Soil Erosion Monitor Based on Fixed Soil Core Eu Tracer and Comprehensive Evaluation for Soil Ferti

The spatial distribution of soil erosion of Jiangjiatang watershed on red soil areas in Lanxi city, Zhejiang province, southern China, was studied using fixed soil core Eu tracer and meanwhile an appraisal on the soil integrated fertility index was also conducted using mathematical methodology. Two types of functions for calculating the values of soil fertility indices were developed according to principal of fuzzy mathematics, and these indices weight value were calculated applying the analysis hierarchy program, then soil integrated fertility indices in different units were also calculated. According to the results of the calculation, soil fertility was divided into high (>0.45), middle(0.25～0.45), low(<0.25)grades. The spatial distribution of soil erosion and the characteristics of soil fertility in this watershed were analyzed by ARCVIEW3.1, a GIS based software. The results were as follows: Soil erosion was serious in the upper parts of slopes with less plant coverage, but in the lower sections of the slopes with more plant coverage soil erosion was light. Soil erosion on slope land with traditional cultivation and less plant coverage was serious, but was less on slope land with terraces or more plant cover, in both these cases soil was deposit on the lower sections of the slopes. The areas of soil with serious erosion (erosion modulus: >100 t/hm2·a), modest erosion (10～100 t/hm2·a), light erosion (1～10 t/hm2·a), less erosion (<1 t/hm2·a) accounted for 15.67%, 22.13%, 5.60%, 34.23% of total watershed area respectively. Most of the soil in Jiangjiatang watershed was of middle and lower fertility, which accounted for 55.60% of area of this watershed or 71.62% of slopes in this watershed. The spatial distribution of soil integrated fertility index was in concordance with the spatial distribution of soil erosion. The soil fertility index in slope land, where the soil erosion was serious, was lower, and conversely, the soil fertility index was higher in areas where soil erosion was less serious. The coefficient of correlation between modulus of soil erosion and soil integrated fertility index was 0.801(n=33), which was positively significant.