| Abstract: | Abstract The extended logistic model relates seasonal dry matter and plant nutrient uptake to applied nutrient level. It has been shown to apply to data for annuals such as corn (Zea mays L.) and perennials such as bermudagrass (Cynodon dactylon L.) and bahiagrass (Paspalum notatum Flügge). The linear parameters in the model have been shown to depend on water availability and harvest interval (for perennials). Further work is needed to relate model parameters to plant characteristics. In this article, data from a field experiment with corn at six nitrogen levels (0, 0.5, 1.0, 2.0, 3.0, and 5.0 g N plant?1) and three plant population densities (3, 6, and 9 plants m?2; 3, 6, and 9 104 plants ha?1) are used to provide insight into this question. It turns out that all five model parameters are dependent on plant density, approaching maximum values at 8.3 plants m?2. Three of the parameters approach zero as density approaches zero, which seems intuitively correct. It is concluded that lower and upper limits of plant nitrogen concentration are independent of population density and are functions of the particular plant species. Detailed procedures are described for estimation of model parameters. |
