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Ifhd river Field Laboratory Mimeo Report IRL 66-1 *-*
\ March 1, 1966
ti 71, \\ THE CONTRIBUTION OF STYLOSANTHES HUMILIS, A SUMMER LEGUME,
fRFL bL-I TO PASTURE PROGRAMS IN SOUTH FLORIDA
Albert E. Kretschmer, Jr.l/
Production of pangolagrass and other improved grasses generally is adequate
in the summer. However, even well fertilized grasses tend to have low protein.
contents in the late summer and early fall. The addition of a high protein
legume to grass pastures would increase protein levels and might reduce the need
for nitrogen fertilizer materials. Such a legume must be competitive with grasses
in the summer, persist under moderate to heavy grazing, add materially to the
quality of the legume-grass mixture, and be acceptable to cattle. Desirable
characteristics should permit the use of white clover in the normal way, allow
deferred grazing in the fall, and permit hay making without adversely affecting
normal haying operations.
Stylosanthes humilis, a summer-growing, self-regenerating annual legume
appears to satisfy most of the requirements described above. Results of three
years work in small plots and in small commercial field tests with S. humilis
have shown the following differences between it and white clover (and other tem-
perate legumes). S. humilis is: (1) more sensitive to frost, (2) more drought
resistant, (3) more woody, (4) more tolerant of acid soils, (5) more tolerant
of low fertility, (6) less acceptable to cattle, (7) more heat resistant, (8) a
better competitor with pangolagrass, and (9) less effective in fixing nitrogen.
Dry matter production of S. humilis is greatest in the summer and seed production
occurs in the. fall. This legume requires "cow-pea" type inoculant (is less specific
in Rhizobium bacteria needs).
Similarities exist between white clover and S. humilis. Both persist in
spite of heavy grazing, produce large quantities of hard seed, and can survive
short periods of flooding.
The contribution of S. humilis in production and crude protein content when
grown with pangolagrass was estimated by clipping tests during three summers and
is explained graphically in the accompanying Figures. To complete the over-all
yearly production scheme, data on pangolagrass receiving large and small amounts
of nitrogen and white clover-pangolagrass mixtures are also presented. Curves
are based on results from replicated clipping experiments with these mixtures.
The yield data are reported on a basis of pounds of dry matter per week and the
crude protein contents are presented as percentages.
FIGURE 1.--DRY MATTER PRODUCTION
Pangolagrass--Growth curves for pangolagrass heavily or lightly fertilized are
similar with respect to the period of maximum production. However, the high
fertilization rates markedly increased production. Pangolagrass grows slowly
until about May. Maximum growth commences after this time. In September or
October, the growth rate is reduced markedly regardless of fertilizer rates.
1/ Associate Agronomist, Indian River Field Laboratory, Florida Agricultural
Experiment Stations, Ft. Pierce, Florida.
Deferred grazing which permits late summer.grass growth to accumulate can provide
considerable feed in November and December.
Pangolagrass + White Clover--Growth of white clover in late winter and early spring
contributes only slightly to the dry matter production. During this period, how-
ever, the feed supply from.good quality grasses is almost nil and the addition
of this high:quality feed assures the utilization of any roughages that remain
in the pasture. The yearly yields from white clover-pangolagrass mixtures are
guided by the relative large contribution from summer grass growth. In late
summer the quality.and quantity of the grass generally decreases more rapidly
under a white clover pangolagrass pasture than under heavily fertilized pangola-
Pangolagrass + Stylosanthes humilis--The addition of S. humilis to pangolagrass
resulted in a large increase in dry matter production compared to pangolagrass
receiving 30 pounds of nitrogen per acre per year. Yields were less than highly
fertilized pangolagrass. Although seedlings of S. humilis appear in early spring,
the maximum growth of S. humilis begins about the first of June and continues until
seed production begins in September or October. Deferred grazing would result in
a greater quantity of the grass-legume mixture for early winter and also permit
maximum seed production.
Pangolagrass--Pangolagrass protein percentages were greater in the winter and
early spring than in summer. Because of the.fast grass growth in the summer,
the absorbed nitrogen is diluted. In the winter the grass growth has practically
stopped, and the nitrogen is not diluted. Pangolagrass fertilized with 50-pounds
of nitrogen per acre.after each six-weeks cutting in the summer produced protein
contents of about 8.0 or less at the end of six weeks growth.
Pangolagrass + White Clover--The protein contribution of white clover to the
mixture is very large, and the need for high quality forage in the spring cannot
be overlooked. During summer, protein contents in'the grass decrease rapidly
(unless nitrogen is applied).. When white clover grew well into the summer then
protein contents of the mixtures were between 8.0 and 9.0.percent when plots
were harvested on a monthly basis. When clover persistence was poor, crude
protein contents were below 6.0 percent.
Pangolagrass + Stylosanthes humilis--The addition of Stylosanthes humilis to a
pangolagrass sod resulted in a large increase in crude protein percentages in the
summer and fall. About 100 pounds of nitrogen per acre was available in harvest-
able forage as a result of nitrogen fixation by S. humilis. Some of the nitrogen
was available to the grass as evidenced by the greener color compared to pangola-
grass growing alone. S. humilis-pangolagrass mixtures reserved for late November
makes good quality.hay (crude protein contents of about 8.0 have been found) that
can be field cured as easily as pangolagrass alone. Probably there would be
enough mature seeds in the hay to establish new stands of S. humilis when fed
to cattle on grass pastures in the winter or spring.
The addition of S. humilis to pangolagrass (or pangolagrass + white clover)
increased forage production (compared to lightly fertilized pangolagrass) and
increased the crude protein contents in summer and fall. The mixture can be
reserved for late November grazing or haying, and makes good quality feed.
Figure l.--Oven Dry Weight Yields
of Pangolagrass and Pangolagrass
Plus White Clover and Stylosanthes
S(45 to 50 lbs. nitrogen per acre
after each 4 or 6 weeks cutting)
(30 lbs. nitrogen
per -acre in the fall)
S 45 to 50 lbs. N/A
* '- After Each 4 or
^ 6 Weeks Cutting
.- ~-. 4-'
Pangolagrass 30 lbs. N/A in the Fall
LI t- ______
S F M A M J J
.--Estim.ated Crude Protein Contents
lagrass and Pangolagrass Plus White
nd Stylosanthes humilis
r I I -