Background The red soil region is one of the eight soil and water conservation districts in China, and it is an important production base for grain, oil, crop and timber. Soil and water erosion process in this area is complicated and difficult to be controlled, thus comprehensive managements are needed. Reasonable analysis of the effects of these managements in easing erosion is important to soil and water conservation planning.

Methods This study was conducted based on the data from two national soil erosion surveys (Ministry of Water Resources 2002, 2011), and erosion indexes (EI) were calculated to quantify soil erosion risk. Field measured data from typical watersheds and key project counties were also adopted to analyze the effects of comprehensive harness in soil and water erosion from multi-scales. Besides, EI is a comprehensive index value based on the quantitative classification of soil erosion area and total land area in a unit, and weight transformation.

Results 1) Soil erosion area in the whole region declined by 5 000 km² recently with the moderate erosion level contributed the most. However, the erosion area of the light level increased. Generally, the soil erosion risk in Jiangxi, Hubei, Zhejiang, Fujian, Hunan and Anhui provinces have been controlled at different degrees. Nevertheless, the erosion risk in Guangxi, Guangdong, Hainan and Jiangsu provinces still need to be improved. 2) From the perspective of 177 key project counties, the soil erosion risk of 112 counties had a downward trend, accounting for 63.3%. Among them, the average value of EI in ecological civilization project declined the most, followed by national key prevention and control region, technology demonstration parks and clean small watersheds. From the aspect of distribution area, those in southern Jiangxi, central Hunan, western Anhui, Zhejiang and Fujian coastal counties showed obvious efficiency in erosion controlling. The counties in southern Hunan, southern Anhui and eastern Guangdong are still suffering relatively high erosion risk. According to national key prevention and control regions, erosion area and EI in upstream protection region of Xiang River, Zi River, Yuan River, and Li River and upstream protection region of Dong River increased obviously. 3) In the watershed scale of typical rivers, the runoff showed an inconspicuous upward trend during the past decades, while the sediment showed a significant declining trend. On the other hand, with the increase of vegetation coverage and the per capita net income of farmers, the average soil erosion modulus in the small watersheds also descended. Both indicated that the soil and water erosion control in the region has achieved remarkable results.

Conclusions After years of treatment, the soil and water erosion risk in the region showed a general improvement and partial deterioration. The results revealed the effects of soil and water erosion control from different scales, which are of great significance for future soil and water conservation layout in the red soil region.