The extended logistic model has proven very convenient for describing crop response (yield and plant nutrient uptake) to applied nutrients such as nitrogen. Model parameters are easily evaluated from field data for a particular crop, including annuals and perennials. In this article data from a five-year study for Pensacola bahiagrass (Cynodon dactylon Flügge) grown on an Entisol (excessively drained soil) and a Spodosol (poorly drained soil) in Florida are analyzed. The model described the

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... ern in the data quite well for both soils. Average yield over the five-year period for the Entisol was 56% of that for the Spodosol. Detailed analysis showed that even with high a level of nitrogen and water, yield for the Entisol would still only be 71% of that for the Spodosol. Comparison of various model parameters between the two soils is included.