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Title: Range Cattle REC newsletter
Series Title: Range Cattle REC newsletter
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Creator: Range Cattle Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida
Publisher: Range Cattle Research and Education Center, University of Florida
Publication Date: June 2003
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Volume ID: VID00016
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University of Florida, IFAS
Range Cattle Research and Education Center
June 2003
Volume 6, Number 2




RANGE CATTLE REC NEWSLETTER


Calendar of Events
Month Date(s)
June 18-20
August 7-8


Event
FCA Annual Convention
NCBA/CME Cattle Marketing
Workshop


Location
Marco Island, FL
Kissimmee, FL


IN THIS ISSUE
Page

Effect of Stocking Rate on Measures of Cow-Calf Productivity and Nutrient Loads in Surface Water
R u n o ff ....................................................................................................................................................... . 2
Effectiveness of selected Pasture herbicides on spring broadleaf weed control........................................ 6
G row ing Leucaena in south Florida.............................. ..................... 4
Keeping an Eye on Tropical Soda Apple Infestation on Your Pasture ..................................................... 5
R CRE C Field D ay a Success! .......................... .. .. .................... 7
Where Does Nitrogen Come from in Your Bahiagrass Pasture? .......................... ..... .............. 6
Y yellow ing in B ahiagrass P astures .......................................................... ........ ...... 7


The Institute of Food and Agricultural Sciences is an equal 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, age, handicap, or national origin. For information on obtaining other
extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service/Institute of Food and Agricultural
Sciences/University of Florida/Christine Taylor Waddill, Director.










Effect of Stocking Rate on Measures of Cow-Calf
Productivity and Nutrient Loads in Surface
Water Runoff


The presence of beef cattle at three
stocking rates had no impact on nutrient
load (P and N) of surface runoff water
when compared with pastures containing
no cattle.



Rationale
The University of Florida-IFAS, formed a
partnership with Archbold Biological Station, South
Florida Water Management District, USDA-ARS,
Florida Department of Agriculture and Consumer
Services, and the Florida Cattlemen's Association.
The goal of this partnership was to design
sustainable, environmentally sensitive management
practices for cattle grazing operations. This
partnership is currently completing a
comprehensive research study investigating, among
other things, the interrelationship between beef
cow-calf stocking rate and surface water quality.
Study Site and Experimental Methods
This research was conducted at Buck Island
Ranch near Lake Placid, Florida over three
production cycles from 1999 to 2001. Both summer
and winter pastures were used. Summer pastures
consisted of eight, 50-acre pastures with established
bahiagrass on flatwoods soils with extensive
ditching to facilitate drainage. Winter pastures
consisted of eight, 80-acre pastures with mixed
forages, predominantly bahiagrass, on similar soils
with less extensive ditching
Three stocking rate treatments were used
which represented 3.7, 6.5, and 8.6 acres per cow
over the combined total of 130 acres of the summer
(50 acre) and winter (80 acre) pastures. These
treatments were chosen to illustrate differing levels
of cattle stocking rates common in south Florida
(high, medium, and low, respectively). A fourth
treatment containing no cows (Control) was also
used. Summer, but not winter pastures, received a
spring application of ammonium nitrate fertilizer
(50 lb N/acre).


