Effects of Short-Term Intercropping of Forage Crops on Soil Microbial Communities in Ziziphus jujuba cv. “Lingwuchangzao” Orchards in Northwest China

In the transitional region between agriculture and livestock rearing in northern China, planting forage crops in rows among fruit trees as feed in orchards represents an effective strategy for enhancing the ecological environment while addressing the increasing demand for livestock feed. Nonetheless, the impact of short-term mowing of cover forage crops for livestock feed on the quality of soil remains unclear. A two-year field experiment was conducted in Ziziphus jujuba cv. “Lingwuchangzao” orchards located in Lingwu County, Ningxia Hui Autonomous Region, in arid and semi-arid Northwest China. The experiment consisted of four treatments: (A) clean tillage (CK), (B) plantation with Lolium perenne (LP), (C) plantation with Trifolium repens (TR), and (D) plantation with Vicia villosa (VV).The results showed that short-term intercropping of forage crops may lead to a reduction in most soil nutrients in Z. jujuba cv. “Lingwuchangzao” orchards, particularly in the 0–20 cm soil layer. However, intercropping with TR can mitigate this declining trend and may even enhance nutrient levels within the 0–40 cm depth. Furthermore, intercropping of forage crops had a more pronounced effect on the α-diversity of fungal communities than on bacterial communities. This practice also altered the relative abundance of bacterial genera such as Sphingomonas, Bacillus, and Flavobacterium in the 20–40 cm depth and dominant fungal genera Fusarium and Mortierella in the 0–20 cm soil layer. The effects of soil physicochemical properties on bacterial communities were more significant than those on fungal communities.These results indicate that the short-term intercropping of forage crops in Z. jujuba cv. “Lingwuchangzao” orchards in arid and semi-arid Northwest China have varying impacts depending on the type of forage crop used.