标题：Fates and Use Efficiency of Nitrogen Fertilizer in Maize Cropping Systems and Their Responses to Technologies and Management Practices: A Global Analysis on Field 15N Tracer Studies
摘要：Nitrogen (N) fertilization has boosted grain production during the past century, while excess N fertilization with declining N use efficiency (NUE) has led to severe pollution in many regions. To achieve the goal of sustainable food production, Technologies and Management Practices (TMPs, e.g., optimum N application rate and methods, N-transformation inhibitors) have been developed to improve crop yield and NUE and to reduce N losses. However, it remains unclear how N fate has been changed by environmental factors and TMPs. Here, we compiled a dataset of 366 field 15 N tracer observations from 74 publications worldwide and conducted a meta-analysis to examine how environmental conditions and management practices influence the fertilizer-N fate one growing season after the fertilization of maize. We show that the proportion of 15 N taken up by aboveground biomass (NUE 15N ), was significantly lower in China (33%) than that in North America (42%) and the European Union (54%). Soil organic carbon was the most critical environmental factor positively correlated with NUE 15N . Among the nine selected categories of TMPs, deep placement of fertilizer and split application increased the grain yield and decreased the fertilizer-N loss consistently among studies. Reducing the fertilizer-N rate could increase the NUE 15N but presents risks of yield reduction in some regions. This study demonstrates the importance of SOC and varying impacts of TMPs on the efficiency of fertilizer use in cropping systems globally and provides critical information for farmers and policymakers to improve N management for higher productivity and less pollution. Plain Language Abstract The efficient use of Nitrogen (N) fertilizer benefits both food security and environmental quality. To characterize the fate and the efficiency of fertilizer-N in maize production, we conducted a comprehensive meta-analysis with existing field 15 N-tracer trials. Our results show that higher organic carbon content in the soil is associated with higher 15 N recovery under conventional management practices. Among nine N management practices developed for more efficient use of N, deep placement in the soil (rather than surface application) and split application of N fertilizer (dividing annual fertilization into two or more smaller applications) improved yield, 15 N recovery, and environmental impacts. This study improves our understanding of management practices on the fate of fertilizer-N and provides guidance for farmers and policymakers to improve N fertilizer management.
关键词：fertilizer-N fate;meta-analysis;nitrogen use efficiency;NUE);technologies and management practices
