Benefits of controlled-release/stable fertilizers plus biochar for rice grain yield and nitrogen utilization under alternating wet and dry irrigation

Identifying approaches to producing greater amounts of rice with higher water productivity (WP) and nitrogen use efficiency (NUE) is a major challenge for economical, environmentally friendly rice production. Despite the advantages of controlled-release N fertilizers, few studies have investigated their effects on rice agronomic performance, grain yield, NUE and WP under different irrigation regimes. In this study, a three-year field experiment was conducted in Zhejiang, South China, with two irrigation regimes (flood irrigation, FI; alternating wet and dry irrigation, AWD) and five N application methods (zero N, N0; the conventional N level, PUN100; 80 % of the conventional N level, PUN80; 80 % of the conventional N level applied as controlled-release N fertilizer and urea, plus biochar, CRFN80-BC; and 80 % of the conventional N level applied as stable compound N fertilizer and urea, plus biochar, SFN80-BC) using the indica hybrid rice cultivar Zhongzheyou 1. Compared with FI, AWD significantly increased rice yield, irrigation WP (WPi) and irrigation plus rainfall WP (WPi+r), and the values of these variables under CRFN80-BC and SFN80-BC were significantly higher than those under PUN80 and PUN100 (P