Effect of composted manure plus chemical fertilizer application on aridity response and productivity of apple trees on the loess plateau, China

Soil degradation and aridity due to long-term unbalanced fertilization and scarce precipitation limit the productivity of apple trees in the Loess Plateau of China. The aim of the present study was to investigate the effects of composted manure (CM) plus chemical fertilizer (CF) applications on the aridity response and yield of apple trees. Five treatments [CF (C), CF plus 5/10 kg CM I per tree (CM1-L/H), and CF plus 5/10 kg CM II per tree (CM2-L/H)] were applied in a 10-year-old Red Fuji apple (Malus domestica Borkh.) orchard over a 4-year study period. The application of CM plus CF increased soil organic carbon, decreased soil bulk density, and optimized porosity. Low (5 kg per tree; CML) and high (10 kg per tree; CMH) CM application rates respectively increased soil water storage in the 20–60 cm layer by 1.4% and 4.8%, increased available soil water content in the 0–100 cm soil layer by 4.1%–44.8% and 10.4%–60.2%, elevated the water content of apple leaves (w%) by 1.3% and 3.7%, improved leaf potential by 15.9% and 30.0%, and decreased proline content by 16.1% and 28.5%. Thus, CM application decreased damage due to aridity and enhanced the photosynthetic capacity of apple trees, ultimately elevating apple yield by 8.8% and 13.3% under CML and CMH. The application of CM plus CF is an effective fertilization strategy for mitigating aridity stress and improving apple yield in the Loess Plateau.