|LI, YONG - CHINESE ACAD. AGRIC. SCI.
|ZHANG, Q - CHINESE ACAD. AGRIC. SCI.
|BAI, L - CHINESE ACAD. AGRIC. SCI.
|LI, L - CHINESE ACAD. AGRIC. SCI.
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2005
Publication Date: 1/23/2006
Citation: Li, Y., Zhang, Q.W., Reicosky, D.C., Bai, L.Y., Lindstrom, M.J., Li, L. 2006. Using 137cs and 210pbex for quantifying soil organic carbon redistribution affected by intensive tillage on steep slopes. Soil & Tillage Research. 86:176-184.
Interpretive Summary: Spatial and temporal variation in soil organic carbon (SOC) is of great importance because of global environmental concerns. Accelerated soil erosion by intensive tillage on steep slopes is a major threat for sustainable agricultural production as well as the environment in western China. Depletion of SOC and erosion are interrelated since a decrease in organic carbon increases susceptibility of soil to erosion. Tillage-intensive erosion adversely affects the SOC profile pattern. However, few direct measurements have been conducted to investigate the dynamic process of SOC as affected by intensive tillage at the field level. This work evaluated how radionuclides could be used directly for assessing SOC redistribution as affected by intensive tillage. The profile variations of the radionuclides were measured along the slope before and after 50 plowing operations over a five-day period. The implicit assumption was that 50 tillage operations could be equivalent to 50 years of intensive tillage. The results showed that the radionuclides were significantly correlated with SOC content at all slope locations. The results suggest that radionuclides could be used directly for quantifying dynamic SOC redistribution as affected by tillage erosion. These results are significant to farmers and policy makers in that intensive tillage results in substantial soil redistribution and losses of soil carbon. This information will assist scientists and engineers in developing improved tillage methods to minimize carbon loss and to improve soil carbon management. Farmers can develop and utilize new management techniques for enhancing soil carbon by changing tillage intensity to minimize changing soil properties across a sloping landscape.
Technical Abstract: Spatial and temporal variation in soil organic carbon (SOC) is of great importance because of global environmental concerns. Tillage-intensive erosion adversely affects the SOC profile pattern. However, few direct measurements have been conducted to investigate the dynamic process of SOC as affected by intensive tillage at the field level. Our objective was to test the potential of 137Cs and 210Pbex for directly assessing SOC content redistribution on sloping land as affected by tillage. Fifty plowing operations were conducted over a 5-day period using a donkey-drawn moldboard plow on the steep backslope of the Chinese Loess Plateau. Profile variations of SOC content, 137Cs and 210Pb were measured at upper, mid and lower portion of the slope after 50 plowing operations. The 137Cs concentration was uniformly mixed in the upper 0-30 cm of soil whereas 210Pbex showed a linear decrease at upper and mid portion, and an exponential decrease with soil depth on the lower portion of the control slope. SOC contents of 0-30 cm layers were much higher than the soil layers below 30 cm on the control slope, and showed a similar decrease pattern to 210Pbex on the mid and lower portion of the control slope. Fifty plowing operations resulted in a decrease of SOC content (g/kg) by 38% and by 47% for the soil layers of 0-45 cm at upper portion and mid portion respectively. However, SOC content in the soil layers of 0-100 cm at the lower position increased by 18% after 50 plowing operations. Weighed mean values of 137Cs concentrations decreased from 1.48 Bq/kg to 0.29 Bq/kg at upper position, from 2.53 Bq.kg to 0.33 Bq/kg at mid position, and increased from 1.48 Bq/kg to 2.81 Bq/kg at lower position. Weighed mean values of 210Pbex concentrations decreased from 27.71 Bq/kg to 6.15 Bq/kg at upper position, from 35.46 Bq/kg to 1.57 Bq/kg at mid position, and from 25.53 Bq/kg to 19.40 Bq/kg at lower position. Profile concentrations of 137Cs and 210Pbex were significantly correlated with SOC content with R2 of 0.81 and 0.86 for the control slope, 0.91 and 0.86 for the experimental slope. The results suggested that fallout 137Cs and 210Pbex could be used directly for quantifying dynamic SOC redistribution as affected by tillage erosion.