Opportunities for Improving Vineyard Environmental Impacts.

Although not yet regulated in AB 32 Global Warming Solutions Act, the greenhouse gas nitrous oxide (N2O) is a major concern for California’s agricultural industry. Since March 2011, we have evaluated carbon dioxide (CO2) and N2O emissions from vineyards across three soil types of different geologic history and under varying conventional management systems in the Lodi Wine-grape District in the Central Valley of California. Soils of the District vary in space as a result of the depositional history of the parent materials and subsequent weathering. We sampled the following soils from this soil sequence: 1) Slightly weathered granitic alluvium with low clay content located on the southern side of the district; 2) Intermediately weathered soils derived from granitic alluvium with high clay content located on the northern side of the district; and, 3) Highly weathered soils derived from metavolcanic and metasedimentary alluvium with intermediate clay content and rocky soils located on the eastern side of the district. The climate is Mediterranean with cool, moist winters and hot, dry summers. Initial findings indicate that emissions vary across the soil landscape during pulse events (e.g., irrigation, fertigation, tillage), and that alleys between vines have greater emissions than the soils under the vines. Further, we are integrating these findings with the DeNitrification/DeComposition model and Life Cycle Assessment (LCA) of two winegrowing regions, Napa and Lodi, with contrasting production practices to determine ‘hotspots’ within the winegrape production systems that influence environmental impacts.