The goal of whole farm nutrient balancing is to produce crops, meat, milk, and eggs efficiently while balancing nutrient inputs, such as feed, fertilizer, manure, irrigation water, and legume nitrogen, with animal and plant needs.  In addition to economic benefits, maintaining nutrient balances can minimize environmental impacts including leaching, runoff, and odors.  Current problems in achieving nutrient balances include over application of manure and fertilizers, excessive nutrients in diets, variable nutrient content of manures, insufficient storage capacity, variations in manure application, and conflicting regulations.    Diet studies indicate that substituting synthetic amino acids in place of crude protein, and using phytase to improve phosphorous availability, can reduce the amount of nitrogen and phosphorous excreted by 35% and 41% respectively, while having a minimal impact on animal yield.  Synthetic amino acids can also be formulated to reduce odor compounds present in manure.  Nutrient losses during manure storage are greatest in lagoons.  Nitrogen is lost through volatilization of ammonia and much of the  phosphorous and potassium are not available for land application unless the lagoon is agitated.  Land application of manure also causes nitrogen losses due to ammonia volatilization.  During periods of high rainfall and over the winter, nitrification inhibitors may be effective in keeping nitrogen in the form of ammonium so that it binds to soil organic matter, decreasing leaching.  To limit the build up of phosphorus, rotating corn with soybean crops can be used to remove phosphorus from the soil.  Additional interdisciplinary research that investigates whole systems is needed to help producers achieve efficient and economic nutrient balances.  Other research opportunities include water, air and soil quality, human health, and social and economic impacts.