What Is Whole Farm Nutrient Balance?
|Take Home Message|
|WFNB is a method for defining the overall nutrient use facility on a livestock facility including both the animal and cropping system. It encourages comparison of all nutrients entering and exiting a livestock farm with the goal of achieving a ratio of 1 lb input to 1 lb managed output. It also can be used to evaluate all nutrient management options for achieving a sustainable production facility for nutrients.|
A Whole Farm Nutrient Balance (WFNB) is a comparison of the quantity of nutrients, typically nitrogen (N) and phosphorus (P) that enter (inputs) and exit (managed outputs) the farm gate. This measure can be visualized as an “Nutrient Yardstick”. In many ways, it is similar to feed input/output efficiency for animal (lbs of feed per lb of gain). These indicators compare inputs used to achieve a useful output. Smaller ratios suggest better performance. A WFNB describes the “whole farm’s” efficiency for utilizing nutrients and is an important indicator of a farm’s environmental performance.
Common sources of nutrients entering a farm (Inputs) include purchased animals, feeds, and fertilizers. Nitrogen fixed by legumes and nitrate contained in irrigation water represent additional N inputs. The Managed Outputs (useful products) include animals and crop sold and manure shipped to off-farm uses.
If there are more Input nutrients than Managed Output nutrients, the difference is a nutrient Imbalance. This Imbalance represents nutrients that may be lost to the environment by either air and water pathways as well as those nutrients that accumulate on the farm (e.g. increased soil P levels). An Imbalance suggests a potential environmental risk.
This balance measures only those nutrients that cross the boundary of the farm and does not directly track nutrients flows within the farm. Using the feed to gain analogy, as a pork producer you are not too concerned about the efficiency of internal organs such as the gastrointestinal tract’s ability to capture nutrients for the pig to utilize. However, you are aware that these internal processes affect the overall feed to gain ratio. Similarly, those internal processes (e.g. efficiency of utilization of manure in the cropping system) affects the quantity of nutrient inputs into the farm (e.g. purchased fertilizer inputs to the farm). Thus, a WFNB measure is reflective of multiple internal on-farm processes affecting nutrient efficiency.
WFNB also provides an indicator of the magnitude of direct nutrient losses (e.g. ammonia into the air or nitrate in the soil) and accumulations that add to a farm’s environmental risk (e.g. P buildup in the soil). Regulatory agencies are increasingly asking questions about these losses and accumulations. WFNB provides a producer with a relatively simple method for understanding these losses and accumulations and a means of tracking management changes that produce environmental benefits.
Why is A Measure of WFNB Important?
Permitted livestock operations are being asked to provide annual reports to a permitting authority (state regulatory agency or EPA) that provide indirect indicators of nutrient plan implementation. Producers are also required to keep extensive records of planning procedures, plan implementation, sampling, and inspections. Again these records provide indirect indicators of environmental performance. Finally, all producers are required to implement the same best management practices (BMP) whether they are producing pork in Nebraska, North Carolina, or Indiana. However, the effectiveness of these BMP is highly site and size specific.
WFNB provides a “potential” opportunity to set a common performance based goal for all livestock producers but allow individual producers latitude in determining how to reach that goal. It also provides a means of measuring an individual farm’s progress towards that goal. Setting environmental goals based upon a WFNB measure may give a producer greater flexibility and control in achieving an environmentally sustainable animal operation. It may also provide a simpler and more accurate means of documenting environmental performance.
It must be emphasized that WFNB only has the “potential” for achieving these goals. It has been used in policy implementation in Europe but has seen only limited application in the US. At this time WFNB is strictly a voluntary tool a producer may chose to use to track environmental performance.
What Decisions Might Result from Understanding WFNB?
- A farm’s WFNB can be used to evaluate alternative nutrient strategies. For example by knowing the magnitude of the fertilizer input, the potential improvement in WFNB that might result from an improved manure use plan can be forecasted. Other nutrient strategies contributing to an improved WFNB can also be evaluated including manure export, alternative cropping systems, alternative feeding programs.
- A farm’s WFNB provides a mechanism for comparing fertilizer vs. feed inputs, typically the two largest sources of nutrients. A recognition of which input is larger provides guidance as to which of those nutrient strategies that will be most effective for reducing an imbalance.
- A farm’s WFNB can be compared to a larger set of farms to gage a farm’s performance relative to its peers.
What Information Would a Producer Need to Assemble?
Several tools are available for estimating WFNB including a pork specific spreadsheet “Calculating My Farm’s Whole Farm Nutrient Balance”. To use this product you will need to have access to the information in table 1.
|Nutrient Flow||Information Required||Information Source||Do I Have This?|
|Purchased Feed||Quantity||Farm records||space|
|Protein and P concentration||Farm record of feed analysis||space|
|Purchased animals||Number of animals||Farm records||space|
|Average animal weight||Farm records||space|
|N and P concentration||Book value in spreadsheet||space|
|Purchased Fertilizer||Product type and amount||Farm records of purchased fertilizers||space|
|N and P concentration||Book value in spreadsheet with option for adjustment||space|
|Legume Fixed Nitrogen||Acres not manured||Farm records||space|
|Legume crop yield||Farm records||space|
|Nitrates in Irrigation Water||Amount of water pumped||Farm records||space|
|Water sample with nitrate concentration||Farm records||space|
|Managed Nutrient Outputs|
|Crops Sold||Type and Quantity||Farm records||space|
|Protein and P concentration||Book Value in spreadsheet with option for adjustment||space|
|Animals Sold||Number of animals||Farm records||space|
|Animal weight||Farm records||space|
|N and P concentration||Book value||space|
|Manure Transferred to Off-Farm Users||Amount||Farm records||space|
|N and P concentration||Farm records – Manure analysis||space|
Results of On-Farm Measurement of WFNB
Authors: Rick Koelsch, University of Nebraska; Joe Lally, Iowa State University; Alan Sutton, Purdue University
This project was funded by The National Pork Board