Assessment of soil organic carbon stocks : a comparison between open burning paddy field and organic paddy field

Abstract

Most farmers in Asia including Thailand select burning methods because it is a conventional way to remove stubbles and prepare for the next crop cycle. Air pollution arising from open burning paddy field is a major concern for public health. However, a controversial issue of its impacts on the amount of soil organic carbon (SOC) still remains. This study aimed to i) compare SOC stock content between open burning paddy field and organic paddy field. ii) determine the relationship between physical-chemical properties of soil and organic carbon stock in soil. iii) spatially assess the soil organic carbon stock distribution between open burning paddy field and organic paddy field. Two sets of soil samples were collected from two paddy fields based on minimum consecutive five-year periods of burning versus non-burning practices. Twenty soil samples were collected from each paddy field at a 30-cm depth, which made up a total of 40 soil samples. Organic carbon was analyzed by the Walkley and Black method. The average of SOC content in burning paddy field (2.17±0.38%) was observed significantly higher than organic paddy field (1.33±0.15%) (p-value < 0.05). The estimated average SOC stocks per unit area were 9.96±0.07 kg C m⁻² in the open burning paddy field, and 6.42±0.04 kg C m⁻² in the organic paddy field. Spatial distribution of SOC and C/N allowed farmers to have a rough idea of which location should be prioritized in terms of soil improvement. This way is beneficial to farmers both for economic and environmental aspects. On the basis of results obtained, despite the positive effects found in burning paddy soil, a better management approach should be introduced to counterbalance the negative impacts on other environmental aspects and to create a sustainable land management system.