Testing the Rothamsted Carbon Model against data from long‐term experiments on upland soils in Thailand

Abstract

We tested the Rothamsted Carbon Model (RothC) against three long-term (27-28 years) experimental sites on Thai upland soils in order to see how this widely used 'temperate' soil carbon turnover model performed in a typical farming region in the tropics. We were able to verify -over a much longer period than had been examined in previous studies -that RothC performs well in a tropical region in plots used for continuous cropping experiments of maize and cassava without organic matter application. However, the model overestimated soil organic carbon (SOC) in some plots to which large amounts of organic matter (rice straw or cassava stalks) were applied. This overestimate could not be attributed to errors in estimating either the amount of C input to the soil or the ratio of decomposable plant materials to resistant plant materials entering the soil. Among many factors affecting SOC dynamics (e.g. weather conditions, soil characteristics, etc.), which are different in tropical regions from temperate regions, we conclude that the activity of soil fauna might be a major factor which makes the performance of RothC worse where much organic matter was applied. We suggest that care should be taken when applying RothC to tropical soils with large amounts of added organic matter.

Carbon balance in maize fields under cattle manure application and no-tillage cultivation in Northeast Thailand

“…The rapid turnover may result in little or no increase in org-C in the soil in the CV treatment, even though the carbon input was 3.6 Mg C ha -1 year -1 by residue returning and weed incorporation. Comparing this to other studies, longterm experiments in Thailand (Shirato et al 2005) found that: (1) SOC in the 0-15 cm soil depth of a maize field with NPK application and residue incorporation (carbon input: 2.5 Mg C ha -1 year -1 ) in Phraphuttabat (11.4% clay content) increased from 13.4 Mg C ha -1 to 15-18 Mg C ha -1 over 27 years, (2) SOC in the 0-20 cm soil depth of a cassava field with NPK application and stalk incorporation (carbon input: 1.9 Mg C ha -1 year -1 ) decreased from 16.1 Mg C ha -1 to 14-16 Mg C ha -1 over 28 years in Nakhon Ratchasima (11.4% clay content), (3) SOC in the 0-20 cm soil depth of a cassava field decreased with NPK application and stalk incorporation (carbon input: 2.7 Mg C ha -1 year -1 ) from 13.8 Mg C ha -1 to 10-12 Mg C ha -1 over 27 years in Khon Kaen (6.9% clay content). These results show that, under conventional cultivation, the carbon stock in low clay content soils in tropical areas is 10-18 Mg C ha -1…”

Evaluating the Sustainability of a Small-Scale Low-Input Organic Vegetable Supply System in the United Kingdom

“…Organic farming can increase 1.85 ton C per hectare per year compared with the conventional farming system. This value also agrees with the data that Shirato et al [12] obtained from paddy fields in Thailand. The rate of increase in SOC stock resulting from changes in land-use and adoption of recommended farming practices, follows a sigmoid curve that attains the maximum 5-20 years after adoption of recommended farming practices [8].…”

Carbon stock assessment and soil carbon management in agricultural land‐uses in Thailand

“…Several Asian developing countries have experienced a rapid forest decline in the recent past including Thailand where the remaining forest area is 25 per cent of the total area and the agriculture is a dominant land-use covering 41 per cent of the area (FAO, 2005). C sequestration studies of agricultural systems, therefore, hold particular importance in Thailand but such studies are largely limited, except few plot level studies (Matsumoto et al, 2002;Shirato et al, 2005). Nonetheless, it is essential to assess the C pool of present agricultural land-uses at sufficiently large scales where there is marked effect of soil, climate and management conditions.…”