COUPLING OF DRY-MATTER AND NITROGEN ACCUMULATION IN MILLET AND RYEGRASS

The logistic model has proven very useful in relating dry matter produ ction of warm-season and cool-season forage grasses to applied nitroge n (N). A recent extension of the model coupled dry matter and plant N accumulation through a common response coefficient c. The objective of this analysis was to apply the extended model to both warm season pea rl millet [Pennisetum typhoides (Burm.) Staph and C. E. Hubb.] and coo l season ryegrass [Lolium multiflorum Lam.], and to establish a common response coefficient, c, between accumulation of dry matter and plant N for the two grasses in rotation. Analysis of variance established t he validity of this hypothesis. The model accurately described respons e of dry matter, plant N removal, and plant N concentration to applied N, with an overall correlation coefficient of 0.9954. Furthermore, th e model closely described the relationship between yield and plant N r emoval. The logistic equation is well behaved and simple to use on a p ocket calculator. It can be used to estimate yield and plant N removal in evaluation of agricultural practices and the influences on environ mental quality.