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Technical Report

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Numerical analysis, runoff, infiltration, poultry litter, mineralization, plant uptake, groundwater


A computer program was written to simulate the transport of nitrogen after an application of poultry litter to a pasture. The program was written in FORTRAN 77 to run on an IBM PC/AT or compatible personal computer or on a Sun SPARCSTATION. Simulation of water, solute and heat transport was by finite difference. Partition of rainfall into infiltration and runoff was by the SCS curve number method. A comparison was made of the computer model output with the results of a field experiment established at the Main Agricultural Experiment Station at Fayetteville. Poultry litter was applied at a rate of 4 tons/acre to a Tall Fescue pasture. The soil was a Captina silt loam. The test covers the period from 13 October, 1989 until 30 June, 1990. The predicted runoff data were compared to the results of the runoff from the field experiment. The computer model predicted slightly higher runoff volumes over the entire test period than determined in the field, but captured the shape of the monthly rainfall. The predicted NH4-N concentration released from the litter followed a flush pattern between rainfall events. It was removed from the topsoil quickly by conversion to N03-N and plant uptake. The predicted N03-N concentration distribution was higher than that of the NH4-N during most of the test period especially in the lower portion of the soil profile.

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