Study on the benefits of different soil and water conservation measures in hillside citrus orchards in karst rocky desertification area of northern Guangxi Zhuang Autonomous Region

Abstract

[Objective] In order to explore the optimal soil and water conservation measures for hillside citrus orchards in karst rocky desertification area, [Methods] a runoff observation plot method was developed to monitor the hillside citrus orchards in the karst area of northern Guangxi. The runoff, sediment, and nutrient loss under three soil and water conservation measures—vegetation planting, brick-and-stone enclosure, and PVC board enclosure—were analyzed at different rainfall levels(heavy rain, rainstorm, and heavy rainstorm). Additionally, the entropy-weight fuzzy comprehensive evaluation method was used to perform a quantitative analysis of the comprehensive benefits. [Results] The result showed that:(1) whether rainfall levels were considered or not, vegetation planting demonstrated the best nitrogen and phosphorus reduction benefits, and PVC board enclosure had the best sediment reduction benefits. In general, the reduction benefits of the brick-and-stone enclosure were lower than those of the other two measures. Vegetation planting provided the best runoff reduction benefits under heavy rain and rainstorm, while PVC board enclosure had higher runoff reduction benefits than vegetation planting under heavy rainstorm.(2) The water, soil, and nutrient loss, as well as the reduction benefit indicators of soil and water conservation measures, did not all change monotonically with the increase in rainfall level. Specifically, runoff yield and nutrient loss increased monotonically with the increase in rainfall level, while most other indicators did not show a monotonic change. The change trends in indicators such as runoff reduction, sediment reduction, nitrogen reduction, and phosphorus reduction of the same measure varied with different rainfall levels.(3) When rainfall levels were not considered, the comprehensive benefits of implementing PVC board enclosure in hillside citrus orchards in karst rocky desertification area were the best, followed by vegetation planting. When rainfall levels were considered, the comprehensive benefits of implementing vegetation planting were the best under rainfall levels of heavy rain and rainstorm, and the comprehensive benefits of implementing PVC board enclosure were the best under heavy rainstorm. [Conclusion] The implementation of vegetation planting, PVC board enclosure, and brick-and-stone enclosure in hillside citrus orchards in karst rocky desertification area all provide certain soil and water conservation benefits.

Keywords

rainfall / runoff / karst hillside / soil and water conservation / erosion / fuzzy comprehensive evaluation / citrus orchard