Assessment of Effectiveness of Soil Conservation Measures in Reducing Soil Erosion and Improving Soil Quality in China Using Fallout Radionuclide Techniques

China is one of the countries perhaps suffering from the most serious soil erosion in the world. Soil erosion and associated sediment production has become a major environmental problem. A wide variety of soil conservation measures, such as re-vegetation, terracing, and conservation agriculture practices, exist in China but they require an effective evaluation to establish specific regional recommendations of integrated soil and water management practices. Using fallout radionuclide techniques, IAEA-funded studies for the assessment of soil erosion and soil conservation have been undertaken in three sites from SW China through to NE China (Baiquan County of North East China, Fengning County of Northern China and Xichang city of South Western China). In the Baiquan County of North East China, the study showed that soil erosion, measured by the fallout 137Cs tracer, decreased by 16% due to terracing and 54% due to contour cultivation as compared to downslope cultivation practice. In the Fengning County of Northern China, the authors assessed the short term impact of conservation agriculture practices on soil erosion and soil quality parameters. The data from 7Be measurements indicated that all sites with conservation practices contained higher 7Be inventories than the conventional tillage treatment site. Four years of no tillage with high amount of crop residues reduced soil erosion by 44% and no tillage with low residue amounts reduced soil erosion rates by 33% as compared with conventional tillage practices in the Fengning site. In Xichang city of South Western China, the results showed that shrubs and grasses increased soil organic carbon (SOC) stocks more than trees as compared with bare land. Re-vegetation, especially by using shrubs and grasses increased SOC, available nitrogen (AN) and available phosphorus (AP) indicating a significant positive role of vegetation restoration in improving soil quality. Re-vegetation increased SOC stocks under trees, shrubs and grasses by 61%, 1.53 and 1.86 fold, respectively. The AN under shrubs and grasses increased by 9.5% and 10.5%, respectively, but the mean value of AN was less than the bare land on the entire eroded hillslope. Trees increased AP by 2.9 times and AP in the shrub-land and grassland increased 4.5 and 5.7 fold in SW China. (author)