[Response of grain filling characteristics of maize to sowing date.]

To study the effect of different sowing dates on the process of grain filling characteristics, Jingke 528 (JK528) and Zhengdan 958 (ZD958) were used in the field experiment with two sowing dates (10th April and 14th May). The results showed that the 100-grain dry mass and yield of JK528 and ZD958 with the early spring sowing were significantly higher than that with the spring sowing date, which increased by 6.8% and 10.1%, 17.8% and 9.2%, respectively. The maximum grain filling rate (Gmax) and the average grain filling rate (Gave) were higher with the early spring sowing than that with the spring sowing date, while the active grain filling period (P) showed an opposite trend. The 100-grain mass and yield of JK528 were significantly improved by 7.4 g and 1189.6 kg·hm-2 compared to ZD958, with the increase of 21.6% and 10.8%, respectively. The P of ZD958 was higher than that of JK528, while Wmax, Gmax, Gave and Tmax of JK528 were higher than that of ZD958. The average grain filling rate of JK528 during early and mid grain filling stages was higher than that of late grain filling stages, which was also higher than that of ZD958 at the same sowing date. Furthermore, correlation analysis revealed that the mean temperature and the accumulated temperature were significantly positively correlated with the grain dry matter accumulation. Therefore, the full use of hot-ray resources and the increase of the mean grain-filling rate could improve maize grain yield. The higher grain filling rate during early and mid grain filling stages in JK528 could compensate for the short active grain filling period, leading to higher yields under different sowing dates.