Title: Myakka
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00089449/00005
 Material Information
Title: Myakka
Series Title: Myakka
Physical Description: Serial
Creator: Department of Soil and Water Science. Institute of Food and Agricultural Sciences. University of Florida.
Publisher: Department of Soil and Water Science. Institute of Food and Agricultural Sciences. University of Florida.
Publication Date: Spring 2002
 Record Information
Bibliographic ID: UF00089449
Volume ID: VID00005
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.


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A Soil and Water Science Department Publication

Volume 2 Number 1 Institute of Food and Agricultural Sciences Spring 2002

SWSD Thrust Area:


Students, staff and faculty
conducting research at dairy spray
field in the Suwannee River Basin

Organic subsidence (2002) in the
Everglades Agricultural Area


Pam Marlin
Darryl Palmer
Dr. Vimala Nair

Visit the SWS website:


pollution of our
streams, rivers,
wetlands, and
estuaries is
closely linked to the management practices
used in agricultural and urban land
ecosystems. The question of immediate
concern is: Are the current practices used in
these ecosystems compatible or adequate to
sustain or improve the quality and productivity
of our natural resources? Many current
practices are compatible, but not all are
adequate to sustain natural resource quality.
Our stakeholders demand that natural
resource quality be protected, placing a
greater demand on producers to deliver
environmentally sound goods. Understanding
the ability of the soil resource to maintain
sustainable productivity and to buffer or
improve water quality is fundamental to
meeting this challenge. A holistic, integrated
approach to research, education, and
outreach is required to develop alternative
practices that will maintain environmentally
sound nutrient management in these
ecosystems. This expanded Soil and Water
Science Department (SWSD) newsletter
primarily focuses on our efforts in addressing
nutrient management issues in a wide range
of agricultural ecosystems in the State of
Florida and beyond.

All nutrient management programs in the
SWSD are multi-disciplinary, or regional,
national and international in nature. Our
faculty are located at all the major IFAS
Research and Education Centers statewide
providing localized solutions for efficiency
enhancement in nutrient management while
integrating with statewide efforts to create and
disseminate cutting-edge science based tools.
In addition to several UF-departments, our
collaborators in the state also include the

FDACS, FDEP, NRCS, Water Manage-
ment Districts, county governments,
Waste Management agencies, and private

Some examples of nutrient management
programs are highlighted in this news-
letter. These include: Suwannee River
Basin, citrus ecosystems, Everglades
Agricultural Area, vegetable and
horticultural crop production, turfgrass
and topical fruits ecosystems. In
collaboration with departments of
Agricultural and Biological Engineering
and Environmental Engineering Sciences,
we have initiated a major research and
education effort in the Okeechobee Basin
to address phosphorus management and
remediation issues. This program is
funded by FDACS, FDEP, and the South
Florida Water Management District.

In the past three decades, we have made
major efforts in addressing environmental
issues related to soil and water quality in a
number of ecosystems in agricultural
lands. The SWSD continues to lead IFAS
in resolving critical and sensitive nutrient
management issues for current day
agricultural, natural resources and
environmental stakeholders.

The SWSD is facing some new
challenges. With our senior faculty retiring
or leaving for other positions, replacement
of these positions is vital to maintaining
the department's ability to serve our
clientele. The department is blessed with
excellent faculty, staff and students and as
this group has done in the past, once more
they will be ready to meet any new

V^ -

DrK Raes Redy Chair Soi and Wae Scec Dearmet 10 Neel Hall Bo 1 050 Unvrst ofFoiaGievle


From the Chaiir...

Spring 2002
lJoel Ca,.,ley Plh 0 Adsor \\I F DeBusl
Chakesha P.artin AS 4dCLso'r JP I \nte
P.lonika Tkaczyk PhD Ad\iso.r J I\
Ja litz
Isabella Torres PhD K' P Pedd.

