Impact of biochars on CO2 emissions and physic-chemical properties in Malaysian Tropical soils: Factor analysis and weighted contribution

Abstract

Global climate change is the most serious challenge that modern society faces. Soil-biochar carbon sequestration is a promising natural solution for capturing carbon. This study monitored the CO₂ emissions of five biochar incubated Malaysian Tropical soils (MT-Soil). The recalcitrance index of palm kernel shell biochar (PKS) was higher than that of wood chip biochar (WCB), bamboo biochar (BB), coconut shell biochar (CHB) and rice husk biochar (RHB), and was different from the observed CO₂ emission characteristics (WCB > CHB > RHB > BB > PKS). Thus, the carbon sequestration potential of biochar could not be evaluated solely by the recalcitrance index. This CO₂ emission is linked not only to the total organic carbon (TOC) and total carbon (TC) of the biochar but also associated with mobile matter (MM), water holding capacity (WHC), available phosphorus (AP), exchangeable potassium (AK), and nitrogen content. The multiple linear regression analysis (MLRA) shows that the weights of these factors on CO₂ emissions are as follows: TC > pH > MM > WHC > AP > AK. The results show that in addition to biochar stability, pore structure and available phosphorus release also affect carbon dynamics through indirect effects on microbial activity. This means that to minimize CO₂ emissions during application of biochar, it is necessary to use soil that is rich in phosphorus and biochar that has undeveloped pore structure and high stable carbon. Finally, this study provides valuable theoretical underpinnings biochar application in MT-Soil.