Whole farm nutrient mass balance calculator for New York dairy farms

Melanie Soberon1, Quirine Ketterings1, Karl Czymmek1,2, Sebastian Cela1, Caroline Rasmussen1
Cornell University Nutrient Management Spear Program, 2PRODAIRY

Striking a whole farm balance
Environmental awareness and the desire for social, economic and environmental sustainability have led to more proactive management of farm nitrogen (N), phosphorus (P) and potassium (K) balances. Nutrient accumulation is when the amount of imported nutrients on farm exceeds the amount of nutrients exported from the farm. The implications of nutrient accumulation include degradation of water and air quality, which is reason for increased pressure on animal agriculture by the public, litigators and state and federal regulators. Similarly negative consequences can result from whole farm nutrient losses, when exported nutrients exceed the amount of nutrients imported on the farm. In these situations, the soil can be mined of nutrients, decreasing soil fertility and, when deficiencies start to occur, also crop yields. Thus, a clear understanding of the imbalances between farm nutrient exports and imports, and how they relate to farm management practices, is key to developing long-term, sustainable solutions for individual farms, and the animal industry in general.

Fig. 1: Whole farm nutrient mass balance assessment.
Fig. 1: Whole farm nutrient mass balance assessment.

Adaptive management
Sustainable solutions require improved nutrient use efficiency across the whole farm, balancing the nutrient flows of both the animals and the land. However, when it comes to whole farm nutrient management, it can feel like there are more questions for producers than time to evaluate and answer. Is cropland being fertilized at the proper times in sufficient quantities to supply nutrients to crops without accumulating nutrients? What nutrients need to be supplied in purchased fertilizer and feed this year to prevent nutrient loss? And once all those questions have been dealt with for the year, a new year comes around and the process begins anew. This is where a method of keeping track of nutrient management records from year to year in a systematic way can save time, money and conserve nutrients. The idea behind the adaptive management concept is to maintain nutrient management records in such a way that one can assess the nutrient status of the whole farm (Fig. 1), pinpoint the areas where improvements can be made, and then track the progress of those improvements year to year. The whole farm nutrient mass balance (NMB) calculator is a tool that was developed to help in the assessment.

A whole farm assessment tool
The whole farm NMB calculator was first developed by Stuart Klausner at Cornell University, and modified and reprogrammed in Microsoft Visual Basic in more recent years. The software and supporting information (manual etc.) are downloadable from the whole farm nutrient mass balance project page of the Cornell Nutrient Management Spear Program (NMSP): http://nmsp.cals.cornell.edu/projects/massbalance.html. The NMB calculator is targeted for use by dairy farms, though it can be used to determine NMBs of any type of livestock operation. A data questionnaire was developed to help gather the data listed in Table 1.

Ketterings paper 1 table 1Within the NMB calculator, there are four basic pools where nutrients can be allocated on a farm: (1) they are imported to the farm in the form of purchased products; (2) they are exported from the farm as products sold/exported; (3) they remain on the farm to be recycled; or (4) they are lost to the environment. The NMB program calculates N, P, and K imported onto and exported from the farm in the form of feed, fertilizer, animals, crops, milk, manure and bedding. The difference between nutrients imported and nutrients exported is expressed as N, P and K balance per acre of cropland, and per unit (cwt or hundred weight) of milk produced (Fig. 1). Negative values are not sustainable over time, as they indicate that more nutrients are being taken off the farm than are replaced. However, large positive balances are not desirable either, as they indicate nutrient inefficiencies and increased risk for environmental losses.

To demonstrate how the NMB calculator assists producers in evaluating best management practices, data from a central New York dairy farm were analyzed over the course of 8 consecutive years (2003-2010). In the initial assessments, NMB values were high, and 76, 69 and 64% of the imported N, P, and K remained on the farm (Fig. 2). However, by gradually matching feed and fertilizer purchases with animal and crop needs, the farm reduced its nutrient imbalances, and only 45, 34 and 31% of the imported N, P, and K remained on the farm in recent years. Moreover, the improvements made resulted in a milk production per cow increase from a little less than 23,000 to more than 24,000 lbs of milk over the same time period.

Fig. 2. Nitrogen, phosphorus and potassium mass balances (lbs/acre) measured by a New York case study dairy farm over 8 years.
Fig. 2. Nitrogen, phosphorus and potassium mass balances (lbs/acre) measured by a New York case study dairy farm over 8 years.

Farmer feedback
Farmers and their advisors can utilize the NMB calculator to increase nutrient use efficiency on the farm and monitor progress over time. They can also compare their farm’s nutrient balance to those of peers in the dairy industry with similar milk production. Comments of participating farmers included:

“Pulling together the information is useful in itself and it gets me to look at numbers in a different way.”

“Participating in the NMB is one way to show that we are doing our best to comply with regulations; it demonstrates that we are good environmental stewards.”

In summary
Whole farm adaptive management approaches to nutrient management have been recognized by the Natural Resources Conservation Service (NRCS) in its new national NRCS590 standard and many states are currently discussing approaches for implementation. The NMB calculator generates an overall summary of N, P and K balance of a particular farm using recorded imports and exports; these annual summaries can assist producers in making management changes that lead to more efficient production and resource conservation.

Additional resources

  • Soberon, M.A., Q.M. Ketterings, C.N. Rasmussen, and K.J. Czymmek. 2013. Whole Farm Nutrient Balance Calculator for New York Dairy Farms. Nat. Sci. Educ. 42:57–67.

Ketterings ack imagesAcknowledgments
Thanks to all the farmers, consultants, SWCD and NRCS staff, and Cornell Cooperative Extension educators that participated in this study. Thanks also to Françoise Vermeylen from the Cornell University Statistical Consulting Unit for statistical advice. This work was supported by grants from the Northern New York Agricultural Development Program (NNYADP), Northeast Sustainable Agriculture Research and Extension (NESARE), Federal-Formula Funds, and a USDA-NRCS Conservation Innovation Grant. For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/

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