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ti ` September 30,2002 Job Number:LG02-335 Page 9 percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. Due to the sandy soils, the denitrification factor is estimated to be about 10 percent. ` An estimate of the quantity and quality of rainfall was required for the analysis. The deep percolation of rain was estimated to be 4.94 inches and the calculation is shown on Plate 8. The ` nitrate concentration of rain fall was estimated to be 0.17 mg/L-N.' Nitrates from Agriculture 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 minimize 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?Proper ` management of agricultural property significantly reduces the potential nitrate impact to ground water. The almond orchard existing on the site is leased to Willie Derma who lives across the street from the site at 5656 E. Verigin Road, Manteca. Mr.Derma was unavailable for interview regarding the fertilization and irrigation practices applied to the orchard existing on the property. Mr.Paul Verdegaal,Farm Advisor, UC Davis Cooperative Extension San Joaquin County was contacted regarding his knowledge of the site. Mr. Verdegaal did not have any site specific knowledge of the site or Mr. Derma. Mr. Verdegaal indicated that typically fertilizers in this area can be applied in either a liquid or solid form. Typically in several-smaller applications. The total yearly application can range from 100 to 200 units of Nitrogen per acre. Each unit is one (pound)of nitrogen. A typical annual application rate being 125 to 150 units per acre. The application rate depends on the orchard yield goals and soil conditions. No public permits or records were available for the property regarding the fertilizer practices of the orchard. Two (2) soil samples were collected by a representative of our company at opposite ends of the site within the orchard to characterize the nitrate concentration of the soil in the almond orchard(Plate 1). Each sample was collected at a depth of 4 to 6 inches below the ground. The L 9 Vitosh,M.L.,J.W.Johnson and D.B.Mengel,July 1995.Tri-state Fertilizer Recommendations for Com,Soybeans,Wheat and Alfalfa,Extension Bulletin E-2567. L s O 4