Reduced nitrogen application rate with dense planting improves rice grain yield and nitrogen use efficiency: A case study in east China

Abstract

Dense planting could be a feasible method for reducing nitrogen (N) application rates without compromising rice grain yield in northeast and central China. It is still unclear whether reduced N application with dense planting (RNDP) can achieve higher rice yield and N use efficiency (NUE) in Jiangsu, east China. Three japonica inbred rice (JI) and three indica hybrid rice (IH) cultivars were grown in a field experiment. Their grain yield, NUE, and related traits were compared under two cultivation treatments: conventional high-yielding practice (CHYP) and RNDP. JI showed similar yields under the two treatments, while IH showed lower yield under RNDP than under CHYP, and the partial factor productivity of N and N use efficiency for grain yield increased (P < 0.05) in both JI and IH under RNDP. Compared with CHYP, RNDP reduced spikelets per panicle but increased panicles per m2 and filled-kernel percentage of JI and IH, and JI’s kernel weight was increased (P < 0.05) under RNDP. Shoot biomass weight and nonstructural carbohydrate (NSC) content in the stem at heading and maturity of JI and IH were reduced under RNDP, while harvest index and NSC remobilization reserve were increased (P < 0.05) under RNDP, especially for JI. Our results suggest that RNDP could achieve a higher rice grain yield and NUE, particularly for JI, a dominant rice cultivar type in Jiangsu. For JI, the increased panicles per m2, sink-filling efficiency, harvest index, and NSC remobilization after heading under RNDP contributed to a grain yield similar to that under CHYP.

Keywords

• Japonica inbred rice
• Grain yield
• Nitrogen use efficiency
• Reduced nitrogen rate
• Dense planting