Polyaspartate Urea and Nitrogen Management Affect Nonstructural Carbohydrates and Yield of Rice

In rice (Oryza sativa L.), nonstructural carbohydrates (NSC) play an important role in grain yield. To investigate the effects of urea type (polyaspartate urea versus conventional urea) and N management method (farmer's fertilizer practice and optimized N management) on NSC accumulation and remobilization in rice, field experiments were conducted in Wenjiang, China, in 2014 and 2015. Grain yield, effective panicles, and total number of spikelets were positively related to NSC accumulation in aboveground parts and remobilization of stored NSC (RSN) in the stem plus sheath from 20 d after heading to maturity. Polyaspartate urea, in place of conventional urea, increased NSC accumulation in the leaf lamina and the stem plus sheath at the heading stage and promoted RSN in the stem plus sheath from 20 d after heading to maturity, improving grain yield and total aboveground biomass. Compared with farmer's fertilizer practice, optimized N management showed a 5% reduction in NSC accumulation in the stem plus sheath from planting to heading and a 22% decrease in RSN in the stem plus sheath from heading to 20 d after. Optimized N management increased RSN in the stem plus sheath from 20 d after heading to maturity, increasing NSC accumulation in the panicle and grain yield. Using polyaspartate urea with optimized N management may indeed be a practical and feasible way to enhance grain yield of rice in subtropical humid monsoon climates.