BAHIAGRASS RESPONSE TO APPLIED NITROGEN AND HARVEST INTERVAL

A growth model has been developed for warm-season perennial grasses wh ich relates seasonal distribution of dry matter to calendar time throu gh the probability equation, and which relates total seasonal dry matt er to harvest interval through a linear-exponential equation. The mode l is used to describe response of 'Tifton-9' bahiagrass (Paspalum nota tum Flogge) to time and harvest interval at Quincy, FL. It is also sho wn that yield response to applied nitrogen (N) is described by the log istic equation, in agreement with earlier results for bahiagrass and o ther forage grasses. This model removes the restriction of harvest int erval to 6 or 7 wk of the previous linear growth model. Maximum dry ma tter yield exceeded 20 Mg ha(-1). Maximum incremental dry matter respo nse to applied N occurred at approximately 140 kg N ha(-1). A harvest interval of 8 wk provided peak dry matter production. The mean and sta ndard deviation of dry matter distribution were 28.5 wk and 6.0 wk, re spectively. Correlation coefficients of the models with data exceeded 0.99. Effects of harvest interval and applied N are easily accounted f or with this model, which uses analytical functions and avoids the nee d for finite difference techniques.