Regulation of Nutrient Losses from Dairy Farms

The Clean Water Act requires states to identify, prioritize and report to the US EPA those waterbodies whose quality is threatened or impaired by point and non-point source pollution. Nutrient management regulations in New York and most other states in the US have addressed the Clean Water Act of 1972 by requiring Concentrated Animal Feeding Operations (CAFO) to have Comprehensive Nutrient Management Plans, using the NRCS 590 Standard for nutrient management. The NRCS 590 standard focuses on reducing risk to water quality as the result of over-application of fertilizer and manure, and prevention of direct manure losses to streams and lakes; this is accomplished through the use of the phosphorus (P) runoff index, the nitrate leaching index, and land grant university crop nutrient guidelines.

The Clean Water Act states that point sources must be controlled first and in cases where water quality goals cannot be met by post-point-source intervention, states must develop and implement Total Maximum Daily Loads (TMDL) for the waterbody (US EPA, 1991). This TMDL (point and non-point sources combined) states how much of a given pollutant is allowed to enter (“load”) a waterbody to achieve (or maintain) a water quality goal (US EPA, 1991). TMDL development for a given watershed requires “load allocations” be quantified for each point and non-point source (US EPA, 1991). From a watershed perspective this can be viewed as “backing” the pollutant load up the watershed and assigning an allowable amount to its various sources (including agriculture). Communities seeking to manage watersheds to meet a set TMDL must consider all sources of a given pollutant, and then prioritize watershed management based on the relative proportions of source loads and cost/benefit analysis of source management controls. In essence, this requires nutrient management planning to occur at the basin, sub-basin, community, and farm level. Research, extension, and teaching activities need to focus on predicting the impacts that best management practice (BMP) alternatives have on the farm nutrient fluxes.

Future regulations - The European Example

The European Union has been developing and implementing N policy since 1991 (Henkins and Van Keulen, 2001). The EU Nitrate Directive obliges EU member states to reduce the nitrate loading from agriculture to surface and ground water. Once acceptable levels are reached, controls must be in place to limit further pollution. The target nitrate level the EU is using is 50 mg/l nitrate (similar to our 10 mg/l nitrate-N). The agricultural objective is to balance the use of manure and chemical fertilizer with crop requirements.

Unlike our dairy industry, countries such as England and the Netherlands have relied on high nitrogen applications to maximize grass yield and quality (rates as high as 450 lbs N/a). The EU directive thus far has been focused on decreasing N loading in the cropping system (with a 170 to 250 lb/a range being discussed). Their approach to regulation is slightly different in that they are regulated based on farm-gate nutrient balances that include acceptable environmental emissions. Failure to meet farm-gate balances results in fines with the current P fine being approximately $9 per kg in excess and N resulting in $2.25 per kg in excess. Nitrogen and phosphorus imports are closely tracked, and in the Netherlands , feed and fertilizer companies are required to submit all invoices including N and P content to the regulating agency. Fines are determined annually and added to the farms income tax charges with many of the on-farm calculations being done by financial accountants.

The decision as to how a farm meets the regulations (the within farm nutrient flow) is flexible as long as best management practices are followed to limit N losses to the environment. The Dutch are beginning to look at how animal production and diets impact excretion. They are hopeful that through diet manipulation, they can decrease ammonia emissions; however given that most of their diets are grass silage/pasture based and they must import most of their carbohydrate sources, accomplishing this will be difficult. Other areas they are pursuing include animal number reductions, exporting manure, and maximizing herd management and production per cow. Herd management and cow production are meant to improve the farm-level N efficiency. They are attempting to minimize cull rates to minimize the size of the replacement herd as growth is much less N efficient compared with milk production. Additionally, milk production exports N off the farm whereas growth remains on the farm; thus, growing animals negatively impact their farm-gate N balance.