Winter wheat source-sink relationships under various planting modes, complementary irrigation, and planting densities

Various agronomic practices can affect the processes of aboveground dry matter accumulation (source) and grain filling (sink), resulting in yield differences. Improved source-sink relationships can facilitate the production and accumulation of assimilates to increase the productivity of winter wheat (Triticum aestivum L.). A two-season field experiment was undertaken on winter wheat during 2020-2021 and 2021-2022. In a split-split-plot design with three replicates (randomized blocks), we compared two planting modes (ridge-furrow planting with plastic mulching [RFPM]; traditional flat planting [TF]), two complementary irrigation levels (I30+30: 30+30 mm; I0: no irrigation), and three planting densities (D1, D2, and D3: 240, 360, and 480 plants m-2). The results showed that RFPMI30+30 significantly increased maximum yield by 28.5% compared with TFI0. Although D3 increased the number of effective spikes per unit area and duration of grain filling compared to D2, it reduced the number of grains per spike, 1000-grain weight, and average filling rate. Compared to TF and I0, RFPM and I30+30 improved the sink/source ratio by 5.3% and 6.5%, respectively. Grain yield peaked at D2 in the RFPM and at D3 in the TF. Medium planting density (D2) and complementary irrigation (I30+30) during the wintering and reviving periods under RFPM can achieve better source-sink balance relationships and the maximum grain yield of winter wheat. Overall, we believe that in most cases, wheat yields are source-limited and can be improved by ridge-furrow planting with plastic mulching, complementary irrigation, and planting density regulation. Logistic and beta-sigmoid models well fitted aboveground dry matter accumulation and grain filling processes. Effects of planting modes, complementary irrigation, and planting densities on grain filling were explored. A higher yield was obtained at medium planting density under ridge-furrow planting with plastic mulching. Irrigation of 30 mm at wintering and reviving periods increased grain yield by an average of 13.5%.