Impact of long-term agricultural management practices on soil organic carbon and soil fertility of paddy fields in Northeastern Thailand

Soil organic carbon (SOC) is an essential indicator of soil quality and soil fertility. Agricultural management practices can influence SOC and soil fertility. The objective of the present study was to evaluate the impact of agricultural management practices on SOC and soil fertility of paddy fields in the northeastern region of Thailand over a 10-year period. Initial data on SOC and soil fertility parameters in the top 20 cm under indigenous management (compost amendment) in Maha Sarakham Province were collected in 2007 by the Khon Kaen Rice Research Center. The data on SOC and soil fertility parameters were collected again in 2016 after 10 years from 130 farmers' fields located in close proximity to the sites from where the initial data were collected in 2007. The impacts of the conversion of indigenous agricultural management practice into government-promoted management practices on SOC and soil fertility were evaluated. The practices were continuous compost amendment (CA) during 10 years as the control, the shift from CA to biofertilizer (BF), to green manuring (GM), and to rice straw (RS) incorporation. Measurements made at the end of the 10-year period showed that the adoption of government-promoted agricultural management practices generally increased SOC and soil fertility. The incorporation of RS resulted in the largest change in total nitrogen (156% increase), SOC concentration (152% increase), and SOC density content (149% increase) over the 10-year period. The same management practice (RS) had the greatest SOC sequestration rate (1.43 Mg ha⁻¹ yr⁻¹). Results demonstrate the value of RS incorporation into agricultural soils over time for improving SOC and soil fertility. Soil incorporation of compost (CA) could be another option for its potential to improve soil fertility.