Tag: whole farm nutrient balance

What Is Whole Farm Nutrient Balance?

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.

Whole Farm Nutrient Balance estimates nutrient use efficiency by comparing products entering (inputs) and exiting (managed outputs) the farm. Only products with an N or P component are included.

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?

1. 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.
2. 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.
3. 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.

Results of On-Farm Measurement of WFNB

2006 Results – Appendix A

2007 Results – Appendix B

Return to Introductory Page for WFNB Resources

Authors: Rick Koelsch, University of Nebraska; Joe Lally, Iowa State University; Alan Sutton, Purdue University

This project was funded by The National Pork Board

Click here for introduction to WFNB

Farm size as measured by animal capacity is often the basis for determining which animal production facilities will be regulated and to what extent. For swine operations, a threshold of 2400 pig capacity (finishing and reproductive herd) often triggers the requirement of a federal permit under Concentrated Animal Feeding Operations rules of the National Pollutant Discharge Elimination System program. However, for the 13 farms involved in this study of Whole Farm Nutrient Balance (WFNB), size proved to be a poor indicator of the efficiency of nutrient utilization or potential for nutrient losses from the farm.

Whole Farm Nutrient Balance (WFNB) vs. Swine Facility Size

Size of the pig operation does not explain the variability in WFNB as illustrated by the flat regression lines in Figure 1 for both nitrogen (N) and phosphorus (P) balances. Based upon an analysis of WFNB, three farms experience N or P whole farm balance ratios of 2 to 1 or greater. They included a 2000-head and a 3,400-head finisher, as well as a 6,200 sow and finish facility. These results suggest that farm size has little impact on the efficiency with which nutrients can be managed.

Figure 1: Whole farm N and P balance for 13 swine farms vs size of pork production unit.
¹ WFNB Ratio is a ratio of all nutrients, N and P for this summary, that enter the farm (inputs) to all nutrients that exit the farm as managed products (managed outputs). See WFNB Introduction for a more complete explanation.
² Grow finish equivalents included nursery pigs and sows. Nursery pigs and sows were converted to a grow-finish equivalent based upon a comparison of average feed intake.

WFNB vs. Cropland Base

Access to a larger land base has often been associated with better utilization of manure nutrients. However, producers have found options for managing manure in situations where the land base is insufficient. In one of the case studies a farm with no land base had a WFNB of 2.1, similar to other producers with much larger land bases. Data from the 13 case farms (Figure 2) demonstrates that access to greater land areas does not result in improved efficiency of nutrient utilization by the participating swine farms.

Manure export was used by seven of the 13 producers in one or more years as a means of accessing land base that they do not own or manage. Others employed diets low in crude protein or phosphorus to partially compensate for limited land access. These modifications to the overall farm’s management of nutrients resulted in a level of WFNB that does not change with the size of the land base owned or managed by the participating producers.

Figure 2: Whole farm N and P balance for 13 swine farms vs crop production land base.
¹ WFNB Ratio is a ratio of all nutrients, N and P for this summary, that enter the farm (inputs) to all nutrients that exit the farm as managed products (managed outputs). See WFNB Introduction for a more complete explanation.
² Grow finish equivalents included nursery pigs and sows. Nursery pigs and sows were converted to a grow-finish equivalent based upon a comparison of average feed intake.

The concentration of animals to the land base is also an important consideration and is reviewed in a separate fact sheet accessible from the Introductory Page.

Results of On-Farm Measurement of WFNB

2006 Results – Appendix A

2007 Results – Appendix B

Return to Introductory Page for WFNB Resources

Authors: Rick Koelsch, University of Nebraska; Joe Lally, Iowa State University; Alan Sutton, Purdue University

This project was funded by The National Pork Board Project

Click here for introduction to WFNB

The relationship between the numbers of pigs raised on a swine farm to the numbers of acres to support this production unit is often called animal density. This measurement has been used in the past to relate the estimated amount of manure nutrient production from pigs to the amount of land that can utilize these nutrients for productive purposes i.e., crop production. However, using this measurement may give erroneous results because of the variety of nutrient management options available to pork operations. A whole farm nutrient balance (WFNB) study was conducted for two years (2006-2007) on 13 swine farms in the Midwest US. This fact sheet summarizes a comparison of animal density with WFNB or the farms overall measure of nutrient use efficiency. For more information about the farms involved in this study go to Overview of Nutrient Management Lessons Learned. Following are some observations from this study concerning the relationship of pig density to WFNB.

Pig Density

The relationship of pig density (grow-finish pig capacity per acre of available land area that can receive manure applications for crop production) to the WFNB for nitrogen (N) and phosphorus (P) as a ratio of N or P inputs to managed outputs was analyzed for the 13 swine farms during the two year study. Figure 1 shows the results of this relationship. There was a very weak conclusive effect or relationship of pig density per acre of land area on both N and P balance.

Figure 1: Whole farm nutrient balance for 13 swine farms vs. animal density.
¹ WFNB Ratio is a ratio of all nutrients, N and P for this summary, that enter the farm (inputs) to all nutrients that exit the farm as managed products (managed outputs). See WFNB Introduction for a more complete explanation.
² Grow finish equivalents included nursery pigs and sows. Nursery pigs and sows were converted to a grow-finish equivalent based upon a comparison of average feed intake.

Therefore, animal density alone is not effective in describing the nutrient use efficiency as describe by WFNB Ratio of a specific farm. Nutrient balance is also impacted by storage system type, feed program, crop nutrient management plan implementation, and export of manure (see additional fact sheets for details). As noted in Figure 1, there was considerable variation in the relationship of pig density to N and P balance with more variation in P balance than N balance. This reinforces the need to evaluate each specific farm independently for N and P balance considering the unique characteristics of the farm management, resources and other factors that can impact nutrient flow. A spreadsheet is available to determine the WFNB on any specific producer’s swine farm.

Summary

Pig density (pig capacity per acre land) is not a very effective indicator alone for N and P balance on a pork production unit. Many other aspects of the farm must be considered and evaluated to determined direct impact on N and P balance.

Results of On-Farm Measurement of WFNB

2006 Results – Appendix A

2007 Results – Appendix B

Return to Introductory Page for WFNB Resources

Authors: Alan Sutton, Purdue University; Rick Koelsch, University of Nebraska; Joe Lally, Iowa State University

This project was funded by The National Pork Board Project