Precision feeding and forage management effects on phosphorus loss modeled at a watershed scale

Delaware County and the Cornell Cooperative Extension of Delaware County of New York State have initiated a farm-scale precision feed management (PFM) program to g 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 1) 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 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 Soil and Water Assessment Tool (SWAT) model. Using the SWAT Model, manure With reduced P concentration was applied to cropland while grass-forage crop productivity was increased through N fertilizer application. The SWAT model g simulation revealed decreased particulate phosporous and soluble phosphorus losses by 22% and 13%, respectively Predicted reductions Of average, particulate phosphorus and Soluble phosphorus losses 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 also demonstrated an appreciable decrease in field-level soil-P during the growing season, Indicating increased soil-P uptake by the unproved grass-forage. For the growing season, reductions tor predicted active and labile 11 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 pools, respectively. Overall, the PFM Strategies were found to have a potential for reducing soil-P build-tip and 11 losses both at field and watershed levels. Performing a model-based environmental evaluation of farm management Strategies at I watershed level helps to integrate farm management plan Smallest management unit) into watershed level planning. Also, evaluating fill-Ill management strategies at a watershed scale provides valuable and comprehensive information for assessment the potential for long-term, cost-effective, and permanent reduction of P loss from dairy agriculture to the Cannonsville Reservoir.