Good nutrient balance quite valuable

A mass nutrient balance plan could be more effective than monitoring wells in dairy farms.

All New Mexico dairies are required to have a permit from New Mexico Environment Department, which among other things, requires dairy farms to install wells to monitor groundwater nutrient quality. These monitoring wells are unpopular among dairy producers because they are expensive, need maintenance, do not yield clear information, might contribute to groundwater contamination, and might not pinpoint the actual source of contamination, if any.

The dynamics of the aquifers including groundwater movement and volume is still a not well-understood science. It is highly difficult to ascertain nutrient water quality impacts from surface activities by sporadic (time and space) measurements. This fact, together with evidence that previous land uses might be influencing today’s measurements, makes this technique, in many cases, misleading and uncertain. In addition, there is a valid claim that the construction of monitoring wells opens a direct pipeline between the surface and groundwater, introducing a higher risk of direct contamination.

On the other hand, a mass balance of nutrients in a whole dairy farm system can be a more efficient and effective venue to assess a farm’s nutrient environmental status. A nutrient balance finds out the amount of nutrients remaining in the farm, if any, by subtracting the quantity of nutrients leaving the farm from the quantity of nutrients entering the farm. This balance is time sensitive and when performed with solid and validated data has no room for inconsistencies.

Dairy farmers have lab tests of their feeds and they weigh each ingredient in their herd’s diets, consequently, they know the quantity of nutrients in feed entering the system on a daily basis. They have daily milk tests and they know exactly how much milk has been produced every day, consequently they know exactly the quantity of nutrients leaving the farm on a daily basis. Therefore, they know the amount of nutrients remaining in the farm as manure.

Dairy farmers usually recycle this manure in field crops as an organic fertilizer. They know the nutrient composition of their crops and the biomass produced in their fields. Therefore, they know the quantity of manure nutrients that could be recycled in crop fields. A nutrient balance plan is a great decision-making tool that allows producers to maximize on-farm nutrient recycling through the development and application of best management practices that include field manure applications that are timely and spatially appropriated to provide the right amount of nutrients to the crops while protecting the environment.

The dairy extension program at the New Mexico State University has developed a series of simple, user-friendly, and interactive nutrient balance spreadsheets to help dairy producers, consultants, and regulatory agencies in their tasks of assessing nutrient balances in dairy farms. These are available through the New Mexico dairy extension program Web site at dairy.nmsu.edu: Tools.

Victor Cabrera is an extension dairy specialist at New Mexico State University’s Agricultural Science Center at Clovis. He can be contacted at (505) 985-2292, ext. 107, [email protected].