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UNIVERSITY OF FLORIDA
'IFAS INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
f RI---MG- Central Science.
Library GAI, SVIE. -FLORIDA
AGRONOMY DEPARTMENT OCT 23 1987
Agronomy Research Report AY UniversMty of Florida
SUBTERRANEAN CLOVEPUrOCsO Iof Florida
SUBTERRANEAN CLOVERTRODUeT-ION IN-FLORIDA-
G. M. Prine, 0. C. Ruelke, D. D. Baltensperger, and L. S. Dunavin1
Subterranean clover (includes Trifolium subterraneum L., T. yanni-
nicum and T. brachycalyinum) is a new crop to Florida and the South,
even though it has been grown-at Experiment Stations periodically over
the last half century. Subterranean clover is widely grown along the
west coast of USA, particularly California, where Mediterranean climates
(hot, dry summers, and cool, wet winters) occur. Following promising
recent research results in Mississippi, Texas, Arkansas and Florida,
seed companies are beginning to import and sell subterranean clover
seed in the Southeast.
Subterranean clover (sub clover) is seeded on over 60 million acres
in Australia. Sub clover is best adapted to Mediterranean climates
where it germinates in the fall and matures in the spring. In Florida
we have the mild winter temperatures and usually have adequate winter
rainfall needed for growing sub clover. However, rainfall may be low
and undependable during the fall establishment period (late September,
October and early November). Our heavy summer rainfall does not affect
Continued next page...
SUB CLOVER PLANTING RECOMMENDATIONS
Cultivars: Tallarook, Mt. Barker and Woogenellup cultivars have
yielded well both in Florida (Table 1) and in other Southeastern states.
Mt. Barker and particularly, Woogenellup have both reseeded better
than Tallarook in our trials at Gainesville (Tables 1 and 2). Seed of
several sub clover cultivars can be mixed together in seeding to give
better seasonal distribution of growth and better reseeding.
Continued on page 3...
SIrofessors and Assistant Professor, Department of Agronomy, Gainesville,
SFla. 32611 and Associate Professor of Agronomy, Agricultural Research
Center, Route 3, Jay, Fla. 32565, respectively.
COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATIONS COOPERATIVE EXTENSION SERVICE
SCHOOL- OF FOREST RESOURCES AND CONSERVATION CENTER POR TROPICAL AGRICULTURE
The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research,
educational information and other services only to individuals and institutions that function without regard to race, color, sex, or national origin.
the growth of sub clover plants but can affect reseeding. The dormancy
and hardness of sub clover seed are often not as great during summer as
for some of our other reseeding annual clovers, such as crimson and
arrowleaf clovers. Consequently the seeds of sub clover sometimes
germinate during summer and seedlings die before cool weather. How-
ever, Mt. Barker and Woogenellup sub clover seed have both germinated
well in the fall at Gainesville. It is probable that some of the other
sub clovers will reseed equally well, but most are inferior in forage
The growth of sub clover is prostrate with stems growing close to
soil and leaves forming a dense canopy. In fact, over one-half of
foliage dry matter may be produced in the first two inches above soil.
For this reason sub clover is used mainly for grazing. If grown in a
mixture with a grass such as ryegrass, sub clover will develop erect
growth that can be harvested as hay. However, in Florida it is suggested
that if you are primarily interested in producing hay that you should
plant a taller growing clover, such as red, crimson or arrowleaf clover.
The life cycle of sub clover is quite similar to that of crimson
clover. When soil moisture is available the late maturing cultivars
may grow from late September or early October until about the first of
May. In Australia where sub clover is mainly grazed by sheep, the dead
foliage and seed pods furnish feed during their long dry summers. In
Florida, the dead foliage breaks down rapidly during the humid, rainy
summers, releasing nitrogen to summer grasses.
Sub clover gets its name from the fact that the seeds are produced
in burs below soil surface. However, seed burs of some cultivars may
be mainly produced on the soil surface. Flowers are small and incon-
spicuous and are often hidden from view in the foliage. Sub clover
forage has high quality and compares favorably with that of other clovers.
