Nutrients arrive on the livestock farm (Inputs) in the form of purchased feed, fertilizer, and animals or as N fixed by legumes or transported with irrigation water. It is desirable that these nutrients leave the farm as marketed products (Managed Outputs) such as animals or crops. Any imbalance between Input and Managed Outputs will either (1) be added to soil reserves (adding to future environmental risks) or (2) lost directly to the environment.
Excess N will be lost to the air as ammonia gas or to surface and groundwater as nitrate or ammonium. Excess P is commonly stored in the soil, contributing to soil P levels in excess of agronomic requirements. A high soil P level increases the potential for P movement to surface waters, contributing to eutrophication issues (see Lesson 1, Principles of Environmental Stewardship).
Understanding the whole farmís nutrient balance as well as the sources of nutrient inputs is critical to identifying a nutrient management strategy for reducing an imbalance and achieving an environmentally sustainable operation.
This balance is interested only in the nutrients that cross the border of the farm. It is not concerned with nutrients recycled within the farm. For example, homegrown crops fed to animals raised on your farm will not be considered because they do not cross the farmís boundary. Purchased feed products will be included because this nutrient input crosses the farmís boundary.
The boundary of the farm includes all owned or rented land that you farm (do not include land that is rented to others) and all livestock production facilities. This nutrient balance is to be estimated for a one-year period.
For estimating Nutrient Inputs and Outputs, information is required on the total commodity weight and nutrient content (feeds, forages, crops, and fertilizers). If a nutrient concentration is unknown, please select a representative feed, forage, or fertilizer value from the reference tables at the end of this appendix.
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