Improving crop productivity by optimizing straw returning patterns to delay senescence of wheat leaves

Abstract

Early senescence in the conventional pattern of wheat production is widespread, leading to decline in potential for increased and stabilized yield. Straw returning could effectively improve soil quality and extend the growth period of wheat. However, the response mechanism of straw returning in delaying leaves senescence and increasing crop productivity by regulating the internal physiological and biochemical processes of leaves is not clear. A field experiment was conducted in northwest China in 2013 (the data used in the text from 2021–2023) with four straw returning patterns: no tillage with straw mulching (NTSM), no tillage with straw standing (NTSS), conventional tillage with straw returning (CTS), and conventional tillage with straw removing (CT, the control). The antioxidant enzyme activities, cellular osmotic contents, endogenous hormones contents, stay-green capability of wheat leaves, photosynthetic source, and crop yield were investigated and analyzed. We found that no tillage with straw mulching (NTSM and NTSS) could effectively enhance the antioxidant and cell osmoregulation capabilities of wheat leaves during the grain filling process. Compared to CT, the SOD activity of NTSM and NTSS increased by 24.9–28.2% and 18.6–20.4%, respectively. Soluble protein content increased by 37.3–43.2% and 25.2–57.1%, and proline content increased by 37.3–78.4% and 26.5–31.4%. However, malondialdehyde content decreased by 20.3–21.4% and 19.2–23.2%. It was evident that the NTSM treatment provided a solid physiological foundation for delaying leaves senescence. NTSM could also help to maintain the homeostasis of endogenous hormones in wheat leaves during the grain filling period. Compared to CT, the contents of zeatin, salicylic acid, and jasmonic acid of NTSM increased by 23.3–27.2%, 18.5–22.0%, and 15.2–15.3%, while abscisic acid content of NTSM decreased by 9.4–10.2%. Based on physiological changes within the leaves, NTSM and NTSS reduced stay-green of leaves before 45 d post-emergence by 20.6–20.9% and 17.5–17.8% compared to CT. After 45 d post-emergence, NTSM and NTSS increased stay-green of leaves by 21.9–23.0% and 17.0–19.1% over CT. Thus, the grain yield of NTSM was 15.0–22.2% and 9.0–11.3% higher than that with CT and CTS, primarily due to the synchronous increase in ear number and thousand grain weight. Therefore, no tillage with straw mulching promoted the mobilization of antioxidant and cellular osmoregulatory responses, optimized endogenous hormones signaling, and maintained higher photosynthesis source and stay-green during the grain filling stage, thus delaying leaves senescence and increasing crop productivity in arid irrigated areas.