Responses of soil respiration and organic carbon to organic soil amendments in upland paddy

Carbon dioxide (CO2) is a significant greenhouse gas (GHG) accounting for 60% of the total greenhouse effect. Soil respiration is a measure of the CO2 released from soil. Rice was the largest contributing plant commodity of total emission by 12%. In the event of growing threats of global warming due to GHG emissions, reducing CO2 emission by sequestering C in the soil is of supreme concernment. Improved management practices can rebuild C stocks in agricultural soils and help mitigate CO2 emissions. A field study to assess how organic soil amendments influence soil respiration, C-organic content, and soil properties was conducted in upland paddy field. Treatments were: chemical fertilizer (F1), combination of chemical fertilizer and cow dung manure (F2), chemical fertilizer and vermicompost (F3), chemical fertilizer and liquid vermicompost powder (F4), cow dung manure+biochar (F5), vermicompost+biochar (F6) and liquid vermicompost powder+biochar (F7). All treatments tested almost had the same pattern of respiration rates starting before the application of the organic soil amendment until three months after planting. The highest respiration rate was found at 1 month after planting. Soil amendment (F4 and F7) had the lowest soil respiration rates in some measurements. The highest organic C content at three months after planting was found in the F6 and F3 treatments. The most influential factor on the respiration rate are soil moisture content and soil temperature. The results demonstrate the viability of vermicompost either in combination with chemical fertilizers or alone for soil amendment to maintain organic soil carbon for short period of time (similar to 3 months).