Effects of the combination of mulching and deficit irrigation on the soil water and heat, growth and productivity of apples

Mulching and deficit irrigation are often used to alleviate the contradiction between the water supply and consumption in the apple industry in the Loess Plateau of China. However, the effects of the combination of mulching and deficit irrigation on the soil environment and the growth and productivity of apple trees are not clear. Field experiments were conducted in 2018 and 2019, which included three mulching methods-horticultural fabric mulching (FM), corn straw mulching (SM), and clear tillage treatment with no mulching (TL)-and three irrigation strategies-full irrigation (W1), moderate deficit irrigation (W2), and severe deficit irrigation (W3). The results showed that both SM and FM significantly increased the soil water content (SWC), especially in the early stage of the growth period. SM significantly reduced and stabilized the soil temperature during the whole growth season and effectively delayed the onset of flowering, while FM had no significant effect on the soil temperature. Both mulching and irrigation significantly increased the net photosynthetic rate (Pn) of leaves, and SM inhibited the occurrence of midday depression. A significant improvement of the yield was found in the SM and FM treatments, and there was little difference between them. Differences of the yield under different irrigation amounts were only reflected in the TL treatment in 2019, as a high soil moisture content under mulch counteracts part of the irrigation effect. Taken together, the results indicate that SM and FM have the potential to increase apple yields in the Loess Plateau by improving the soil environment and regulating the growth and physiology of apple trees.