Pregnant, Brahman crossbred cows, ranging
in age from 4 to 9 years, were used in the stocking
rate study. All cows were exposed to bulls for 120
days starting in mid-January. Cow body condition
was scored on a 1 to 9 scale when they were moved
to winter pastures (start of production cycle), moved
to summer pastures, and at weaning (end of
production cycle). Calf weight was collected when
cows were moved into summer pastures and again
at weaning.
The economic impact of reducing stocking
rates was developed using SPA (Standardized
Performance Analysis). Five years of SPA data
were collected from the commercial ranch at Buck
Island. These data provided an annual average of
itemized production costs, calving percentages, and
calf weaning weights. Costs were grouped into two
categories variable and fixed costs.
Experimental pastures were separated by
berms and all surface runoff from each pasture
collected in ditches and flowed through a separate
flume. Each flume was fully instrumented to record
the total amount of runoff and to take automatic
water samples during periods of flow. Water
samples were analyzed for total phosphorus and
nitrogen.
Results
Cow and calf performance was similar,
irrespective of stocking rate. Production, as
measured by pounds of calf weaned per acre of
dedicated land was greater for high compared to
medium and low stocking rates. Stocking density
had no impact on cow pregnancy rate.
Based on SPA data, total operating costs
declined from the highest to lowest stocking rate.
However, because fixed costs remain constant, the
unit cow costs increased from $167 per cow at the
highest stocking rate to $255 per cow at the lowest
stocking rate. Based on season average Florida calf
prices as reported by the Florida Agricultural
Statistics Service, a rancher who stocked at the
highest rate would have earned positive net returns
every year between 1994 and 2000. On the other
hand, if a rancher stocked at the lowest rate,
positive net returns would have earned in only one
year between 1994 and 2000.
Cattle stocking rate did not effect
concentrations or loads of total P or N measured in







runoff from the plots in 1998 -2001 (Table 1). In
fact, control pastures containing no cattle provided
similar amounts of total P and N in runoff water
compared to pastures containing cattle. Summer
pastures consistently delivered greater P loads in
runoff than did the winter pastures in all years
except the drought year of 2000 (Table 2). Loads of
total N was greater from summer than winter
pastures in 1999 and 2001 (Table 2).
The greater loads of N and P in the summer
pasture runoff than in the winter pasture runoff was
likely due to differences in the long term
fertilization history of the two pasture sites. The
improved summer pastures are fertilized annually
with N fertilizer and, although they currently
receive no P fertilizer, they were fertilized annually
with P fertilizer (30-80 lbs. P205 per acre) for at
least 15-20 years prior to 1987, at which time P
fertilizer use was discontinued. The semi-native
winter range pastures, by contrast, have never been
fertilized.
Implications
In this evaluation, the high stocking density
supported similar cow and calf performance as the
lower stocking densities. When pasture


productivity was considered, the high stocking
density provided the most weight of weaned calf per
unit of dedicated land. A change in stocking rate
has a one-to-one relationship with ranch revenues.
At the same time, unit cow costs increase at an
increasing rate as fewer brood cows are left to
support the ranch's fixed costs. Consequently, ranch
profitability decreases as stocking rates decline.
Stocking rate did not affect the total loads of
P and N in surface runoff. In fact, a similar amount
of total P and N in surface water runoff were found
in pastures containing no cattle compared to
pastures stocked with cattle over three production
cycles. The improved summer pastures provided 5
to 7 times more total P and N in surface water
runoff compared to the semi-native winter pastures.
This is apparently due to past use of P fertilizer
prior to 1987 and does not appear to be dependent
upon the current presence of cattle on these
pastures.
Additional Information
Expanded information on all phases of this
research effort is available in individual discipline
manuscripts. Please contact one of the authors for
further information. (JDA, PB, FMR)


Table 1. Nutrient loads in surface water runoff from summer and winter pastures
stocked at different cattle rates (average 1998-2001).

Summer pastures Winter pastures
Stocking rate1 Total P Total N Total P Total N
------------------------ lbs/acre -------------------
Control 1.22 5.49 0.21 5.17
Low 1.27 5.23 0.17 4.01
Medium 1.13 6.88 0.14 4.40
High 1.15 5.51 0.22 4.54
Stocking rates of 8.6, 6.5, and 3.7 acres/cow correspond to high, medium,
and low rates, respectively.


