Straw Incorporation Coupled with Deep Placement of Nitrogen Fertilizer Improved Grain Yield and Nitrogen Use Efficiency in Direct-Seeded Rice

Abstract

The purpose of this study is to understand how grain yield and nitrogen use efficiency were affected by straw incorporation coupled with deep placement of nitrogen fertilizer in direct-seeded rice in South China. The experimental treatments comprised deep placement of N fertilization coupled with straw return (DS) and without straw return (DO) as well as surface broadcasting of N fertilizer coupled with straw return (SS) and without straw return (SO), whereas no fertilizer placement and no straw return were taken as a control (FS0) in two rice cultivars, i.e., Yuxiangyouzhan (YX) and Wufengyou615 (WF), grown in early and late season of 2018. Results depicted that, compared with FS0, DS significantly (P < 0.05) improved grain yield by 68.7–115.9% owing to higher net photosynthetic rate (Pn) at the heading stage, larger total aboveground biomass, and leaf area index (LAI). Compared with DO, the nitrogen recovery efficiency (NRE) and nitrogen agronomic use efficiency (NAE) in DS were increased by 19.3–188.6% and 1.9–33.8%, respectively. Furthermore, the nitrate reductase (NR) activity of the flag leaves at heading stage for DS was increased by 10.6–93.0% as compared with DO treatment. Therefore, straw incorporation coupled with deep placement of nitrogen fertilizer could be a feasible technique with the increase of grain yield and nitrogen use efficiency in direct-seeded rice (DSR) in South China.