Optimizing orchard mulching regimes is a pivotal strategy for mitigating the detrimental effects of water scarcity and soil degradation on kiwifruit productivity in the Guanzhong Plain, China. To characterize the integrated effects of varying mulching patterns, a two-year field study was conducted in a kiwifruit (Actinidia deliciosa) orchard, evaluating four treatments: (1) FG: intra-row fabric with inter-row grass (multiple mulch); (2) FN: intra-row fabric with inter-row bare soil; (3) NG: intra-row bare soil with inter-row grass; and (4) NN: intra-row bare soil with inter-row bare soil. Understanding the impacts of these regimes on the edaphic environment, photosynthetic performance, and sugar metabolism is essential for improving kiwifruit production under semi-arid conditions. The results demonstrated that the FG treatment significantly improved soil water storage (SWS), with an increase of 1.83–55.16 mm, and enhanced the soil nutrient content (NH4+-N, NO3−-N, and soil organic matter), thereby optimizing the rhizosphere environment. During the critical phenological stages, the FG treatment increased the leaf photosynthetic parameters, such as the net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs), while reducing the intercellular CO2 concentration (Ci). Specifically, grass mulching (FG and NG) elevated the chlorophyll a content during early growth and carotenoids levels throughout reproduction, whereas fabric mulching (FG and FN) enhanced the chlorophyll b content throughout the entire reproductive period. Collectively, these improvements bolstered photosynthetic efficiency and may have contributed to improved carbon allocation and sugar accumulation. All three mulching treatments (FG, FN, and NG) significantly improved the fruit yield-related parameters, including the total fruit number per plant (PFN), single fruit weight (SFW), and yield (Y), as well as the fruit sugar-related indices, such as soluble solids content (TSS), total soluble sugar content (TS), reducing sugar (TRS), and the sugar–acid ratio (SAR). The partial least squares path modeling (PLS-PM) revealed that these improvements were primarily driven by the synergistic optimization of SWS and photosynthetic productivity. Notably, the model identified a physiological trade-off between yield formation and sugar accumulation, while the overall fruit quality exerted a strong positive influence on sugar metabolism. The correlation analysis indicated that the higher fruit sucrose accumulation under the FG and FN treatments were associated with increased sucrose phosphate synthase (SPS) and sucrose synthase (SS) activities, suggesting a potential link between mulching-induced improvements in plant physiological status and sucrose metabolism. These findings suggest that the combined use of intra-row fabric and inter-row grass mulching (FG) provides a sustainable strategy for enhancing soil conditions and fruit quality in water-limited kiwifruit orchards.
Li et al. (Sun,) studied this question.