GRADUATES Spring 2002
James Bonczek PItD 4daisor P Nkeci,-

Quentin Clark AIS c]flsor P Pecdd\
Larry Ellis A7S 4cf usoi ME Colhins
luri Herzfeld Al S 4Adisor \\ F DeBuslS
Mark C:'u AlM g -4cIfsor P Nledi-ri"zza
.lichelle Rau Ml S AduEsor K P Pedd.

Spring 2002
Scott Prospect

GRADUATES Spring 2002
Andre,,; Strickland

Christine Bliss won first place poster at David Sylvia accepted the position of John White was nominated President-
the campus-wide Graduate Student Forum Head, Department of Crops and Soilect of the University of Florida
on April 4th in the Environmental, Sciences at the Pennsylvania State Chapter of the Sigma Xi Scientific
Agriculture and Life Sciences Division. University. We wish David all the best in Research Society.
his new assignment.
Kevin Grace won second place in the Oral
Presentation in the Environmental,
Agriculture and Life Sciences Division. The Third Annual
Soil and Water Science Departmental Research Forum
Travis Hanselman was awarded first place September 5, 2002
(Soil and Environmental Quality) in the J. Wayne Reitz Union UF-Campus
2002 Graduate Student Paper Contest of
the Soil and Crop Science Society of
Florida. The Third Annual Soil and Water Science Research Forum is scheduled for
September 5, 2002, in Gainesville. Florida. The forum is designed to bring
Don Graetz was awarded UF Research together representatives from state and federal agencies, and private
Foundation Professor for 2002-2005 in industry, faculty and graduate students, and prospective students
recognition of his outstanding research interested in soil and water science. The forum will provide an opportunity
accomplishments and scholarship. for all interested in soil and water science to interact with our students,

Lena Ma was awarded the Gamma Sigma faculty and administrators on campus.
Delta Junior Faculty Award in March 2002.
Several of graduate students and post-doctoral research associates, and
Ramesh Reddy was awarded the Senior faculty are planning to make either oral or poster presentations at the
Faculty Research Award from the forum. Our faculty will be available to discuss collaborative projects.
University of Florida Chapter of the Sigma Register at our web site: http://soils.ifas.ufl.edu/forum.
Xi Scientific Research Society.


Off-Campus Distance Education Master of Science Degree
with Environmental Science Track

The UF-SWSD off-campus Master of Science degree (non-thesis or thesis option)
with Environmental Science Track is available beginning Fall term 2002. Courses
are offered via distance education to accommodate place-bound students
interested in environmental issues related to the soil and water quality of
agricultural lands, forested lands, range lands, urban lands, or wetlands. The
program is offered in conjunction with faculty at the off-campus Research and
Education Centers (REC) located statewide.

Students wishing to enroll in this graduate track should have a bachelor's degree
from an accredited college or university with a major in soil and water science or
an equivalent degree in an allied field such as geology, natural resources, biology,
ecology, hydrology, microbiology, environmental science, horticultural science,
environmental engineering, agricultural engineering or agronomy. Those students
who do not meet these requirements will be expected to make up deficiencies
early in their graduate programs. Admission criteria include a B average or better
for the last two years of the baccalaureate program, and satisfactory scores (total
of 1000 in verbal and quantitative portions) on the General Test of the Graduate
Record Examinations (GRE).

Dr. Sabine Grunwald, Assistant Professor of Land Resources assumed the
responsibilities of the Distance Education Coordinator. For additional information,
contact Dr. Grunwald at: SGrunwald@mail.ifas.ufl.edu or browse through our web
site: http://DistEduc_SWS.ifas.ufl.edu.

PAGE 2 1

Nutrient Management in the
Suwannee River Basin:
Geographic Considerations

Several SWS faculty are involved in
research projects addressing nutrient
management issues in the Suwannee
River Basin. These projects assess risks
associated with nitrate and phosphate
applications. The risks relate to
geographic factors.

The Lower Suwannee River Basin spans
several Florida counties (Figures A and
B) where agricultural activities have
potential to affect the groundwater, river,
and estuary. The path of water movement
strikingly differs between the eastern and
western part of the Basin, along a line
(black line, Figure C) tracing the
approximate western extent of the
contiguous Hawthorn (H; yellow area)
Geologic Group. Superimposing that
same line on a map of the streams
(Figure D) shows that stream density is
much greater to the east of the line, over
the Hawthorn and beyond. The high
stream density is due to low permeability
of some strata within the Hawthorn, which
divert water laterally.