Table 2. Nutrient loads of surface water runoff from summer and
winter pastures (average 1998-2001).
Mean nutrient load
Pasture type Total P a Total Nb
---------- lbs/acre ---------
Summer 1.19 5.77
Winter 0.18b 4.53
Pooled SEM 0.07 0.59







a Significant differences between pasture types for total P were noted in
each year except the drought of 2000, P < 0.05.
b Significant differences between pasture types for total N were noted in
1999 and 2001, P < 0.05


Growing Leucaena in south Florida

Bahiagrass is the grass of choice in most
ranches in south Florida where more than 80% of
the cattle in Florida are raised. The grass provides
more than adequate herbage in the summer, but the
nutritive value is low. Both available forage and
nutritive value are also low in the fall. Animal
performance can be improved by having a legume
in the pasture at these times. The worldwide
importance and contributions of forage tree legumes
in areas that have similar soil and climatic
conditions as Florida suggest a role for tree legumes
in the cow-calf industry.
Leucaena is a tropical forage tree legume
that could meet the forage needs of cattle in south
Florida. Studies carried out in central and south
Florida, have confirmed the outstanding yields and
quality of the forage. Clipping studies at
Brooksville showed that leucaena produced up to
12, 500 lbs./acre/year of highly digestible dry leaf
matter when harvested every 5 to 6 weeks during
late spring and summer. The forage contained 22-
35% protein. At Ona, heifers and steers grazing
leucaena + bahiagrass pastures from June to January
gained 75 lbs./head, about three times the weight
gained by those grazing bahiagrass alone. When
access to leucaena was delayed till July, the animals
gained 117 lbs./head, seven times the weight gain of
those on bahiagrass alone. Delaying grazing of
leucaena till late in summer ensured that the trees
accumulated adequate forage and thus contributed
the most when the quality of bahiagrass was at the
lowest. Thus, leucaena is a dependable perennial
legume for south Florida.
The future acceptance or widespread use of
leucaena by cattlemen will depend on the
identification of suitable selections or varieties,
development of cultural practices for uniform field
establishment, and demonstration of potential
economic contributions of the tree legume to the
cow-calf industry. Even in Australia where the use
of leucaena is widespread, commercial plantings
were slow before the 1980s. However, within the
decade about 40, 000 acres was planted to leucaena.


Research at Ona is aimed at gathering practical
knowledge of suitable selections, and establishment
and management requirements that hopefully will
spur rapid development of the tree legume-grass
pasture concept for sustainable cow-calf production
in south Florida.
Leucaena can grow in a wide range of soil
and climatic conditions. In south Florida some
environmental factors create some problems for
growing leucaena. These include the plant's lack of
tolerance of frosts, poorly drained or waterlogged
soils, soil acidity, and low soil fertility. The plant is
best adapted to warm, well-drained deep calcareous
soils. Light frosts will cause leaf shedding while
heavy frosts will kill above ground, but the crown
will survive in the next summer with multiple
branches. This eliminates the necessity of cutting to
keep the plants within the reach of animals under
grazing.
We evaluated the abilities of 8 selections of
leucaena to grow and persist in waterlogged soil.
The seeds were sown in either well-drained or
waterlogged soil. After 15 days, none of the seeds
germinated in the waterlogged soil compared with
85-100% germination in well-drained soil. The
seedlings in the well-drained pots are being
subjected to the waterlogging treatments. After 15
days, no mortality has been recorded and seeds are
growing rapidly. Therefore, germination is more
sensitive to waterlogging than subsequent seedling
growth. Research elsewhere had indicated that
leucaena once established is able to persist because
the plant transpires water very rapidly as a way of
surviving waterlogging.
Another characteristic of the growing
conditions in Florida is varying water table. We
examined how this would affect leucaena seedlings
by growing them in well-drained soil, or where
water table was maintained at 15 cm below soil, at
soil surface, or 3 cm above soil surface. After 42
days, all the seedlings are persisting; there has been
no mortality. This observation confirms that the
overriding effect of poor soil drainage is on seed
germination and not seedling persistence.
Interestingly, seedlings growing where the water







level is at soil surface or above soil surface have
developed aerenchyma tissues (gas-filled) on the
stem bases up to 1 cm above the soil surface or
water level. Aerenchyma is a type of "bark" that is
induced by lack of oxygen in waterlogged soil. It
facilitates movement of oxygen. Aerenchyma can
be seen at the base of common aeschynomene and
aeschynomene evenia. We have not seen any other
report of this observed in leucaena in literature. It
would, in addition to rapid loss of water by
transpiration, explain the ability of established
leucaena plants to persist under waterlogged
conditions.
Work will continue on understanding and
overcoming the major factors associated with poor
establishment of leucaena, and in identifying
leucaena selections that are well adapted to the
unique growing conditions of south Florida. The
overall goal is in testing the potential of tree
legume-grass pasture concept for greater
sustainability and profitability of the cow-calf
industry in Florida. (IVE)

