Abstract:

To investigate the effects of straw biochar combined with controlled-release urea on rice yield and nitrogen use efficiency, a two-year field experiment was conducted using indica-japonica hybrid rice variety ‘Yongyou 15’ as test material and polymer-coated urea. The experiment employed a randomized complete block design to examine rice yield, nitrogen uptake, and nitrogen use efficiency under two biochar-based treatments: biochar with conventional urea, and biochar with polymer-coated urea. The results showed that, compared with conventional urea applied at full nitrogen rate, a single application of polymer-coated urea with 20% nitrogen reduction maintained stable rice yield and significantly increased nitrogen recovery efficiency (>50%). Compared with conventional urea alone, biochar combined with conventional urea significantly reduced rice yield in the first year, but no significant difference was observed between the two treatments in the second year. Meanwhile, biochar combined with polymer-coated urea did not compromise the positive effect of polymer-coated urea. All controlled-release urea treatments significantly increased nitrogen content in various rice plant parts and enhanced nitrogen recovery efficiency. This study provides a theoretical basis and scientific reference for developing efficient nitrogen fertilization strategies for indica-japonica hybrid rice.

Key words: straw biochar, indica-japonica hybrid rice, coated urea, nitrogen use efficiency, yield