This study aimed to evaluate the effects of crop rotation on soil fertility, colloidal particle composition, soil particle content and the loss of humus and nutrients in typical sierozem soils affected by irrigation erosion. The research focused on comparing 3-year-old alfalfa-plowed land with long-plowed soil. Soil samples from the 0–30 cm layer were analysed to determine humus content, colloidal particle group composition and nutrient losses. Results showed that humus content in the plowed layer of 3-year alfalfa fields was 0.38 % in unwashed soil, 0.31 % in heavily washed soil and 0.24 % in areas where particles accumulated from the slope. The proportion of easily decomposable colloid particles (zero group) decreased, while stable first- and second-group particles increased. Soil particle washing was 3.6 times higher in eroded areas. Losses of humus, nitrogen, phosphorus and potassium were reduced by 2.7-, 2.2-, 2.8- and 3.1-fold, respectively. These findings indicate that crop rotation with alfalfa improves soil fertility, enhances colloidal particle stability and reduces nutrient loss in irrigated sierozem soils.
