Intercropping Gramineae Herbage in Semiarid Jujube Cultivar ‘LingwuChangzao’ (Ziziphus jujuba Mill. cv. LingwuChangzao) Orchard Improves Productivity, Plant Nutritional Quality, and Soil Quality

Abstract

Forest-grass intercropping has great advantages in exploiting the potential of biological resources, improving the productivity of agriculture. Nevertheless, research on intercropping of ‘LingwuChangzao’ (Ziziphus jujuba Mill. cv. LingwuChangzao) with Gramineae herbage is less frequently reported. In this study, we measured the land equivalent ratio (LER), the nutritional quality of fruit and forage, and soil properties when ‘LingwuChangzao’ jujube was intercropped with Gramineae herbage compared to when grown in a corresponding monoculture, using clean tillage as a control. The results indicated that ‘LingwuChangzao’ jujube/Gramineae herbage intercropping significantly improved the LER in the system, the appearance traits, and the quality of jujube fruit (e.g., the total soluble solids, soluble sugar, vitamin C, anthocyanin, and flavonoids). Conversely, some nutritional quality indicators, such as dry matter, crude protein, crude fat, and neutral detergent fiber of forage, were lower than the corresponding monoculture. The physical properties in the soil improved with increased soil water content, electrical conductivity, total nitrogen, available phosphorus, etc. Further, intercropping systems had significant effects on soil organic carbon fractions and most of the C-N cycling enzyme activities. Redundancy analyses (RDA) revealed that electrical conductivity and total nitrogen were the dominant soil factors that influenced the C-N cycling enzyme activities and four soil organic carbon fractions correlated with C-N cycling soil enzyme activities. In conclusion, these results demonstrated that ‘LingwuChangzao’ jujube/Gramineae herbage intercropping significantly altered C-N cycling enzyme activities by driving the soil physicochemical properties and soil organic carbon fractions. Our findings show how to improve the productivity of ‘LingwuChangzao’ jujube and they provide insights into the mechanisms underlying healthy, biodiverse soils in agroecosystems.