Karst Seepage

To the west of this line lies karstt", a
landscape underlain by limestone where
water is not laterally diverted near enough
to the surface to develop extensive surface
drainage. The black line drawn in Figures
C and D roughly parallels the Cody Scarp,
which separates the dissected terrace to
the east from the lower, less sloping area
to the west.

Here is what this geologic-hydrologic-
landscape relation means for soils and
nutrients: (i) Soils to the west, on karst
landscapes, are characterized
by good drainage and vertical water
movement. These conditions minimize
denitrification, and hence nitrate leaching
is a risk. Also, phosphate environmental
risks are related to leaching rather than
surface runoff. (ii) Soils along sideslopes
just to the west of the line tend to be
imperfectly drained due to seepage. They
also commonly contain high natural
levels of phosphate due to the influence
of the phosphatic parent materials
(Hawthorn Group formations). A valid
question: what is the ecological influence
of these naturally-phosphatic soils? (iii)
Soils on the flatwoods further to the east,
on the less-dissected part of the terrace,
tend to be poorly drained (promoting
denitrification), and constitute less risk of
nitrate leaching. However, they are highly
vulnerable to phosphate movement via
runoff or shallow subsurface flow in
unreactive soil horizons.

For additional information contact W.G.
Harris (wghs@mail.ifas.ufl.edu).

Nutr 1Wient Managem~Imten Pract. k JiesW[(~.~ for An1imal. t irIiU Waste an Frilie App4~1~licaionsI [] I

OaI,,,pty y l uuI u VValVtttr r utinLUr y IVvvvl at a
dairy farm

The Soil and Water Science Department,
along with other UF departments and
centers (Agricultural and Biological
Engineering, North Florida Research and
Education Center), state agencies
(Department of Agricultural and Consumer
Services, Department of Environmental
Protection) and federal agencies (Natural
Resource Conservation Service) are
cooperating in a 319-funded project
entitled "Effectiveness of Best
Management Practices (BMPs)

for Animal Waste and Fertilizer
Management to Reduce Nutrient Inputs
into Ground Water in the Suwannee
River Basin." Recent data have
indicated increasing levels of nutrients,
especially nitrate, in ground water,
spring water, and private drinking water
wells. This has brought about a need for
agency efforts to find nutrient
management solutions to the problem.
As a result, public agencies and the
agricultural community are taking the
lead in implementing a watershed-based
process for BMP development,
demonstration, refinement, and
implementation to reduce nutrient
loadings to ground water and surface
water, involving stakeholders throughout
the basin. These cooperators have
formed the Suwannee River Basin
Nutrient Management Working Group
(SRBNMWG) also known as the
Suwannee River Partnership.
Information on the partnership is
available at http://www.srwmd.
state.fl.us/waterquality/srbnmwg. html

As one component of partnership
activity, the 319-funded project
addresses BMPs on a dairy, a poultry,
and a vegetable farm in Lafayette and
Suwannee Counties in the Middle
Suwannee River Basin. Each farm
has been instrumented with a ground
water monitoring well network. Wells
and soil profiles are being intensively
monitored to determine pre- and post-
BMP nitrate concentrations on each of
the farms. A one-year pre-BMP
monitoring phase has been completed
on all the farms and BMPs are now
being implemented to address the
elevated nitrate concentrations
observed in some of the monitoring
wells. The overall goal of this project
is to demonstrate that effective BMPs
can be implemented to reverse the
increasing trend of nitrate
concentrations in the ground water
and springs of the Middle Suwannee
River Basin.

For additional information contact
D.A. Graetz (dag@mail.ifas.ufl.edu).

