Greenhouse Gas Emissions in No-till Vegetable Production.

Agricultural soils are a major source of greenhouse gases (GHG) due to tillage and nutrient management.  Carbon dioxide is emitted from the soil atmosphere during tilling and tilling also increases the availability of organic matter to microbial decomposition.  No-till has been shown to have lower emissions of both CO₂ and N₂O relative to conventional tillage.  The goal of this study was to determine if no-till organic vegetable production has lower GHG emissions than conventional tillage. Spader-tillage was compared to a no-till treatment where a shank pulled in-line with a coulter was used to cut cover crop residue and dig a 10 cm deep by 5 cm wide trench through cereal rye terminated with a roller/crimper.  To measure the effect of tillage on greenhouse gas emissions gas samples were collected throughout the growing season.  Chambers were placed both in planting rows and between rows. Gas samples were collected over 30 minutes during tilling, irrigation, post-harvest and freeze/thaw events for two years.   Samples were analyzed for CO₂ and N₂O in a GC and the fluxes were calculated using both linear and non-linear models with HMR.   Primary results show that CO₂ emissions increase immediately after tillage and slowly decrease with time.  N₂O emissions are less predictable, but decrease on the day of tilling and return to pre-till levels with time.