[Objective] The spatial variations of the soil moisture content and soil nutrient content in an eroded gully catchment of sloping farmland were explored to reveal the effects of black soil erosion on the grain production of sloping farmland.[Methods] The erosion gully catchment area of a typical black-soil sloping farmland region was selected as the study area. Field experiments were conducted to systematically observe the soil moisture properties and soil nutrient content during the entire growth period. The soybean and maize yields were also measured during the autumn. The spatial heterogeneity and correlation between the soil moisture content, soil nutrient content, and soybean and maize yields were determined, and the effects of gully erosion on the soil quality and crop productivity were analyzed.[Results] ① Gully-slope erosion had a significant effect on the soil moisture content of the black soil in the sloping land. The coefficient of variation of the soil moisture content at a depth of 0—20 cm in ridge and furrow soils ranged from 12.2% to 17.4% (i.e., of a medium level), and the nugget/sill was 0.2. There was a strong spatial correlation, and the nugget/sill was close to 0 during the rainy season. This indicated that the soil moisture content in the catchment area was strongly affected by the runoff migration caused by the topography and other structural factors. The spatial effective correlation distance was relatively small (55.2 m). ② The contents of soil organic matter, total nitrogen (N), total phosphorus (P), alkali-hydrolyzed N, available P, and available potassium (K) were 23.9~49.7 g/kg, 0.8~1.7 g/kg, 0.3~0.6 g/kg, 70.3~183.8 mg/kg, 27.8~78.9 mg/kg, and 71.2~202.1 mg/kg, respectively. The effective spatial correlation distance of soil organic matter content was < 100 m, and the maximum effective spatial correlation distance of the total P content was close to 500 m. ③ The soybean and maize yields varied from 1 669 to 3 223 kg/hm² and from 8 177 to 10 871 kg/hm², respectively.[Conclusion] Gully-slope erosion aggravates the spatial heterogeneity of the soil moisture and nutrient contents in the watershed, and also reduces the productivity of cultivated land.