Effects of Intercropping Morel Mushrooms between Apple Tree Rows on Soil Properties and Tree Performance

To investigate the effects of intercropping Morchella (morel mushrooms) between apple tree rows on fruit quality and orchard soil properties, a field experiment was conducted using a cultivation system combining plastic film mulching with small arched tunnels. Morchella was planted in the interrows of five-year-old apple trees, and after harvest, the spent mushroom substrate was returned to the soil via rotary tillage. Plots without Morchella cultivation served as the control. The experiment assessed the yield and quality of both apples and morels, as well as the overall impact on tree performance. In addition, soil physicochemical properties and enzyme activities were analyzed across the 0-40 cm soil profile at different depth intervals. The results demonstrated that: (1) Inter-cropping Morchella in apple interrows proved to be agronomically feasible, yielding a fresh mushroom production of 1333.737 g/m². Moreover, this cultivation system significantly enhanced the nutritional quality of the harvested morels, as evidenced by marked increases in crude fiber, total sugars, reducing sugars, and free amino acid contents. (2) In the 0-20 cm soil layer, the Morchella cultivated plots exhibited significantly higher natural water content compared to the control. The measured values for soil pH, alkali-hydrolyzable nitrogen, organic carbon, catalase activity, and sucrase activity were 5.46, 6.733 mg/kg, 38.303 g/kg, 411.859 μ mol/h/g, and 9.885 mg/d/g, respectively, all significantly greater than those in the control (p < 0.05). In the 20-40 cm layer, however, soil available potassium and organic carbon contents were 418.370 mg/kg and 28.453 g/kg, respectively, both significantly lower than the control (p < 0.05). Across both treatments, the values of soil pH, alkali -hydrolyzable nitrogen, organic carbon, available phosphorus, available potassium, and the activities of urease, amylase, catalase, and sucrase generally decreased with increasing soil depth. Notably, in the non-cultivated control plots, the contents of alkali-hydrolyzable nitrogen and organic carbon increased with depth. (3) Morchella intercropping significantly improved apple fruit quality, as reflected by marked increases in individual fresh weight, fruit shape index, reducing sugars, total sugars, and soluble solids content. (4) The treatment also substantially enhanced the photosynthetic performance of apple trees, with significant increases in transpiration rate, intercellular CO₂ concentration, and stomatal conductance. Collectively, our findings demonstrate that intercropping Morchella between apple tree rows confers substantial agronomic advantages. This practice not only elevates the productivity and quality of both the mushroom crop and the apples, but also ameliorates key soil physicochemical characteristics and boosts foliar photosynthesis. The cumulative positive effects highlight its considerable promise as a viable and scalable agroecological strategy.