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 attracting attention to be an effective soil organic carbon (SOC) management to prevent land degradation, though quantitative information of its effect on carbon dioxide (CO2) flux and associated microbial responses is still scarce, especially in degraded tropical agroecosystems. We conducted a 27‐month field experiment with periodically measuring environmental factors, CO2 efflux rate, microbial biomass C (MBC), and SOC stock, and evaluated the impact of land management (control (C), biochar (B; 8.2 Mg C ha−1), farmyard manure (FYM) (M; 1.1 Mg C ha−1 yr−1), and a mixture of both (BM) on CO2 flux, microbial responses (MBC and qCO2 as microbial activity) and C budget, in tropical alkaline cropland of southern India. Based on the relationship between the CO2 efflux rate and environmental factors, cumulative CO2 flux was estimated at 2.4, 2.7, 4.0, and 3.7 Mg C ha−1 in the C, B, M, and BM treatments, respectively. Biochar application increased soil moisture though did not affect CO2 flux, causing a positive C budget (6.7 Mg C ha−1), because of the limited response of microbes to increased soil moisture due to the small amount of SOC. Biochar and FYM combined application did not increase CO2 flux compared with FYM alone, contributing to the largest SOC increment (8.9 Mg C ha−1) with a positive C budget (9.1 Mg C ha−1), due to little difference of microbial responses between the two treatments. Hence, biochar application combined with FYM could be an effective SOC management in the degraded cropland of southern India.

Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions

“…Although biochar has not yet been recognized as a method for generating C offsets, its potential should not be ignored because of its long residence time in soils, ranging from decades to thousands of years (Jiang et al., 2020; Kuzyakov et al., 2009; Major et al., 2010). Therefore, biochar application can be a valuable BMP to build SOC stocks (Chages et al., 2022; Seki et al., 2022) and reduce GHG emissions (Shakoor, Arif, et al., 2021; Stavi, 2012). However, to fully assess biochar as a potential C negative technology, its GHG emission mitigation benefits should be accounted for in addition to SOC sequestration (Terra Global Capital, 2010; The Climate Trust, 2010).…”

Global patterns and controls of soil greenhouse gas fluxes and crop yield under biochar application

“…Biochar application (directly or indirectly) affects the microbiota associated with soil C and N cycling by altering soil properties and ultimately regulating soil GHG fluxes (Jia et al, 2023;Schmidt et al, 2021;Seki et al, 2022). Studies have reported that the physical adsorption and encapsulation effects of biochar on soil organic matter can reduce CO 2 emissions (Kaiser & Guggenberger, 2000), whereas enhanced labile C input and belowground biomass caused by biochar can accelerate CO 2 emissions (Luo et al, 2011;Smith et al, 2010).…”