Environment especially minimum temperature affecting summer maize grain yield through regulating ear differentiation and grain development

Ear differentiation, grain development and their interaction with the growing environment such as temperature, solar radiation and precipitation greatly influence grain number and grain weight, and ultimately affect summer maize production. In this study, the 3-year field experiments of sowing dates were to evaluate the effects of temperature factors, average solar radiation and total precipitation on growth process, ear differentiation, fertilization characteristics, grain filling and yield of summer maize with different growth duration. Four hybrids were evaluated in HHHP from 2018 to 2020 under five sowing dates. Results showed that the grain yield formation of summer maize was extremely impacted by the environment from silking (R1) to milking (R3) stage. Average minimum temperature (ATmin) was the key environmental factor to determine yield. The reduction in the length of the growing season (r=-0.556, P<0.01) and the total floret number on ear (R2=0.200, P<0.001) were found when ATmin was elevated from emerging (VE) to R1 stage. Both grain filling rate (R2=0.520, P<0.001) and the floret abortion rate on ear (R2=0.437, P<0.001) showed quadratic relationship with ATmin from R1 to physiological maturity (R6) stage, while the number of days after R1 stage (r=-0.756, P<0.01) were negatively correlated with ATmin. Rising ATmin was beneficial to the promotion of yield while it was not exceeded certain extent (above 23°C during R1-R3 stage and 20-21°C during R1-R6 stage). Enhanced solar radiation and precipitation during R1-R6 increased grain filling rate (R2=0.562, P<0.001 and R2=0.229, P<0.05). Compared with short-season hybrids, full-season hybrids showed more powerful suitability to critical environment. Coordinated regulation of ATmin, ear differentiation and grain development pro- and post-silking stage improved maize yield by increasing total floret number, grain filling rate and reducing floret abortion rate on ear.