), as well as the neutralization of HCO 3 − by the reaction with Ca2+. This treatment also improved soil organic matter content and macroaggregate structure. Also, these amendments significantly increased the abundance of nifH and amoA genes, while concurrently decreasing the abundance of nirK gene. The structural improvements and the lowering of Na + concentration in and alkalinity decreased cumulative NH 3 volatilization, and leaching of 15N and NO 3 − to the deep soil layer (20–30 cm). FGD gypsum increased the 15N stocks and inorganic N stocks of saline-alkali soil, whereas vermicompost not only increased the 15N and inorganic N stocks, but also increased the total N stocks, the combination of vermicompost and FGD gypsum can not only increase the available N storage capacity, but also enhance the potential for N supply. Therefore, vermicompost and FGD gypsum decrease N loss and increase N storage capacity through structural improvement, and lowering of Na+ concentration and alkalinity, which is crucial for improving the productivity of saline-alkali soil. • Decreasing Na + could reduce NH 3 volatilization, NO 3 − leaching and 15N loss rate. • Decreasing alkali and increasing amoA genes could reduce NH 3 volatilization. • Vermicompost and FGD gypsum improved available N storage capacity. • Vermicompost increased the total N stock to enhance potential for N supply. [ABSTRACT FROM AUTHOR]

Nitrogen (N) fertilisation is critical for sugarcane crop production. Consequently, overuse of N fertiliser in sugarcane is widespread and it is most prevalent in China. Yet, a comprehensive analysis of sugarcane N balance accounting for different reactive N (Nr) loss pathways, crop N use and soil N retention using 15N labelled fertilisers under commercial high-input cropping conditions is lacking. A two-year field experiment with 5 N levels (0–560 kg N ha−1; N0, N210, N300, N390, N560) was conducted to quantify the effect of N rate on sugarcane yield, Nr loss through different loss pathways, crop N use and soil N retention, and to identify an optimal N rate that sustain high yield whilst reducing Nr loss in Southern China. The results showed that optimal N rate (N300) had similar yield compared with farmer practice (N560) for the plant crop and the ratoon crop. Nitrogen leaching and ammonia loss were increased significantly with increase in N rate, with farmer practice recording the highest Nr loss. Compared with farmer practice, under optimal N application, N leaching was reduced from 211 kg ha−1 to 107 kg ha−1 and from 244 kg ha−1 to 165 kg ha−1 for the plant and ratoon crops, respectively. The ammonia volatilization from the plant crop and the ratoon crop in the optimal N treatment was 24.8 kg ha−1 and 27.0 kg ha−1, respectively, which are considerably less compared with the emission from the farmer practice. There was no significant difference in nitrous oxide emission between optimal N rate and farmer practice. 15N labelling studies showed that crop N recovery, soil N residue and fertiliser N lost at the optimal N rate were 20.9%, 24.9% and 54.2%, respectively, as opposed to 12.5%, 14.8% and 72.7%. respectively, under farmer practice. To the best of our knowledge, this study forms the first comprehensive evaluation of sugarcane N balance accounting Nr loss, N use and native N soil stock covering a wide range of N supply simultaneously in the plant and ratoon crops under commercial crop production condition. This study thus provides very valuable new knowledge not only for crop N supply optimisation in high-input sugarcane production systems as in China but also for sugarcane greenhouse gas accounting studies particularly from climate change mitigation and bioenergy production context. [Display omitted] • First detailed sugarcane crop N balance (Nr loss, N use, soil N stock) estimated. • Current average sugarcane crop N input in China (560 kg N ha−1) very excessive. • Large reduction in N input and Nr loss without yield loss in multi-year field trials. • Leaching, the single largest N loss pathway in sugarcane crop. • Large crop N recovery, fertiliser N loss reduction with optimal N use (300 kg N ha−1). [ABSTRACT FROM AUTHOR]

Excessive use of nitrogen fertilizers is a common problem for intensively cultivated cropping systems. Introducing cover crops during fallow periods is a good practice for encouraging the sustainable use of N resources in such cropping systems. Although individual previous studies assessing the interception of soil residual N by cover crops and its mineralization for subsequent N supply abound, a comprehensive synthesis of cover crop effects on N retention and supply from such studies is still lacking, especially in fertilizer-intensive cropping systems. This paper aims to assess the influences of cover crop practices on soil N retention and supply on the basis of published literatures. Cover crop biomass accumulation, N absorption capacity, root-induced rhizosphere deposition, N-stratification and biological nitrification inhibition all play a part in temporal N storage and leaching reduction. Excessive pre-absorption, residue-induced immobilization or the negative priming effect can result in a negative after-effect, increasing the risk of yield reduction and reducing the likelihood of cover crop introduction. Comparisons between different cover crops, especially the mostly reported leguminous and non-leguminous species, are carried out in this review and the influences of cover crop management practices including species selection, planting and termination time are also discussed. There is a need to develop adaptive cover crop management practice for specific cropping systems based on its effects on N retention and supply. [ABSTRACT FROM AUTHOR]

Agricultural nitrogen (N) non-point source pollution in the North China Plain is a major factor that affects water quality and human health. The characteristics of N leaching under different N application conditions should be further quantified accurately in winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation farmland in North China, and a basis for reducing the risk and evaluation of N leaching in this area. A three-year field experiment was conducted using an in situ leakage pond method at a typical farmland in Henan in 2017–2020. Crop yield, soil nitrate N residues, and N utilization were also studied during the study period. Five N fertilizer rates were established with 0 (CK), 285 (LN), 465 (MN), 510 (MNO), and 645 (HN) kg N ha−1 for one rotation cycle. MNO was applied with chemical and organic fertilizers. The concentration of nitrate N in the soil leaching solution of CK, LN, MN, MNO, and HN was 0.81-, 1.49-, 3.65-, 5.55-, and 7.57-fold that of the World Health Organization's standard for underground drinking water. The exponential relationship between the N application rate and leaching was obtained when the annual N input exceeded 300 kg ha−1, and the N leaching rate increased greatly. The leaching rate of nitrate N in the total N was 50.6–82.4% under different treatments of N application. The combination of chemical and organic fertilizers treatment (MNO) reduced the amount of N that was leached in dry years. The nitrate leaching amount of summer maize accounts for 83.0%, 49.4%, and 72.0% of the total nitrate leaching amount of the whole rotation cycles in 2017–2020. LN and MN were recommended as the optimized N application here (285–465 kg N ha−1) with the two-season rotation grain yield of 17.2 ton ha−1 (16.5–17.9 ton ha−1) and nitrate N leaching of 21.6 kg ha−1 (12.6–30.5 kg ha−1). [ABSTRACT FROM AUTHOR]

