The logistic model has proven very useful in relating dry matter produ
ction of forage grasses to applied nitrogen. A recent extension of the
model coupled dry matter and plant N accumulation through a common re
sponse coefficient c. The objective of this analysis was to establish
the validity of the extended model for each of the three major nutrien
ts (N, P, K), with a common coefficient c between dry matter and each
applied nutrient. Analysis of variance established the validity of thi
s hypothesis. The model accurately described response of dry matter, p
lant nutrient removal, and plant nutrient concentration to applied nut
rient, with overall correlation coefficients of 0.9928, 0.9972, and 0.
9975 for applied N, P, and K, respectively. Furthermore, the model clo
sely described the relationship between yield and plant nutrient remov
al, as well as between plant nutrient concentration and plant nutrient
removal, for each nutrient. This work confirmed earlier results for a
pplied N with various grasses and established the validity of the mode
l for applied P and K for the first time. The logistic equation is wel
l-behaved and simple to use on a pocket calculator. It can be used to
describe yields and nutrient removal in evaluation of agricultural pro
duction and environmental quality.