This article is drawn from two articles in the Cornell Field Crops Newsletter written by Quirine Ketterings, Melanie Soberon, Sebastian Cela, Karl Czymmek (also from PRODAIRY), Steve Crittenden and Caroline Rasmussen of the Nutrient Management Spear Program, Department of Animal Science, Cornell University. While their work focuses on assisting dairy farms, the concepts are important no matter what you raise.
When a milk truck pulls out of the driveway, nutrients are being exported off the farm. The same is true if the farm exports crops or animals. Each animal, bushel or ton of crop, or gallon of milk contains nitrogen, phosphorus and potassium. As a result, a farm cannot remain productive in the long run without importing nutrients to offset what it exports. For the last 10 years, we’ve been working with dairy farmers and their advisors to figure out how dairy producers can create a better balance without giving up on milk production.
Nutrient Mass Balance
Nutrient Mass Balance (NMB) is short for “whole farm nutrient mass balance.” It’s the difference in nitrogen (N), phosphorus (P), and potassium (K) imported onto the farm in the form of feed, fertilizer, animals, and bedding, and nutrients exported off the farm in milk, crops, animals and manure. Farms with a positive balance may be bringing in more nutrients than they need to. Making changes can save money and reduce potential environmental impacts due to nutrient run-off. Other farms might have a negative balance because they’re mining soil nutrients and thus need to import more nutrients to sustain productivity in the long term.
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.
To make it easier to figure out what’s coming and going, we draw a line around the farm and look at only those nutrients that are being imported or exported across the boundary. The analysis gives us a balance for N, P, and K per acre of cropland, and per hundred weight of milk produced. 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.
A Whole Farm Assessment Tool
The whole farm nutrient mass balance (NMB) calculator is a tool that was developed to help in this assessment. The first calculator was created by Stuart Klausner at Cornell University, and has been 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 below.
Within 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.
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.
Where Should Your Whole Farm Balance Be?
A sustainable nutrient mass balance should allow dairy farms to be economically profitable, environmentally sustainable, and flexible enough to allow for the many variations among farms. We defined “feasible” nutrient mass balances per acre and per cwt of milk produced as shown in Table 2, based on our work with a set of 102 New York dairy farms.
Combining both balances (per acre and per cwt), the most efficient farms have balances in the green area (the “Optimum Operational Zone” or “Green Box”) in Figure 2. This example in Figure 2 is for nitrogen. Evaluations so far have shown that farms operating outside of the green box have opportunities for improvements in nutrient use.
Farms that complete the assessment for at least four years have shown great improvements over time without giving up on milk production. A number of farms have reduced balances while increasing milk production due to more precise feeding. We don’t have farm financial records, but the fact that balances were improved without giving up on milk production strongly suggests that the farms gained by keeping track of their mass balances. Each farm is unique so management practices that allow a farm to become more efficient with nutrients were also farm specific. Some common themes for review are careful evaluation of cow feeding programs, change of feed imports where possible, focus on increasing homegrown forage production through better crop and pasture management and better allocation of fertilizers to fields to support the crops. some farmers made crop rotation changes, while others decided to increase acreage, or export more crops and/or manure.
Farmers can do the assessment themselves by using the tool on our website and generate a report once all data are entered. The farmers that share their data with us or submit their completed input sheets to us receive a comprehensive report that includes a comparison of their farm data with the data of all other farms in the database (all farm names are kept confidential). Farmers can learn from each other by comparing their operations and by discussing the results in their own management team. Here is some feedback from participating farmers about the benefit of doing the balance and sharing results:
“With enough farms in the database that are similar in size and cropping program to ours, we can make valid comparisons. It helps us to see what can be achieved and gives us a good sense of where we stand in our goal to be as nutrient efficient as is possible.”
“Immediately it makes you think of things in a different light or from a different perspective, than we normally look at things in either dollars and cents or feed pounds or feed pounds wasted or what we are feeding the cows it steps back one step further and makes you look at the big picture.”
“When we share the information with the whole farm team it sparks useful and important conversations about our farm’s philosophy and practical applications to concrete practices such as manure application, crop sales and purchases.”
Don’t hesitate, join us and let’s learn together. The software and supporting information (manual, input sheets, etc.) are freely downloadable from the whole farm nutrient mass balance project page of the Cornell Nutrient Management Spear Program (NMSP) website: http://nmsp.cals.cornell.edu/NYOnFarmResearchPartnership/MassBalances.html. Download the input sheets and derive the balance yourself or let us join your evaluation! The software works on IBM computers and is currently not available for Macs.
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 feel free to contact Quirine M. Ketterings at firstname.lastname@example.org.
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