Effect of planting density and nitrogen application on yield and nitrogen uptake and utilization of japonica rice cultivar D46

Objective To explore the optimum nitrogen (N) application rate and planting density and N use efficiency of rice production in Chengdu plain, and provide a basis for establishment of rational cultivation management.

Method Field experiments were carried out to investigate the interactive effect of N application rates (N 150、225、300 kg·hm^-2) and planting densities (2.000×10⁵、2.667×10⁵、4.000× 10⁵ seedlings·hm^-2) on rice yield and N uptake and utilization efficiency of japonica rice cultivar D46 in Chengdu plain.

Result Both N application rate and planting density showed significant effects on the rice yield (P < 0.05). The rice yield increased with the increase of N application rate (< 225 kg·hm^-2) and planting density (< 2.667×10⁵ seedlings·hm^-2). The highest rice yield (7 580 kg·hm^-2) was found with the N application rate of 225 kg·hm^-2 and planting density of 2.667×10⁵ seedlings·hm^-2, which was significantly higher than that of other treatments (P < 0.05). Increasing N application amount could significantly decrease N agronomic efficiency (NAE), N physiological efficiency (NPE), N partial factor productivity (NPFP) and N use efficiency for grain output (NUEG) (P < 0.05), while harvest index (NHI) and nitrogen apparent utilization rate (NAUR) had no obvious change. NAE, NPE and NPFP decreased with the increase of planting density, especially for NAE and NPE, while the planting density had little effect on NUEG, NHI and NAUR.

Conclusion The combination of N 225 kg·hm^-2 and 2.667×10⁵ seedlings·hm^-2 is the best for high yield and high N use efficiency of japonica rice D46 in Chengdu plain.