Carbon mineralization and carbon dioxide emission from organic matter added soil under different temperature regimes

Information on carbon dioxide (CO2) emission from different organic sources and their temperature sensitivity to decomposition is scarce in Bangladesh. Therefore, this study quantified the rates of CO2 emission and carbon (C) degradation constants from different organic material mixed soils at variable temperatures in two laboratory experiments.

The first experiment was conducted at room temperature for 26 weeks to study CO2 emission and C mineralization using vermicompost, chicken manure, cow dung, rice straw, and rice husk biochar. Weekly CO2 emission was measured by alkali absorption followed by acid titration. The second experiment comprised two factors, viz. four organic materials (vermicompost, chicken manure, cow dung, and rice straw) and six temperature regimes (25, 30, 35, 40, 45, and 50 °C). Organic materials at 2.5 g C kg−1 soil were mixed in both experiments.

CO2 emission reached the peak at 5th weeks of incubation and then decreased with irregular fashion until 21st week. The C emission loss followed in the order of chicken manure > rice straw > vermicompost > cow dung > rice husk biochar, and C degradation constants indicated the slower decomposition of rice husk biochar compared to cow dung, vermicompost, chicken manure, and rice straw. Temperature positively enhanced the mineralization of organic materials in the order of 50 > 45 > 40 > 35 > 30 > 25 °C, which contributed to higher availability of soil phosphorus.

High temperature increased mineralization of tested organic materials. Because of slower decomposition rice husk biochar, cow dung and vermicompost application can be considered as climate-smart soil management practices that might help in reducing CO2 emission from soil.