VALUE AND USE
SPECIES: Digitaria californica | Arizona Cottontop 



WOOD PRODUCTS VALUE : 
NO-ENTRY


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Arizona cottontop responds quickly to spring and summer rains, grows
rapidly, and provides highly palatable green forage.  The foliage cures
well, and some stems remain green in winter so that it is an important
winter feed [20].  It also makes rapid growth following winter rains,
and furnishes earlier forage than most associated grasses [15].




PALATABILITY : 
Arizona cottontop provides good graze for livestock and fair graze for
wildlife [14].

Arizona cottontop was given a high palatability rating for cattle [2].
It is palatable throughout the year [14].  It is preferred by cattle
over most other grass species at all seasons of the year [8].

In a study of preferential grazing of native grasses and the introduced
grass species Lehmann lovegrass (Eragrostis lehmanniana) in Arizona,
cattle consumption of native grasses was greater than 75 percent, versus
less than 20 percent for Lehmann lovegrass.  Arizona cottontop was a
preferred species even among the native grasses [29].

When compared to Arizona cottontop plants outside the canopy cover,
cattle grazed Arizona cottontop closely and preferentially under
mesquite.  This may have been due to the greater palatability of those
plants because of their higher nutrient content [29].



NUTRITIONAL VALUE : 
NO-ENTRY


COVER VALUE : 
NO-ENTRY


VALUE FOR REHABILITATION OF DISTURBED SITES : 
Arizona cottontop can be successfully reseeded on upland areas receiving
at least 11 inches (280 mm) of annual precipitation, provided a good
seedbed has been prepared.  In New Mexico, Arizona cottontop gave the
best germination of all native forage plants tested, but seedlings made
slower growth than most other plants.  Thus, moisture had to be
available for a longer period for Arizona cottontop seedlings.  However,
once plants are established, they are drought hardy.  Populations are
maintained by establishment of new plants from seed during wet years.
Once established, Arizona cottontop can be quite long lived.  Some
plants live for more than 15 years, even when grazed [8].

In less favorable sites, reseeding efforts may not succeed.  In the
Sonoran and Chihuahuan deserts extreme drought, overgrazing, sheet and
gully erosion, and plowing caused extreme deterioration of rangeland.
Native species, including Arizona cottontop, failed to persist after
reseeding efforts, and were replaced with introduced grasses, forbs, and
shrubs [10].

The accumulated heat needed for Arizona cottontop seeds to germinate is
on the low end for warm-season range grasses tested, and Arizona
cottontop is therefore one of the easier species to establish.  It is a
good choice for native grass reseeding provided that the moisture
requirement for seedling establishment is met [22].



OTHER USES AND VALUES : 
NO-ENTRY


MANAGEMENT CONSIDERATIONS : 
Arizona cottontop tolerates relatively heavy grazing over long periods.
Dormant-season grazing averaging over 65 percent use for periods up to
15 years had no apparent effect on longevity, changes in basal area, or
changes in plant height [8].  In studies of productivity, cottontop
succeeded about as well in dry as in wet years [28,30].

Arizona cottontop will thrive under most management strategies, provided
that the intensity of grazing is held to a reasonable level [8].
Grazing, particularly at the beginning of the growing season, actually
increases the sprouting and growth of axillary shoots, leading to
increased productivity [9].  However, because it is highly palatable
throughout the year, it is frequently overgrazed [20].

Two management practices are recommended to maintain optimum Arizona
cottontop productivity [8]:
  1.  If Arizona cottontop is dominant, utilization should be based on
      50 percent use of cottontop.  If it is not the dominant grass, its
      use should average a little less than 60 percent.
  2.  Defer or reduce grazing by about 50 percent during the growing
      season, 2 years out of 3.  This will lessen the grazing impact on
      Arizona cottontop, but still provide the stimulus for axillary
      sprouting.

Under moderate grazing in Arizona, Arizona cottontop was somewhat more
dense under a year-long grazing schedule than under a rotation system,
but the difference was slight.  These results were attributed to initial
plant densities near the maximum, and to moderate grazing.  On range
that was initially in poor condition, rotation grazing improved
cottontop productivity [28].  Consistent heavy grazing during the summer
growing season adversely affects vigor and productivity of Arizona
cottontop [8].

An established stand of Arizona cottontop competes strongly with velvet
mesquite seedlings (Prosopis velutina) and deters the spread of velvet
mesquite into grasslands.  However, in a mature stand of velvet mesquite
there can be great reduction of cottontop production.  On many sites,
removal of velvet mesquite releases Arizona cottontop, with subsequent
large increases in cottontop production [8].  In Texas, when honey
mesquite (P. glandulosa var. glandulosa) was removed Arizona cottontop
increased most when the mesquite was cut at ground level and the stump
was painted with herbicide.  Arizona cottontop remained consistently
above the control in its abundance with aerial spraying of honey
mesquite.  However, it decreased or was completely replaced when
grubbing and chaining of honey mesquite induced a lower seral stage due
to soil disturbance [5,21].  Rootplowing produces a highly disturbed
seedbed, which reduces cottontop density and increases competition from
weeds [32].

In desert soils with very poor nutrient status, Arizona cottontop can be
much more productive under mesquite (Prosopis spp).  However, under
these conditions cattle will preferentially graze Arizona cottontop
beneath the mesquite, which can result in scanty vegetational cover on
these sites.  A manager might then conclude that mesquite is inhibiting
Arizona cottontop growth and should be eliminated, when the opposite may
be true [35].  Therefore, soil nutrient status should be assessed before
mesquite removal, and also before reseeding efforts.  Deficiencies may
need to be corrected with commercial fertilizers [25].

Removal of the crown cover of redberry juniper (Juniperus pinchoti)
which had been killed by herbicide resulted in an increase in Arizona
cottontop on the site.  However, cottontop was only found beneath the
dead junipers, and not between them [16].

In the Chihuahuan and Sonoran deserts a series of studies showed that 
substantial increases in native forage production, including Arizona
cottontop, can be obtained if [10]:
  1.  Plant competition from shrubs and forbs is reduced (by
      mechanical means or with herbicides)
  2.  Dead standing litter remains in place after treatment
  3.  Grazing is excluded or reduced.

Related categories for Species: Digitaria californica | Arizona Cottontop