The effect of climate and cultivation on soil organic C and N

Here, we investigate the response of soil organic carbon (SOC) and soil organic nitrogen (SON) to cultivation within two different climatic regimes by comparing large soil data sets from India and the Great Plains. Multiple regression models for both regions show that SOC and SON, as well as C/N ratios, increase with decreasing temperatures and increasing precipitation, trends also noted in soil data organized by Holdridge life zones. The calculated difference between natural and cultivated soils in India revealed that the greatest absolute SOC and SON losses occurred in regions of low temperatures and high precipitation, while the C/N ratio decreased during cultivation only with decreasing temperature. In India, the fractional loss of SOC relative to undisturbed soils increases with decreasing temperature whereas, in the Great Plains, it increases with increasing precipitation. Also, the fractional loss of SOC increased in India with increasing amounts of original C, whereas no relationship between fractional loss and original C was noted for the Great Plains. The differential response of each region to cultivation is hypothesized to be due to differences in both climate and management practices (crop cycles, fertilization). These findings suggest that estimates of soil C loss due to cultivation should be based on an array of factors, and that it is unlikely that a constant relative C loss occurs in any region.