Sub clover should be looked on primarily as a reseeding winter
annual in perennial grass sods. The production of seed under grazing
and the large seed which produce a large vigorous seedling are sub
clover's biggest advantages over other annual clovers. Sub clover is
self-pollinating and does not need bee pollination for good seed pro-
duction. Continued on page 4...
SUB CLOVER PLANTING RECOMMENDATIONS (Continued)
Seeding rate: Twenty pounds per acre in pure stand, 12 pounds
per acre if in mixture with small grains, ryegrass or other clovers.
Soils: Sub clover should be grown on soils with moderate to good
drainage and medium to high water holding capacity. Sub clover is not
recommended for flatwoods soils which flood under high rainfall or
other poorly-drained soils. White and/or red clovers should be grown
on these latter soils. Growth of sub clover on drought sands is often
Seeding depth: Varies with soil type from about 3/8 to 1/2 inch
on clay soil to about 1 inch on sands.
Time for seeding: Seed on prepared seedbed anytime in October that
soil moisture is favorable and minimum temperatures have dipped below
600 F. Seeding into perennial grass sods should wait until late October
or early November when grass growth is reduced by night temperatures
below 500 F. Seeding should follow rainfall which has wet the soil to
at least 10 inches depth.
Liming and fertilization: These are similar to other cool season
clovers. Soils should be limed to pH of 6.0 to 6.5 and have CaO content
of at least 900 pounds per acre and MgO content of 100 pounds or more
per acre. Fertilize according to soil test recommendation or apply 300
to 500 pounds per acre of 0-10-20 or 0-10-30 fertilizer at planting. In
sandy soils apply 300 pounds per acre of the above fertilizer at planting
and 200-300 pounds per acre in late December or January. The fertilizer
should also furnish sulfur at rate of 16 to 20 pounds per acre per
season. Minor elements should be added to soils where they are deficient.
Inoculation: Use a commercial inoculant specifically made for sub
clover at 2 to 5 times the recommended rate on packages. The inoculant
should be stuck to the seed. Commercial sticker coatings, such as
PELINOC1 developed by the Nitragin Company, have worked well for us and
are probably worth the expense. If the seed has been preinoculated,
be on the safe side and inoculate the seed again at planting. If you
fail in getting good inoculation, sub clover will give very unsatisfac-
Adaptation: The further south sub clover is grown in Florida, the
shorter is the life cycle and the lower is the forage yield. It is
unlikely that sub clover will produce enough forage to merit seeding
south of the 28th parallel which goes across the state at Tampa. Best
sub clover growth is expected north of Lake City and in the panhandle.
Grazing: Sub clover can be closely grazed even during seed pro-
duction. Sub clover, or any clover, must have enough leaf surface to
adequately absorb sunlight and fix an optimum amount of this energy as
plant food. If you can readily see the soil surface and horizontal
Continued on page 5...
The dry matter production of sub clover cultivars for seven
seasons at Gainesville is given in Table 1. The distribution of forage
yield over the growing season for sub and other clovers is shown in
Table 2. The dry matter yields of sub clover harvested with a plot
mower which cuts at 1i to 2 inches height is usually low compared to
other annual clovers grown in Florida because most of the stems
produced by sub clover are not harvested. Multiply the sub clover
yields in Table 1 times 1.7 and you will have a better estimate of
total yield in comparison with other clovers. When all top growth
including seed burs of sub clover is harvested, as in 1968-69 season
at Jay (Table 3), the yield of sub clover becomes very competitive
with other clovers.
The very low dense growth of sub clover is demonstrated by the
shortness of sub clover compared to other clovers in Table 3. Under
grazing sub clover may regenerate itself more rapidly because less of
total plant is removed by the grazing animal as compared to other
clovers. Sub clover grown with ryegrass and small grains tends to grow
In January, 1977 a severe cold period caused damage to top growth
of sub clovers at Gainesville. Ratings of damage during this freeze
are shown in Table 4. The better yielding sub clover cultivars, Woogen-
ellup, Mt. Barker, Howard and Tallarook had little cold damage. It is
suggested that if the severely cold damaged Clare, Seaton Park, Dinninup
and Yarloop cultivars are grown that they not be seeded alone but as one
component in a mixture.
