Comparison of population photosynthesis characteristics and grain yield of wheat under various sowing dates and seeding rates

This study investigated the effects of sowing dates and seeding rates on photosynthetic characteristics and grain yield in wheat (Triticum aestivum L.). A field experiment was conducted with three sowing dates—early sowing date (SD-E), normal sowing date (SD-N), and delay sowing date (SD-D)—and three seeding rates—90 low seeding rate (SR-L), 108 moderate seeding rate (SR-M), and high seeding rate 126 kg ha⁻¹ (SR-H). The results revealed that the grain yield at SR-L in the SD-E regime, SR-M in the SD-N regime, and SR-H in the SD-D regime was increased by 7.48%–9.93%, 14.1%–16.7%, and 19.0%–41.6%, respectively, compared to other combinations under the same sowing date. Consistent with the yield performance, the aboveground biomass accumulation, nonstructural carbohydrates (NSC) accumulation in stems, and NSC remobilization amount from anthesis to maturity were the highest at SR-L in the SD-E, at SR-M in the SD-N, or at SR-H in the SD-D regime, among other treatment combinations. Improved canopy photosynthetic characteristics (i.e., leaf area index, leaf photosynthetic rate, canopy photosynthetically active radiation interception rate, and radiation use efficiency) were also observed at the SR-M in the SD-N or at SR-H in the SD-D regime. Collectively, a suitable sowing date combined with an optimum seeding rate could enhance grain yield, and increasing the seeding rate could mitigate the yield loss when sowing was delayed by optimizing traits photosynthesis in wheat.