EXTENDED LOGISTIC MODEL OF FORAGE GRASS RESPONSE TO APPLIED NITROGEN AS AFFECTED BY SOIL EROSION

摘要

Mathematical models can be used to evaluate crop response to management factors such as applied nutrients, water availability, and tillage. The extended logistic model has proven particularly useful for this purpose. In this article, we use this model to link annual dry matter yield and plant nitrogen uptake to applied nitrogen for bahiagrass ( Paspalum notatum Flügge) and bermudagrass ( Cynodon dactylon L. Pers.) as affected by past soil erosion. The model describes response curves and phase relationships rather well for Pensacola and Tifton 9 bahiagrasses and Tifton 44 bermudagrass. Analysis showed that 60 kg N ha -1 is required to raise dry matter production of the severely eroded soil up to that of the non-eroded soil, while 70 kg N ha -1 is required to make plant N uptake equivalent for the two cases. Soil erosion has the effect of reducing N availability. We conclude that the ratio of minimum to maximum plant N concentration is the same for the three grasses and two soil conditions. The model accounts for the effect of soil erosion on forage production