No tillage with straw mulching enhanced radiation use efficiency of wheat via optimizing canopy radiation interception and photosynthetic properties

Context: Conservation tillage practices are widely used in dryland areas of China to intensify ecological resource use and improve crop yields. However, the response mechanisms of canopy radiation interception and use efficiency for wheat to straw retention remain unclear. Objective: This study aims to explore the potential mechanisms by which straw retention affects canopy radiation interception characteristics, photosynthetic properties, grain yield, and radiation use efficiency during the growth period of wheat. Methods: We conducted a three-year field experiment in Northwest China to study how straw retention affects canopy radiation interception and photosynthetic properties of wheat. The experiment included four treatments: no tillage with straw mulching (NTSM), no tillage with straw standing (NTSS), conventional deep tillage with straw incorporation (CTS), and conventional deep tillage without straw retention (CT, the control). Results: Straw retention (NTSM, NTSS, and CTS) optimized the dynamics of canopy radiation interception during the wheat growth season. These practices helped maintain higher canopy cover and lower penetration ratio, thereby increasing canopy radiation interception of wheat. NTSM showed the most significant advantage, with 20.8%, 17.2%, and 7.2% increase in canopy radiation interception of wheat over NTSS, CTS, and CT. NTSM also helped to delay the degradation of chlorophyll a, b after the wheat anthesis stage. This delay was particularly notable for chlorophyll a, resulting in a 9.2 % increase in chlorophyll a/b compared to CT. Straw retention also optimized photosynthetic mechanisms, promoted carbon assimilation, and enhanced photosynthetic production during wheat grain filling. The net photosynthetic rate of wheat at 45 d after emergence was increased by 16.4% and 11.5% with NTSM and NTSS over CT, and enhanced by 12.7% and 8.0% over CTS. This was because NTSM increased key photosynthetic enzyme activities (Rubisco, GAPDH, and FBA) by 38.1 %, 13.5%, and 40.2% compared to CT, with corresponding gene expression levels rising by 11.8%, 28.1 %, and 11.7%. The content of D1 and D2 proteins in PSII with NTSM increased by 21.7 % and 11.1 % over CT. As a result, NTSM had higher grain yield and canopy radiation use efficiency of wheat, increasing by 20.5% and 9.1 % compared to CT. Conclusions: No tillage with straw mulching enhanced radiation use efficiency of wheat by optimizing canopy radiation interception and photosynthetic properties. Implications: Our research reveals the mechanisms for improving the canopy radiation use efficiency of wheat and its response to no tillage with straw mulching, offering valuable insights for long-term wheat production in irrigated arid areas.