We know that fruit production, especially in the Mediterranean, will need to adapt to climate change to ensure the sustainability of fruit tree-based agroecosystems. However, there is a lack of evidence on the long-term effects of this change on sustainability indicators. To fill this gap, we used a fruit tree model, QualiTree, to analyze the impacts ofclimate change on the ecosystem services provided by apple orchards in south-eastern France. To do this, a blooming model was parameterized to simulate blooming date on the basis of climate data, and QualiTree was supplemented with a model of nitrogen processes in the tree and a soil module describing resource input (irrigation, mineral and organic fertilization), transfer in the soil (water and nitrogen) and metabolic transformation-immobilization (mineralization, (de)nitrification). This type of extension makes it possible to simulate a wide array of ecosystem services, including C sequestration, nitrate leaching and nitrous oxide emissions. The model was compared with data from an apple orchard in southeastern France. The predicted daily mean and variability over time of fruit growth, composition and soil water content were consistent with observed data. QualiTree was then used to assess the potential impacts of climate change on the ecosystem services supplied by apple orchards. For this purpose, weather variables from 2020 to 2100 were generated for three contrasted greenhouse gas emission scenarios, and simulations were performed under two irrigation schemes (no restriction and restricted use of water). Model outputs indicated that, on average, marketable apple yields would increase until 2050 and then subsequently decrease. The fruit refractometric index, an indicator of fruit quality, was projected to sharply decrease with the intensity of climate change. Ecosystem services such as C sequestration by the orchard will decrease with climate change severity, mainly due to a higher mineralization of soil humus, whereas N 2 O emissions will increase with larger denitrification rates. Soil water availability, fertility, drainage and leaching were predicted to depend more on the irrigation strategy than on climate change severity. The new functions performed in QualiTree broadened its predictive capabilities and allowed for a better understanding of ecosystem service delivery in fruit orchards under varying climate conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Abstract Excessive use of inorganic nitrogen (N) fertilizers is the primary anthropogenic cause of low N use efficiency and environmental damage in wetland rice agriculture. However, little is known about the performance of traditional inorganic N sources used in paddy rice production. Biochar (BC) is considered to be a climate change mitigation tool that can enhance N uptake and utilization in N‐fertilized crops. To test this hypothesis, we performed a pot experiment to study the fate of 15N‐labeled urea, ammonium nitrate, and ammonium sulfate with and without BC at tillering, heading, and maturity stages of rice in the early and late seasons of 2019. Fertilizer N leaching was significantly reduced by 75.69% and 110.32% in BC vs. non‐BC treatments across growth stages in the early and late seasons. The rate of leaching was lower for urea than for ammonium nitrate and ammonium sulfate. Furthermore, the addition of BC resulted in 55.58% and 41.33% higher soil 15N concentrations in the early and late season, respectively, indicating that BC increased N adsorption. 15N uptake by roots, stems, leaves, panicles, and grains averaged 52.39%, 37.14%, 40.86%, 36.37%, and 29.94% higher in BC‐amended pots than in BC‐free pots in both seasons. There were significant differences (p ammonium sulfate > ammonium nitrate. Overall, our results indicate that urea with BC is a preferable N source for double rice cropping systems compared with ammonium nitrate and ammonium sulfate.

• Simultaneous immobilization and mineralization of biochar PAHs during composting. • Biochar favors a slower release of mineral N from mature compost. • Biochar increases water holding capacity and decreases bulk density of compost. • The high C:N ratio did not hinder the composting process. Composting recycles nutrients and biodegrades organic pollutants, but often results in N leaching. Biochar can enhance the composting process and reduce N losses. Research, however, has focused on composting N-rich residues; also, information on the fate of biochar polycyclic aromatic hydrocarbons (PAHs) during composting is scarce. We explored the composting of biochar with N-poor organic residues as a strategy to reduce N losses and biochar PAHs. A small-scale composting experiment was performed with three treatments: 100% yard residues and two mixtures of 85% yard residues and 15% gasification- or pyrolysis-derived biochar. Temperatures were recorded daily during composting and N losses and changes in PAHs loads were calculated. Results across all treatments showed overall low N losses, likely caused by low temperatures and N contents, circumneutral pH values, and absence of leachate, and simultaneous immobilization and mineralization of PAH contents. Treatments with biochar showed a slower release of inorganic N (NO 3 --N and NH 4 +-N), although they also had overall lower inorganic N contents. This slower release of inorganic N may relate to biochar's high surface area. We conclude that biochar provides valuable benefits for N-poor composting, and that composting should be further explored as a promising strategy to reduce the contents of PAHs in biochar. [ABSTRACT FROM AUTHOR]

The main C and N fluxes of a winter rapeseed field in Central Estonia were quantified for one year to identify the highest fluxes and major sources of uncertainty. Greenhouse gas emissions were measured with the closed chamber method, leaching losses were estimated by combining the soil water balance and leachate analyses, and soil C and N changes were also monitored. Gross primary production (GPP) and di-nitrogen (N2) fluxes were estimated from the C and N mass balance, respectively. The field was a net C sink (3366 kg C ha−1 yr−1) because of the high C absorption rate through GPP (17,215 kg C ha−1 yr−1). The N outputs markedly exceeded the inputs, which translated into soil N losses. The highest measured N fluxes were those of N leaching (44 kg N ha−1 yr−1) and nitrous oxide (N2O) emissions (26 kg N ha−1 yr−1). Approximately 60% of the total N2O emissions occurred during the first 50 days after slurry application, promoted by field and weather conditions. The unaccounted soil N loss was attributed to N2 emissions (estimated at 668 kg N ha−1 yr−1). After conversion to CO2-eq, the positive balance of carbon dioxide (CO2) emissions remained the dominant flux (34,571 kg CO2-eq ha−1 yr−1), but N2O emissions were also notable (11,218 kg CO2-eq ha−1 yr−1). The methodology used in this study provided estimates for the main fluxes in the C and N cycles, but also allowed the identification of methodological limitations and challenges. Main components of the C (orange) and N (blue) budget considered in the study. [ABSTRACT FROM AUTHOR]

