Assessment and analysis of soil quality changes after eleven years of reclamation in subtropical China.

Abstract Soil quality is one of the most important factors in sustaining the global biosphere and developing sustainable agricultural practices. It has been defined in several different ways in recent years from view points of bioproductivity, sustainability, environmental protection, and human and animal health. In this paper, soil quality refers to its capacity to meet the need of plant growth. Land use and management practices greatly impact the direction and degree of soil quality changes in time and space. Understanding the effects of land use and management practices on soil quality and its indicators has been identified as one of the most important goals for modern soil science. This paper presents a method for assessing and mapping soil quality changes in time and space in small watersheds. It was developed and used to evaluate the changes in soil quality after 11 years of reclamation at Qian-Yan-Zhou experimental station (QYZES), which is located in subtropical China. Changes in soil quality was assessed and analyzed for cropland, citrus orchards, pastureland, grassland, sparse weed land, artificial forests, natural forests, bare land and other land uses. The Qian-Yan-Zhou Soil Quality Information System (QYZSQIS) has been developed using ARC/INFO and FOXBASE software. Two concepts of Relative Soil Quality Index (RSQI) and its difference (ΔRSQI) are introduced and used in the evaluation and analyses. By combining the QYZSQIS with databases of soil properties for different time periods, the system provides an effective method for evaluating soil quality changes in time and space in small watersheds. The RSQI provides a standard for comparing regional soil quality and the ΔRSQI a standard for evaluating soil quality changes over time. After 11 years of reclamation, there was a decrease in the area of both low quality and high quality soils, while medium quality soils increased. In terms of land use systems, the soil quality in paddy fields, vegetable fields and citrus orchards was dominated by improvement, whereas fuel woods, sparse weed land, and bare land were mainly degraded. Annual grass played an important role in the conservation and improvement of soil quality in the area. Except for land uses and management practices, original soil quality level also plays a major role in soil quality changes. Soils with higher quality were degraded more rapidly, because they usually need more nutrient input to maintain their quality status than those with lower quality. These analyses show that it is of equal importance to improve soil quality in degraded locations and to sustain it in high-quality areas.