Abstract: To reveal the impact of high temperature on grain filling and yield of early season rice, an experiment with four sowing dates was conducted in 2022 in Nanchang, Jiangxi province, with four sowing dates, in which the Xiangzaoxian45 rice variety was used. The four sowing dates were March 11 (denoted as B1), March 24 (denoted as B2, regular sowing date), April 5 (denoted as B3), April 15 (denoted as B4), and analyzed the variation characteristics of the high temperature days during the heading and filling period of early season rice in Jiangxi in past 62 years (1961−2022) under four sowing dates. The results showed a downward trend in yields, seed set rates and 1000-grain weights as the planting date was pushed back. The high temperature days had a significant negative correlation with yield, seed setting rate, and 1000-grain weight (P＜0.05). Yields sown on March 11 were significantly higher than yields sown after March 5. Although high temperature increased the early season rice grain filling rate 10−15 days after heading, it was not conducive to maintaining the grain filling rate after 15 days. During the four sowing growth periods, high temperature days in B4 were significantly higher than in B1 during the grain filling period of the early season rice from 1961 to 2022. Since 2000, there had been a significant increase in the number of high temperature days during the head and grain filling phases of early season rice. The high temperature prone area overlaps with Jiangxi main early season rice growing area. Therefore, to reduce the impact of high temperature damage on the yield of early season rice, early season rice planting areas could be properly sown earlier to reduce the adverse effects of high temperatures.

Key words: High temperature, Early season rice, Grain filling rate, Yield, Growth period