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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #301907

Title: Assessing groundwater phosphorus in forage-based agroecosystem with cow-calf operation

item Sigua, Gilbert
item Chase, Chadwick - Chad
item Stone, Kenneth - Ken

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/20/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Phosphorus (P) fertilization is a vital component of productive farming. Phosphorus is an essential macronutrient that is required to meet global food requirements and make crop and livestock production profitable. While adequate levels of P soils are essential to grow crops, P has the potential to induce eutrophication in our water systems. Recent assessments of water quality status have identified eutrophication as one of the major causes of water quality “impairment” not only in the United States, but also around the world. Assessing and controlling P inputs are thus considered the key to reducing eutrophication and managing ecological integrity. In this paper we monitored and evaluated P concentrations of groundwater (GW) compared to the concentration of surface water (SW) P in forage-based landscape with managed cow-calf operations for three years (2007-2009) in central Florida. Groundwater samples were collected from three landscape locations along the slope gradient (GW1: 10-30% slope; GW2: 5-10% slope; and GW3: 0-5% slope). Surface water samples were collected from the seepage area (SW: 0% slope) located at the bottom of the landscape. Of the total P collected (averaged across year) in the landscape, 62.6% was observed from the seepage area or SW compared with 37.4% from GW (GW1 = 8.0%; GW2 = 10.9%; GW3 = 18.4%). Phosphorus in GW ranged from 0.02 to 0.20 milligram per liter (mg/L) while P concentration in SW ranged from 0.25 to 0.71 mg/L. The three-year average of P in GW of 0.09 mg/L was lower than the recommended goal or the Florida’s numeric nutrients standards (NNS) of 0.12 mg phosphors per liter. The three-year average of P concentration in SW of 0.45 mg/L was about four-fold higher than the Florida’s NNS value. Results suggest that cow-calf operation in pasture-based agroecosystem would contribute more P to SW than in the GW. The risk of GW contamination by P from animal agriculture production system is limited while the solid forms of P subject to loss via soil erosion could be the major water quality risk from P.