Temperature sensitivity and carbon release in an acidic soil amended with lime and mulch

Abstract

Lime is commonly applied on agricultural lands for ameliorating soil acidity. However, lime dissolution and its concomitant contribution to carbon dioxide (CO2) fluxes with the addition of organic residues at varying temperatures in acidic soils are not well known. We conducted laboratory incubation experiments for 96days (20+/−1°C and 40+/−1°C) to quantify the priming effects of lime (0.46 and 0.92% w/w) and mulch (0.5% w/w) additions on carbon (C) release in a Chromic Luvisol. The C released from lime (δ13C of −8.67‰), mulch (−13.02‰) and soil (−25.2‰) was quantified using their distinct δ13C values. Total lime derived C in soils without mulch constituted approximately 32% and 17% of the total C fluxes at 20°C and 40°C, respectively. During the 96-day incubation period, in the absence of mulch addition between 64% and 100% of the applied lime C was released as CO2 at both incubation temperatures. Furthermore, lime derived, mulch derived and soil derived C increased by 59, 48 and 284% respectively, when the incubation temperature was increased from 20°C to 40°C. These results suggest that mineralization of native soil C was more sensitive to temperature than the C released by lime dissolution and mulch mineralization. Temperature sensitivity of soil derived C was lower in treatments with mulch and lime addition compared to soil without C amendments. We obtained a Q10 value of 2.41±0.06 for the C released by the lime dissolution in the acidic soil. These findings are important for modelling the contribution of different C sources to atmospheric CO2 concentrations in soils, such as the acidic limed and mulched soils.