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BACKGROUND: Effective nitrogen (N) management measures are required to control environmental problems caused by N fertilizer use in intensive maize production systems. Soil N losses associated with high precipitation and over‐fertilization in maize production can cause substantial environmental problems, whereas there is a lack of quantitative data and effective study countermeasures. A 2‐year field study was conducted in the subtropical maize production system in Southwest China to quantify N leaching under varying N application rates of 0, 90, 180, 270 and 360 kg N ha−1 yr−1. RESULTS: The results indicated that N leaching accounted for 16–38% of N fertilizer input. For farmer practice treatment (360 kg N ha−1 yr−1), N leaching loss was high at 110 kg N ha−1 yr−1and accounted for 31% of the N applied. As an indicator of the ambient water quality pollution, the grey water footprint across all treatments ranged from 376 to 1092 m3 Mg−1, with an average of 695 m3 Mg−1. Reducing N rate to agronomically optimized treatment (180 kg N ha−1 yr−1) significantly decreased N leaching by 77%, and maintained high grain yield of 8.1 Mg ha−1. The grey water footprint was reduced by 52–63% with N rates from 270 or 360 kg N ha−1 yr−1 to 180 kg N ha−1 yr−1. CONCLUSION: Nitrogen surplus (applied N rate minus N uptake by maize) resulted in higher soil residual nitrate concentration and consequently high N leaching. High precipitation and low soil pH were the main ecological factors leading to high N leaching. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Farmers provided excessive nitrogen fertilizer to obtain high cotton yield in Xinjiang, Northwest China. Although drip irrigation could save water resources and improve nitrogen use efficiency, it is not known if leaching is occurring or not and whether leaching will harm the water environment under different nitrogen application. The purpose of our study was to estimate the effect of different nitrogen (N) application on the N leaching loss in drip irrigated cotton fields in South Xinjiang. A field experiment was conducted with N application rates of 317(N317), 395(N395) and 476(N476) kg hm ^−2 from 2021 to 2022. The characteristics of N pattern and leaching amount were analyzed. The concentration of NO _3 - and total nitrogen in the leaching water significantly decreased with the decrease of N application. The proportion of NO _3 –to total nitrogen reached the highest values of 51.52%–58.16%, 49.53%–56.91%, and 57.52%–62.87% at bud, flower, and boll stages of cotton, respectively. Moreover, the proportion of NO _3 – to total nitrogen remained at a stable level, which indicated that NO _3 –was the main pattern of N leaching. The N loss in the treatment N395 and N317 was 79.67% and 67.48% of that in the N476 treatment (1.23 kg hm ^−2 ), while the yield was 120.56% and 112.46% of that in the N476 treatment. Compared with conventional fertilizer application (476 kg hm ^−2 ), the reasonable N fertilizer application would not only reduce the amount of N leaching, but also increase the cotton yield.

A 15N tracing pot experiment was conducted using two types of wood-based biochars: a regular biochar and a Kon-Tiki-produced nutrient-enriched biochar, at two application rates (1% and 5% (w/w)), in addition to a fertilizer only and a control treatment. Ryegrass was sown in pots, all of which except controls received 15N-labelled fertilizer as either 15NH4NO3 or NH415NO3. We quantified the effect of biochar application on soil N2O emissions, as well as the fate of fertilizer-derived ammonium (NH4+) and nitrate (NO3−) in terms of their leaching from the soil, uptake into plant biomass, and recovery in the soil. We found that application of biochars reduced soil mineral N leaching and N2O emissions. Similarly, the higher biochar application rate of 5% significantly increased aboveground ryegrass biomass yield. However, no differences in N2O emissions and ryegrass biomass yields were observed between regular and nutrient-enriched biochar treatments, although mineral N leaching tended to be lower in the nutrient-enriched biochar treatment than in the regular biochar treatment. The 15N analysis revealed that biochar application increased the plant uptake of added nitrate, but reduced the plant uptake of added ammonium compared to the fertilizer only treatment. Thus, the uptake of total N derived from added NH4NO3 fertilizer was not affected by the biochar addition, and cannot explain the increase in plant biomass in biochar treatments. Instead, the increased plant biomass at the higher biochar application rate was attributed to the enhanced uptake of N derived from soil. This suggests that the interactions between biochar and native soil organic N may be important determinants of the availability of soil N to plant growth. [ABSTRACT FROM AUTHOR]

Agricultural nitrogen (N) non-point source pollution in the North China Plain is a major factor that affects water quality and human health. The characteristics of N leaching under different N application conditions should be further quantified accurately in winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation farmland in North China, and a basis for reducing the risk and evaluation of N leaching in this area. A three-year field experiment was conducted using an in situ leakage pond method at a typical farmland in Henan in 2017–2020. Crop yield, soil nitrate N residues, and N utilization were also studied during the study period. Five N fertilizer rates were established with 0 (CK), 285 (LN), 465 (MN), 510 (MNO), and 645 (HN) kg N ha−1 for one rotation cycle. MNO was applied with chemical and organic fertilizers. The concentration of nitrate N in the soil leaching solution of CK, LN, MN, MNO, and HN was 0.81-, 1.49-, 3.65-, 5.55-, and 7.57-fold that of the World Health Organization’s standard for underground drinking water. The exponential relationship between the N application rate and leaching was obtained when the annual N input exceeded 300 kg ha−1, and the N leaching rate increased greatly. The leaching rate of nitrate N in the total N was 50.6–82.4% under different treatments of N application. The combination of chemical and organic fertilizers treatment (MNO) reduced the amount of N that was leached in dry years. The nitrate leaching amount of summer maize accounts for 83.0%, 49.4%, and 72.0% of the total nitrate leaching amount of the whole rotation cycles in 2017–2020. LN and MN were recommended as the optimized N application here (285–465 kg N ha−1) with the two-season rotation grain yield of 17.2 ton ha−1 (16.5–17.9 ton ha−1) and nitrate N leaching of 21.6 kg ha−1 (12.6–30.5 kg ha−1).

