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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #280336
Title: Nutrient concentrations of runoff as affected by the diameter of unconsolidated material from feedlot surfaces

Author
item Gilley, John
item BOONE, GREG - Former ARS Employee
item MARX, DAVID - University Of Nebraska

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2014
Publication Date: 7/21/2014
Citation: Gilley, J.E., Boone, G.D., Marx, D.B. 2014. Nutrient concentrations of runoff as affected by the diameter of unconsolidated material from feedlot surfaces. Transactions of the ASABE. 57(3):749-759. DOI: 10.13031/TRANS.57.10191.

Interpretive Summary: Beef cattle feedlots contain unconsolidated materials that accumulate on the feedlot surface during a feeding cycle. This study was conducted to: (1) determine the effects of varying diameter of unconsolidated surface materials on nutrient concentrations of runoff and (2) identify the effects of selected runoff rates on nutrient concentrations of runoff from unconsolidated surface materials containing variable particle diameters. Unconsolidated surface materials of varying diameter were placed within a plot area. Flow was then introduced at the top of the plots in successive increments and runoff samples for water quality analyses were obtained. Particle diameter significantly influenced runoff concentrations of dissolved phosphorus, particulate phosphorus, total phosphorus, and NH4-N. Runoff rate also significantly affected concentrations of dissolved phosphorus, particulate phosphorus, total phosphorus, and NH4-N for each of the particle size classes except the smallest diameter material. Thus, both the diameter of unconsolidated materials from feedlot surfaces and runoff rate may significantly influence nutrient concentrations of runoff.

Technical Abstract: Beef cattle feedlots contain unconsolidated material that accumulates on the feedlot surface during a feeding cycle. This study was conducted to measure the effects of varying diameters of unconsolidated surface material and varying flow rates on nutrient concentrations in runoff. Unconsolidated surface material with an average diameter of 4.76, 9.53, 19.1, or 47.5 mm and a composite sample with a 15.2 mm mean diameter were placed within 0.75 m wide × 4.0 m long plot areas. Flow was then introduced at the top of the plots in successive increments, and runoff samples for water quality analyses were obtained. Particle diameter significantly influenced runoff concentrations of dissolved phosphorus (DP), particulate phosphorus (PP), total phosphorus (TP), NH4-N, and solids transport. Concentrations of DP, PP, TP, and NH4-N for the composite material were 1.90, 1.28, 3.18, and 3.81 mg L-1, respectively, and solids transport was 19.8 g min-1. Runoff rate significantly affected concentrations of DP, PP, TP, NH4-N, and solids transport for each of the particle size classes except the 4.76 mm diameter material. For the composite material, concentrations of DP, PP, TP, and NH4-N decreased from 4.30 to 0.34 mg L-1, from 5.52 to 0.41 mg L-1, from 9.82 to 0.75 mg L-1, and from 25.8 to 0.49 mg L-1, respectively, as runoff rate increased from 0.02 to 1.10 L s-1. Nutrient concentrations of runoff from feedlot surfaces are affected by both varying diameters of unconsolidated surface material and varying flow rates.