Precipitation Events and Management Practices Affect Greenhouse Gas Emissions from Vineyards in a Mediterranean Climate

To evaluate the effect of precipitation events, management practices, and soil type in wine grape (Vitis vinifera L. ssp. vinifera) vineyard systems and provide data for greenhouse gas (GHG) emissions calculators, we monitored nine vineyards in the Lodi wine grape district, California, from April 2011 to December 2012. These commercial vineyards exist on three soil series (Redding, San Joaquin, and Tokay), representing a spectrum of soil textures and degrees of soil development. We hypothesized that soil characteristics would be a dominating factor affecting GHG fluxes, but the magnitude of fluxes would be influenced by precipitation and management events. We measured N2O fluxes, soil NO3-N and NH4-N, and gravimetric water content (GWC) from vine and intervine (alleys) rows bimonthly (April-October) and monthly (November-March). Monthly, we collected soil samples for dissolved organic C (DOC) and dissolved organic N (DON) determination. Path analysis revealed that the effects of soil type and vineyard zone on N2O emissions were influenced by soil texture (i.e., gravel and clay contents) but that this effect was mediated by GWC through soil temperature and soil inorganic N content. Management practices such as irrigation, fertigation, cover cropping, and tillage affected differences between vine rows and alleys for soil inorganic pools, DOC, and DON from June to October 2012. This 20-mo study indicated that precipitation events strongly influenced N2O fluxes.