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Nitrogen (N) input from atmospheric deposition is a concern in the North China Plain (NCP). To quantify the magnitude of the problem, the total airborne N deposition to agroecosystems in the NCP was quantified using a manual ITNI (integrated total nitrogen input) system and a long-term experiment (LTE). Total estimated N deposition averaged 83. 3kgNha−1 across the sites Dongbeiwang (DBW) of Beijing, Wuqiao (WQ) and Quzhou (QZ) of Hebei, with atmospheric N input 14kgNha−1 in the period from flowering to maturity, when maize (Zea mays) was the monitoring crop. The 15N-supply level in the ITNI system seemed not to affect the estimation of N deposition significantly. However, the N deposition value was only 48. 6kgNha−1 on average when ryegrass (Lolium multiflorum) was cultivated during the same period of maize (May–September), suggesting that total airborne N input varies with the monitoring crop, largely because of the different surface areas. The total annual N deposition obtained from zero-N plots of LTE at Changping (82. 8kgNha−1) supported the N deposition results from the maize-based ITNI systems. [Copyright &y& Elsevier]

Abstract: There is increasing interest in nitrogen (N) deposition because of its importance as a nutrient resource and a component of acid deposition within the overall global N cycle. Precipitation samples were collected for periods varying from 6 months to 6 years (1998–2004) from seven sites in the Beijing area to determine the amount and seasonal distribution of N (bulk/wet) deposition. Bulk deposition of N ranged from 26.6 to 38.5kgNha−1 year−1 and averaged 30.6kgNha−1 year−1. Bulk deposition of NH4–N was, on average, 2.1 times the NO3–N deposition, suggesting that reduced N is the major form of N deposition in the study area. Concentrations of NH4–N and NO3–N in rainfall averaged 4.8 and 2.2mgNL−1 and showed great temporal variation from month to month. A negative relationship between rainfall and NH4–N or NO3–N concentration in rainwater was observed by an exponential equation, indicating dilution of NH4–N and NO3–N with increasing precipitation. Bulk deposition of inorganic N occurred mainly from April to September (>80% of total bulk deposition), which was consistent with both the monthly distribution of precipitation and the times of fertilizer applications in local agricultural land. Wet-only deposition of inorganic N, however, was 8.3–8.4kgNha−1 lower than that of bulk deposition during similar periods in 2003 (June–November) and 2004 (April–November), suggesting the potential contribution of dry deposition to total N deposition in the Beijing area. [Copyright &y& Elsevier]

Nitrogen (N) is the key nutrient for crop growth in most agricultural systems, but excessive N fertilizer applications have led to very large ammonia (NH 3) and greenhouse gas (GHG), especially nitrous oxide (N 2 O), emissions, resulting in severe air pollution and making a major contribution to global warming. To clarify the effects of improved N management on NH 3 and N 2 O emissions and crop production, a 2-year field experiment was carried out in a maize-wheat rotation in the North China Plain (NCP), testing four optimized N management practices including reducing the fertilizer (urea) N rate and using N 'synergists' with the fertilizer. NH 3 emissions were significantly reduced only by the urease inhibitor (UI) LIMUS®, with an average reduction of 66.9 % relative to emissions from the untreated urea. At the same N rate, N 2 O emissions were reduced by 30.8–76.7 % by all the synergists (UI, a nitrification inhibitor DMPP (NI) and urea with a bacterial agent (UB)), and crop yields were improved by 14.4 % and 15.2 % under the UI and UB treatments, respectively. An 15N tracer experiment showed that using N synergists decreased the total N loss by 10.9–58.7 %, and significantly increased the recovery efficiency of N (RE N) by 16.9–44.8 % over the whole rotation. Reducing the N rate reduced the GWP and yield-scaled GWP (GHGI) by 10.6 % and 8.4 %, respectively. Using the N synergists, GHGI was significantly decreased by 19.2–26.7 % (P < 0.05), while GWP was reduced by 13.2–18.1 % only by the application of DMPP or LIMUS®. Overall, the study showed that reducing N 2 O and NH 3 emissions is important for increasing N utilization and mitigating global warming. Reducing N rate and using synergists can address the joint problems of environmental pollution and agricultural efficiency. In particular, the application of the optimal amount of urea (33% reduction over rates typically applied by farmers) amended with the urease inhibitor LIMUS® to maize-wheat rotations in the NCP proved to be the most effective method for the 'green' and sustainable development of agriculture and the mitigation of global warming in that region of China. • Optimizing N rate decreased environmental impact while maintaining crop yield. • Cropland NH 3 emissions were halved by incorporating a urease inhibitor. • A nitrification inhibitor reduced cropland N 2 O emissions. • Both inhibitors increased the recovery efficiency of fertilizer N by 16.9–44.8 %. • Optimizing fertilizer N rate plus appropriate inhibitor mitigated GWP and GHGI. [ABSTRACT FROM AUTHOR]

