Responses of Lycium barbarum fruit quality and microclimate to interplanting with different species of cover grass in Ningxia, China

To investigate the impact of different species of cover grass on the quality of Lycium barbarum fruit (wolfberry) and the orchard microclimate , we conducted field comparison test with clean tillage as the control. Three grass species were used: natural grass, artificially planted Lolium perenne, and artificially planted Trifolium pratense. The study analyzed changes in soil water content, temperature, CO₂, and the quality of Lycium barbarum L fruit. The results showed that compared to the clean tillage treatment, the artificially planted Lolium perenne L. treatment increased the relative humidity of the canopy air. It also increased the soil water content in the 0－20 cm soil layer by 2.71% during the flowering period, compared to the natural grass treatment. Additionally, the greatest decrease in daily average temperature in the 0－10 cm soil layer was obtained under the artificially planted Lolium perenne L. treatment, with a decrease of 0.86 ℃. The average CO₂ emission rate also decreased significantly under the artificially planted Lolium perenne L. and Trifolium pratense L. treatments (P < 0.05), with decreases of 1.57% and 1.53% respectively relative to the clean tillage treatment. An analysis of the quality of Lycium barbarum L. fruit showed that the artificially planted Lolium perenne L. treatment increased the polysaccharide content of summer fruit by 31.31%, while the artificially planted Trifolium pratense L. treatment increased the total sugar content of summer and autumn fruit by 6.91% and 9.26% respectively. Furthermore, the artificially planted Lolium perenne L. and Trifolium pratense L. treatments increased the vitamin C content of summer and autumn fruits and significantly increased the betaine content of autumn fruits. RDA Redundancy analysis revealed the relative humidity of the canopy had the greatest impact on the formation quality of summer and autumn fruits, followed by the rate of CO₂ emission. Hence, interplanting cover grass, particularly artificial planting of Lolium perenne L., could be employed as an effective management strategy for Ningxia Lycium barbarum L. orchards.