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Redistribution and loss of soil organic carbon by overland flow under various soil management practices on the Chinese Loess Plateau

Jin, K., Cornelis, W.M., Schiette, W., Lu, J.J., Buysse, T., Baert, G., Wu, H.J., Yao, Y., Cai, D.X., Jin, J.Y., De Neve, S., Hartmann, R., Gabriels, D.
Soil use and management 2008 v.24 no.2 pp. 181-191
Triticum aestivum, carbon, conventional tillage, farmers, labor, loess soils, mulches, no-tillage, overland flow, rainfall simulation, reduced tillage, runoff, sediments, soil erosion, soil organic carbon, subsoiling, topsoil, winter wheat, China
Field rainfall simulations with intensities of 85 and 170 mm/h were conducted in 2002 and 2005 on a 15-m long slope on a loess soil in Luoyang, Henan Province, P. R. China to study the effects of different soil management practices on the redistribution and loss of soil organic carbon (SOC) by runoff and soil erosion. Field plots under winter wheat (Triticum aestivum L.) were set up in 2001 and included the following soil management practices: subsoiling with mulch (SSM), no-till with mulch (NTM), reduced tillage (RT) and conventional tillage control (CT). The results showed that SOC for topsoil (0-20 cm) increased in the NTM and SSM plots when compared with results from 2002 and 2005. For all treatments, SOC in the lower part of the plots was higher in 2005 than in 2002. The values from the upper parts of the plots were only lower in 2005 compared with the overall values for 2002 for RT and CT. The enrichment ratio of organic carbon (ERoc) in runoff sediment varied from 1.01 to 2.24 with a mean of 1.25. During the simulated rainfall events, ERoc was initially high and then reduced after a short period to reach a steady value at the end of the event, always remaining >=1. The change in SOC loss rate was more dependent on the sediment loss rate than on the changes in SOC concentration in the sediment. The best results in terms of a reduction in soil and SOC loss were obtained with NTM: no runoff and hence no soil and SOC loss were observed. SOC losses observed for SSM were on average only 4% of those observed for CT. RT resulted in 71% SOC loss compared with CT although the runoff reduction was not pronounced. For farmers, SSM and NTM are the best alternatives in terms of SOC conservation. NTM has the additional advantage that it requires less labour and is more beneficial from economic and environmental perspectives.