Priming Effect of Pigeon Pea and Wood Biochar on Carbon Mineralization of Native Soil Organic Carbon and Applied Municipal Solid Waste Compost

Abstract

A laboratory incubation experiment was conducted for 36 days to study the effect of pigeon pea biochar (PPB) and wood biochar (WB) on carbon mineralization of native soil organic carbon (SOC) and municipal solid waste compost (MSWC) applied to soil. The MSWC addition enhanced soil respiration by 2-fold (231 mg C kg^-1 soil) over the control (118 mg C kg^-1 soil). The PPB addition significantly (P < 0.05) increased cumulative loss of carbon as CO_2, whereas WB significantly decreased the cumulative loss of C over control. Addition of PPB at 5% and 10% levels increased SOC mineralization (positive priming) +22.9% and +31.2%, respectively; whereas reduction in SOC mineralization (negative priming) was noticed in WB (5% and 10%) treated soils by -3.1% and -21.7%, respectively. Similarly, WB induced strong negative priming effects (-21.9% and -29.5%), while PPB caused a weak positive priming effect (+3.0% and +11.6%) at 5% and 10% levels on mineralization of added labile carbon substrate (MSWC), respectively. Results indicate the hardwood (Prosopis juliflora) biochar exhibits refractory properties that inhibit mineralization of both native SOC and applied organic compost (MSWC), and thereby it can be used as an amendment to stabilize native and applied organic matter in soil, which may significantly contribute to soil carbon sequestration.