feeding side. In a case study on one farm, instituting a crop nutrient plan that focuses on efficient use of manure nutrients increased profits by $3,000. Use of a computer model, the Cornell Net Carbohydrate and Protein System (CNCPS), to accurately predict animal requirements and feed nutrients available to meet requirements while improving feeding management resulted in an additional annual increase in returns over feed costs of $42,000, while reducing nitrogen and phosphorus excretion by 25 to 33 percent.
Equations and coefficients in CNCPS and similar computer models are derived from the Committee of Animal Nutrition (CAN) reports and supplements, as well as published data. So, current summaries about nutrient requirements are important for modelers to accurately predict independent effects of variables that influence requirements and feed nutrient availability and utilization.
We have conducted studies on a range of dairy and beef cattle feeding farms (the smallest was a 40-cow pasture-based dairy and the largest were a 500-cow dairy and a 1000-head beef feedlot) to determine if there were problems with excess nutrients. Measurements revealed that 59 to 85 percent of the nitrogen from nitrogen fixation and the phosphorus and potassium from feeds was retained on the farm and not exported as milk or meat, regardless of type or size. Volatilization of nitrogen contributed to a 67 to 75 percent loss of excess nitrogen. On one farm, a leaching model, based on soil type characteristics and rainfall, predicted that 10 percent of excess nitrogen enters ground water. This was validated when we measured levels of nitrogen and phosphorus above federal water quality guidelines during the growing season in a stream containing only surface and groundwater from that farm’s cropland.
Our conclusion is yes; we in agriculture have a problem with excess nutrients and we must assume ownership of its potential for impacting water quality. It will be of increasing concern, because everyone desires clean water and air. But producers must recognize that they may have problems with excess nutrients. A survey of 25 dairy farmers in 1995 revealed they believed that farms did not create environmental problems; instead, they believed the problems were created by people who talked about the environment. They also stated that they planned to continue to make decisions based on economics, and not the environment, until regulated to do so. In our state, we are working to create an awareness that there is a problem and to encourage farmers to become proactive to address the problem voluntarily.
To better understand the problem of excess nutrients and their impact on water quality, we conducted a study at Cornell’s Animal Science Teaching and Research Farm. Our data revealed a 50 percent increase in milk production with no increase in cow numbers over the 15-year period studied and with no change in crop acres or yields. As a result, this increase in milk production was