Issue link: http://winesandvines.uberflip.com/i/74666
GRAPE GRO WING Farming inputs responsible for 96% of contamination T he study of nitrate contamination in groundwater covers the Tulare Lake Basin and the Monterey County por- tion of the Salinas Valley. About 2.6 million people in these regions rely on groundwater for their drinking water. Agriculture in these regions accounts for about 40% of the pro- duction on California's irrigated cropland, and it hosts more than half of California's dairy herd. Furthermore, these regions include some of the poorest communities in the state and have limited means to treat the drinking water to ensure that it is safe. The UC Davis study found that nitrate contamination of groundwater is widespread and increasing. Fifty-seven percent of the current population in the study area use a community public water system with nitrate concentrations of untreated (raw) water that have exceeded California Department of Public Health's maximum contaminant level (MCL) of 45mg per liter at least once between 2006 and 2010. Most of these people are protected by water system treatment or alternative wells, require far less nitrogen per year (10-20+ pounds per acre, with some vineyards in some years requiring no additions) compared to that required by many other crops (e.g. almond farmers use more than 200 pounds per acre per year), vineyards are not going to be singled out as fields requiring closer scrutiny. However, if a RWQCB requires farm fields to have written nutrient management plans and demonstration of practices that minimize leaching of nitrates, then vineyards will need to comply, too. Good viticulture involves written nutrient management plans based on the however 10% are at risk because their water comes from untreated small delivery systems or individual untreated home wells. The study determined that 96% of the nitrates in the groundwater came from the leaching of nitrogen inputs applied to crops but not removed by harvest, volatilization or runoff. This was broken down to 54% from synthetic fertilizer, 33% from manure and 8% from irrigation water. Only 2% came from wastewater treatment and food-processing facilities. C.O. budget approach. If this approach is a part of your vineyard management program, you will have no trouble meeting any requirements the RWQCB decides to implement. Dr. Cliff Ohmart serves as vice president of professional services for SureHarvest. He is the author of "View from the Vineyard: A practical guide to sustainable winegrape growing," published by the Wine Appreciation Guild. Previously he served as research/IPM director at the Lodi-Woodbridge Winegrape Commission. He has been writing about sustainable winegrowing issues for Wines & Vines since 1998. Search Online for PEST CONTROL Vineyard Suppliers Vineyard Equipment Vineyard Services Vineyard Supplies ONLINE SEARCH WWW.WINESANDVINESBUYERSGUIDE.COM WINES & VINES AUGUST 2012 59