The North China Plain (NCP) is an intensive agricultural area and ammonia (NH 3) emission hotspot in China. Urgent mitigation actions are needed to reduce its environmental impact. A field trial was conducted, and results combined with a synthesis of existing data to assess the NH 3 loss and mitigation potentials in a wheat-maize double-crop rotation, a dominant crop production system in the NCP. Ammonia volatilization losses from N fertilizer applied to summer maize and winter wheat were 9.1% and 5.0%, respectively, based on the data synthesis, and were significantly affected by fertilizer application method and N fertilizer type. From the field trial, optimized reduction in N application rate, compared with conventional practice, had great efficiency for NH 3 mitigation. Despite their high NH 3 reduction potential, the higher input costs associated with the use of controlled-release fertilizers, replacement of urea with calcium ammonium nitrate or inclusion of double inhibitors (urease and nitrification inhibitors) with urea limited their applicability from an economic perspective. The inclusion of a urease inhibitor with urea achieved over 70% reduction in NH 3 emission and also gave a significant improvement in grain yield, net income and N use efficiency. Future adoption of NH 3 mitigation options in the NCP should focus on establishing a reduction target and consider the cost-benefits of simultaneous implementation of multiple mitigation techniques. [Display omitted] • Placement of fertilizer and fertilizer types significantly influence NH 3 emissions. • High cost of fertilizer amendment compromised economic benefits. • Using urease inhibitor showed good economic and environmental performance. [ABSTRACT FROM AUTHOR]

Grazing considerably affects ecosystem nutrient cycling and element stoichiometry at the regional and global levels according to synthesized studies. However, the effects of grazing, especially its intensity, on the plant litter decomposition stage of key processes in biogeochemical cycles are not clearly understood. Here, a meta-analysis of 65 published papers was undertaken to examine the responses of eight variables associated with litter decomposition to grazing or grazing intensity. We also explored whether experimental and environmental factors altered the effects of grazing on litter decomposition. Our results indicated that grazing significantly promoted litter decomposition when all the data was averaged, and that the magnitude of its effects on litter decomposition became weaker as grazing intensity increased. Grazing did not affect mixed root litter decomposition, but increased single root litter decomposition, and light grazing had a stronger positive effect. Specifically, grazing significantly accelerated litter C and P release, and significantly increased single N release by single above-ground litter, but not root or mixed aboveground litter. In addition, environmental factors (e.g., elevation, and mean annual precipitation) and experimental factors (e.g., experiment duration and litterbag size) affected the litter decomposition responses to grazing. These results suggest that the effects of grazing on litter decomposition and nutrient release depend on grazing intensity, litter type, and plant organs. Grazing alters terrestrial plant litter decomposition and grazing intensity plays an important role in regulating the magnitude of the effect during litter decomposition and nutrient cycling. • Effect of grazing on litter decomposition and nutrient release was examined. • Light grazing showed a stronger promoting effect on litter decomposition. • Effect of grazing on litter decomposition depends on plant organ and litter type. • Effect of litterbag area on litter decomposition should be considered in subsequent studies. [ABSTRACT FROM AUTHOR]

