Abstract
Application of soil organic amendments changes soil characteristics. Hence, a study was carried out to assess the effect of different organic amendments on soil pH, electrical conductivity (EC), organic carbon retention and the moisture absorption of Reddish Brown Earth (RBE) soils. A pot experiment was conducted using three organic amendments: compost, acacia leaf litter, and rice biochar, along with an unamended control. The amendments were applied at three rates (5, 10, and 15 t ha⁻¹) and incubated at room temperature for eight weeks in a Completely Randomized Design (CRD) with four replicates. Soil moisture content in each pot was maintained at 75% of field capacity throughout the study period. Soil pH, EC, organic carbon and water drop penetration were measured at the beginning (initial), 2nd, 4th, and 8th weeks during incubation period. The results demonstrated that both the type and application rate of organic amendments influenced the selected soil properties. Rice biochar produced the greatest increase in soil pH, particularly at the higher application rates, whereas compost and acacia leaf litter had comparatively limited effects on soil pH. Soil EC generally increased during the initial four weeks, reflecting the release of soluble ions from the amendments, and subsequently stabilized. Soil organic carbon declined during incubation, with greater reductions observed in compost and acacia leaf litter amended treatments, indicating greater decomposition and mineralization of relatively labile carbon. In contrast, rice biochar treatments showed comparatively greater carbon retention, which can be attributed to the recalcitrant nature of biochar carbon. Water drop penetration time generally decreased with incubation, suggesting a reduction in water repellency over time and indicating that amendment induced changes in soil wettability were largely transient. Overall, rice biochar showed greater potential for improving soil pH and retaining organic carbon while maintaining relatively stable soil properties. Rice biochar therefore appears to be a promising organic amendment for improving selected properties and supporting the long-term sustainability of RBE soils.