Excessive use of inorganic nitrogen (N) fertilizers is the primary anthropogenic cause of low N use efficiency and environmental damage in wetland rice agriculture. However, little is known about the performance of traditional inorganic N sources used in paddy rice production. Biochar (BC) is considered to be a climate change mitigation tool that can enhance N uptake and utilization in N‐fertilized crops. To test this hypothesis, we performed a pot experiment to study the fate of 15N‐labeled urea, ammonium nitrate, and ammonium sulfate with and without BC at tillering, heading, and maturity stages of rice in the early and late seasons of 2019. Fertilizer N leaching was significantly reduced by 75.69% and 110.32% in BC vs. non‐BC treatments across growth stages in the early and late seasons. The rate of leaching was lower for urea than for ammonium nitrate and ammonium sulfate. Furthermore, the addition of BC resulted in 55.58% and 41.33% higher soil 15N concentrations in the early and late season, respectively, indicating that BC increased N adsorption. 15N uptake by roots, stems, leaves, panicles, and grains averaged 52.39%, 37.14%, 40.86%, 36.37%, and 29.94% higher in BC‐amended pots than in BC‐free pots in both seasons. There were significant differences (p < 0.05) among N sources in terms of fertilizer N loss, residual N, and N uptake, and performance was ranked in the order urea > ammonium sulfate > ammonium nitrate. Overall, our results indicate that urea with BC is a preferable N source for double rice cropping systems compared with ammonium nitrate and ammonium sulfate. [ABSTRACT FROM AUTHOR]

Biochar is beneficial for improving soil quality and crop productivity. However, the long‐term effects of biochar addition on temporal dynamics of plant shoot and root growth, and the changes in soil properties and nitrogen (N) leaching are still obscure. Here, based on a long‐term (7 years) biochar field experiment with rice in northwest China, we investigated the effects of two biochar rates (0 and 9 t ha−1 year−1) and two N fertilizer rates (0 and 300 kg N ha−1 year−1) on shoot and root growth, root morphology, N leaching, and soil physicochemical properties. The results showed that both biochar and N fertilizer significantly promoted rice growth, with their interaction significant only in some cases. Both fertilizers enhanced rice shoot biomass and N accumulation in various growth stages as well as increased grain yield. Nitrogen fertilizer significantly promoted root growth regardless of biochar application. However, biochar application without N fertilizer increased root biomass and length during the whole growth period, except in the booting stage; biochar with N application promoted root growth at tillering, reduced root biomass but maintained root length with low root diameter and high specific root length during the jointing and booting stages, and then delayed root senescence in the grain filling stage. Long‐term applications of biochar and N fertilizer reduced 10%–12% bulk density of topsoil compared to the control treatment with no N fertilizer and no biochar. Long‐term biochar application also improved soil total organic carbon and concentrations of available N, phosphorus, and potassium. In addition, biochar and N fertilizer applied together significantly reduced nitrate and ammonium concentration in leachate at different soil depths. In conclusion, biochar could regulate root growth, root morphology, soil properties, and N leaching to increase rice N fertilizer‐use efficiency. [ABSTRACT FROM AUTHOR]

Besides causing acidification, acid sulfate (AS) soils contain large nitrogen (N) stocks and are a potential source of N loading to waters and nitrous oxide (N2O) emissions. We quantified the stocks and flows of N, including crop yields, N leaching, and N2O emissions, in a cultivated AS soil in western Finland. We also investigated whether controlled drainage (CD) and sub-irrigation (CDI) to keep the sulfidic horizons inundated can alleviate N losses. Total N stock at 0–100 cm (19.5 Mg ha−1) was smaller than at 100–200 cm (26.6 Mg ha−1), and the mineral N stock was largest below 170 cm. Annual N leaching (31–91 kg N ha−1) plus N in harvested grain (74–122 kg N ha−1) was 148% (range 118–189%) of N applied in fertilizers (90–125 kg N ha−1) in 2011–2017, suggesting substantial N supply from soil reserves. Annual emissions of N2O measured during 2 years were 8–28 kg N ha−1. The most probable reasons for high N2O emission rates in AS soils are concomitant large mineral N pools with fluctuating redox conditions and low pH in the oxidized subsoil, all favoring formation of N2O in nitrification and denitrification. Although the groundwater level was higher in CD and CDI than in conventional drainage, N load and crop offtake did not differ between the drainage methods, but there were differences in emissions. Nitrogen flows to the atmosphere and drainage water were clearly larger than those in non-AS mineral soils indicating that AS soils are potential hotspots of environmental impacts. [ABSTRACT FROM AUTHOR]

To what extent might a crop with increased plant N uptake efficiency and/or N demand increase plant biomass and soil carbon storage, decrease N leaching, and reduce the need for N fertilisation? This was assessed for a fertilised sandy loam site in central Sweden cultivated with spring barley for a four year period using a process based crop and soil simulation model (SOILN) calibrated to fit observations of field experiments with non-modified crops. Crop properties were changed in accordance with previous model applications to other crops with higher N uptake and utilisation efficiencies, to resemble potential effects of breeding. For the modified crops a doubling of daily uptake efficiency of soil mineral N and/or increase of radiation use efficiency by 30%, increased plant biomass by 3%–30%, decreased N leaching by 1%–30% and increased soil organic carbon (SOC) content by 1–12 g C m−2 year−1. The larger changes were mainly due to increased uptake efficiency. Fertilisation of the modified spring barley crop could be reduced while still producing the same plant biomass as the non-modified crop. The plant biomass to N leaching ratio of the modified crops increased. The simulated changes in plant biomass and SOC were sensitive to weather conditions suggesting that in situ experiments would need to cover a large range of weather conditions to evaluate the performance of new crop traits under climatic variability. The study suggests a strong need that field experiments are accompanied with model applications, when exploring the potential of the modified crops under variable conditions.

N leaching in dry farmland is one of the most important reason for the environmental non-point pollution. The control measures for soil N leaching in dry farmland has been reviewed from the aspects of fertilizer management (including chemical fertilizer reduction and balanced fertilization), water management (including regime and method of irrigation, water-retaining agent), and soil amendment such as slow/controlling-releasing fertilizer and biochar. Needs about the future study on the N-leaching control measures have been proposed that the technique of the control measures and field monitoring should be designed specially for the certain location, the cost of performing control measures should be reduced, and the different control measures could be assembled systematically. The review provided some helps on improving the N fertilizer use efficiency and solving the problems of non-point pollution caused by N leaching in dry farmland. [ABSTRACT FROM AUTHOR]

