International Journal of Plant & Soil Science

Biochar–manure co-application has the potential to modify soil carbon turnover and nutrient release, but the magnitude and direction of these changes depend on amendment type, ratio, and incubation time. An experiment was conducted to evaluate carbon mineralisation following the incorporation of wood biochar with farmyard manure (FYM), vermicompost (VC), and poultry manure (PM) in an Inceptisol. A total of 11 treatments were evaluated in a completely randomised design with three replications, with observations recorded at 0, 15, 30, 60, 90, and 120 days of incubation. The treatments included an untreated soil control, wood biochar alone, the three organic manures alone, and manure–biochar combinations at 1:1 and 1:2 ratios. CO2-C evolution was determined using standard soil analytical procedures. CO2-C evolution increased from the beginning of incubation to approximately 60 days and subsequently declined or became comparatively stable. Total CO2-C mineralisation was studied using the discarding method, and the maximum value (209.76 mg CO2-C 100 g⁻¹ soil) was observed following incubation of soil + vermicompost @ 8 t/ha + biochar @ 16 t/ha (1:2 ratio) over 120 days. Overall, incubation of wood biochar with vermicompost, poultry manure, or FYM at a 1:2 proportion was found suitable for carbon mineralisation during 60–90 days of incubation, compared with 103.74 mg CO2-C 100 g⁻¹ soil in the control. The soil + vermicompost @ 8 t/ha + wood biochar @ 16 t/ha (1:2 ratio) treatment also produced the highest CO2-C evolution at 15, 30, 90, and 120 days, whereas soil + FYM + wood biochar at 1:2 produced the highest value at 60 days (47.08 mg CO2-C 100 g⁻¹ soil). Thus, manure type and biochar proportion may be selected according to the intended soil-management objective.