Empirical and phenomenological models were used to analyze two sets of field data from the same location in Georgia. It was shown that cumulative dry matter production over the season followed a straight line on normal probability paper and that total annual yield exhibited linear dependence on harvest interval, both for intervals up to 6 weeks. The data were used to evaluate the three coefficients of the empirical model and the four coefficients of the phenomenological model. Auxiliary functions were used to relate all coefficients to applied nitrogen.