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June 21, 2000 Job Number: LG00-173 Page 7 to quantify the average concentration of these inputs. Nitrate from Agriculture Fertilizer Application Leaching losses of nitrate fertilizer occur when soils have more incoming water(rain or irrigation)than the soil can hold. As water moves through the soil,the nitrate(NOO that is in soil solution moves along with the water. Ammonium(NH4')forms of N have a positive charge and are held by the negative sites on the clay in the soil;therefore,NH4' forms of N leach very little. In sands where there is very little clay, ammonium forms of N can leach. Coarse-textured sands and some muck soils are the only soils where ammonium leaching may be significant. One way to minirnize N leaching and denitrification is to minimize the time the N is in the soil before plant uptake. This cuts down on the time when conditions are favorable for losses.' The soil profile within the proposed septic field was found to consist of fine to medium sand with silt, silty sand, �- and sandy silt. Cabernet vineyards presently growing on the property are earmarked to fiunish the proposed winery with grapes for wine making. Zinfandel grapes from another location will also be processed at the site. The irrigation system used in the vineyard consists of a drip system which also delivers nitrogen fertilizer to the plant twice a year in the spring and fall seasons. Mr. Mike Manta—the current vineyard grower who is leasing the land—indicated that soil _ amendments(grape skins, leaves, seeds, and twigs) are placed between the vineyard rows once a year. Supplemental nutrients —not provided by the soil amendments—was provided to the vineyards by applying fertilizer through the drip irrigation system twice a year, once in the spring and fail season. The amount of fertilizer applied to a vineyard is determined by a method of measuring the soil sample for nutrients(including nitrogen),by measuring plant tissue sample (petioles) for nutrients(including nitrogen), and by measuring the nitrate level of the ground water in the irrigation well.' Mr. Manta indicated the samples were either taken to Dellavalle or FGL analytical laboratories for analysis and a recommendation of the fertilizer application rate. ' Vitosh,M L.,J. W.Johnson and D.B. Mengel,July 1995.Tri-state Fertilizer Recommendations for Corn, Soybeans,Wheat and Alfalfa,Extension Bulletin E-2567. 7 Christensen,P.,Date Unlmown,Use of tissue analysis in viticulture,U.C.Kearney Agricultural Center, University of California,Davis.