Keeping an Eye on Tropical Soda Apple
Infestation on Your Pasture

Tropical soda apple (TSA) has invaded
pastures in south Florida since 1990. Serious
efforts were made to control TSA in Florida in the
mid 1990s but the enthusiasm eventually waned.
Currently, there are more than 500,000 acres of
TSA infestation in Florida.
Tropical soda apple is spread to new
locations by cattle movement, wildlife,
contaminated hay, grass seed and sod. It is on the
list of Florida State's Noxious Weed according to
Florida Law (Fla Admin. Code 5B-57-007) and as
such it is unlawful to introduce, possess, or move
TSA plants deliberately except under permit issued
by Florida DACS or the USDA. Recently, some
southern states including Georgia, Mississippi, and
Alabama have considered passing legislation to
regulate the movement of cattle from Florida to
their states in order to stop the spread of TSA in
southeastern USA. Such legislation, if adopted,
would require the quarantine of Florida cattle at
specified locations for up to one week during/prior
to shipment. The quarantine period allows ingested
TSA seed to pass through and out of the
gastrointestinal tract. The expense of such


confinement will be charged to the cattle owner and
will tend to increase cattle production costs in
Florida.
Therefore, South Florida cattlemen need to
pay greater attention to TSA infestation on their
pasture and engage in renewed efforts at preventing,
monitoring and controlling TSA as follows:

Sparse Stand:
For sparse stands in south Florida, spot
spray individual TSA plants in November with a
0.5% solution of Remedy (tryclopyr) + 0.1% non
ionic surfactant. Wet foliage completely to the
point of dripping with solution and use a color
maker in the spray mix to ensure all plants are
treated. Monitor the weed problem through winter
and spot-spray new/regrowth of TSA plants on that
pasture again in February of the following year.
Monitor plants through spring and if there are still
some live TSA plants on the pasture, spot-spray a
third time in May followed by continued monitoring
through summer. Monitoring and repeated spot-
spraying at about 60 d intervals over 2 years will
prevent TSA fruits form maturing seed and help
clean up a sparse stand of TSA on a pasture unless
pasture is re-infested with seed introduced from
outside.

Dense Stand:
Dense stands of TSA on pasture in south
Florida must be mowed repeatedly to a 3-inch
stubble in November, February and April to prevent
fruit setting/seed maturation. Repeated mowing
every 50-60 days can in itself cause 50-60 %
mortality in mature TSA plants. After the April
mowing, allow the TSA plants to regrow for about
60 days and broadcast spray 1 qt /A of Remedy +
0.1% non-ionic surfactant in June. Next, monitor
TSA plants through September and spot-spray
remaining plants in October with a 0.5% Remedy
solution + the non-ionic surfactant and the color
marker. Continue monitoring TSA for at least
another year and spot spray emerging plants every
60 days as described for sparse stands until pasture
is completely cleaned up.
There are hopeful signs that a variety of
biological agents (insects, virus) for TSA control
will soon become available to increase our arsenals
on this noxious pasture weed. But for the
meantime, prevention, monitoring and repeated







spraying with Remedy provide the key to
successful tropical soda apple control in south
Florida. (MBA)

Where Does Nitrogen Come from in Your
Bahiagrass Pasture?

