Soil properties and quality evaluation of desert steppe under different management measures in arid windy and sandy areas

This study aims to clarify the impact of different management measures on the soil quality of grassland. The desert steppe was selected in the arid windy sandy area of eastern Ningxia, China. Four management measures were set: grazing enclosure (GE), warm season rotational grazing (WG), free grazing (FG), and Caragana korshinskii cultivation (CC). A systematic analysis was implemented on the physical, chemical, and biological characteristics of 0-10, ＞10-20, ＞20-30, and ＞30-40 cm soil layers. The correlations among soil factors were determined as well. The soil quality of grasslands was finally evaluated under different management measures using a minimum data set (MDS) and soil quality index (SQI). The results showed that: 1) There were generally higher contents of soil organic carbon, total nitrogen, alkali-hydrolyzale nitrogen, available potassium, and soil water in the GE and WG grasslands, compared with the FG and CC grasslands. While the opposite was found in the soil bulk density and soil available phosphorus content. Soil microbial biomass C, N, and P were generally higher in the FG grasslands, while lower in the CC grasslands. There were inconsistent variations in the soil cellobiohydrolase activity, alkaline phosphatase activity, polyphenol oxidase activity, and peroxidase activity of grasslands under different management measures. 2) The soil quality of desert steppe depended mainly on the soil's physical, chemical, and biological properties, and they interacted with each other. Soil organic carbon, total nitrogen, alkali-hydrolyzale nitrogen, and peroxidase activity were significantly positively correlated with each other, while significantly negatively correlated with the soil bulk density and available phosphorus content. Soil total nitrogen content was significantly negatively correlated to the soil microbial biomass C. Soil total phosphorus content was significantly negatively correlated to the soil alkaline phosphatase activity. Soil available phosphorus content was significantly positively correlated to the soil microbial biomass C, microbial biomass P, cellobiohydrolase activity, and alkaline phosphatase activity. Soil available potassium content, microbial biomass C, microbial biomass N, microbial biomass P, cellobiohydrolase activity, and alkaline phosphatase activity were also significantly positively correlated with each other. Soil available potassium content was significantly negatively correlated to the soil polyphenol oxidase activity. 3) The MDS included the soil organic carbon content, alkali-hydrolyzale nitrogen content, total phosphorus content, available phosphorus content, microbial biomass N, cellobiohydrolase activity, and soil water content. The MDS could replace the TDS to evaluate the soil quality of desert steppe under different management measures. The SQI of the desert steppe was ranked in the descending order of GE > WG > FG > CC grasslands after MDS evaluation. The research suggested that the management measures caused the variation in the soil quality. The soil's physical, chemical, and biological properties exhibited relatively consistent variations in the desert steppe of arid windy sandy areas. The GE and WG also improved the soil nutrients and soil quality better than FG and CC. The preferred options were then given for the desert steppe in arid windy sandy areas.