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IV. CONCLUSIONS AND RECOMMENDATIONS The data presented above gives an approximate estimate of what is occurring at the subject facility with regard to nitrogen production and crop uptake. There are numerous factors involved in adequately assessing and correlating crop needs and uptake of available nitrogen. From the results of the balance equation, the amount of nitrogen produced by the dairy operation is approximately 82% of the nitrogen needed for optimum crop growth. When large numbers are formulated to assess nitrogen produced vs. nitrogen required, the margin of error can be±10%. Therefore, it is recommended that sampling and analysis be performed on the 1.) Wastes applied, 2.) Cropland soil and 3.) Tissue samples of the crops to check for N excess. By analysis of these different parameters, it can best be determined which form of nutrient(solid vs. liquid) to apply to _ a particular field. Additionally, the Estimated Nitrogen Release (ENR) must be taken into consideration when determining nutrient application quantities. The procedures for determining crop nutritional needs, particularly nitrogen, without overloading the cropland can be a complex process. In an effort to simplify the information required to make best management decisions for optimum crop growth and nutrient utilization, we have provided a Manure Analysis Reference Guide attached with this report. This Guide is published by A & L Agricultural Laboratories and provides one of the best sources of information to determine crop nutrient utilization from animal wastes. The suitable rate of solid and liquid applications is determined by the ability of the soil and crop combination to immobilize and utilize the nutrients in the applied manure, which is detailed on the Worksheets found in this Guide. In our opinion, the actual dairy site is the primary area of concern with respect to nitrate/nitrogen loading, followed by the cropland. The calculated nitrogen contribution from the on-site sewage disposal systems is comparatively insignificant, especially when the surrounding land use low density factor is considered. _ One of the most significant nitrate mitigating factors discovered from this investigation is the process known as denitrification: The microbial reduction of nitrate to nitrogen gas and nitrous oxide. This process is one of the explanations for the relatively low levels of nitrate found in the _ cropland soils and underlying groundwater. Due to the high clay content cropland soils, the denitrification process prevails in the subsurface anaerobic conditions within the microsite pore spaces of the clay. Caution must be exercised when irrigating cropland. Tailwater must not be allowed to enter any of the canals or ditches surrounding the cropland. The infiltration and permeability of all nutrient .. application acreage is comparatively slow and runoff can occur readily. In addition, wastes must be managed at the south end of the corral area so that no solids or liquids enter Nagler Draw. From the analysis of the groundwater, the gradient and estimated directional flow, nitrate impact to downgradient domestic wells from the subject dairy exclusively, appears remote. An increase in animal units may be made, up and above the numbers used. However, if an increase in AUs is proposed, an analysis must be made to quantify the additional nitrogen production, in combination with new waste management techniques (e.g., freestall flush system). 8 Vaffey Ag Pcsearck