Of course you would say, "from the N in
fertilizer for which I paid such a dear price." This is
partially correct. Although data are variable,
research has shown that bahiagrass will recover 50
to 80% of applied N with little difference between
forms of N used. The amount of recovery of
applied N varies with the rate (recovery increases
with N rate) and age of bahiagrass (recovery
increases in older stands due to mature stolons).
These data are calculated by subtracting N taken up
by grass in unfertilized plots from N taken up by
fertilized bahiagrass. Unfertilized bahiagrass will
easily take up 100 lb N/acre/year, and bahiagrass
fertilized with 50 lb N/acre in March can take up
150 lb N/acre/year. Much of the non-fertilizer N
comes from a biological break down of organic
matter in a process referred to as mineralization.
Research in Florida using isotopes of N, which are
labeled forms such as 15N, show that much of the N
used for spring bahiagrass growth comes from
fertilizer applied in spring, but that almost all of the
summer growth comes from non-fertilizer N. In a
pasture, the N we add becomes part of the system,
and it is recycled through organic matter. Some is
lost by leaching and some is lost by denitrification
or volitalization. One of the most interesting topics
is that of the addition of unaccountable N. Dr.
Blue, a UF soil scientist now retired, conducted
long-term research with bahiagrass and found that
in a period of over 25 years, there had been the
addition of about 700 lb/acre of N into the soil-plant
system. That is about 28 lb of N/acre/year that
came into the system in an unexplainable way.
Biological N fixation by bacteria for grasses is
possible and has been the focus of research,
especially in Brasil. A bacteria (Azotobacter
paspali) specific for grasses of the genus
Paspalum, of which bahiagrass is a member, has
assimilated about 110 lb N/acre under laboratory
conditions. I strongly suspect that we have a small
amount of biological N fixation in our bahiagrass
pastures in Florida. (RSK)


Effectiveness of selected Pasture herbicides on
spring broadleaf weed control

There is a continuous need to determine the
effectiveness of pasture and hayfield herbicides for
weed control and the tolerance of improved pasture
grasses to these herbicides. Most herbicides
registered for pasture and hayfield weed control are
used as post-emergence applications. That is,
herbicides are applied after weed emergence and
several inches of growth. Herbicides should be
applied to small actively growing weed seedlings.
This provides good control with minimal herbicide.
The application of herbicides on perennial weeds
should be withheld until spring regrowth when
plants attain adequate surface area for herbicide
coverage and translocation into the roots.
Three pasture herbicides were applied in late
March of 2002 to determine their effectiveness on
broadleaf weed control and herbicide tolerance of
improved tropical pasture grasses. Recommended
rates of Cimarron 3/10 oz/A, Redeem R&P 1
qt/A, and Weedmaster 1.5qt/A were applied with
the surfactant Silkin at 10 oz/100 gal water. All
herbicides were applied at a total volume of 30
gal/A.
Cimarron provided excellent control of
Stiff verbena, dogfennel, thistle, Oldfield toadflax,
Broadleaf pink purslane, pokeberry, Carolina
geranium, goatweed, Wondering cudweed, Florida
pellitory, amaranth (pigweed), and lambsquarters.
The activity of this chemical is very slow, requiring
60 days for complete control. Cimarron has no
grazing or hay cutting restrictions for either
lactating or non-lactating cattle or for horses.
Redeem R&P provided excellent control of
thistle, Oldfield toadflax, Yellow woodsorrel,
Carolina geranium, Wandering cudweed, Spreading
dayflower, and Black nightshade within 45 days.
Redeem R&P has 0 days restriction for grazing, 7
days for hay cutting and 3 days for cattle slaughter;
14 days for grazing and 1 year hay cutting for
lactating cattle and no information for horses.
Weedmaster provided excellent control of
dogfennel, Oldfield toadflax, Primrose willow,
Carolina geranium, Wondering cudweed, Spreading
dayflower, amaranth, lambsquarters, and Mexican
tea within 45 days. Weedmaster has 0 days
restrictions for grazing, no information on hay







