Soil greenhouse gas emissions in contrasting strawberry production systems in the Central Coast of California

Background/Question/Methods

Agriculture is an important source of greenhouse gas (GHG) emissions. In particular, N₂O emissions from soils may account for substantial GHG emissions from agriculture. However, on-farm management practices can dramatically influence soil GHG emissions and may provide opportunities to mitigate the overall global warming potential (GWP) in agriculture. However, the majority of agricultural GHG studies are from geographical areas, crops types, and cultural practices that vary dramatically from California’s intensively grown, specialty crops. To evaluate the role of management practices on GHG emissions, we compared three organic and three conventional strawberry farms along the Central Coast of California (Santa Cruz and Monterey counties). We measured soil gas flux using vented static chambers on a bi-weekly and event-driven (i.e. fertilization and irrigation) basis from October 2010 through November 2012. We also measured soil moisture and available nitrogen (N) as potential drivers of GHG production.

Results/Conclusions

GHG emissions did not significantly differ between organic and conventional farms. In fact, most of gas emissions were due to site characteristics, where actual management type (organic versus conventional) seemed to have little overall affect. To support this, we found that nitrous oxides were not related to drivers such as available N or N₂O fluxes and soil moisture. Granted even as bulk soil measures, these predictors often have little power in predicting GHG emissions, nevertheless, we were surprised by the variation associated with sites that could not be ascribed to proxy measures that drive microbial processes responsible for N₂O production. Finally, after complete farmer management records have been collected, we will also evaluate GHG flux results within the overall GWP.