Location: Crops Pathology and Genetics Research2011 Annual Report
1a. Objectives (from AD-416)
Develop alternative 'in row' weed management practices that both provide effective weed management, do not negatively impact grapevine growth and juice, and improve soil nitrogen (N) retention by minimizing inorganic N leaching and nitrous oxide (N2O) emissions.
1b. Approach (from AD-416)
Frequent monitoring of weed establishment, bimonthly N2O emissions, and vine nutrient status. Specific periods of dynamic N transformations such as fertigation will be monitored to accomplish objectives.
3. Progress Report
The agreement was established in support of Objective 4 of the in-house project, the goal being to investigate the impacts of vineyard practices on soil microbial ecology. The project's goal is to develop "in-row" weed management practices that both provide effective weed management, do not negatively impact grapevine growth and juice, and improve soil nitrogen retention by minimizing inorganic nitrogen leaching and nitrous oxide emissions. The establishment of ‘in-row’ treatments was initiated in October of 2009. Greenhouse gas emissions (nitrous oxide, N2O and carbon dioxide, CO2) were collected bimonthly, and carbon (C) and nitrogen (N) dynamics in response to events that increase greenhouse gas emissions were measured from October, 2009 to the present. These measurements will continue through the study’s third year. Preliminary findings indicate that ‘pulse’ events such as cultivation, compost addition, fertigation, irrigation and rainfall are major periods of greenhouse gas emissions. When cultivation occurred just after compost addition, N2O and CO2 emissions increased and were greater than the cover crop and herbicide treatments. When rainfall occurred immediately after this cultivation, N2O and CO2 emissions were also greater than the other treatments, highlighting the interactive effects of management (i.e., cultivation and compost) and rainfall on greenhouse gas emissions. When treatments were irrigated, both N2O and CO2 were greatest from the cultivated treatment, followed by the cover crop and herbicide treatments, respectively. Although the cultivated treatment emitted more GHGs, further analysis will determine the net carbon footprint of each respective treatment. The cover crop and herbicide treatments tended to have greater nitrate leaching than the cultivated treatment. Temporal dynamics of leaching differed among treatments, suggesting that management practices could be adjusted over time to minimize these losses. Data from this study will be incorporated into the GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement network) database to develop predictive models of greenhouse gas emissions in response to agricultural management. Furthermore, findings from this study will be included in the development of an interactive process model for grower use assessing GHG emissions associated with different management practices, a project that was awarded to the California Sustainable Winegrowing Alliance by CDFA SCBG (“Field Testing a Carbon Offset and Greenhouse Gas Emissions Model for California Wine Grape Growers to Drive Climate Protection and Innovation”).