Base cation‐enhancing role of corn straw biochar in an acidic soil

Abstract Biochar affects base cation retention and leaching when it is used to enhance the base cation status of acidic soil. However, the details of its contribution are not yet clear. In this study, six loadings of corn straw biochar (0%, 2%, 4%, 6%, 8% and 10%, w/w) were applied to an acidic Ferralsol and incubated for 1 year. The results showed that the content of water‐soluble and exchangeable base cations of K, Na, Ca and Mg increased with increasing levels of biochar in amended soil. The percentage of water‐soluble Na, Ca and Mg of amended soil significantly decreased, while the percentage of exchangeable K, Ca and Mg increased significantly after the addition of biochar. For K and Na, biochar affected their leaching concentrations both as a source and by increasing the pH. For Ca, biochar reduced Ca leaching when the biochar loading was ≥4%, and the contribution increased from 30.8% to 100% at 4%–10% loading. For Mg, biochar reduced Mg leaching at biochar loadings 2%–10%, the reduction increasing from 22.0% to 70.5%. The results show that corn straw biochar can increase the content of the soil nutrient base cations K, Ca and Mg by increasing their exchangeable forms and enhance soil retention by decreasing their leaching. Thus, corn straw biochar can be used to effectively improve acidic soil base cation fertility.