TheImprovement ofTropical and Subtropical Rangelands

GRAZING MANAGEMENT 121
seed production is important for reproduction. Similarly, vegetative
reproduction of certain species can be encouraged by manipulating
the time of grazing.
Desirable perennial plants produced on rangeland must be used
moderately during the growing season; thus the old guideline: use
half and leave half. Where additional soil protection is required,
herbage utilization should not exceed 40 percent. Heavy use of
perennial forage plants, followed by prolonged drought, can result in
the death ofmany desirable plants. On the other hand, usage greater
than 50 percent is beneficial under some conditions. Ephemerals,
often annual plants, generally are grazed by animals extenaively
when they are available. The forage crop may vary greatly from one
time to another because ofprecipitation differences. It is not unusual
for the annual forage crop on rangeland to vary between 50 and 150
percent of its average productivity.
DISTRIBUTION 01 GRAZING
Proper grazing use of forage plants most often calls for an even
distribution of livestock. In the large range units, prevalent in most
arid and semiarid areas, it is poesible to find serious overgrazing near
watering points (figure 6-1) and no use of forage in other portions
of the unit. Animal distribution can be improved by (1) increasing
the number of watering points (though this must be done carefully,
since increuing the number of waterpoints increases the number
of cattle and can lead to overgrazing), (2) establishing salting and
supplemental feeding areu 1-3 km from watering points, (3) using
more fencing or herding, (4) building trails, (5) fertilising selectively,
and (6) using a different clauoflivestock. Any practice that improves
animal distribution will increase range productivity.
Provided that water and protection are available throughout the
grazing areu, traditional systems of herding found in many tropical
and subtropical countries largely overcome the distribution problem
and have Usually evolved to use the area for optimum productivity.
TYPEOIANEMALGRAUNG
Another method of favoring the desirable forage species for one
type of animal is to use different kinds of livestock or wildlife to
reduce temporarily the less desirable plants.
Animal species use plants in significantly different ways. For
example, camels can eat more woody shrubs (figure 6-2) than any