Loss of soil and water from sloped farmland is a major cause of regional soil degradation and declining productivity. We conducted a preliminary study on the characteristics of sloped farmland in the black soil region of Northeast China using natural rainfall-runoff plot experiments in the field. In 0-20 cm soil depth, clay content (<0.002 mm), silt content (0.002-0.02 mm), specific surface area, <0.002 mm and 0.002 to 0.02 mm microaggregates content, available phosphorus, and total phosphorus tended to increase from the top to the bottom of the slope, while sand content (>0.05 mm), 0.02 to 0.05 mm and 0.05 to 0.25 mm microaggregates content, tended to decline. This suggests that soil material and nutrients were gradually transported from the top to the bottom of the slope because of erosion, soil tended toward desertification in texture, and fertility was degraded. The content of available phosphorus and total phosphorus was positively linearly related to clay content, specific surface area, and 0.002 to 0.02 mm microaggregates content. This indicates that soil nutrients migrated down with fine particles. Therefore, soil erosion leads to the migration and loss of soil nutrients, <0.002 mm fine particles and 0.002 to 0.02 mm microaggregates on the slope, which was the main cause of soil fertility degradation.
Characteristics of Material Migration During Soil Erosion in Sloped Farmland in the Black Soil Region of Northeast China