Background The degradation of the sloping farmland in the black soil region not only reduces the quality of the land and the water resources, but also causes the deterioration of the ecological environment. This study explores the change rule of the soil thickness and the degradation of the sloping farmland in the black soil region of the Northeast China, and it provides theoretical foundation for the prevention and control of the soil erosion on sloping field.

Methods 6° and 10° sloping farmlands in Dongliao county of Jilin province were selected as the main research objects, and a 8° farmland with soil and water conservation measures implemented in the near area was as CK field. We studied the degree of soil erosion by measuring the thickness of soil and investigated the degradation at different slope positions on the slope farmland in the black soil region via corresponding mechanical and chemical methods. We employed Excel, SPSS20.0, ANOVA to process data and cluster analysis for the classification of the soil degradation.

Results 1) The place with cultivated soil layer of 20 cm was the critical point, and when the soil thickness was < 20 cm, it meant that the soil erosion was strong on this sloping position. 2) The soil physical and chemical properties and the soil thickness statuses of the 6°slope and the 10° slope were significantly worse than those of the CK field(P < 0.05), and the soil physical and chemical properties rank of the 10° slope was as "bottom > top > middle", and the rank of the 6° slope was as "bottom > middle > top". 3) The thinner the soil thickness was, the worse the physical and chemical properties and the yield were, that meant the more serious the erosion was, the more serious the degradation was. 4) The soil degradation degree of the 6° slope and 10° in the study area were classified into 5 types, type 1 was characterized by the slight erosion and the relative high yield; type 2 was characterized by the low moisture content and the low rapidly available phosphorus and rapidly available potassium content; type 3 was characterized by the high bulk density, the low organic matter content; type 4 was characterized by the good soil physical and chemical properties and the high yield, and type 5 was characterized by the low moisture content, the high bulk density, the low nutrient content and the low yield.

Conclusions The reduction degree of soil thickness and the degradation degree in the study area are relatively serious, and the reduction and degradation rule between the 10° slope and the 6° slope are different, and the results may provide theoretical support for the prevention and control of the degradation of the sloping farmland in the black soil region.