A field experiment with separately tile‐drained plots was used to study the ability of oilseed radish (Rhaphanus sativus L.), as a cover crop sown after harvest of a main crop of cereals or peas, to reduce nitrogen (N) and phosphorus (P) leaching losses from a clay loam in southern Sweden over 6 years. In addition to oilseed radish in pure stand, two cover crop mixtures (hairy vetch (Vicia villosa) and rye (Secale cereale) for 3 years and oilseed radish in mixture with buckwheat (Fagopyrum esculentum) for 2 years) were tested. The cover crop plots (three replicates per treatment) were compared with unplanted plots as a control. Plots cropped with oilseed radish during autumn (August–November) had significantly smaller yearly mean N concentration in drainage water over 5 of 6 years compared with unplanted controls. Mineral N content in the soil profile in autumn was significantly less in oilseed radish plots than for control plots in all years. The cover crop mixtures of hairy vetch and rye or buckwheat and oilseed radish also showed the potential to reduce soil mineral N in autumn and N concentration in drainage water, compared with unplanted controls. The cover crops had no impact on P leaching. In conclusion, oilseed radish has the ability to reduce leaching losses of N, without increasing the risk of P leaching. [ABSTRACT FROM AUTHOR]

Corrosion-induced nitrogen (N) leaching limits the long-term applications of N-doped carbon (NC) catalysts for electrocatalytic oxygen reduction reaction (ORR). Anchored N for NC can suppress their corrosion and thus restrain the loss of catalytically active sites, resulting in the improved ORR durability. Herein, we report our strategies to suppress the leaching of N by embedding the NiCo alloy nanoparticles in NC nanowires and thus creating the interfacial metal-N units (M-N) for the robust ORR durability in alkali over 50 h. Also, the synergistic effects of Ni/Co–N, abundant active sites and favourable kinetics bring the high ORR activity over the Pt/C benchmark. Thus, our strategies with the improved durability and activity could create promising ORR catalysts with ∼5 times of activity-durability factor over the NC catalysts. Image 1 [ABSTRACT FROM AUTHOR]

Excessive N fertilizer application contributes to a surge in reactive N (Nr) emissions from agroecosystems, consequently threatening global ecosystems' quality and security. Adding functional microorganisms to agricultural soils, namely microbial inoculants (MI), is a promising method for ensuring sustainable agriculture, but general assessment of microorganism-driven N losses and mediating factors (such as climate conditions, soil properties, and field management practices) remains unclear. Therefore, a comprehensive meta-analysis on the effect of MI addition on NH 3 volatilization, N 2 O emissions, and N leaching in soil-crop systems was conducted by integrating 50 published articles (188 paired observations). The MI application significantly reduced N 2 O emissions and NH 3 volatilization by 29.8% and 24.9%, respectively. The boosted regression tree model showed that the soil organic carbon (SOC) and soil pH significantly affected the efficacy of MI application on both NH 3 and N 2 O loss mitigation. The effects of MI application on N leaching were not clear due to limited data points. Additionally, MI addition significantly increased the abundance of denitrification functional genes (nir K, nir S, and nos Z). In conclusion, MI application presented a high potential to reduce Nr from croplands, future adoption of MI techniques should consider the effects of soil properties and field practices on its efficacy in order to achieving sustainable N management in crop production systems. [Display omitted] • MI amendment mitigated N 2 O and NH 3 losses from fertilized soils. • N fertilizer management had great contribution to variation of MI efficacy. • Soil pH had significant impact on mitigation efficiency of N 2 O and NH 3 by MI. • MI amendment increased denitrification genes abundance. [ABSTRACT FROM AUTHOR]

• NH 4 +-N, TN mainly leached through sediment, whereas NO 3 ‾-N through runoff. • Runoff velocity was a critical driver of N leaching. • Preference should be given to Pinus elliottii to minimize N leaching. Nitrogen (N) leaching is a complex process regulating N exchange between the soil and aquatic ecosystems and may result in groundwater pollution, threatening ecosystem security. However, the mechanisms driving N leaching in subtropical forests have not been fully elucidated. Here, we present a quantitative analysis of vegetation-soil relationships in response to N leaching in a subtropical forest located in southern China. The results reveal that N leaching in runoff at lower simulated precipitation intensities (60 mm/h, 90 mm/h) and in sediment generated under higher intensities (120 mm/h, 150 mm/h) were significantly different across five vegetation restoration types. NH 4 +-N and TN were mostly lost through sedimentation, whereas NO 3 ‾-N was primarily leached in runoff (80%–88%). N leaching was positively correlated with runoff, sedimentation rate, geometric mean diameter, mean weight diameter, and fine sediment particles (<0.25 mm), but negatively correlated with fractal dimension and coarser sediment particles. Random forest analysis demonstrated that runoff velocity was a critical driver of N leaching, suggesting that the impact of plant restoration on N loss should be considered. In order to minimize N leaching and resultant water pollution, guidelines informing the design of vegetation restoration projects in subtropical monsoon forests should emphasize the importance of planting Pinus elliottii. This result emphasized the importance of leaching erosion in forest ecosystem management and the need to understand the intricacies in the soil nitrogen sequestration potential at a regional scale in a changing climate. [ABSTRACT FROM AUTHOR]

Winter cereals are excellent candidates for biosolid application because their nitrogen (N) requirement is high, they are broadly cultivated, and their deep root system efficiently takes up mineral N. However, potential N leaching from BS application can occur in Mediterranean soils. A two-year study was conducted to determine how biosolids affect biomass and grain yield as well as N uptake and N leaching in barley (Hordeum vulgare L.), common wheat (Triticum aestivum L.), durum wheat (Triticum turgidum L. var. durum), and oat (Avena byzantina C. Koch). Cereals were fertilized at rates of 5, 10, and 15 Mg ha−1 dry weight (called B5, B10, and B15, respectively) of biosolids (BS). Mineral-fertilized (MF) and unfertilized (C) controls were included. Overall, results highlight that BS are valuable fertilizers for winter cereals as these showed higher yields with BS as compared to control. Nevertheless, whether 5 Mg ha−1 of biosolids could replace mineral fertilization still depended on the particular cereal due to the different yield physiology of the crops. Moreover, nitrate leaching from B5 was comparable to MF, and B15 increased the risk by less than 30 N-NO3 kg ha−1. We therefore concluded that with specific rate settings, biosolid application can sustain yields of winter cereals without significant additional N leaching as compared to MF.

