关键词: 水稻产量, 施肥量, 移栽密度, 灌浆速率, 有效灌浆时间

Abstract: In order to explore the effects of nitrogen (N) application rates on rice yield and grain-filling properties under different transplanting densities, this paper studied the population yield formation from the differences of grain-filling characteristics among different positions of grains by field experiments. The objective was to provide a theoretical basis for further improvement of rice yield potential. The experiment evaluated a split plot designed with different nitrogen application amounts as the main plots and transplanting density as the sub-plots. Richards equation  was used to describe the gain-filling process of superior and inferior rice gains. The results indicated that: ① The yields of N treatment were averagely increased by 36.6% and 34.6%, respectively, and the yield increased with increasing N application. Under high density (27×104 plants/hm2, 33×104 plants/hm2) conditions, N treatment could averagely increase the yield by 30.8% and 18.8%, respectively, but the seed-setting rate was decreased averagely by 2.0% and 1.6%, respectively, and the yield increased firstly then decreased with N application increase. ② The grain-filling characteristics showed that the nitrogen application increased the maximum grain-filling rate of the superior grains (GRmax), which was increased by 3.5% compared with that of N0 treatment, and increased firstly then decreased with N application increase. Transplanting density had significant effect on the average grain filling rate (GRmean). Under low density (15×104 plants/hm2, 21×104 plants/hm2) conditions, the GRmean of superior grains with N treatment was decreased by 2.1% and 3.1%, respectively, compared with that of N0 treatment. However, it was increased by 1.0% and 3.7%, respectively, under high density (27×104 plants/hm2, 33×104 plants/hm2) conditions. The GRmax and GRmean of inferior grains of N treatments were increased by 14.3% and 14.4%, respectively, compared to that of N0 treatment, and increased firstly then decreased with N application increase. ③The grain-filling characteristics of different stages indicated that the maximum contribution rates of superior and inferior grains were reached 58.6% and 57.3%, respectively, in the middle gain-filling stage. The average grain-filling rates (MGR) in the middle and late grain-filling stage were increased firstly then decreased with N application increase. The contribution rate and grain-filling lasting days were all increased with transplanting density increase. There was a significant positive correlation between 1 000-grain weight and GRmax and GRmean of inferior grains, but it had a significant negative correlation with the initial grain-filling potential (R0) and the active grain-filling period (D) of inferior grains. The seed-setting rate was negatively correlated with GRmean of inferior grains, while had a positive correlation with R0. The grain-filling rate and grain-filling lasting days were all improved by rational planting density and raising of nitrogen fertilization level (27×104 plants/hm2, 165kg/hm2). Whilst increasing the panicles per unit area, the individual grouting rate and effective grain-filling lasting days were all improved. Finally a high yield was formed, due to the plumpness of grain-filling.

Key words: rice yield, nitrogen application rate, transplanting density, grain-filling rate, effective grain-filling time