R es e. arch

UF/IFAS Role in the Development of the Florida Phosphorus Index

son prone snowing reaoximorpnic
features at the Bt horizon

GPR image showing presence of a
sink hole

The Phosphorus Index (P-Index) is a
site specific, qualitative vulnerability
assessment tool that allows selection
of sites that are potentially the least
vulnerable to off-site movement of P.
The P-Index also allows the selection
of conservation practices to reduce
the risk of P loss from a given site.
Major participants in developing the
Florida P-Index include the Soil and
Water Science Department,
Agriculture and Biological Engineering
Department, NRCS, Florida
Department of Agriculture and
Community Services, the USDA-
Agricultural Research Service, as well
as other agencies, organizations and
private individuals.

The Florida P-Index was concurred on
November 13, 2000, by the USDA
State Technical Committee and
adopted by T. Niles Glasgow, NRCS
State Conservationist. With the aid of
a 4-year USDA-IFAFS grant awarded
in September 2000, Soil and Water
Science investigators, in
collaboration with the USDA-ARS

Research Laboratory in Tifton,
Georgia, are testing the Florida and
Georgia P- indexing schemes on
highly leachable soils and karst
landscapes. Preliminary information
suggests that karst landscapes may
require further refinement of the
"leaching criterion" in the P-Index,
based on water moving preferentially
through breaches in Bt horizons or
through redox-depleted zones within
the Bt horizon.

Systematic profiling using ground
penetrating radar (GPR) is expected
to provide the necessary
information related not only to the
leaching criterion, but also to
establish the presence of sink holes
that may constitute elevated risk for
the "potential to reach water body"
criterion as defined in the P-Index.
Details of the Florida P-Index are
available at http://www.fl.nrcs.usda.

For additional information contact
V.D. Nair (vdna@mail.ifas.ufl.edu)

Soil tests were originally designed and calibrated to evaluate soil fertility for crop production. However, in Florida and most of the US,
soil fertility tests for phosphorus (STP) are currently used for environmental evaluation of P saturation even though calibration for such
purposes is minimal. For example, STP is a management factor in the Florida P-Index. The Degree of P Saturation (DPS), a concept
first introduced in the Netherlands, relates a soil's extractable P to its P sorbing capacity and is reportedly a predictor of the P likely to
be mobilized from a soil system. DPS, expressed as a percent, is calculated by dividing the ammonium oxalate-extractable P value by
the sum of oxalate-extractable Fe and Al. Soil profiles with weighted DPS values >25% have been identified as contributing to
groundwater pollution with P.

Oxalate extraction is not common in Florida, so use of the DPS approach would require additional analyses. Mehlich 1 is the common
soil test extractant for P and Mehlich 3 is becoming increasingly popular as a soil test extractant. We determined DPS for several
manure-impacted surface and subsurface soils as originally expressed (DPSox) and compared the results with DPS calculated using
Mehlich 1 (DPSM1) and Mehlich 3 (DPS M3) as the extractants for P, Fe, and Al. In all three cases of DPS calculations (using oxalate,
Mehlich-1, or Mehlich-3), it was noticed that the relationship between water-soluble P (WSP) and DPS has an abrupt slope change at
about 25% DPS. If the 25% DPS value is taken as a critical DPS for Florida soils, a large percentage of manure-impacted surface
soils will exceed the value, and could potentially be a risk to water quality.

Given that DPSM1 can be readily obtained in Florida soil testing programs and there is strong evidence in the literature for the 25%
DPS being a critical value for environmental risk, it may be desirable to replace STP with DPS M1 as an indicator of P release potential
in the management factor in Florida's P-Index. For additional information, contact V.D. Nair (vdna@mail.ifas.ufl.edu).

