Mitigating Nitrous Oxide Emissions, Nitrate Leaching, and Weed Pressure in Vineyards.

The goal of this research was to 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. Weed control is an area of substantial cost and effort for vineyard operations, emphasizing the need to reduce both inputs and resources required for this practice. Moreover, N leachates have detrimental impacts on water quality, and N2O is a greenhouse gas with significant impacts on global warming and climate change. Our earlier findings indicate that a balance between ‘in-row’ weed control and reducing offsite impacts of N loss may be possible. In October 2009, ‘in-row’ treatments were established: 1) a standard herbicide application, 2) an under-the-vine cover crop, and 3) furrow cultivation with compost. Soil pits were sampled to characterize baseline conditions in the vineyard, and automated sensors for soil water content and temperature, and resin bags to collect N-leachate were installed. Preliminary data indicate that soil profiles are enriched in soil organic carbon (C) and N pools in the surface, and that treatments generally are similar in soil characteristics at the beginning of the experiment. As expected, preliminary biweekly measurements of N2O and CO2 emissions among weed management treatments did not differ. Nonetheless, leached nitrate collected on resin bags was greater in the herbicide treatment than in the remaining two treatments. Furthermore, during pulse events, N2O emissions differed among treatment. Immediately after tillage was implemented to control under the vine weeds, pulses of N2O and CO2 were observed. Study of C and N dynamics in response to events that increase greenhouse gas emissions (i.e., irrigation, fertilization) in the vineyard system will continue through 2012, and those from summer 2010 will be included here.