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A review of two mandatory and two voluntary nutrient management strategies is …


Biology Articles » Agriculture » Evaluating Livestock System Environmental Performance with Whole-Farm Nutrient Balance » Methods and assumptions

Methods and assumptions
- Evaluating Livestock System Environmental Performance with Whole-Farm Nutrient Balance

 

 
The following discussion reviews the effects of key aspects of the CAFO nutrient planning regulations on a case-study farm's ability to reduce the farm's whole-farm nutrient imbalance (Fig. 1) following procedures established by Klausner (1995) and Koelsch (2001) and using a whole-farm nutrient balance analysis tool (University of Nebraska, 2004). By conducting a mass balance of nutrients entering and leaving (as managed products) a livestock operation, one can estimate a whole-farm nutrient imbalance. The imbalance represents the quantity of direct nutrient losses (e.g., ammonia volatilization) or increased nutrient inventories (e.g., increased soil P level) within a livestock operation. For N, most imbalances will be direct losses to the environment as ammonia into the air or nitrates into the ground water. While the soil has significant potential for storing N, most manure-related N will be available within a few years and either is utilized by the crop or lost to the environment. An imbalance in P is more commonly seen as increased inventories of P in the soil, increasing site-related runoff risk to local surface waters.

For the purpose of this paper, we apply four BMPs (two based on USEPA CAFO regulations and two voluntary changes) to a case-study farm and evaluate effects on the whole-farm nutrient balance. For brevity, we focus primarily on P balance. This case-study farm is a 2500-head beef finisher feedlot located in Nebraska. The farm participated in a survey of 33 farms from which data were collected for the purpose of estimating a whole-farm nutrient balance for each farm (see Table 2). To protect the identity of the farm, the case-study farm used in this discussion is shown on a site (Fig. 2) different from the farm's actual site but with a comparable land base and production potential. Specific information about the farm and its land application sites are summarized in Table 2 and Fig. 2. This case-study farm is used in producer training in Nebraska on nutrient management planning.



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