* Surface Horizon

Horizon ,
A Subsurface -
Horizon H oiz
A A 'A

0 25 50 75 100

0 25 50 75 100 125 150 175

0 25 50 75 100 125 150

DP 3

Precision Agriculture to Identify Limiting Soil Factors in
Citrus Production

Nutrient management research
conducted by Arnold Schumann,
Assistant Professor of Plant Nutrition at
the Citrus Research and Education
Center (CREC), Lake Alfred, concerns
the citrus soil-water-plant system.
Together with cooperators at the CREC
and Gainesville campus, improvements
in citrus nutrition are being developed,
especially better nitrogen (N) use
efficiency while sustaining profitable
yields and maximizing environmental
protection (N-BMPs). New precision
agriculture projects are focusing on the
causes and effective remedies for in-
field soil variability which causes
unacceptable spatial yield variability and
low profitability per acre. This requires
developing and implementing rapid in-
field soil and tree nutrient /water
sensing methods which improve the site-
specific diagnosis and management of
spatially variable soil and tree nutrients.
Aerial photographs, yield maps and in-
field observations of many Florida citrus
groves have suggested strong links
between under-performing areas of
groves and soil factors, especially in the
flatwoods regions. The objective of this
study is to identify soil-limiting factors for
citrus production and to devise
strategies for remediating these factors.
Spatial variability of soil conductivity
measured with an EM38 (Geonics, Ltd)
electromagnetic induction soil profiler
and georeferenced with a DGPS in
study sites in south Highlands and north
Hardee counties demonstrated the
important contribution of soil to spatial
variability of citrus growth and
production. Ground truthing data
collected to date have revealed a link
between apparent soil conductivity
measured down to 1.5 m by the EM38
and the characteristics (depth,
development, thickness) of the Bh or Bt

horizons underlying E horizons. Ground
water monitoring also showed large
spatial variations related to soil
conductivity, which may be from water
table perching on these poorly drained
impervious subsoil horizons. Different soil
series within citrus blocks, displaying a
range of texture, organic carbon content,
CEC and soil water relations are
responsible for much of the observed
yield variability in north Hardee county.
Soil water sensors placed in the rooting
zone of trees have shown very different
responses of these adjacent soils to
irrigation, rainfall and evapotranspiration.
Possible solutions for improving overall
citrus profitability in highly variable
groves include soil amendments of clay
or organic matter, and improved
scheduling of nutrition and irrigation
preferably applied at variable rates.
For additional information contact A.
Schumann (awschumann@lal.ufl.edu).

Typical installation of an instrument-sensor
cluster, measuring rainfall, irrigation water
pressure, watertable depth, and volumetric
soil water in the citrus root zone

About 20 years ago, freezes in the
northern part of Florida's citrus-growing
region resulted in a relocation of much
of the industry to the warmer southern
peninsula. The impact of this move
was felt strongly in southwest Florida,
where grove area more than tripled
from 57,000 acres in 1982 to 180,000
acres in 2000. Southwest Florida now
produces almost 25% of the Florida

citrus. Growers moving south
encountered a change of soil type from
deep, well-drained central ridge Entisols
to poorly drained flatwoods Spodosols
and Alfisols. Citrus nutrient
management is somewhat different on
these soils due to restricted root zones
resulting from shallow water tables and
subsurface hardpans.
Con't on page 6

Decreasing Nitrogen
Leaching During Turfgrass

ShIaenu TiaLIS 5tidaaa

Establishment of ne golf courses or
renovation of e sting turfgrass sites
suCh as public parks and sports fields is
common practice in Florida During
establishment large amounts of nitrogen
fertilizer and after are used to ensure
rapid turf coverage This can lead to
increased nitrate leaching to
ground,.,ater Tra-is Shaddo. in Dr
Jerry Sartain s research program
recently completed a study in which
nitrate leaching as influenced by fertilizer
type and application method during
turfgrass establishment ,.as investigated
The study consisted of applying a soluble
nitrogen fertilizer or that fertilizer m ed
,.,ith a controlled-release fertilizer ith
each being applied according to .r,.o
methods The standard method
consisted of applying the same amount
of nitrogen each ...eek for 12 r..eeks The
progress e method consisted of
applying lo' amounts of nitrogen during
the initial ...eeks of gro, .th and then
increasing that amount as the turf
biomass increased Results from the
study sho.r. that the addition of the
controlled-release nitrogen source
decreased leaching by 40".. Nitrate
leaching ..as further reduced under the
progressive application method
EstablIShment ,r.as not affected by either
fertilizer type or application method ,ith
full co'..erage under the standard and
progress e method being achie ed at 36
and 34 days after planting respectr.'ely
The practical implications of this
research are that nitrogen loss ia
leaching during turfgrass establishment
can be reduced r..i.thout adversely
affecting establishment by applying a
combination of soluble and controlled-
release nitrogen fertilizer in a
progress e-type application method

