Seasonal effects of drip irrigation on soil quality index, microbial stoichiometry, and carbon use efficiency in an apple orchard

The soil quality index (SQI) is a comprehensive indicator that reflects the agricultural productivity of soil, as well as playing important roles in understanding microbial nutrient metabolism and carbon use efficiency (CUE). However, it is unclear how drip irrigation treatments in apple orchards affect the SQI, eco-enzyme stoichiometry, and soil microbial CUE. Thus, in the present study, we tested three different treatments in orchard plots: T1 (50–60 % field water capacity (θf)), T2 (65–75 % θf), and T3 (80–90 % θf), as well as control with no drip irrigation (CK). The study focused on the effects of these treatments during two key stages: bud breaking and fruit maturity. During the bud breaking stage, we observed that water availability had a more pronounced influence on the SQI when soil moisture was limited. Specifically, in the 0–20 cm soil layer, the T2 treatment showed a significantly lower SQI value compared to T3, with a decrease of 31.89 %. On the other hand, there were no significant differences among all the irrigated treatments during the maturity stage. Both vector length and angle were significantly affected by water availability during the bud breaking stage, while only the vector angle was impacted during the maturity stage. The vector length and angle were both influenced by SQI (Mantel's test: p