A grazing simulation model: GRASIM B: Field testing
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A comprehensive grazing simulation model, GRASIM, that links all components of the pasture system was developed. The model predicts growth rate, water drainage, nitrogen leaching, and factors affecting animal intake. In order to ensure validity of the simulation, field testing of GRASIM was conducted using local experimental data. These tests were also performed for better parameter estimation. Field testing and evaluation of GRASIM components, grass growth, nitrogen, and water budget to central Pennsylvania conditions is presented. The model was tested for 1993 and 1994 and two fertilizer treatments - with and without animal manure. Statistical tests indicated a good fit between predicted and observed data for accumulated biomass, nitrate leaching and amount of water drained. Because of the mechanistic nature of the GRASIM, the model did not require any calibration. The model can be used in its present form by researchers, extension personnel, and trained farmers to increase the efficiency of pasture use.
