Adjusting the sowing date of spring maize did not mitigate against heat stress in the North China Plain

Abstract

Heat stress due to increases in temperature reduces grain number and yield of spring maize in the North China Plain (NCP). To mitigate heat stress, previous research recommended that postponing the sowing date of spring maize to late May in the NCP. However, other field experiment indicated that early sowing could achieve high grain yield. To resolve the discrepancy in previous studies, a two-year sowing date experiment was conducted from 4 April to 13 June with 14-day interval without drought stress. It was found that high grain yields were obtained in early sowing dates (early and mid- April) in both years. The grain yield and kernel number had no significant relationships with the heat stress in the crucial period bracketing silking, when kernel number is determined (15 days pre- and post- silking). Moreover, the historical meteorological data elucidated that high temperature continued from mid-June to early-August, which contained the silking window of different sowing dates. Additionally, the heat stress risk around silking (>33°C) for different sowing dates was high throughout the past 30 years (>23%), except for 13 June (7%). Moreover, the simulated yields under full irrigation also indicated that adjusting the sowing date to late May did not increase grain yield. We concluded that adjusting sowing date did not mitigate the heat stress around silking, and other factors, such as drought, overcast and rainy stress, influenced the grain number and yield of spring maize in the NCP.