干旱区生态环境知识资源中心

In arid and semiarid regions, the emergence of a dry soil layer can limit apple (Malus domestica Borkh.) tree growth, development, and yield. This study investigated the spatiotemporal variability and income/expenditure of soil moisture in apple orchards in the Weibei rainfed highland, northwest China, in order to provide a reference for irrigation management and sustainable development of the fruit industry. We chose both young (fewer than 10 years) and old (greater than 20 years) orchards, as well as cropland (control), that had the same site conditions. Stratified sampling was Performed at different growth stages of apple trees from March to September, and moisture was monitored in the 0 to 150 cm (0 to 59 in) soil profile using the oven-drying method. In young orchards, heavy water stress (soil moisture content <= 60% field capacity, 12.96%) appeared in the topsoil (0 to 10 cm [0 to 4 in]) in late March to late April and mid to late June, while it occurred in the deep soil (40 to 80 cm [16 to 31 in]) in mid-June to mid-July. The degree of heavy water stress and depth of desiccation were greater in old orchards than in young orchards, namely 0 to 20 cm (0 to 8 in) in late April to early May and 0 to 100 cm (0 to 39 in) in late June to late July. The drought conditions in cropland were greater than for the orchards, and the level of soil moisture was lower than the wilting coefficient (9.21%) above the 80 cm depth from early June to early July, indicative of a serious water deficit. Orchard soil moisture gradually decreased from mid-March to early July (loss phase), followed by an increase to the end of September (recovery phase). During the recovery, "seasonal interior water stress" could be restored in apple orchards; there was no "dead" dry soil layer showing difficult recovery or nonrecovery, and the water budget was balanced. Therefore, there is a significant reduction in bare-soil evaporation after planting apple trees in the Weibei rainfed highland, which is beneficial to improve water use efficiency and promote sustainable development of the fruit industry.