| Phosphorus (P) inputs to fresh waters can accelerate the eutrophication process. Agricultural nutrient runoff has been shown to be a contributor of P and nitrogen (N). Broiler production areas were evaluated for their potential to contribute P and N to runoff. Broiler house dust (BHD) samples were analyzed and compared to broiler litter (BL), rainfall simulations were conducted on plots adjacent to broiler house fans to evaluate nutrient enrichment in runoff from deposited dust, and runoff was automatically sampled at two culverts draining the land around broiler houses. Following this, an on-farm byproduct containment and nutrient removal structure was designed to reduce concentrations of P and N in runoff from land adjacent to fan outlets. The BHD ranged in water extractable phosphorus (WEP) concentrations from 4,720 to 6,580 mg kg-1, which was at least 1.6 times greater than the BL from which it originated. Water extractable P has been shown to be the most consistent and reliable indicator of P runoff potential. Runoff concentrations from plots adjacent to fans ranged from 2.3 to 16.6 mg L -1 total P (TP) and 15.0 to 122.3 mg L-1 total N (TN), and were comparable to those from pastures to which large quantities of BL had been applied. To evaluate for their potential use in the nutrient removal structures, iron filter cake (RM) and aluminum water treatment residual (WT) were tested for their P adsorption capacities and hydraulic conductivities. Phosphorus removal study results revealed an average of 56 and 57% were removed by the ≤6-mm fraction treatment combination of RM and WT, respectively, and both transmitted sufficient flow to accommodate a 25-fold 25-year 30-minute storm of 5.5 cm min-1. Data compiled for four on-farm containment structures for 25 storm events show reductions in TP concentrations to an average of less than 0.90 mg L-1 for RM and 0.40 mg L -1 for WT. Phosphorus and N concentrations are elevated in runoff both at the nutrient source and at the edge of the production area. Nutrient removal at the source is an efficient method to reduce these concentrations. |
