The effects of two different biochars on the characteristics of saline acid sulfate soil

Biochar can be a potential bio-amendment for remediating saline acid sulfate soil and its effects may be dependent on its properties. The current study sought to assess the effects of two different biochars on the properties and quality of saline acid sulfate soil. The experiment was implemented by mixing soil with biochars made from longan branches (LBs) and coconut coir biochar (CB) at five rates of 0%, 0.7%, 1.5%, 3%, and 6% (w/w). After 100 days of incubation in a greenhouse, soil samples from experimental pots were taken and analyzed for 11 parameters. The results showed that biochar significantly enhanced pH while declining the concentration of SO42- and exchangeable Al and Fe. Mechanisms responsible for these effects could be due to the high alkaline properties of the added biochar. Coconut biochar raised the concentration of exchangeable Na, K, and Mg more strongly than LB. Consequently, coconut biochar greatly increased the soil electrical conductivity (EC) value, while longan biochar exhibited no significant effect. The soil quality index of the 6%-LB-added soil increased by 64% and that of the 6%-CB-added soil increased by 45%, compared with the zero-biochar-added soil. Lower soil quality induced by CB compared with LB may be attributed to CB's initial properties, which had higher EC, Cl-, and Na levels than LB. The findings suggested that biochar addition can improve overall quality but alter individual properties of saline acid sulfate soil in different directions, depending on the properties of the added biochar, which requires more studies to clarify its ameliorative effects.