Optimal nitrogen management increases nitrogen use efficiency of direct-seeded double-season rice using ultrashort-duration cultivars

Optimal nitrogen (N) management is critical for achieving both high grain yield and N use efficiency (NUE) in rice production. However, limited information is available on N management for ultrashort-duration cultivars matured within 95 days in direct-seeded double-season rice (DSD), an important simplified rice cropping system in central China. A two-year field experiment was conducted to investigate the effects of four N management treatments on the grain yield and NUE of four ultrashort-duration cultivars in both early (ES) and late (LS) seasons in DSD. The N treatments included real-time N management (Nreal) with the timing of in-season N application based on leaf N status determined by a chlorophyll meter, weekly N application to achieve steady nutrient supply (Nweek), conventional practice of N management (Nconv), and zero-N (Nzero) as the control. Results showed that Nreal produced the average yield of 7.31 t ha−1 in ES and 6.60 t ha−1 in LS, which were comparable to those of Nweek and Nconv. However, the total N rates of 90 kg ha−1 in ES and 70 kg ha−1 in LS in Nreal were largely reduced by 25.0–40.0 % in ES and 33.3–41.7 % in LS, compared with Nweek and Nconv. As a result, agronomic NUE of Nreal was significantly increased by 39.1 % in ES and 70.2 % in LS compared with Nconv, although these differences were relatively small between Nreal and Nweek. Compared with Nreal, Nconv and Nweek exhibited higher stem number and leaf area index before heading and total N uptake at maturity due to increased N application rate, but there were small differences in yield components and dry matter accumulation at maturity among them, suggesting a luxury N consumption in Nconv and Nweek. Nreal increased NUE without reduction in grain yield for ultrashort-duration cultivars in DSD. Thus, fine tuning of N management is needed to improve NUE and sustain grain yield of ultrashort-duration cultivars in DSD, which was vital to promote sustainable rice production in central China. •Nitrogen (N) management was studied for direct-seeded double-season rice (DSD).•N treatments affected N use efficiency of DSD with ultrashort-duration cultivars.•Real-time N management (Nreal) reduced total N rates of DSD substantially.•Nreal increased N use efficiency of DSD without reduction in grain yield.