Effects of Fertilization on Quality of Range Forage 
Don A. DUNCAN?! and LYNN O. HYLTON, Jr.? 
The effects of fertilizers on the quality of 
range and pasture forage could be the subject 
of a sizable book. However, we will summarize 
only part of the pertinent literature and some 
current studies on the effects of inorganic fer- 
tilizers. Remember that fertilizers may affect 
both the quantity and the quality of forage, 
and that the literature does not always draw a 
distinction. The quality of forage growing 
under range conditions is affected by many in- 
teracting factors that are difficult to measure 
or control. 
Fertilization is an important cultural prac- 
tice used to change, and usually to improve, 
forage quality. The amount of fertilizers ap- 
plied can be measured and controlled. But cau- 
tion is needed in attributing any changes in 
forage quality directly to fertilizer alone. Con- 
siderable insight into the entire ecosystem is 
needed before the effects of fertilization on for- 
age quality can be interpreted correctly. 
Our review will cover: (1) changes made in 
forage quality by changes in the nutrient com- 
position of range plants and (2) changes made 
in forage quality by changes in the botanical 
composition of rangelands. 
CHANGES IN NUTRIENT COMPOSITION 
OF RANGE PLANTS 
Nitrogen fertilization in the northern Great 
Plains is a valuable cultural practice to in- 
crease the percentage and the total yield of 
plant protein and, hence, to improve forage 
quality (Clark and Tisdale 1945; Cosper et al. 
1967; Lodge 1959; Smoliak 1965). In North 
Dakota, fertilization of 90 pounds of nitrogen 
per acre for both of 2 years on a heavily 
grazed pasture did more to improve the condi- 
tion of the forage plants than did 6 years with- 
out grazing (Rogler and Lorenz, 1957). 
Nitrogen fertilization has significantly in- 
creased the protein content in prairie grasses 
(Burzlaff et al. 1968; Dee and Box 1967;), in 
seeded grasses on mountain rangelands in 
northeastern Utah and southeastern Idaho 
(Hull 1963), and in intermediate wheatgrass 
in the southwestern ponderosa pine zone 
(Lavin 1967). The protein content of nitrogen 
fertilized tobosa was generally 20 to 35 percent 
higher than that of unfertilized tobosa on flood 
plains in the semidesert grassland (Herbel 
1963). Many of these nitrogen-fertilizer stud- 
*Range Scientist. Annual-Plant Range Research Pro- 
ject. Headquarters for the project is Fresno, Calif. The 
project is under the jurisdiction of the Pacific South- 
weal Forest and Range Experiment Station, Berkeley, 
alif. 
ies have shown increased succulence of forage 
and extended periods of green growth, as well 
as increased protein contents. 
Nitrogen fertilization has generally in- 
creased both the percentage of protein in ear- 
ly-growing grasses and the total yield of pro- 
tein from flood meadows (Cooper 1956; Rum- 
berg 1963) and from high-altitude meadows 
(Wilehite et al., 1955). 
In California annual grassland, about 160 
pounds of nitrogen per acre was required to in- 
crease the percentage of nitrogen in nonlegum- 
inous plants harvested at the end of the grow- 
ing season (Jones 1963; Jones and Winans 
1967). If less than half that amount was used, 
it increased only the percentage of plant nitro- 
gen during the vegetative stage. These studies 
pointed out that the percentage of nitrogen in 
the plant at maturity may be less with nitro- 
gen fertilization than without fertilization— 
especially in high rainfall areas where the 
added nitrogen is used by the plant for in- 
creased growth. Total yield of protein, how- 
ever, was generally higher with nitrogen fer- 
tilization. 
McKell et al. (1960) reported some benefits 
of fertilizing annual ranges in a dry year. 
They found that total nitrogen contents of for- 
age ranged from 1.32 percent with no nitrogen 
fertilizer application to 1.95 percent total ni- 
trogen from plots treated with 200 pounds of 
nitrogen per acre. Phosphorus and sulfur fer- 
tilizers added to nitrogen caused only minor in- 
creases in the nitrogen content of the forage. 
Total yield of protein was 83 pounds per acre 
from forage on nonfertilized plots and 153 
pounds per acre from forage on plots fertilized 
with 80 pounds of nitrogen per acre. The appli- 
cation of 100 pounds of nitrogen per acre 
brought the total protein yield up to only 186 
pounds per acre; 150 pounds of nitrogen up to 
188 pounds per acre; and 200 pounds of nitro- 
gen up to 202 pounds. 
Fisher and Caldwell (1959) reported a yield 
of 320 pounds of protein per acre from coastal 
bermudagrass without nitrogen fertilization 
and 3,635 pounds of protein per acre with 
1,332 pounds per acre of nitrogen fertilizer. 
Ten to 40 percent more nitrogen fertilizer was 
required for maximum protein production than 
for maximum hay production. Fisher and Cald- 
well (1959) also concluded that phosphorus, 
potassium, and lime were required to maintain 
high-quality forage when high rates of nitro- 
gen were applied under high rainfall condi- 
tions. 
Timely use of nitrogen on adapted grasses 
57 
