Manipulation of Forage Quality: Objectives, Procedures, and 
Economic Considerations 
VINSON L. DUVALL? 
Most rangeland-management practices influ- 
ence quality of forage. This paper describes 
measures applied specifically to alter nutrient 
content, palatability, season of growth, or di- 
gestibility. The objective of such manipula- 
tions is usually increased consumption of nutri- 
ents by livestock, improved distribution of 
grazing, or both. However, on sites sensitive to 
grazing, palatability of forage is sometimes in- 
tentionally depressed to minimize damage. 
METHODS OF REGULATING QUALITY 
Fertilization 
Few, if any, methods for improving forage 
quality have recently received more attention 
from range investigators than fertilization. 
Studies of herbage responses to nitrogenous 
and phosphatic fertilizers have predominated ; 
efforts have been directed mainly toward 
remedying deficiencies of protein and phos- 
phorus. 
In many trials the application of nitrogen, 
either alone or with phosphorus, has materi- 
ally increased protein content of forage. On a 
pine-bluestem range in the humid South, nitro- 
gen increased protein in mature herbage by 
one-third (Duvall and Grelen 1967). Favorable 
responses have also been reported for climatic 
zones ranging from subhumid to arid (Cosper 
et al. 1967; Freeman and Humphrey 1956; 
Powell and Box 1967). 
Even heavy applications of nitrogen are 
often quickly expended or lost by leaching, and 
the quality of subsequent growth declines 
sharply. Periodic fertilization with small 
quantities usually benefits quality more 
throughout the growing season than a single 
heavy application, but the cost of spreading be- 
comes prohibitive. Hydrocarbon carriers that 
slowly release fertilizer elements have recently 
shown promise on turf grasses (Skogley and 
King 1968) and may prove useful on forage 
species. 
In humid regions, increases in herbage phos- 
phorus following application of phosphate 
have been even more spectacular than protein 
gains after adding nitrogen. On Florida range, 
rock phosphate increased phosphorus content 
of several important grasses about sixfold 
* Assistant Director for Research on Watershed 
Management, Recreation, Range Management, and 
Wildlife Habitat, Southern Forest Experiment Station, 
New Orleans, La. 
(Lewis 1963). As with nitrogen fertilization, 
forage response to phosphorus application has 
not been confined to areas of high rainfall. Su- 
perphosphate on desert grassland in Arizona 
materially increased phosphorus in the pre- 
dominant grasses (Freeman and Humphrey 
1956). 
Much of the fertilization research has been 
primarily concerned with forage response dur- 
ing the growing season, whereas protein is 
most often deficient in winter forage. In cer- 
tain instances the deficit may be remedied by 
fertilization. In a Texas trial (Dee and Box 
1967) most grasses that received ammonium 
nitrate in June contained adequate protein for 
pregnant cows throughout the following win- 
ter; without fertilization protein was deficient 
from December until new growth appeared. 
Fertilization has also lengthened the green- 
feed period. Lavin (1967) found that applica- 
tion of ammonium nitrate on seeded range in 
the southwestern ponderosa pine zone extended 
the growing season into late summer and fall. 
Freeman and Humphrey (1956) reported 
somewhat similar results for desert grassland. 
Some responses to fertilizer may be greater 
on forested range than on grassland. Burton et 
al. (1959) reported that increases in protein 
and calcium and a reduction in available car- 
bohydrates accompanied both fertilization with 
nitrogen and reduction of light intensity. 
These changes were greatest when a low in- 
tensity of light was combined with a heavy 
application of nitrogen. 
Fertilization may improve digestibility of 
critical nutrients in forage. For instance, on a 
pasture in south-central Washington, protein 
digestibility for cattle was higher in herbage 
receiving 100 pounds of nitrogen per acre than 
in herbage growing without nitrogen fertilizer 
(Heineman and Evans 1966). Matrone et al. 
(1949) reported that protein digestibility for 
sheep was greater in fertilized than in unfer- 
tilized forage, with the difference entirely at- 
tributable to the gain in protein content of the 
fertilized forage. Mitchell (1942) also reported 
a positive correlation between apparent digest- 
ibility of protein and the quantity present. 
Thus, where fertilization improves protein con- 
tent, digestibility of that nutrient may also in- 
crease. 
Grazing distribution can be altered by fertil- 
izing. Utilization of desert grassland was about 
three, four, and five times greater with 25, 50, 
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