| Abstrakt: |
Delaware County and the Cornell Cooperative Extension of Delaware County of New York State have initiated's farm-scale precision feed management (PFM) program to reduce soil-phosphorus build-up and phosphorus (P) losses to the Cannonsville Reservoir, a major supply source of New York City drinking water. The PFM program includes strategies that more precisely balance dairy cattle dietary P requirements with actual P intake and that improve on-farm forage production and utilization in the animal diet. The goal of the PFM program is to reduce manure P concentration, feed nutrients importation, P imbalance problems, and soil-P build-up while maintaining farm profitability. In this study, several PFM strategies were evaluated with respect to controlling P losses and soil-P build-up at both field and watershed scales using the Sail and Water Assessment Tool (SWAT) model. Using the SWAT model, manure with reduced P concentration was applied to cropland while grass forage clop productivity was increased through N fertilizer application. The SWAT model simulation revealed decreased particulate phosphorus and soluble phosphorus lows by 22% and 13%, respectively. Predicted reductions of average particulate phosphorus and soluble phosphorus loses at the watershed outlet were 16% and 13% respectively. over a three-year period. compared to the baseline (conditions before changes were implemented). Model results ah demonstrated an appreciable decrease in field-level mil-P during the growing season, indicating increased soil-P uptake by the improved grass-forage. For the growing season, reductions for predicted active and labile P pools were 11 and 5 mg kg-1 (0.02 and 0.01 lb tn-1), respectively, compared to the baseline. The corresponding reductions in field-level soil P were equivalent to 8% and 7% for labile and active P pods. respectively Overall, the PFM strategies were found to haw a potential for reducing soil-P build-up and P losses both at field and watershed levels. Performing a model-based environmental evaluation of farm management strategies at a watershed level helps to integrate farm management planning (the smallest management unit) into watershed level planning. Also, evaluating farm management strategies at a watershed scale provides valuable and comprehensive information for messing the potential for long-term, cost-effective, and permanent reduction of P loss from dairy agriculture to the Cannonsville Reservoir. [ABSTRACT FROM AUTHOR] |
