Soil carbon sequestration on a maize-mung bean field with rice straw mulch, no-tillage, and chemical fertilizer application in Thailand from 2011 to 2015

Increasing soil organic carbon (SOC) content in agricultural fields is one of the strategies for mitigating climate change through carbon (C) sequestration, and could improve soil fertility. However, only a few field experimental studies have been conducted to determine the SOC stock changes in tropical areas. A field experiment was conducted under various soil management approaches in a maize-mung bean double cropping system in Lopburi, Thailand, from 2011 to 2015. The following treatment combinations were applied: 1) rice straw mulch (RS) and no organic matter application (NoOM); 2) tillage (Till) and no-tillage (NoTill); and 3) chemical fertilizer application (CF) and no chemical fertilizer application (NoCF). Soil samples were obtained at 0–15 cm depths before plowing and after maize harvest. SOC stock change was higher in RS than in NoOM. These results were attributable to the high organic C input with rice straw in the soil, although the conversion rate of total organic C input to SOC stock change with rice straw mulch did not increase. SOC stock change in NoTill did not differ from that in Till, which might be caused by no increase in the conversion rate of total organic C to SOC stock change in NoTill in this field. In addition, SOC stock change in CF was not significantly different from the stock change in NoCF. Although a large amount of organic C was supplied to the CF soil, the conversion rate of organic C to SOC decreased. The results of this study could contribute to clarifying SOC stock changes in upland crop fields in tropical monsoon conditions.