A laboratory study of soil carbon dioxide emissions in a vertisol and an alfisol due to incorporating corn residues and simulating tillage

Soil organic carbon (SOC) is reduced in annual horticultural systems due to accelerated CO₂ emission from the frequent and intensive tillage required to prepare beds and manage pests. Conversely, crop residue incorporation has the potential to counteract the loss of SOC. We hypothesised that vegetable systems could be made more resistant to SOC loss by including a high-residue grain crop such as sweet corn ('Zea mays var. rugosa' L.) in the rotation. We incubated two Australian soils, an Alfisol and a Vertisol, in plant-free sealed chambers with a ± corn residue treatment and soils either sieved/disturbed or not to simulate tillage. Carbon dioxide-carbon (CO₂-C) flux was measured using air samples collected at 24 hours before , and 1, 120, 240 and 360 h after simulated tillage. Residue incorporation had a larger effect on CO₂-C flux than tillage for both soil types. The tillage x residue interaction accounted for 40% of CO₂-C flux; the effect of residue was highly significant but tillage alone was not significant. The effect of simulated tillage on residue incorporated soil was most stimulatory and the treatment without residue or without simulated tillage was the least stimulatory to CO₂ emission. Residue effects were 22% higher in the Alfisol compared with the Vertisol whilst tillage effects were 26% higher in the Vertisol than in the Alfisol. The Vertisol was more resistant to CO₂ losses than the Alfisol after disturbance as the gas fluxes stabilised more rapidly following soil disturbance. In summary, residue incorporation and tillage interactions were a function of soil type, and fine-textured soils such as the Vertisol may be less prone to CO₂ losses than lighter-textured soils.