The mineralization of urea fertilizer mostly regulates the nitrogen dynamics in the soil. A laboratory-scale study was conducted to compare the nitrogen dynamics in two tropical soil series incubated with either liquid urea (LU) or granular urea (GU) at 0, 300, 400 or 500 mg/kg of soil. The soils samples used in the experiment were the Bungor and Selangor soil series which have a sandy clay loam and clay texture, respectively. The NH4+-N, NO3−-N concentration in the soils were measured for four weeks to determine the urea-N mineralization while ten pore volumes of water were used for the NH4+-N and NO3−-N leaching loss. At the same application rate, higher NH4+-N and NO3−-N concentrations were recorded in the LU applied soils throughout the incubation period in case of N mineralization. Urea-N recovery was higher in GU than LU treated soils in the first two weeks while no urea-N was present in both GU and LU treated soils after the third week of incubation. The leaching of N (NH4+-N and NO3−-N) was higher in GU treated soils than that of LU and leaching was increased with increased application rate in both LU and GU in both soils. The NH4+-N and NO3−-N concentrations were higher in the Selangor soil whereas the total N leaching loss was higher in Bungor soil. The results suggest that the LU was a better N fertilizer source than GU for rapid mineralization, quicker N availability and lower N leaching loss.

Bioenergy crops are a promising option for integrating fossil fuels and achieving European environmental targets. Among these, Short Rotation Forestry (SRF) crops and biogas plants have been considered an opportunity for sustainable agricultural development due to their environmental benefits. In this case study, an N balance was performed by comparing an SRF Platanus hispanica plantation with a permanent meadow, both located in an area with highly permeable soils, using two different amounts of organic fertilization (digestate) for each system (0, 170 and 340 kg-N ha−1 y−1). The results obtained indicate that, in the presence of highly permeable soils, the SRF is not effective in retaining N during the initial stage of growth, despite the use of a suitable application rate of digestate. Higher N leaching rates occurred in SRF crops compared to permanent meadows. Moreover, the N potential removal rate did not vary proportionally with the applied dose of digestate. To avoid N leaching excess, the annual applied N should be not only within 170 kg-N ha−1 y−1 (Nitrate Directive legal limits for nitrate vulnerable zone) but should also follow precise and accurate distribution practices, like: controlled grassing between the tree rows and soil's minimum tillage immediately after the digestate spreading. [ABSTRACT FROM AUTHOR]

Cover crops play an increasingly important role in improving soil quality, reducing agricultural inputs and improving environmental sustainability. The main objectives of this critical global review and systematic analysis were to assess cover crop practices in the context of their impacts on nitrogen leaching, net greenhouse gas balances (NGHGB) and crop productivity. Only studies that investigated the impacts of cover crops and measured one or a combination of nitrogen leaching, soil organic carbon (SOC), nitrous oxide (N2O), grain yield and nitrogen in grain of primary crop, and had a control treatment were included in the analysis. Long‐term studies were uncommon, with most data coming from studies lasting 2–3 years. The literature search resulted in 106 studies carried out at 372 sites and covering different countries, climatic zones and management. Our analysis demonstrates that cover crops significantly (p < 0.001) decreased N leaching and significantly (p < 0.001) increased SOC sequestration without having significant (p > 0.05) effects on direct N2O emissions. Cover crops could mitigate the NGHGB by 2.06 ± 2.10 Mg CO2‐eq ha−1 year−1. One of the potential disadvantages of cover crops identified was the reduction in grain yield of the primary crop by ≈4%, compared to the control treatment. This drawback could be avoided by selecting mixed cover crops with a range of legumes and non‐legumes, which increased the yield by ≈13%. These advantages of cover crops justify their widespread adoption. However, management practices in relation to cover crops will need to be adapted to specific soil, management and regional climatic conditions. [ABSTRACT FROM AUTHOR]

Biochar application to croplands has been proposed as a potential strategy to decrease losses of soil‐reactive nitrogen (N) to the air and water. However, the extent and spatial variability of biochar function at the global level are still unclear. Using Random Forest regression modelling of machine learning based on data compiled from the literature, we mapped the impacts of different biochar types (derived from wood, straw, or manure), and their interactions with biochar application rates, soil properties, and environmental factors, on soil N losses (NH3 volatilization, N2O emissions, and N leaching) and crop productivity. The results show that a suitable distribution of biochar across global croplands (i.e., one application of <40 t ha−1 wood biochar for poorly buffered soils, such as those characterized by soil pH<5, organic carbon<1%, or clay>30%; and one application of <80 t ha−1 wood biochar, <40 t ha−1 straw biochar, or <10 t ha−1 manure biochar for other soils) could achieve an increase in global crop yields by 222–766 Tg yr−1 (4%–16% increase), a mitigation of cropland N2O emissions by 0.19–0.88 Tg N yr−1 (6%–30% decrease), a decline of cropland N leaching by 3.9–9.2 Tg N yr−1 (12%–29% decrease), but also a fluctuation of cropland NH3 volatilization by −1.9–4.7 Tg N yr−1 (−12%–31% change). The decreased sum of the three major reactive N losses amount to 1.7–9.4 Tg N yr−1, which corresponds to 3%–14% of the global cropland total N loss. Biochar generally has a larger potential for decreasing soil N losses but with less benefits to crop production in temperate regions than in tropical regions. [ABSTRACT FROM AUTHOR]

Abstract Catch crop (CC) mixtures of non-legumes (nL) and legumes (L) have been promoted as a strategy to achieve two different goals: to decrease the risk of nitrate leaching and to enhance the nitrogen supply to the subsequent crop. To investigate if two-component mixtures of nL + L have advantages over pure nL stands experiments were carried out over a two year period (2013–2015) at two contrasting field sites in Denmark. Nitrogen (N) uptake by the CCs was measured by aboveground biomass sampling, and N leaching by ceramic suction cups. When grown in pure stands, white clover (Trifolium repens) on coarse sand and common vetch (Vicia sativa) on sandy loam were less effective at reducing N leaching than perennial ryegrass (Lolium perenne) and fodder radish (Raphanus sativus). When the proportion of the nL + L in mixtures was similar or favored the nL, leaching was not significantly different from the nL in the pure stand. However, during one of the years on the sandy loam L (vetch) almost outperformed nL (fodder radish), resulting in N leaching from nL + L similar to L. The yield of the following spring barley was only significantly different from the yield in the plots with previously bare soil in one of the years on the coarse sandy soil. It is concluded that in nL + L mixtures L can take over and thereby lower the effect of the CCs on N leaching while not necessarily enhancing the N supply for the subsequent crop. Highlights • In monocultures legumes were less effective at reducing N leaching than non-legumes. • Non-legume/legume mixtures were as effective as non-legume catch crops in reducing N leaching. • When non-legume/legume mixtures are not balanced N leaching was similar to that from legumes. • Use a catch crop only increased the subsequent spring yield on the sandy loam in one of the years. • The catch crop had no effect on the yield of the subsequent crop on the clay soil. [ABSTRACT FROM AUTHOR]

