Investigating The Impacts Of Soil Erosion On Soil Quality And Corn Yield In The Typical Black Soil Region

Soil erosion in the black soil region leads to the soil quality decrease and crop productivity decline, which greatly affects food security of our country. Therefore, investigating the impacts of soil erosion on soil quality and crop yield in the black soil region could target to provide important scientific basis for protecting the valuable black soil resources, and also is greatly significant to ensure national food security. A small catchment, called Dongshangou, located at Bin County, Heilongjiang Province, was selected as a research area site. Based on the field investigation, laboratory analysis, radioisotope tracer and GIS technology, the study analyzed the spatial distribution characteristics of soil erosion at the catchment, revealed the feature of the main soil quality indices, evaluated the catchment soil quality level using the total data set(TDS)and the minimum data set(MDS), established the experience model on the relationship between soil erosion, soil quality and crop yield. The main results were as follows:(1) The spatial distribution characteristics of soil erosion at the catchment were analyzed. The soil erosion and deposition rates on the cultivated catchment ranged from-7122 t km-2 yr-1 to 5471 t km-2 yr-1(- means soil erosion and + means soil deposition) and with a mean of 830 t km-2 yr-1, which indicated that the catchment was dominated with soil erosion. At catchment scale, the spatial distribution of erosion and deposition was staggered distribution. Soil erosion was dominated in the upstream area, erosion and deposition were coexisted in the midstream region, and soil deposition was dominated in the downstream area. At hillslope scale, slight soil erosion occurred at the upper slope, severe soil erosion occurred at the midslope, and a great amount of soil material was deposited at the footslope. Soil erosion rate exhibited significant power function relationships with slope gradient and slope length at the study catchment, and it increased with increasing slope gradient and slope length. The effect of slope gradient was much greater than that of slope length on soil erosion rate.(2) The responses of the main soil quality indices to soil erosion and deposition rates were illuminated. The spatial distribution characteristics of 15 soil quality indices including soil physical, chemical and microbiological characteristics were analyzed. The spatial distribution characteristics of the different main soil quality indices were different. Soil organic matter, total nitrogen, available phosphorus, available phosphorus, urease, alkaline phosphatase, and microbial biomass nitrogen were significantly influenced by soil erosion, which showed that soil erosion was the important factor affecting the soil nutrients, enzyme activities and microbial biomass.(3) The soil quality at the catchment was evaluated. Based on correlation analysis and principal component analysis, 15 soil quality main indices were selected as the total data set(TDS) indices, and 7 soil quality main indices(thickness of black soil layer, mean weight diamater of soil aggregate, organic matter, total nitrogen, pH, alkaline phosphatase, microbial biomass nitrogen) were chose as the minimum data set(MDS) indices for soil quality evaluation. The average value of SQIs at the catchment and the typical hillslope using TDS method were 0.419 and 0.471, respectively. The mean value of SQIs at the catchment and the typical hillslope using MDS method were all 0.453. The results of the two soil quality evaluation methods all showed that the soil quality at the catchment was low and lower and serious soil quality degradation have occurred at the catchment. In addition, the two methods showed the very close results and illustrated that the MDS had very good representative. The spatial distribution characteristic of soil quality at the catchment was as follows: downstream > midstream > upstream, and on the hillslope as: lower slope > upper slope > middle slope.(4) The corn yield change and spatial distribution at the study catchment were studied. The change of corn yield was difference in the same year and different years. The spatial distribution characteristic of soil quality at the catchment was as follows: downstream > midstream > upstream. At hillslope scale, the minimum corn yield occurred at the midslope, and the maximum corn yield was at the low slope. There were highly significant correlation between the corn yield and two results of soil quality assessment using TDS and MDS. However, SQI using the MDS method showed better correlation with corn yield, which indicated that the 7 soil indices in MDS was suitable for soil quality assessment in the study catchment.(5) The influence of soil quality and soil erosion on corn yield was analyzed. At the catchment and hillslope scales, the spatial distribution of corn yield was corresponding to soil quality and opposite with soil erosion. Corn yield had a highly significant positive correlation with soil quality. In additional, corn yield was negatively correlated with soil erosion rate, and no significant with soil deposition rate. A model on the relationship between the corn yield and soil quality was established and validated. A model on the effect of soil erosion and soil quality on corn yield was established at this study catchment.