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| Changes on several farms during the study illustrated important factors that improve the efficiency of nutrient use on swine farms. Participating farms improved whole farm nutrient balance between 2006 and 2007 by reducing feed ration P levels, converting an anaerobic lagoon to an earthen basin, reducing legume production, or improving their implementation of the nutrient management plan. |
Click here for introduction to WFNB
Whole Farm Nutrient Balance (WFNB) is a comparison of the quantity of nutrients, typically nitrogen (N) and phosphorus (P), that enter (inputs) and exit (outputs) the farm gate. The purpose of this summary is to discuss impact on WFNB resulting from significant individual farm changes during the 2-year study period on two of the participating farms. The farms were experiencing dynamic change because of market conditions, labor availability, production system design and animal health and management.
Farm C4
Additional acres, crop rotation and dietary formulation changes were observed on Farm C4 from 2006 to 2007. This farm changed from all legume crop (soybean/alfalfa) production to less than half the acres in legumes with corn being added to the rotation. In addition, an increase in total acres occurred. The WFNB nitrogen ratio was reduced from 1.6:1 and changed to 1.5:1, while the phosphorus ratio went from 3.3:1 down to 1.8:1. See Table 1.
| N ratio2 | P ratio2 | Dietary P Concentration | % legumes | |
|---|---|---|---|---|
| 2006 | 1.6 | 3.3 | 0.75% | 100% |
| 2007 | 1.5 | 1.8 | 0.66% | 55% |
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1Appendix A and Appendix B provide a complete nutrient balance on Farm C4. 2For explanation of WFNB Ratio, refer to Introduction to WFNB. | ||||
The combination of these changes produced significant improvements in the whole farm P balance for C4. First, switching from legumes to a legume/corn rotation contributed to an increase in the total phosphorus removal from this farm from 6,200 lbs. P to 10,300 lbs. P as crops. This change also reduced legume fixed nitrogen inputs to the farm by 9000 lbs from 2006 to 2007 or more than 15% of the nitrogen imbalance experienced in 2006.
Second, this farm added 185 acres of corn production while reducing N and P fertilizer purchases by 4,000 and 4,400 lbs respectively from 2006 to 2007. Improvements in the crediting of manure nutrients and residual soil nutrients (manure management plan) were necessary to achieve these changes. The acres available for manure applications also increased.
Finally, the feed ration design also changed with the phosphorus content dropping from 0.75% in 2006 to 0.66% in 2007, the single biggest contributor to the improvement in P balance. The combination of the three changes produced significant improvements in the whole farm P balance.
Farm C1
Farm C1’s decision to change an anaerobic lagoon (storage and treatment function) into an earthen basin (storage function only) is another example of a system design change that occurred over the course of this project. This signaled a significant improvement in the phosphorus ratio from 2.9:1 to 1.2:1, which reflects the premise of lagoons being designed to store phosphorus over a long period of time (years) compared to a basin’s ability to utilize phosphorus annually. The added value of the manure from the earthen basin was the motivation driving this change.
| N ratio2 | P ratio2 | Storage | ||
|---|---|---|---|---|
| 2006 | 2.5 | 2.9 | Anaerobic Lagoon | |
| 2007 | 1.7 | 1.2 | Earthen Basin | |
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1Appendix A and Appendix B provide a complete nutrient balance on Farm C4. 2For explanation of WFNB Ratio, refer to Introduction to WFNB. | ||||
Results of On-Farm Measurement of WFNB
Return to Introductory Page for WFNB Resources
Authors: Joe Lally, Iowa State University; Rick Koelsch, University of Nebraska; Alan Sutton, Purdue University
This project was funded by The National Pork Board Project