Sub clover has good growth potential on flatwoods soils which are
not subject to long term flooding when compared to other clovers as
shown in Table 5. When properly inoculated sub clover makes as much
or more nitrogen available to the summer grass crop as any of the other
clovers as shown by the grass yields in August in Table 5.
Seed dealers should be able to obtain sub clover seed through their
regular suppliers. However, sub clover seed are usually not stocked by
Florida seed dealers, so you should advise your seed dealer of your
sub clover seed needs several months in advance. Some sub clover seed
is produced in Pacific Coast States, but often seed must be imported
SUB CLOVER PLANTING RECOMMENDATIONS (Continued)
stems where you have good stands of sub clover you are over-grazing.
Sub clover is usually ready for grazing soon after it begins to
develop full-sized leaves instead of the smaller juvenile leaves.
Under good conditions the sub clover plants should continue to grow
these large leaves until after start of flowering when leaves become
smaller, especially near tip of stems.
Table 1. The dry matter yield of sub clover and other clover cultivars grown on well-drained soil
(Arredondo fine sand) at Gainesville during seven growing seasons.
Dry matter forage yields
1975-76 1976-77 1977-78 1978-79 1979-80 1980-81 1980-82 7-season
Sub clover cultivarst season season season season season season season average
pounds per acre
Woogenellup* 2260 2740 4640 3140 2980 4840 2590 3310
Mt. Barker* 2750 2550 4290 2890 3980 5150 3290 3560
Tallarook* 2570 2540 2600 3090 4790 1930 2920
Dinninup* 1240 2730 -
Dwalganup* 1840 2150 -
Howard* 2390 3820 2360 -
Mississippi Ecotype* 1760 2870 -
Geraldton* 1090 1560 -
Clare* 1290 2810 2020 -
Yarloop* 1360 1830 -
Seaton Park* 1420 2890 2250 -
Yuchi arrowleaf clover 5440 3880 5620 5630 3380 5770 5230 4990
Amclo arrowleaf clover 4200 3790 5210 5760 3480 6730 4720 4840
Nolin red clover 4940 4290 4710 4290 -
Tibbee crimson clover 5210 3850 5700 5360 5090 6510 4050 5110
Number of harvests 2 2 3 3 3 3 3 -
Planting date Nov. 13 Oct. 13 Oct. 13 Oct. 13 Oct. 17 Oct. 17 Oct. 15
The data in Table for sub clover are actual yields, consisting mainly of leaves and leaf petioles. To
get an estimate of total yields including the horizontal stems and leaves, multiply the yield data
shown by 1.7. The latter value compares more favorably with the yields shown of other clovers where
stems were included in harvested forage.
IThe yields of individual harvests for the first three seasons are reported in Agronomy Research Report
AY 79-1. Performance of winter forage legumes at Gainesville, Fl during 1975-76, 1976-77, and 1977-78
0 1 sub clover cultivars are of species T. subtei nre except Clare (T. brachycalycinum) and Ya op
(T. yanninicum). W
Table 2. The dry matter yield of sub and other clovers at various
harvests on well-drained soil (Arredondo fine sand) at Gaines-
ville during five growing seasons, 1977-78 through 1981-82.
Dry matter yield
Clover First Second Third Seasonal
cultivar harvest harvest harvest Yield
pounds per acre
Woogenellup sub 1300 1550 990 3840 (5)*t
Mt. Barker sub 1130 1550 1240 3920 (5) t
Tallarook sub 810 1130 1160 3100 (4) t
Howard sub 550 1600 940 3090 (2) t
Clare sub 480 1460 530 2470 (2) t
Seaton Park sub 640 1350 580 2570 (2) t
Yuchi arrowleaf 1400 1980 1780 5160 (5)
Amclo arrowleaf 1310 1740 2210 5260 (5)
Nolin red 210 1700 2600 4510 (2)
Tibbee crimson 2170 1520 1670 5360 (5)
Wilton rose 570 1850 2350 4770 (3)
Kondinin rose 880 1820 650 3350 (3)
*The number in parenthesis is the number of years during the five-year
period that this clover was tested.
