Conservation Tillage of Cover Crops as a Means of Improving Carbon Sequestration and Diminishing Greenhouse Gas Emissions in California Vineyard Soils

Reducing greenhouse gas emissions from agriculture and other sectors of Califorrnia?s economy has become one of the most important environmental concerns of State and Federal regulatory organizations. This is the result of 1) the passage of the California Global Warming Solutions Act, Assembly Bill 32 (AB32) in June of 2006, 2) the US EPA?s recent endangerment finding for GHGs of CO2, N2O and CH4 ( This project represents an overarching effort to accurately quantify greenhouse gas emissions from California vineyards and currently focuses on CO2, N2O and CH4, quantifiable estimates of soil carbon (C) sequestration and above and belowground annual net primary productivity of C. The project coordinates with efforts by Dr. William Salas (Applied Geosolutions LLC), Dr. Changsheng Li (University of New Hampshire, Institute for the Study of Earth, Oceans and Space) and Alison Jordan of the Wine Institute to calibrate the DeNitrification DeComposition model (DNDC). The model will be embedded into a decision support system (DSS) for use by practitioners for carbon assessments ( The modeling exercises will allow us to test multiple management practices in order to lessen (mitigate) N2O emissions from California vineyards. The data is being made available to Dr. Alissa Kendall and Sonja Brodt of the Department of Agricultural and Environmental Engineering and Agricultural Sustainability Institute to assemble life cycle analyses for carbon footprints of vineyards and orchards. This second collaboration involves the use of our comprehensive GHG budget. We are quickly approaching that objective for a conventionally managed vineyard and a vineyard managed under minimum-till conditions to increase soil C sequestration. There is currently tremendous uncertainty concerning the quantity of GHGs produced and consumed in vineyards (Carlisle et al., 2008). In a recent report it was estimated that in vineyard land managed under no-till, soil carbon sequestration would greatly increase, (Kroodsma and Field, 2006) but little data exists to support this contention. Our research aims to construct working budgets of GHGs and C sequestration in a Napa Valley vineyard being managed with a cover crop under ?conservation? and conventional tillage practices. The GHGs being studied are those defined by the International Panel on Climate Change?s 2006 Assessment (IPCC, 2006) and consist of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). It is essential that we improve the understanding of vineyards? role in emitting or absorbing these gases. Little research is so far available on these topics for California vineyards (Carlisle et al., 2008).