Impact of Manure and Soil Test Phosphorus on Phosphorus Runoff from Soils Subjected to Simulated Rainfall

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Title: Impact of Manure and Soil Test Phosphorus on Phosphorus Runoff from Soils Subjected to Simulated Rainfall
Author: Roberts, John Christopher
Advisors: dan israel, Committee Chair
Abstract: Runoff from agricultural fields amended with animal manure or fertilizer is a source of phosphorus (P) pollution to surface waters, which can have harmful effects such as eutrophication. The objectives of this study were to evaluate the impact of soil P status and the P composition of manure sources on P in runoff, characterize the effects of manure sources on mass loss of dissolved reactive P (DRP), total dissolved P (TDP), algal available P (AAP) and total P (TP) in runoff, and enhance the PLAT database with respect to soluble P attenuating factor (SPAF) and non-soluble P attenuating factor (NSPAF) values. Soil boxes set at 5% slopes received 7.5 cm hr-1 of simulated rainfall. Study soils included a Kenansville loamy sand (loamy siliceous subactive thermic Arenic Hapludults, a Coastal Plain soil) and a Davidson silt loam (kaolinitic thermic Rhodic Kandiudults, a Piedmont soil). Soil test P concentrations ranged from 16 to 283 mg P kg-1. Sources of P included broiler litter (BRL), breeder manure (BRD), breeder manure treated with three rates of alum (Al2(SO4)3) BRD0-0 kg m-2, BRDL-3.9 kg m-2, and BRDH-7.8 kg m-2 and DAP along with an unamended control. All manure sources were applied at 66 kg P ha-1. Water extractable P (WEP) represented an average of 10 ?b 6% total P in manure. Runoff samples were taken over a 30-min period. Piedmont soil contained greater amounts of clay, Al and Fe concentrations, and higher P sorption capacities that produced significantly lower DRP, TDP, AAP, and TP losses than the Coastal Plain soil. Runoff P loss did not differ for low and high STP soils of same taxonomy with the exception of AAP mass losses for Coastal Plain soil samples. Water extractable P in manures accounted for all DRP lost in runoff with DRP correlating strongly with WEP concentration (0.9961). A weak relationship between DRP in runoff and WEP applied to soil boxes was observed (R2=0.6547) and increased when a possible outlying manure treatment, BRL, was omitted from regression data (0.9927). Overall, manures containing the highest WEP concentrations supplied the largest losses of DRP in runoff. Manure treated with 3.9 and 7.8 kg m-2 of Al2(SO4)3 (alum) decreased DRP in runoff by 29%. Values calculated for PLAT SPAF and NSPAF coefficients were higher for Coastal Plain soil than Piedmont soil and overall higher than default values in PLAT. Management based on these results should help minimize harmful effects of P in runoff.
Date: 2005-10-16
Degree: MS
Discipline: Soil Science

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