【摘 要】
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Deep placement of nitrogen fertilizer is a key strategy for improving nitrogen use efficiency. A two-year field experiment was conducted during the early rice growing seasons (March-July) of 2016 and 2017. The experimental treatments comprised two rice cu
【机 构】
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State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources,College of Ag
论文部分内容阅读
Deep placement of nitrogen fertilizer is a key strategy for improving nitrogen use efficiency. A two-year field experiment was conducted during the early rice growing seasons (March-July) of 2016 and 2017. The experimental treatments comprised two rice cultivars: Wufengyou 615 (WFY 615) and Yuxiangyouzhan (YXYZ), and three N treatments: mechanical deep placement of all fertilizers as basal dose at 10 cm soil depth (one-time deep-placement fertilization, namely OTDP fertilization);manual sur-face broadcast (the common farmer practice) of 40％N fertilizer at one day before sowing (basal fertilizer) followed by broadcast application of 30％each at tillering and panicle initiation stages;and no fertilizer application at any growth stage as a control. One-time deep-placement fertilization increased grain yield of both rice cultivars by 11.8％-19.6％, total nitrogen accumulation by 10.3％-13.1％, nitrogen grain pro-duction efficiency by 29.7％-31.5％, nitrogen harvest index by 27.8％-30.0％, nitrogen agronomic efficiency by 71.3％-77.2％, and nitrogen recovery efficiency by 42.4％-56.7％for both rice cultivars, compared with the multiple-broadcast treatment. One-time deep-placement fertilization reduced CH4-induced global warming potential (GWP) by 20.7％-25.3％, N2O-induced GWP by 7.2％-12.3％, and total GWP by 14.7％-22.9％for both rice cultivars relative to the multiple-broadcast treatment. The activities of glutamine syn-thetase and nitrate reductase were increased at both panicle-initiation and heading stages in both rice cultivars following one-time deep-placement fertilization treatment. Larger leaf area index at heading stage and more favorable root morphological traits expressed as larger total root length, mean root diam-eter, and total root volume per hill were also observed. One-time deep-placement fertilization could be an effective strategy for increasing grain yield and nitrogen use efficiency and lowering greenhouse-gas emissions under mechanical direct-seeded cropping systems.
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