Fertilized cropland is a significant source of ammonia (NH 3) emissions. Urea, the dominant synthetic nitrogen (N) fertilizer, makes the largest contribution to NH 3 volatilization from cropland in China. To improve environmental quality and resource utilization efficiency, stabilized urea (UI: Urea amended with the urease inhibitor Limus®) was tested in an intensive cropping system in the North China Plain (NCP). A two-year field trial and an extensive demonstration experiment at five sites were carried out in Quzhou county, NCP, to quantify the effect of RNUI (Reduced N rate + Urea Inhibitor) technology on NH 3 mitigation from farms. NH 3 emission, crop yield and N use efficiency (NUE) were measured to evaluate the efficacy of UI and a questionnaire-based survey used to investigate farmers' attitudes to the technology. In the field trial, UI significantly reduced NH 3 emissions by 60.5–62.9% and 39.7–52.3% during wheat and maize growing seasons, respectively, compared to untreated urea applied at the same rate. NUE was significantly increased by 34.6–62.7% in the wheat season and 14.9–66.6% during the maize season. No significant crop yield improvement was observed, but UI significantly reduced yield-scaled NH 3 emissions. Similar results were found at the five demonstration sites in Quzhou, but there was a small yield increase for maize. On average there were 49.0% and 38.5% reductions in NH 3 emissions, and 50.5% and 46.3% reductions in yield-scaled NH 3 emissions for wheat and maize, respectively, compared to typical farmer practice. Farmers' willingness to adopt RNUI technology depended mainly on crop yield, the convenience of using RNUI and government subsidy to reduce costs. Results emphasized the importance of on-farm demonstration experiments, integrated field management, government subsidies and legislation for the promotion of RNUI technology, achieving sustainable high yields and NUE for mitigating agricultural NH 3 loss at a county level in the NCP. • Field and demonstration trials were conducted to mitigate NH 3 emission in Quzhou. • Urease inhibitor (UI) halved NH 3 emissions from a wheat-maize rotation. • UI with reduced N input (RNUI) increased NUE on farms by 47.8–57.0%. • Government subsidy was essential for promoting UI/RNUI application by farmers. [ABSTRACT FROM AUTHOR]

• Soil biodiversity is positively related to agroecosystem multifunctionality. • Management practices are most important driving factors of multifunctionality. • High multifunctionality depends on high inputs of straw residues, organic and inorganic fertilizers. • Management practices are determined by smallholders' socioeconomic factors. Agroecosystems provide multiple goods and services that are important for human welfare. Despite the importance of field management practices for agroecosystem service delivery, the links of socioeconomic factors, management practices and ecosystem multifunctionality have rarely been explicitly evaluated in agroecosystems. Here we used a county-scale database with 100 farmer households and their farmlands, and analyzed the relative importance of management practices, soil abiotic environment and soil biota on multifunctionality under three distinct ('smallholder's viewpoint', 'sustainable soils' and 'equal weight') scenarios. Furthermore, we also analyzed the effect of smallholders' socioeconomic factors on management practices. Our results found that smallholders' high inputs of fertilizers and agrochemicals were associated with their high agricultural income and less farmland area, but total land area had a positive effect on straw incorporation. Total soil biota index was positively related to multifunctionality, however, management practices (fertilizer input, agrochemical input, organic fertilizer amount and straw incorporation) had stronger effect on multifunctionality than that of soil biota or the abiotic environment. Their strength varied with distinct scenarios. Our work suggests that increasing organic materials (organic fertilizers and crop residues) and decreasing agrochemicals are beneficial for maintaining or increasing ecosystem multifunctionality in smallholder-dominated agroecosystems. Moreover, improving management practices of smallholders needs to take into account the effects of their socioeconomic factors. [ABSTRACT FROM AUTHOR]

• Nitrogen stabilizers could improve fertilizer-N recovery in the soil-crop system. • Nitrogen stabilizers could reduce fertilizer-N losses to the environment. • Urease and urease + nitrification inhibitors had better performance in improving NUE. • Soil pH has large impact on efficacy of N stabilizers. Nitrogen (N) fertilizer stabilizers (including urease inhibitors (UI), nitrification inhibitors (NI) and double inhibitors (DI)) are promising tools to mitigate N pollution from agricultural production. For a better understanding of how N stabilizers impact on the fate of fertilizer-N, we conducted a comprehensive meta-analysis of data from experiments that used the 15N as a tracer to investigate the effects of N stabilizers on fertilizer-N recovery in the soil-crop system. We combined this with boosted regression tree (BRT) model analysis to further interpret the contribution of soil properties and experimental conditions. The dataset consisted of 72 papers (227 observations). Our results suggest that UI, NI and DI significantly enhanced the fertilizer-N uptake by the crop by 24.1, 10.5 and 47.6 %, respectively, the fertilizer-N retention in the soil by 5.8 % (UI) and 15.0 % (NI), and the fertilizer-N recovery in soil-crop system by 16.4, 10.2 and 27.5 %, respectively. On the contrary, the fertilizer-N loss is reduced by 32.9, 14.5 and 37.6 % for UI, NI and DI, respectively. Soil pH, organic matter content, inhibitor compound and nitrogen application rate were the most important explanatory variables for the impact of UI and NI amendments on fertilizer-N recovery. These findings have major implications for N stabilizer application strategies in agricultural systems, where an important consideration is the mitigation of potentially detrimental environmental consequences. [ABSTRACT FROM AUTHOR]