Author
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GHEBREMICHAEL, LULA - PENN STATE UNIV |
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Gburek, William |
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Veith, Tameria - Tamie |
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HAMLETT, JAMES - PENN STATE UNIV |
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Submitted to: Soil and Water Conservation Society Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 7/20/2006 Publication Date: 10/13/2006 Citation: Ghebremichael, L., Gburek, W.J., Veith, T.L., Hamlett, J. 2006. Economic and Phosphorus-related Effects of Precision Feeding and Forage Management on a dairy farm: Cannonsville Reservoir Watershed, NY[abstract]. Soil and Water Conservation Society Proceedings. p. 55-56. Interpretive Summary: An interpretive summary is not required. Technical Abstract: The Cannonsville Reservoir, which supplies drinking water to New York City, exhibits eutrophication partly due to phosphorus (P) losses from upstream areas dominated by dairy farms. Best management practices (BMPs), which are mainly structural and management-based practices, have been implemented throughout the Cannonsville Reservoir Watershed (CRW) in an effort to reduce off-field P losses to the reservoir to maintain a potable water supply. However, long-term water quality control efforts in the CRW are hindered by continuing P build-up in the soils as the result of farm P imports exceeding exports. Addressing the CRW P imbalance problems while maintaining economic viability of the watershed’s farm enterprises requires a system-level redesign of farm management; i.e., development and implementation of sets of farm planning strategies with consideration of the whole farm. One such approach, Precision Feed Management (PFM), is a farm-scale “BMP” that directly targets at the root cause of P build-up on the CRW farms. Precision feed management (PFM) involves more precisely balancing dairy cattle diets and improving production and utilization of homegrown forage in the animal diet in an effort to reduce importation of feed nutrients and soil-P build-up while maintaining the profitability of the farms. This study employed farm- and watershed-scale models to assess effectiveness of several PFM variations in controlling P losses, reducing soil P build-up, and maintaining farm profitability. The Integrated Farming System Model (IFSM) and the Soil and Water Assessment Tool (SWAT) were selected for this study. The IFSM was employed on a CRW dairy farm, which covers an entire sub-watershed within the CRW, to assess economic and environmental impacts of the PFM strategies. The SWAT was applied on the farm watershed to evaluate environmental impacts of the PFM strategies. IFSM simulation of more accurate feeding of P integrated with increased productivity of grass-forage, and the proportion of forage in the diet, resulted in a farm P balance reduction of 75% and a soluble P loss reduction of 17%. Feed supplement purchases declined by 29 kg/cow/year for mineral P, and by 285 kg/cow/year for grain and concentrates through adoption of the improved system. Thus farm profitability was increased. The SWAT simulation for the same strategy also demonstrated an appreciable decrease in field-level soil P during growing season indicating increased soil P removal by the improved grass-forage. Predicted soluble P loss reduction from cropland due to such strategy was 15%, agreeable to the IFSM-simulated soluble P loss reduction presented previously. Predicted soluble P loss reduction at watershed outlet was 10%. Results from the two models were comparable in determining environmental effects. Together, they provided more comprehensive picture. For example, IFSM provided economic and environmental effects at farm scale, while SWAT enabled evaluation of environmental effects of the strategies at watershed outlet and at field-edge. Such model-based studies done at farm and watershed levels will provide a comprehensive tool for assessing the potential for long-term, cost-effective, and permanent reduction of phosphorus loss from dairy agriculture to the Cannonsville Reservoir. |
