The logistic model has proven very useful in relating dry matter produ
ction of warm season perennial forage grasses to applied nitrogen. A r
ecent extension of the model coupled dry matter and plant N accumulati
on through a common response coefficient c. The objective of this anal
ysis was to apply the extended logistic model to cool season Gulf annu
al ryegrass (Lolium multiflorum Lam.) and to establish a common respon
se coefficient c between accumulation of dry matter and plant N. Analy
sis of variance established the validity of this hypothesis. The model
accurately described response of dry matter, plant N removal, and pla
nt N concentration to applied N, with an overall correlation coefficie
nt of 0.9954. Furthermore, the model closely described the relationshi
p between yield and plant N removal, as well as between plant N concen
tration and plant N removal. The logistic equation is well-behaved and
simple to use on a pocket calculator. It can be used to estimate yiel
ds and plant N removal in evaluation of agricultural production and en
vironmental quality.