Soil carbon dioxide emissions in eggplants based on cover crop residue management

In this study, cover crop residue management as a strategy to identify agricultural practices suitable for increasing soil carbon (C) storage and contributing to the mitigation of CO2 in a cover crop–eggplant sequence was evaluated. The treatments applied were: (a) four winter managements [three cover crops (hairy vetch, oat and oilseed rape) and a bare soil]; and (b) three residue managements [residues incorporated into the soil at a depth of 0.3 m as deep tillage (DT), residues incorporated into the soil at a depth of 0.1 m as shallow tillage (ST), and residues left on soil surface (RS)]. Eggplant biomass and C content, soil CO2 flux, soil temperature and moisture were measured. Hairy vetch under DT showed the highest emission rate during the eggplant cultivation. At eggplant harvest time, CO2–C emissions were high in hairy vetch, intermediate in oat and oilseed rape, and low in bare soil (5.4, 4.2 and 3.3 Mg ha−1, respectively). Among residue managements, CO2–C emissions were higher in ST and DT than in RS (4.5 vs. 3.7 Mg ha−1, respectively). Despite contributing to the highest soil CO2 flux, the decomposition of hairy vetch residues supports the production of eggplant crop, as it is shown by the carbon input/output ratio, especially under RS conditions representing a temporary sink of CO2–C. As a system, hairy vetch RS is the most productively sustainable because it is simultaneously yielding the high eggplant crop biomass and retaining C residues in the soil.