Highlights • A modelling approach was used to test different irrigation managements. • In a shallow soil more frequent irrigation resulted in a higher pasture production. • In deep soils pasture production was not affected by irrigation frequency. • Building up of soil water deficits in less frequent irrigation reduced N losses. Abstract While the benefits of irrigation for agricultural production are well established, the effects of irrigation management on production and environmental consequences are not well quantified. We used the APSIM (Agricultural Production Systems sIMulator) model to simulate the effect of six different irrigation management scenarios on pasture production and nitrogen (N) losses from both urine patches and non-urine affected areas using New Zealand farming systems as a test case. Nitrogen losses included nitrate (NO 3) leaching, and gaseous emissions via ammonia (NH 3) volatilisation and denitrification (nitrous oxide (N 2 O) and dinitrogen (N 2) emissions). The effects of different climate and rainfall regimes were simulated for three different soil types – deep, poorly drained (Otokia), deep, well drained (Templeton) and shallow, well drained (Eyre) soils, using 20 years of data from two climate stations with mean annual rainfall amounts of 600 and 800 mm. In the shallow soil with the least plant available water, more frequent irrigation with higher total annual amounts resulted in a significant increase in predicted pasture production compared with less frequent irrigation due to less plant water stress. However, predicted N losses through leaching, denitrification and N 2 O emissions also increased. In the deep soils pasture growth was not affected by the frequency of irrigation, whereas denitrification increased with higher frequency irrigation, especially in the poorly drained soil, leading to increased N 2 O emissions. Based on these modelling results, N losses can be reduced with little effect on production by irrigating less frequently and maintaining soil water deficits. [ABSTRACT FROM AUTHOR]

Abstract Application of controlled release urea (CRU) is recommended to reduce the undesirable environmental effects resulting from urea application. However, the overall effects of CRU on maize productivity and reactive nitrogen (N) losses remain unclear. Our global meta-analysis based on 866 observations of 120 studies indicated that application of CRU instead of urea (same N rate) increased maize yield by 5.3% and nitrogen use efficiency (NUE) by 24.1%, and significantly decreased nitrous oxide (N 2 O) emission, N leaching and ammonia (NH 3) volatilization by 23.8%, 27.1% and 39.4%, respectively. The increase of NUE and reduction of N 2 O emission by CRU application were greater with medium and high N rates (150 ≤ N < 200 and N ≥ 200 kg N ha−1) than with low N rates. The reduction in N 2 O emission and N leaching with CRU application were enhanced when soil organic carbon (SOC) content was <15.0 g kg−1, and soil texture was medium or coarse. The reduction in N 2 O emission and NH 3 volatilization with CRU were greater in soils with pH ≥ 6.0. We concluded that use of CRU should be encouraged for maize production, especially on light-textured soils with low organic matter content. Graphical abstract Image 1 Highlights • The integrated effects of controlled release urea (CRU) on maize were quantified. • CRU increased maize yield by 5.3% compared to urea in this global meta-analysis. • N 2 O and NH 3 emissions, and N leaching were decreased by CRU more than 20%. • CRU was most effective in light-textured or low organic carbon soils. The agronomic and environmental effects of controlled release urea (CRU) on maize production were quantified based on global scale meta-analysis. The use of CRU in maize production increased yield and nitrogen use efficiency, meanwhile decreased N 2 O emission, N leaching and NH 3 volatilization, especially when N application rates were high and especially on light-textured soils with low organic matter content. [ABSTRACT FROM AUTHOR]

Abstract Vegetable production in solar greenhouses in northern China results in the excessive use of nitrogen (N) fertilizers and water via flooding irrigation. Both factors result in low N use efficiency and high environmental costs because groundwater becomes contaminated with nitrate (NO 3 −). Four consecutive tomato (Lycopersicum esculentum Mill.) cropping seasons were tested whether drip fertigation and/or the incorporation of maize straw (S) may significantly reduce NO 3 − and dissolved organic N (DON) leaching while increasing the water-use efficiency (WUE) and partial factor productivity of applied N (PFP N) of the tomatoes. The following treatments were used: ① conventional flooding irrigation with overfertilization (CIF, 900 kg N ha−1 season−1), ② CIF + S, ③ drip irrigation with optimized fertilization (DIF, 400 kg N ha−1 season−1), ④ DIF + S. We found that (1) DIF significantly increases the PFP N and WUE by 262% and 73% without compromising the yield compared with CIF, respectively. (2) For CIF, approximately 50% of the total N input was leached at a NO 3 −/DON ratio of approximately 2:1. (3) Compared with CIF, DIF reduced NO 3 − and DON leaching by 88% and 90%, respectively. Water percolation was positively correlated with N leaching (p < 0.001). (4) Straw application only reduced NO 3 − leaching losses in the first year and did not affect DON leaching overall, although DON leaching was increased in DIF in the first growing season. In conclusion, DIF significantly reduces NO 3 − and DON leaching losses by approximately 90% compared with the current farmer practice (CIF). Considering the significant DON leaching losses, which have been overlooked because previous measurements focused on NO 3 −, DON should be considered as a primary factor of environmental pollution in conventional solar greenhouse vegetable production systems. Graphical abstract Image 1 Highlights • Drip fertigation increases water and nitrogen use efficiency without yield jeopardy. • For conventional flooding irrigation, 50% of total N input was leached. • Dissolved organic nitrogen (DON) accounted for 1/3 of total N leaching. • Drip fertigation reduced dissolved inorganic and organic N leaching by 90%. • Straw addition reduced nitrate leaching in the first year, less affect DON leaching. For CIF, 50% of total N input was leached and DON accounted for 33% of the total leached N. Drip fertigation reduced the dissolved inorganic and organic N leaching by 90% compared with CIF. [ABSTRACT FROM AUTHOR]

