Principal Investigator: Walter G. Knisel (University of Georgia)
Principal Investigator: Matt C. Smith (University of Georgia)
Principal Investigator: Stanley R. Wilkinson (U.S. Department of Agriculture)
Principal Investigator: Matt C. Smith (University of Georgia)
Sponsor: GWRI
Start Date: 1995-04-01; Completion Date: 1995-04-01;
Keywords: GLEAMS, leaching, management, modeling, nitrogen, poultry litter, runoff, water quality
Description:
The GLEAMS model was applied to represent 6 fertilizer and broiler litter management practices on Coastal bermudagrass with multiple cuttings for hay at Watkinsville, Georgia. Observed data from a 7 year study were used to validate GLEAMS with comparisons of runoff volumes, runoff nitrogen, N03-N leached, forage yield, and nitrogen yield. Simulated runoff volumes and runoff nitrogen losses compared well with observed values for the record period. NO3-N leached and maximum monthly weighted concentrations were compared with good representation of the timing of peaks for all treatments. The model over-estimated the mass of No3-N leached; but peak concentrations were both over- and under-estimated. Forage yield was simulated very well, but potential yield was found to be a very sensitive model input parameter. The model under estimated nitrogen yield in the forage very significantly. The optimum nitrogen concentration relations under-estimated N demand, but coefficients for lush nitrogen uptake were very sensitive interactively with potential yield. Lush nitrogen uptake could result in nitrogen deficiency and cause reduced yield which does not occur in observed data. GLEAMS represented the fertilizer and broiler litter management practices, and can be used effectively for relative comparisons. However, it should not be used for quantitative predictions. Model users are urged to se local site-specific data if at all possible to fine-tune values of sensitive parameters.