Title page for ETD etd-04042000-15520059

Type of Document Dissertation
Author Pierson, Sarah Tyson
Author's Email Address spierson@gaes.griffin.peachnet.edu
URN etd-04042000-15520059
Title Surface Runoff Quality in Grasslands Fertilized with Broiler Litter
Degree PhD
Department Crop and Soil Environmental Sciences
Advisory Committee
Advisor Name Title
Evanylo, Gregory K. Committee Chair
Cabrera, Miguel L. Committee Member
Heatwole, Conrad D. Committee Member
Mostaghimi, Saied Committee Member
Radcliffe, David E. Committee Member
  • water quality
  • phosphorus
  • environment
  • ammonium
  • EPIC
Date of Defense 2000-02-11
Availability restricted
Surface application of broiler litter to grasslands can increase concentrations of ammonium (NH4+-N) and dissolved reactive phosphorus (DRP) in surface runoff. It is not known, however, for how long after broiler litter applications that NH4+-N and DRP concentrations remain elevated. Five 0.75-ha, fescue-bermudagrass paddlocks received four broiler litter applications in 1995 and 1996, and only inorganic fertilizer N in 1997 and 1998. Runoff from each paddock was measured, sampled, and analyzed for NH4+-N and DRP. Flow-weighted NH4+-N and DRP concentrations increased from background values of 0.5 and 0.4 mg L-1, respectively, to values as high as 50.7 mg NH4+-N L-1 and 18.8 mg DRP L-1 in a runoff event that occurred immediately after the third litter application. Concentrations remained high while broiler litter was being applied but decreased steadily after the last application, reaching values near 1 mg L-1 (for NH4+-N and DRP) by 19 months after the final application. Among the factors that affected the average concentration of NH4+-N and DRP in cumulative runoff after a litter application were cumulative runoff, rates of total N and NH4+-N applied, and cumulative total litter N, total litter P, and water-soluble litter P applied during the four years of the study. Soil test P also affected DRP concentrations, but its effect depended on when the paddocks last received broiler litter. There is a need for tools to identify situations in which the application of broiler litter may enrich surface runoff with P. One such tool is the simulation model Erosion Productivity Impact Calculator (EPIC). EPIC’s ability to simulate runoff volume and losses of dissolved reactive P (DRP) was evaluated.

Data from the five 0.75-ha, tall fescue-bermudagrass plots that were fertilized with broiler litter during two years, and received only inorganic fertilizer N for the two subsequent years, were compared with EPIC estimates. EPIC simulations of runoff volume in individual events did not show bias in three of the plots but underestimated runoff in one plot and overestimated runoff in another. On an annual basis, the runoff volumes simulated by EPIC were similar to the observed values. A modified version of EPIC yielded better estimates of event DRP losses than the original EPIC and generated estimates of annual DRP loss that were similar to observed values. These results suggest that the modified EPIC may be useful for identifying situations where there is a high risk of large annual P losses from grasslands fertilized with broiler litter.

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