Slope position influences kiwifruit (Actinidia chinensis Planch.) yield through soil water distribution, water consumption, and growth physiology in a subtropical humid region of China

Introduction Yield formation of kiwifruit ( Actinidia chinensis Planch.) is associated with soil water conditions. In the hilly areas of subtropical humid regions in China, sloping cultivation is a common practice. Slope position influences soil water distribution, possibly inducing variations in kiwifruit growth, physiology, and yield. However, the underlying pathways through which sloping cultivation affects kiwifruit yield remain unclear. Methods Therefore, a two-year field investigation was conducted to evaluate the differences in soil water content (SWC), actual evapotranspiration (ET c act ), growth physiology, and yield of kiwifruit between upper and lower slopes. The primary factors influencing kiwifruit yield were identified using the random forest and partial least squares path modeling (PLS-PM). Results Results showed that SWC on lower slopes was significantly higher than that on upper slopes, exceeding the appropriate SWC for kiwifruit growing and yield formation. In contrast, upper slopes exhibited superior growth physiology performance, yield, and water productivity (WP c ), compared to lower slopes. Specifically, upper slopes significantly increased ET c act , WP c , chlorophyll content index (CCI), shoot dry weight (SDW), fruit number (FN), and yield by 4.05%, 34.8%, 10.3%, 52.8%, 33.8%, and 39.3%, respectively. PLS-PM revealed that yield was directly influenced by FN and fruit weight. Soil water (average SWC and SWC at fruit development stage) and water consumption (ET c act and ET c act at fruit development stage) indirectly and positively affected yield by influencing growth physiology (CCI and leaf dry weight per unit shoot leaf area) and yield components. These pathways collectively explained 93.1% of yield variations. Discussion This study can provide a reference for kiwifruit water management under sloping cultivation in subtropical humid regions. Specifically, supplement irrigation on upper slopes is recommended during dry periods, while drainage improvement is recommended on lower slopes to avoid excessive soil water accumulation or prolonged high SWC.