The Effects of Phased Warming during Late Winter and Early Spring on Grain Yield and Quality of Winter Wheat (Triticum aestivum L.)

Phased warming in late winter and early spring can increase winter wheat grain yield. However, the effects of different durations of warming during this period on winter wheat grain yield and quality are not yet clear. Therefore, this study conducted field warming experiments in a movable polyethylene greenhouse during the late winter and early spring stages of the three wheat growing seasons from 2019 to 2022. The results showed that the accumulated growing degree days (GDD) of the warming treatment during the warming period were increased by 87.3&ndash:215.7 &deg:C d compared to the control (CK). The warming treatment advanced and prolonged the duration of vegetative growth and spike differentiation after regreening, promoted spike and flower development, and increased grain length, grain width, and grain area. During the three growing seasons, the longer the warming duration (WD) of the warming treatment, the more obvious were the observed promoting effects on the kernel number per spike and 1000-kernel weight. From 2019 to 2021, compared to the CK, the spike number per unit area and grain yield of the warming treatments increased with the prolongation of WD. However, in the 2022 growing season the spike number per unit area and grain yield of the warming treatment were increased with longer WD, reaching the maximum at WD of 56 days and then gradually decreasing with longer WD. Compared to CK, the grain protein content, wet gluten content, and sedimentation value of the warming treatment decreased with the prolongation of WD. The promotion effect of longer WD on grain starch content and protein yield was more significant. In summary, the accumulated GDD during the warming period compared to CK was 155.8&ndash:181.2 &deg:C d, and at WD of 50&ndash:56 days a relatively higher grain yield and protein yield could be obtained.