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.