IThe date of first harvest varied from January 29 to February 22, the
second harvest from March 18 to March 31 and third harvest from April 24
to May 5.
tMultiplying the season yield of sub clover by 1.7 will give a more
realistic yield for comparing with the other clovers.
Table 3. Dry matter yield of sub clover and miscellaneous other clovers at
Jay, FL during 1968-69 growing season.
April 6 harvest May 13 harvest
Dry matter Plant Dry matter Plant Season dry
Cultivar and crop yield height yield height matter yield
(Lb/A) (in) (Lb/A) (in) (Lb/A)
Bacchus Marsh sub clover 960 3.0 6150* 4.3 7110
Miss. Ecotype sub clover 320 1.8 6180* 4.8 6500
Mt. Barker sub clover 470 2.5 6390* 4.5 6860
Ball clover 310 4.6 3510 8.0 3820
Auburn crimson clover 2460 16.2 310 10.5 2770
Autauga crimson clover 2610 8.8 380 10.0 2990
Chief crimson clover 2830 16.3 740 12.3 3570
Abon Persian clover 320 4.9 2750 16.3 3070
Amclo arrowleaf clover 160 3.9 4170 15.0 4330
Meechee arrowleaf clover 470 3.9 3530 12.5 4000
Yuchi arrowleaf clover 270 3.8 3920 14.5 4190
Harvested near soil surface so horizontal stems were included in yield
Harvested near soil surface so horizontal stems were included in yield.
Table 4. Freeze damage to sub clover cultivars at Gainesville during
January 1977 and growth ratings at Jay during 1978.
Jan. 1977 Sub clover growth rating
Sub clover cultivars freeze* at Jay, FL 1978**
Mt. Barker 2.8 4
Woogenellup 2.8 5
Tallarook 2.0 4
Dinninup 7.3 9
Dwalganup 2.7 -
Howard 2.3 6
Miss. Ecotype 1.0
Nangeela 1.0 -
Geraldton 2.0 9
Seaton Park 8.3 8
Freeze damage ratings were made following the severe freeze of
January 18, 19 and 20, 1977 when minimum temperatures were 200 F
or less each morning. Rating: 0 no damage to 10 = all top growth
killed. All damaged sub clover eventually recovered.
**Growth rating made in April on sub clover plots planted November 17,
1977. Rating: 1 = excellent growth and 10 = no production.
Table 5. Dry matter yield of sub clover and other clovers grown in
mixture with Pensacola bahiagrass on flatwoods soil (Myakka
fine sand) at the Beef Research Unit, Gainesville, 1982.
Dry matter forage yieldst
Cultivars April 20 June 14 August 10 Total
pounds per acre
Mt. Barker sub clover 1,300c** 950a 2,150a 4,400a
Amclo arrowleaf clover 1,750b 1,150a 1,750b 4,650a
Kondinin rose clover 2,200a 850ab 1,300c 4,350a
White clover* 850cd 900ab 1,350c 3,100b
Kenstar red clover 750d 850ab 1,300c 2,900b
Abon persian clover 750d 800ab 1,200c 2,750b
Argentine bahiagrass 350e 700c 1,150c 2,200c
* Average of 12 white clover cultivars.
April harvest was primarily clover in the clover plots.
was estimated as over 1/2 clover in most clover plots.
was primarily bahiagrass.
t All data are the mean of 4 replications planted into bahiagrass sod
November 13, 1981, with 250 lbs of 0-10-20 fertilizer with 30 Ibs
trace elements per 1,000 lbs applied at planting and 300 Ibs of the
same material applied March 11.
**Yields followed by a different letter in the same column are significantly
different at the 0.05 probability level.