No-tillage with straw mulching boosts wheat grain yield by improving the eco-physiological characteristics in arid regions

Straw returning to the field is a technical measure of crop production widely adopted in arid areas. It is unknown whether crop yield can be further increased by improving the eco-physiological characteristics when straw returning is applied in the crop production system. So, a three-year field experiment was conducted with various straw returning treatments for wheat production: (i) no-tillage with straw mulching (NTSM), (ii) no-tillage with straw standing (NTSS), (iii) conventional tillage with straw incorporation (CTS), and (iv) conventional tillage with no straw returning (CT, control). The eco-physiological and yield formation indicators were investigated to provide the basis for selecting the appropriate straw returning method to increase wheat yield and clarifying its regulation mechanism on eco-physiology. The results showed that NTSM and NTSS treatments had better regulation of eco-physiological characteristics and had a higher yield increase than CTS and CT. Meanwhile, NTSM had a relatively higher yield than NTSS through better regulation of eco-physiological characteristics. Compared to CT, the leaf area index of NTSM was decreased by 6.1–7.6% before the Feekes 10.0 stage of wheat, but that of NTSM was increased by 38.9–45.1% after the Feekes 10.0 stage. NTSM effectively regulated the dynamics of the photosynthetic source of green leaves during the wheat growth period. NTSM improved net photosynthetic rate by 10.2–21.4% and 11.0–21.6%, raised transpiration rate by 4.4–10.0% and 5.3–6.1%, increased leaf water use efficiency by 5.6–10.4% and 5.4–14.6%, at Feekes 11.0 and 11.2 stages of wheat, compared to CT, respectively. NTSM had higher leaf water potential (LWP) by 7.5–12.0% and soil water potential (SWP) by 8.9–24.0% from Feekes 10.3 to 11.2 stages of wheat than CT. Meanwhile, the absolute value of difference on LWP and SWP with NTSM was less than that with CT, indicating that NTSM was conducive to holding the stability of water demand for wheat plants and water supply of soil at arid conditions. Thus, NTSM had a greater grain yield of wheat by 18.6–27.3% than CT, and the high yield was attributed to the synchronous increase and cooperative development of ear number, grain number per ear, and 1 000-grain weight. NTSM had a positive effect on regulating the eco-physiological characteristics and can be recommended to enhance wheat grain yield in arid conditions.