For additional information contact J
Sartain ijbs'imail ifas ufl eduI

Citrus N.utr~ ie1rnt Mageme in te 1S1ou est1.
Florida Fl. 00s

PAGE 5 1

Citrus Nutrient Management
in the Southwest
Florida Flatwoods
con't from page 5

Best management practices (BMPs) for citrus
N fertilization are currently being developed in
Florida in response to groundwater nitrate
concerns. During the 1990s, the research
program headed by Thomas Obreza,
Professor at the Southwest Florida Research
and Education Center in Immokalee
evaluated orange yield response to water-
soluble and controlled-release N fertilizer
(CRF) in three flatwoods field experiments to
help define optimum N rates for maximum
fruit production and quality in support of BMP
development. Experiments each lasted 5 to 7
years; two were initiated on newly-planted
trees, and one on established trees. In no
case did orange yield respond positively to
annual N rates above 240 Ibs N/acre, which is
the interim BMP maximum N rate. Yield
responses were not economic above 200 Ibs
N/acre, which is the University of Florida's
maximum recommended rate. The data
suggest that maximum economic yield of
oranges grown in the Florida flatwoods can
be obtained using N rates at or below the
interim BMP rate.

Recently citrus nutrition efforts have shifted
towards P and K fertilization. A calibration
experiment was initiated using Mehlich 1
and 3 extractants in 1998 in a newly
planted citrus grove that was very low in
soil-test P and K. A range of P and K
fertilizer rates were applied annually and
showed increased soil test values for P but
not for K. Tree growth and fruit yield have
responded positively to K fertilizer but not to
P fertilizer despite the fact that soil-test P in
control plots is in the "very low" range. This
research will enable the Florida citrus
industry to more appropriately allocate P
and K fertilizer costs, minimize impact on
surface water quality, and produce higher
quality fruit by understanding the main
effects and interactions of P and K.
For additional information contact T.A.
Obreza (taob@mail.ifas.ufl.edu).

Nutrient Mitigation in the Indian River Lagoon Area

The Indian River Lagoon (IRL), stretching 155 miles from Volusia County down to
Northern Palm Beach County, is a natural resource of regional significance. This
drainage basin was historically long and narrow. However, construction of extensive
drainage canal systems during the early 1900s more than doubled the size of the IRL
drainage basin. These drainage canals collect and transport large volumes of storm
water runoff from a variety of different land-use types within the drainage basin. This
runoff water is the primary source of nitrogen and phosphorus in the IRL, originating
from non-point sources primarily south of Melbourne.

Citrus acreage is one of the largest land-uses in the IRL drainage basin. The majority
of this acreage is located in the "expanded watershed" areas created by the drainage
canal systems built earlier this century. Citrus production, as well as other land-uses,
is receiving heavy local scrutiny regarding its contributions of nutrients to the IRL. In
an effort to help improve the quality of water leaving IRL area citrus groves, a manual
entitled, "Water Quality/Quantity BMPs for Indian River Citrus Groves" was developed.
This manual represents the cumulative effort of several State agencies, local growers,
and IFAS researchers. The development of the manual was facilitated by Brian Boman
(Agricultural Engineering), Chris Wilson (Indian River REC, Ft. Pierce), and Jack Hebb
(St. Lucie County Cooperative Extension Service).

Practices listed in this manual were
selected based on Best Professional
Judgment since research is lacking in
many of the areas. The manual was
published by the FDEP and FDACS in
2000. Current research projects are
evaluating the effectiveness of several of
the recommended BMPs for reducing
nutrient losses from citrus production
areas. These practices cover a wide
range, including: the use of top-
discharging water control structures,
sediment traps, and maintaining
vegetative filter strips on citrus beds and
within water furrows.

