Modeling Plant Species Competition in Conjunction with Selective Grazing

Abstract

The dynamic simulation model GRAZE (Loewer et al., 1987) incorporates plant and beef animal growth in describing the grazing process. GRAZE had its beginnings at the University of Kentucky in 1976 (Walker et al., 1977; Loewer et al., 1981 ; Loewer and Smith, 1986) and was further developed through three regional research projects (Watson and Wells, 1985). Currently, it is being utilized and enhanced by the regional research project S-221 : Development of Profitable Beef-Forage Production Systems for the Southern Region, in part because of its utility in providing biophysical input-output relationships for purposes of economic analysis (Parsch and Loewer, 1987). GRAZE is a FORTRAN model consisting of approximately 15,000 lines of code. An objective of S-221 is to better describe the interface between plants and grazing animals. Initially, GRAZE contained logic that described the selectivity of grazing beef animals. However, paddocks were restricted to a single species. The objective of this paper is to describe version 3.0 of GRAZE that allows for plant species competition in conjunction with the selective grazing process