Enhancing crop production by maintaining a proper synchrony between soil nitrogen (N) and crop N demand remains a challenge, especially in under-studied tropical soils of Sub-Saharan Africa (SSA). For two consecutive cropping seasons (2013-2015), we monitored the fluctuation of soil inorganic N and its availability to maize in the Tanzanian highlands. Different urea-N rates (0-150 kg N ha−1; split into two dressings) were applied to two soil types (TZi, sandy Alfisols; and TZm, clayey Andisols). In the early growing season, soil mineralized N was exposed to the leaching risk due to small crop N demand. In the second N application (major N supply accounting for two-thirds of the total N), applied urea was more efficient in increasing soil inorganic N availability at TZm than at TZi. Such effect of soil type could be the main contributor to the higher yield at TZm (up to 4.4 Mg ha−1) than that at TZi (up to 2.6 Mg ha−1) under the same N rate. The best-fitted linear-plateau model indicated that the soil inorganic N availability (0-0.3 m) at the tasseling stage largely accounted for the final yield. Further, yields at TZi were still limited by N availability at the tasseling stage due to fast depletion of applied-N, whereas yields plateaued at TZm once N availability was above 67 kg N ha−1. Our results provided a valuable reference for designing the N management to increase yield, while minimizing the potentially adverse losses of N to the environment, in different agro-ecological zones in SSA. [ABSTRACT FROM AUTHOR]

Maize is important for the biofuel and bio-based products. Building a clean maize production system could minimize the environment pollution from the N loss from the sloping land and achieve the industrial sustainable development. As a nitrogen-rich source, melamine could be used as a slow-release nitrogen (N) fertilizer, which provides a route for the recycling of melamine waste and the combatting of N loss from fertilizers. Model N release of melamine was compared with urea, sulfur(S)-coated urea via N loss in leaching column under intermittent leaching and under the ploughing fertilizer in the farmland soil. Only 7.12 % of the total nitrogen (TN) was lost from the 21 irrigation events, while the loss of TN from urea reached 77.28 %. TN from urea would be release totally in soil within 14 days in the ploughing fertilizer experiment, but 62 % of melamine was remained after 144 days. In order to evaluate the efficacy of melamine as an N fertilizer, plot experiments with an N rate of 180 kg ha-1 were carried out using pure melamine, urea and S-coated urea as well as mixed melamine/urea at 2:8, 1:1 and 7:3 by the N ratio. Melamine fertilization alone was unable to satisfy the N demand of maize, but the melamine/urea mixture (1:1) was comparable to the commercial S-coated urea in both years in terms of the grain yield (2217 kg ha-1 in 2019, 2368 kg ha-1 in 2020), total aboveground dry matter (5076 kg ha-1 in 2019, 4815 kg ha-1 in 2020), aboveground N uptake (36 kg ha-1 in 2019, 48 kg ha-1 in 2020), partial factor productivity of nitrogen (12.32 kg kg-1 in 2019 and 13.16 kg kg-1 in 2020) and net return (1474 USD in 2019, 1606 USD in 2020). Melamine accumulation in the maize grain measured from ELISA (enzyme-linked immunosorbent assay) ranged from 0.24 to 1.8 mg kg-1. The valorization of the melamine waste into N fertilizer by blending with urea was a possible way of reducing melamine pollution, alleviating N loss in hilly area and building a recyclable agriculture system. [Display omitted] • Valorization of melamine as a slow release was studied in lab and field experiment. • Melamine and urea at one to one ratio suffice the N need of maize. • Melamine for N fertilizer would decrease the N loss in the maize production system. • Melamine and urea at one to one ratio acquired high nitrogen uptake and grain yield in maize production system. [ABSTRACT FROM AUTHOR]

Banana crops in the Caribbean are characterized by the use of high rates of nitrogen (N) fertilization which causes severe environmental damages. The aim of this study was to assess the fertilizer N use efficiency (NUE) of banana crops in the field. To do so, a field trial was carried out during the first (GS1) and the fourth (GS4) growing seasons of banana crops, and the fate of a 15N-labeled pulse applied late in the growing season (flowering stage) was determined. At harvest, NUE (average 24% 15N applied) and the total recovery of fertilizer 15N in the soil–plant system (i.e., 40% in GS1 and 62% in GS4) were low. Low NUE resulted mainly from the dilution in a large soil mineral N pool derived from earlier applications of the labeled-N fertilizer applied at flowering, combined with leaching caused by numerous high-intensity rainfall events (>20 mm d−1). Crop residues from previous cycles present at time of fertilizer application in the fourth growing season, promoted fertilizer N immobilization, which in turn favored fertilizer N recovery by decreasing N leaching. The results suggest that N fertilization after the first season could be reduced by 30% (i.e., −90 kg N ha−1) corresponding to the suppression of two applications from flowering to harvest with the current fertilizer management, as available N derived from earlier applications is sufficient to meet plant requirements.

In a 4-year study, the biannual crop rotation processing tomato−durum wheat was applied to three cropping systems: (i) an innovative organic coupled with no-tillage (ORG+) where an autumn-sown cover crop was terminated by roller-crimping and then followed by the direct transplantation of processing tomato onto the death-mulch cover; (ii) a traditional organic (ORG) with autumn-sown cover crop that was green manured and followed by processing tomato; and (iii) a conventional integrated low-input (INT) with bare soil during the fall−winter period prior to the processing tomato. N balance, yield and N leaching losses were determined. Innovative cropping techniques such as wheat−faba bean temporary intercropping and the direct transplantation of processing tomato into roll-crimped cover crop biomass were implemented in ORG+; the experiment was aimed at: (i) quantifying the N leaching losses; (ii) assessing the effect of N management on the yield and N utilization; and (iii) comparing the cropping system outputs (yield) in relation to extra-farm N sources (i.e., N coming from organic or synthetic fertilizers acquired from the market) and N losses. The effects of such innovations on important agroecological services such as yield and N recycling were assessed compared to those supplied by the other cropping systems. Independently from the soil management strategy (no till or inversion tillage), cover crops were found to be the key factor for increasing the internal N recycling of the agroecosystems and ORG+ needs a substantial improvement in terms of provisioning services (i.e., yield).

Experiments were conducted to evaluate the nitrogen (N) balance in forage rice cultivation using animal manure in 1/2,000a Wagner pots in a greenhouse. The cattle manure and poultry manure were applied at 3 levels of N (0, 14, 28 g available N m–2) without additional chemical fertilizer application. The pots were designed to simulate the fluid percolation in the paddy field. The results indicated increasing levels of N input improved plant height, tiller number, SPAD value and biomass (straw, grain and root) production, however, N leaching from soil (Andosols) due to percolating water also increased. The planting of rice plants proved to reduce 30% of the N leaching loss. N use efficiency, the ratio of N uptake by plant per unit N application, decreased in higher N application. The N uptake by the above-ground parts occupied about 66% of the whole plants.