| Today's society has become more environmentally conscious and more environmentally active. The next generation of rules and regulations that will be imposed on agricultural production need to be based on a stronger scientific footing than we have now. It is necessary and prudent to take steps to understand the roles of nutrients, water and other environmental factors in the production of crops.; The purpose of this dissertation was to explore the validity of mathematical models that describe the accumulation of crop dry matter and nutrients with respect to time, applied nutrients, and water. Two primary models were investigated: the extended logistic model and the expanded growth model. Model parameters were compared from site to site in an attempt to find commonalities among the parameters and to assign physiological meaning to such parameters.; The extended logistic model is composed of multiple nonlinear equations. Normalized data were compared to the dimensionless form of the model with great success. Various nonlinear approaches were successfully used in data analysis and were later compared. Simplified estimation procedures for the extended logistic model are also presented.; A water availability function was used to explain dry matter yield results as a function of evapotranspiration, applied irrigation, and total water applied, with some success. The water availability function was successfully linked with the logistic equation to describe dry-matter accumulation relative to applied water and applied N.; This work demonstrates that the extended logistic model for seasonal dry matter production and nutrient removal can be used in conjunction with the expanded growth model to describe the actual growth of certain agronomic crops. The union of these two models gives further insight into the time-dependent behavior of crops such as corn (Zea mays L.) under different nutrient loading rates and different irrigation levels. |
