Management of a saline–sodic Chromic Luvisol using different biochars

Context The removal of excess salts from saline–sodic soils is often limited by poor drainage resulting from deterioration of soil physical structure. Biochar has been increasingly recommended as a soil conditioner in salt-affected areas, particularly for its potential to improve soil structural attributes. Aims In this study, we: (1) evaluated the effects of biochar on soil water retention, infiltration, and water flux; (2) assessed the influence of biochar on the time required for soil salt leaching; and (3) determined the efficiency of each treatment in reducing soil salinity indicators. Methods A completely randomised design was used with three biochar treatments (sugarcane bagasse, green coconut husk, and biosolids) and four replicates. Soil columns with and without biochar were saturated and leached. Soil samples collected before and after leaching were analysed for electrical conductivity (EC), pH, salt concentration, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR). Key results All biochars reduced bulk density and increased total porosity and water holding capacity. The sugarcane bagasse biochar (SCB) stood out, increasing water retention by 83% and reducing water flux by 69%, thereby lengthening leaching time. The large number of micropores in biochar-treated soils increased water retention. However, it did not prevent salt removal, as confirmed by reductions in EC, SAR, and ESP, possibly due to the presence of stable microaggregates in the soil. Conclusions Biochar improved the physical and chemical properties of salinity-affected soil and proved to be a useful tool to mitigate salinity in degraded soils.