YIELDFIT: A computer program for determining economic fertilization rates
Hector J. Barreto, Robert L. Westerman · Journal of Agronomic Education · 1987
ABSTRACT Fertilizer economics are often omitted or receive very little attention in soil fertility courses. YIELDFIT is a microcomputer program developed to aid soil fertility students in understanding the use of production functions and calculation of maximum economic fertilization rates for a single nutrient source. Routines for fitting Mitscherlich, quadratic, and square root functions are included in the program. The student starts with a set of yield data to which these models are fitted using least squares procedures. Generated equations become yield models for calculation of economic optimum rates. Students can interactively change algebraic functions, prices for crop and fertilizer, and overhead costs. Graphic output allows students to evaluate effects of these changes on gross revenue, net profit, and return on fertilizer investment.