Impact of biochar and manure application on in-situ carbon dioxide flux, microbial activity, and carbon budget in degraded cropland soil of southern India

Abstract

Biochar application is currently considered to be an effective soil\norganic carbon (SOC) management to prevent land degradation by enhancing\nSOC stock. However, quantitative information on the impact of biochar\napplication on carbon dioxide (CO2) flux and associated microbial\nresponses is still scarce, especially in degraded tropical\nagroecosystems. Here, we evaluated the impact of land management\n(control (C), biochar (B; 8.2 Mg C ha−1), farmyard manure (FYM) (M; 1.1\nMg C ha−1 yr−1), and a mixture of both (BM; 8.2 Mg biochar-C ha−1 and\n1.1 Mg FYM-C ha−1 yr−1)) on CO2 flux, SOC stock, microbial biomass C\n(MBC), and metabolic quotient (qCO2) in degraded tropical alkaline\ncropland of southern India, based on a 27-month field experiment.\nCumulative CO2 flux over the experiment was 2.4, 2.7, 4.0, and 3.7 Mg C\nha−1 in the C, B, M, and BM treatments, respectively. Biochar\napplication increased soil moisture and SOC stock, though did not affect\nCO2 flux, MBC, and qCO2, indicating the limited response of microbes to\nincreased soil moisture because of small amount of SOC. Combined\napplication of biochar and FYM did not increase CO2 flux compared with\nFYM alone, due to little difference of microbial responses between the M\nand BM treatments. Additionally, SOC increment (8.9 Mg C ha−1) and the\nrate of C-input retention in soil (0.78) was most significant in the BM\ntreatment. Hence, the combined application of biochar and FYM could be\nsustainable land management by efficient increase of SOC stock in the\ntropical degraded cropland.