ECONOMIC AND PHOSPHORUS-RELATED EFFECTS OF PRECISION FEEDING AND FORAGE MANAGEMENT MODELED AT FARM AND WATERSHED SCALES: CANNONSVILLE RESERVIOR WATERSHED, NY

Open Access
Author:
Ghebremichael, Lula T
Graduate Program:
Agricultural and Biological Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
December 22, 2006
Committee Members:
  • James Michael Hamlett, Committee Chair
  • William J Gburek, Committee Member
  • Clarence Alan Rotz, Committee Member
  • Tamie L Veith, Committee Member
  • Albert R Jarrett, Committee Member
Keywords:
  • land use mangement
  • forage managment
  • phosphorus loss
  • IFSM
  • SWAT
  • precision feeding
  • simulation
Abstract:
Soil phosphorus (P) build-up in the New York Cannonsville Reservoir Watershed (CRW) and, in turn, the poor water quality of the reservoir, is largely due to more P being imported to farms as feed and fertilizer than exported in milk and other products. A precision feed management (PFM) program has been initiated to address the P imbalance problems while maintaining farm profitability. In this study, a model-based evaluation of PFM was performed at two management levels, farm- and watershed-level planning. For two CRW dairy-farms, Integrated Farm System Model (IFSM) simulation of reduced dietary-P integrated with increased grass-forage productivity and use in the diet resulted in reductions of farm P imbalances (78-100%) and soluble P losses (18%). Also, a decrease in feed supplement purchase was achieved, thus increasing farm profitability. Soil and Water Assessment Tool (SWAT) simulation for the same strategy also demonstrated appreciable decrease in soil P (7-8%) during the growing season, thereby indicating increased soil P removal by the improved grass-forage. Predicted soluble P loss reduction from cropland due to such a strategy was 15%, comparable to the IFSM-simulated soluble P loss reduction, which, at the watershed outlet, was 10%. For the watershed-level planning at the Town Brook Watershed (TWB), SWAT simulation of a strategy of converting 50% corn to grass integrated with reduced dietary-P and increased grass-forage productivity resulted in reductions of soluble and sediment-bound P losses from agricultural-crops (15%; 19%) and at the watershed outlet (13%; 16%). When this strategy was applied to a TBW-farm, IFSM predicted 83% reduction in the farm’s P imbalance without negatively affecting farm profitability. However, converting corn to grass without strategic changes in grass-yield productivity and use was found to negatively affect the farm’s profitability and P-balance due to increased P importation in grain-feed supplements. Model-based studies such as those performed in this study at farm and watershed levels provide a comprehensive tool for assessing the potential for long-term, cost-effective, and permanent reduction of P loss from dairy agriculture in the CRW. Similar approaches can be applied to dairy farms throughout the northeastern U.S. where implementation of PFM-strategies are of interest.