Model analysis for partitioning of dry matter and plant nitrogen for stem and leaf in alfalfa

The expanded growth model was developed to describe accumulation of dry matter and plant nutrients with time for annual and perennial crops. It incorporates an environmental driving function and an intrinsic growth function. Previous analysis has shown that the model applies to the annual corn (Zea mays L.) and the warm season perennial bermudagrass (Cynodon dactylon L. Pers.). In this article, the model is used to describe accumulation of dry matter and plant nitrogen by alfalfa (Medicago sativa L.). Data confirm the hyperbolic phase relationship between plant N and dry matter for the whole plant. Further analysis confirms a linear relationship between leaf and stem dry matter. The model is used to simulate growth of stems with time, and a linear equation then used to link leaf and stem mass. Stem and leaf N are then related to stem and leaf dry matter through hyperbolic equations.