Net CO2 and CH4 Gas Fluxes and Concentrations at Conventional and No Tillage Upland Fields.

The quantity of carbon stored in soil is large, so small changes in the stored percentage may have a big influence on global warming. Organic matter decomposition rates fluctuate with land usage, soil temperature and soil water content. Although no-tillage (NT) with a living mulch is thought to reduce organic matter decomposition rates, there is little information about surface CO₂ gas fluxes in NT fields.

The aim of this study is to measure soil surface CO₂ and CH₄ gas fluxes and their concentrations in soil at conventional tillage (CT) and NT field plots. Field plots are 5 x 5 m² with four replications. The soil is a typical Andosol with a sandy loam texture at the surface, which gradually changes to clay with depth. Tomato (Solanum lycopersicum L.) was grown during our measurement period (June-September, 2016).

Net CO₂ gas fluxes tended to be larger in CT (without a living mulch), than NT (with a living mulch) because of mulch photosynthesis. Soil was a sink for CH₄. Soil CO₂ gas concentrations increased and CH₄ concentrations decreased with depth in both treatments. Both gases at 2.5 cm depth were influenced by the gas exchange with the atmosphere. The increase of CO₂ concentration from 20 to 40 cm was big, especially in NT. This might be related with the existence of the hard pan around 20 cm in NT and 40 cm in CT. Soil pF was different at 40 cm from other depth.

In conclusion, CO₂ and CH₄ concentrations with depth were opposite in upland fields. Gas movement is influenced by soil physical properties. Further research is needed to develop soil management systems for mitigating green house gas emissions from agroecosystems.