Effectiveness of Soil Conservation Measures in Reducing Soil Erosion and Improving Soil Quality in China Assessed by Using Fallout Radionuclides

Abstract

China experiences the most severe water and wind erosion problems in the world. Using fallout radionuclide techniques (FRN), our objectives were to assess the extent of soil erosion and to quantify the beneficial effects of soil conservation measures at four sites extending from South West (SW) to North East (NE) China. At the Xichang site of SW-China, the combined use of FRN 137Cs and 210Pbex measurements demonstrated that the effectiveness of vegetation species in reducing soil erosion decreased in the following order: shrubs > trees with litter layer > grasses > trees without litter layer. At the Yan’an site of Loess Plateau, sediment production estimated by 137Cs declined by 49% due to terracing and by 80% due to vegetated (with grass and forest) compared to the cultivated hillslopes. Vegetated hillslope with grasses and forest increased soil organic matter (SOM) by 255%, soil available N (AN) by 198%, and soil available P (AP) by 18% while terracing increased SOM by 121%, soil AN by 103%, and soil AP by 162% compared with the entire cultivated hillslope. Both terracing and vegetating hillslopes were found to enhance soil porosity as shown by a decrease in soil bulk density (1.6 and 6.4%, respectively). At the Baiquan site in NE-China, soil loss as measured by 137Cs tracer, decreased by 14% due to terracing and by 34% due to contoured tillage. At the Fengning site, data from 7Be measurements indicated that 4 years of no tillage with high crop residues (50–56 cm depth) reduced soil erosion by 44% and no tillage with low residues (25 cm depth) reduced soil erosion rates by 33% when compared with conventional tillage practices.