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Agronomy Research Report AY 79-2 September 1978
Department of Agronomy
Agricultural Experiment Station, IFA/^
University of Florida
Gainesville, Florida 32611 /
SUBTERRANEAN CLOVER PRODUCTION
G. M. Prine, 0. C.Ruelke and L. S. :biavin '
Subterranean clover (Trifolium subterraneun L., T". yaninicum and
T. brachycalyinum) is a new crop to Florida and the South,' een though
it has been grown at Experiment Stations periodically over the'- ast. 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, seed companies are beginning to import
and sell subterranean clover seed in the Southeast. This availability
of seed prompted the writing of this report, though research results
with subterranean clover in Florida are still limited.
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 Floridh
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
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, Mount Barker and Woogenellup sub clover seed have both reseeded
well in the fall at Gainesville. It is probable that some of the other
sub clovers will reseed equally well, but we do not have satisfactory
data yet on other cultivars.
SProfessors, Department of Agronomy, Gainesville, Fla. 32611 and Assoc-
iate Professor of Agronomy, Agricultural Research Center, Route 3,
Jay, FL 32565, respectively.
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 inconspicuous
and are often hidden from view in the foliage.' Sub clover forage has
high quality and compares favorably with that of other clovers.
In Mississippi, where much of the recent sub clover research has
been conducted, they have found that the later-maturing cultivars in
general are most productive. Mt. Barker, Woogenellup and Tallarook have
generally been the highest yielding cultivars. Preliminary trials in
Florida indicate these cultivars to be the best or among the best com-
mercial cultivars for Florida (See Table 1.).
SUB CLOVER PLANTING RECOMMENDATIONS
Soils: Sub clover should be grown on soils with good drainage and
medium to high water holding capacity. Sub clover is not recommended for
flatwoods or other poorly-drained soils. White and red clovers should
be grown on these latter soils. Growth of sub clover on drought sands is
Seeding rate: 16 to 20 pounds per acre in pure stand, 9 to 12
pounds per acre if in mixture with small grains, ryegrass or other
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 6 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
extremely 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 20 to 30 pounds per
acre per season. Minor elements should be added to soils where they are
Inoculation: Use a commercial inoculant specifically made for sub
clover at 2 to 5 times the recommended rate on packages. The PELINOC
system developed by the Nitragin Company has worked well for us but
other sticker coatings may work just as well. 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 unsatisfactory growth.
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 sun light and fix an optimum amount of this energy as
plant food. If you can readily see the soil surface and horizonal stems
where you have good stands of sub clover you are probably 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, es-
pecially near tip of stems.
Reseeding: At present 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, like crimson clover, is self-pollinating and does not need
bee pollination for good seed production.
Cultivars: Tallarook, Mt. Barker and Woogenellup cultivars have
yielded well both in Florida (Table 1) and in Mississippi. Mt. Barker
and Woogenellup have both reseeded better than Tallarook in our trials.
Other cultivars may yield well also (Table 1 and 2). We have not tested
most cultivars enough to evaluate their reseeding ability yet. In
Australia, seed of several sub clover cultivars are often mixed together
for seeding to give better seasonal distribution of growth and perhaps
Cold damage: Sub clovers will live through freezes normally expected
for Florida though they may sometimes be damaged. On basis of notes
taken following the January 18, 19, and 20, 1977 freeze (Table 3), it
is suggested that Clare, Seaton Park, Dinninup and Yarloop cultivars not
be seeded alone as they suffered more severe freeze damage than other
sub clover cultivars.
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 in North Florida above the 30th parallel
which crosses the peninsula south of Lake City.
The dry matter production of sub clover cultivars for three seasons
at Gainesville is given in Table 1. The dry matter yields of sub clover
harvested with a plot mower which cuts at 1 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. When all top growth includ-
ing seed burs of sub clover is harvested, as in 1975-76 and 1977-78 seasons
at Gainesville (Table 1) and in 1968-69 season at Jay (Table 2), the
yield of sub clover becomes very competitive with other clovers. Dry
matter yields where all top growth was removed to soil surface could
have been biased toward the high side by soil which cannot be entirely
removed from plant material.
The very low dense growth of sub clover is demonstrated by the
shortness of sub clover compared to other clovers in Table 2. 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 more erect.
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 3. The better yielding sub clover cultivars, Woogen-
ellup, Mt. Barker, Howard and Tallarook had little cold damage.
Seed dealers should be able to obtain sub clover seed through their
regular suppliers. In case they cannot, the following is a list of some
seed distributors planning to carry sub clover seed for distribution
to seed dealers at the writing of this report.
1. Australian Pasture Seeds Inc.
5359 Leake Avenue
New Orleans, LA 50115
2. Brigham Seed Co., Inc.
P. O. Box 1166
Jacksonville, FL 32201
3. Florida Feed and Seed Co.
P. O. Box 1120
Ocala, FL 32670
4. Northrup, King and Company
P. O. Box 12123
Fresno, California 93776
5. Sawan Seed Company
Table 1. The dry matter yield of sub clover cultivars grown on well-drained soil (Arredondo fine sand) at Gainesville
during three growing seasons.
Dry matter forage yields
2 season average
1975-76 1976-77 1977-78 3 season 1975-76 and 1976-77 1976-77 and 1977-78
Sub clover cultivarst season season season average seasons seasons
- - - - pounds per acre - - - - -
Woogenellup 2260 (4880)* 2740 4640 (8840)* 3210 2500 3690
Mt Barker 2750 (4010)* 2550 4290 (6950)* 3200 2650 3420
Tallarook 2570 (5720)* 2540 2560
Dinninup 1240 2730 (7430)* 1990
Dwalganup 1840 2150 (7740)* 2000
Howard 2390 3820 (8870)* 3100
Mississippi Ecotype 1760 2870 (5780)* 2320
Geraldton 1090 1560 (7080)* 1330
Clare 1290 2810 (6630)* 1550
Yarloop 1360 1830 (4840)* 1600
Seaton Park 1420 2890 (8010)* 2160
Yuchi arrowleaf clover 5440 3880 5620 4980 4660 4750
Amclo arrowleaf clover 4200 3790 5210 4400 4000 4500
Nolin red clover 4940 4290 4710 4650 4620 4500
Tibbee crimson clover 5210 3850 5700 4920 4530 4780
Number of harvests 2 2 3
Planting date Nov. 13 Oct. 13 Oct. 13
Numbers in parenthesis are total yield of forage when sub clover top growth was cut to soil surface at the last harvest.
Other yield values were harvested at 1l inch height above soil. The latter method of harvesting cuts off very few of
the horizonal stems so the forage yield is mainly leaves and leaf petioles.
The yields of individual harvests for the 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 growing seasons.
t All sub clover cultivars are of species T. subterreaneum except Clare (T. brachycalycinum) and Yarloop (T. yanninicum).
Table 2. Dry matter yield of sub clover and miscellaneous other clovers at
Jay, FL during 1968-69 growing season.
Cultivar and crop
Bacchus Marsh sub clover
Miss. Ecotype sub clover
Mt. Barker sub clover
Auburn crimson clover
Autauga crimson clover
Chief crimson clover
Abon Persian clover
Amclo arrowleaf clover
Meechee arrowleaf clover
Yuchi arrowleaf clover
April 6 harvest
Dry matter Plant
May 13 harvest
Dry matter Plant
*Harvested near soil surface so horizonal stems were included in yield.
Table 3 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
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.