Model for accumulation of dry matter and plant nutrients by corn1

Abstract

Accumulation of dry matter by warm‐season annuals depends upon time of season, including planting time. A mathematical model has been developed to simulate the growth process. The model contains a Gaussian environmental function and a linear‐exponential intrinsic growth function. Previous work has shown the applicability of the model to data for the perennials bahiagrass (Paspalum notatum) and bermudagrass (Cynodon dactylon). This article applies the model to field data for the annual corn (Zea mays) from four locations. Only two of the five parameters are varied for the different studies to match dry matter simulation with data. A hyperbolic relationship between plant nutrient accumulation [nitrogen (N), phosphorus (P), or potassium (K)] and dry matter accumulation has been included. Parameters for the hyperbolic equation for plant N agree closely for the three locations where plant N was measured. Results for P and K varied. Since the total plant dry matter accumulates at a faster rate than plant nutrients, plant nutrient concentrations for N, P, and K all decrease rapidly with age. A consequence of the growth model is an equation for estimating optimum time of planting in terms of parameter values assumed. Optimum time of planting precedes the mean of the environmental function by 10 to 11 weeks due to the exponential term in the intrinsic growth function.