Phosphorus Non-Point Pollution from Equestrian Wastes and the Need for Recycling

Abstract

South Florida and much of the rest of the World suffers from harmful algal blooms (HABs) and controls of both nitrogen (N) and phosphorus (P) pollution are required to curtail the onset, spread and/or expansion of these blooms. This report covers our studies on several aspects of equestrian waste (viz. horse manure) aimed at yielding an overview of phosphorus and its pollution stemming from non-point horse manure sources in portions of Palm Beach County Florida. Methods included a modified Hedley extraction sequence, emphasizing ‘easily extractable phosphorus’ (EEP), and 31P nuclear magnetic resonance (NMR) spectroscopic identification of organic phosphorus (Po) species. Samples included fresh and aged horse manure, pasture soils, horse feed and pasture grasses, and canal waters adjacent to equestrian or agricultural fields. Easily extractable Phosphorus (EEP) averaged about 54-77% of the total horse manure phosphorus. Total phosphorus ranged from 13,020 – 22,300 mg per kilogram dry weight. (≈60-100 lbs. P2O5 / ton and on a wet weight basis, this equates to 4,000 to 14,818 grams-P/ U.S. ton or 8.8 to 32.6 pounds of phosphorus (≈ 20-75 lb. P2O5) per wet weight ton of horse manure. Considering the values of EEP in fresh samples from a single horse, we found a range of 8,000 – 17,000 mg-P/kg (8-17 g-P/kg) dry weight horse manure. Soil samples yielded the highest P in the NaOH extract of the Hedley sequence. This equates to the Al, Fe and ester forms. Phosphorus (viz. EEP) runoff is viewed here as a non-point P pollution source.