Quantitative assessment of soil productivity and predicted impacts of water erosion in the black soil region of northeastern China.

As Northeastern China is the country's most significant grain production base, soil productivity in this region has consistently attracted attention. National food security is threatened by an ongoing drain of soil nutrients and decline in soil productivity. Black soil is the key natural resource in this region of China, which is thus known as the "black soil region". It is necessary to study the impact of soil erosion on black soil and its productivity to protect this important resource and ensure its sustainable productivity. Through a field investigation and laboratory analysis, the physicochemical properties in 112 soil profiles from a typical black soil sub-region were measured to assess soil productivity using a soil productivity index (PI) model. The soil PI in the study area was relatively high and showed an increasing trend from southwest to northeast. PI values and their spatial distribution were affected by soil organic matter, soil clay content, soil thickness, slope and geomorphological position. Soil productivity and cluster analysis revealed that the southern and northwestern areas of the typical black soil sub-region under study were subject to the greatest risk. To maintain the region's soil productivity, it is vital to prevent the black soil layer, especially the topsoil, from being destroyed.