Nutrient assessment and land reclamation in the Loess hills and Gulch region in the context of gully control

Abstract

Abstract Soil quality is the key to the success or failure of the gully land reclamation project. Studying the variation characteristics of soil nutrients and evaluating the nutrient classes in the gully after the implementation of gully land reclamation project in the loess hilly and gully region can provide a basis for adjusting the spatial layout of gully crops, rational planning and utilization of land resources, and soil nutrient management. In this study, a typical gully in Yan’an City, Shaanxi Province, China was taken as the research object. Based on the data of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK) before 0 year (0a) and after 2, 4, and 8 years (2a, 4a, and 8a) gully remediation. From the spatial distribution characteristics of soil nutrients and its levels, the classical statistical analysis, geostatistical analysis, and matter-element model were used to reveal the variation characteristics of soil nutrients in the gully before and after the gully land reclamation project. The results showed that (1) before remediation, except for AK which reached the level of 1–3, the rest of the nutrients content was generally low and the degree of variation was large, after remediation the degree of variation decreased and the coefficient of variation was between 0.23–0.54, the distribution tended to be uniform. (2) SOM content showed a “decrease–increase” change process, reaching the highest after remediation (8a); TN and AP increased first and then decreased; AK showed a “downward–upward–downward” change process. (3) The soil nutrient grade belongs to the appropriate level. After the implementation of the project, only the gully head is reduced to the poor level. After 4a of remediation, the soil nutrient grade is restored and has the potential to continue to improve. Compared with the slope land remediation, the soil nutrient recovery time of gully land creation is shorter, the spatial layout of crops can be adjusted according to the soil nutrient characteristics of different locations in gully, and different levels and methods of management measures can be implemented to increase food production.