cutting, and 30 days for slaughter of non-lactating
cattle; 7 days for grazing, 37 days for hay cutting
for lactating cattle and no information for horses.
The above three herbicides were tested on
numerous perennial warm season forages grown in
south central Florida. Cimarron had no effect on
stargrass or bermudagrass cultivars tested, however,
a slight suppression effect on Floralta limpograss
and completely killed Pensacola, Tifton 9, Sand
mountain, Tifton 7, and forage cross hybrid
bahiagrasses and no effect was found on Argentine
bahiagrass, well developed ryegrass, and small
grain cultivars.
Redeem R&P had no effect on any warm
season perennial grasses tested, except a slight
suppression on Florakirk bermudagrass. Ryegrass
and small grain cultivars were unaffected.
Weedmaster had no effect on any warm
season grasses except Floralta limpograss which
was severely suppressed, and even death.
Weedmaster had no effect on ryegrass or small
grains that had developed tillers.
In conclusion, there are several herbicide
options available for pasture broadleaf weed
control. The specific herbicide used will depend on
the weed needing to be controlled and the specific
cultivar of pasture grass. (PM)

Yellowing in Bahiagrass Pastures

Yellowing of bahiagrass pasture usually
observed in the spring and early summer is a
common occurrence in Florida. We know that the
yellowing is caused by iron deficiency in the
bahiagrass leaf due to inadequate iron uptake in the
spring. Several years ago we applied iron sulfate in
a liquid fertilizer mixture as a foliar application
(broadcast spray) to large areas of bahiagrass
pasture. The yellowing condition disappeared
within a week
Dr. Jack Rechcigl found that bahiagrass
yellowing could be eliminated by applying iron
chelate to the soil, but the chelate was cost
prohibitive. Application of iron sulfate to the soil
was ineffective.
Dr. Martin Adjei conducted experiments that
evaluated different fertilizer and lime treatments on
bahiagrass plots. One very obvious outcome was
that bahiagrass forage responded to nitrogen
application where lime was applied to increase pH


above 5.0. Where lime was not applied and pH was
4.0 to 4.5, the application of nitrogen fertilizer had a
negative effect on bahiagrass yield and the
yellowing condition was observed. It was best not
to apply nitrogen to bahiagrass plots if lime was not
applied to increase pH to 5.0 or higher because
bahiagrass stand loss occurred.
We experienced a lot of bahiagrass
yellowing at the Ona Research Center in the spring
and summer over many years. Pastures had not been
limed in more than 10 years and soil pH was around
4.5. In January, 2001 we applied 2 tons of dolomite
per acre to 300 acres.
In the spring and early summer of 2001 we
still observed extensive yellowing of bahiagrass
where dolomite was applied. However, in the spring
and summer of 2002 no yellowing of bahiagrass
was evident. This shows that time is required for the
lime source to be dissolved and washed into the
bahiagrass root zone, so a quick response should not
be expected. In the spring of 2003 we have not seen
yellowing in bahiagrass pastures that received
dolomite in January, 2001.
It appears that most of the yellowing
observed in bahiagrass pastures is a result of low
pH which probably prevents bahiagrass roots from
absorbing enough iron. This can be corrected with a
good liming program. University of Florida/IFAS
recommends that the soil pH in bahiagrass pasture
should be 5.0 or better. If you are seeing
considerable yellowing in bahiagrass pasture, first
test the soil pH. If the pH is below 5.0 apply
dolomitic of calcitic lime according to University of
Florida/IFAS recommendations. This should cure
the yellowing problem over time. (FMP, MBA)

RCREC Field Day a Success!

The faculty and staff of the Range Cattle Research
and Education Center would like to thank the three
hundred plus guests that came out for our field day
on May 15t. You made all of our hard work worth
the effort. Here are a few photos of the day that we
would like to share.




















Everyone enjoying the steak lunch.


Dr. B,
lunch.


Ur. Jonn Artnington discusses the woods project.


Drs. Ike Ezenwa and Rob Kalmbacher discuss the
silvopasture project.


the steak


Dr. Paul Mislevy discusses the search for a
Bahiagrass with winter growth characteristics.

Contributors
Adjei, Martin B.
Anton, T. E., Ed.
Arthington, John D.
Bohlen, Patrick1
Ezenwa, Ike V.
Kalmbacher, Rob S.
Mislevy, Paul
Pate, Findlay M.
Roka, Fritz M.2

1MacArthur Agro-ecology Research Center
2University of Florida, IFAS, SWFREC




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