Studies are also being conducted to evaluate sampling frequency necessary to
accurately characterize phosphorus loadings at a watershed sub-basin scale within a
typical, flashy water control district. Additional research is focusing on the use of
natural and innovative biofiltration technologies for reducing concentrations of nitrogen
and phosphorus in surface water.

For additional information contact C. Wilson (pcwilson@mail.ifas.ufl.edu).

PAGE 6 1

Best Management Practices to Improve Water Quality in
the Everglades Agricultural Area (EAA)

Nutrient Management for
Improved Lychee Yields

The Everglades Agricultural Area (EAA)
comprises 700,000 acres of highly
productive land south and downstream
of Lake Okeechobee. The soils in the
EAA are organic and artificially drained
for crop production. The majority of the
land is in sugarcane production, with
other crops including rice, sod, sweet
corn, lettuce and other vegetables. The
University of Florida/Institute of Food
and Agricultural Sciences (UF/IFAS)
Best Management Practices (BMP)
research and education projects to
reduce phosphorus (P) concentrations
and load reduction from the EAA started
in 1986.

Current research and extension efforts
at the EAA are multi-faceted. Research
includes development of management
strategies to address particulate P
source and transport mechanisms.
Farm-level studies showed that
particulate P in drainage water samples
accounts for up to 60% of total P leaving
the farm. An extensive array of
monitoring instruments were installed at
seven farms to track changes in P
concentrations, and drainage water
discharge. Appropriate BMPs were
adopted at each site, and the effects of
implemented practices assessed at
each farm.

The farm level reductions appear to be
reflected in basin-level monitoring data
collected by the South Florida Water
Management District (SFWMD).
Hydrologically adjusted farm-level load
reductions, expressed as the SFWMD
adjusted unit area load (AUAL), averaged
54.9 % for the project sites (7-year
average referenced to WY93-94). The
EAA basin-level AUALs decreased by
approximately 41.4% and total P
concentrations by 7.9%.

Extension efforts involve BMP training
workshops for growers, extension
publications, on-farm demonstration plots,
and individualized consulting with growers
to improve their BMP implementation to
further reduce P leaving their farms.

For additional information contact S.H.
Daroub (sdaroub@mail.ifas.ufl.edu).

06 0 e Mode Improve m O nt

Agricultural production of vegetable
and horticultural crops in Florida's
sandy soils and humid subtropical
climates typically involves a number of
intensive management practices for
purposes of maintaining optimum soil
water, aeration, nutrient, thermal, and
pest-free soil environments for crop
root systems. A system of parallel,
plastic-covered soil beds separated by
bare furrows is commonly utilized for
intensive production of high-value
crops such as strawberry. The raised
beds provide drainage of excess water
during rain storms, as well as elevated
soil temperature. During cooler winter
Months, plastic films over the beds alter
the hydrothermal environment of

soil in the beds by providing a warming
effect and minimizing evaporative
water loss from the soil. Starter
fertilizer is typically applied in
concentrated bands to the soil bed and
pesticides are applied to minimize
adverse effects of pests to plant root
systems. Drip irrigation and
subsurface drainage practices are
utilized to minimize periods of
inadequate and excessive soil water
environments, respectively. During
periods of rain storm events, plastic
covers minimize excess water
infiltration and thus inhibit excess
leaching of agrichemicals from the soil
Con't on page 8

Lychee iLitchi chinensis Sonn i is gaining
popularity in American markets and is
becoming a high .alue crop in south
Florida Ho,,.e er. unreliable flo ering
and yield seriously impact lychee
production Flowering normally follo..,s
cold or drought stress Warm weather
high rainfall and ecess5ie nutrients
cause unreliable flowering and fruit set
When ecessi ely --atered and fertilized
lychee trees gro ..Igorously and
produce ..egetati e flushes e ery two or
three months The lack of maturity of
late *egetati..e flushes in the late fall or
early, ..inter presents flo..'enng in
January and February I uncong Li and
his colleagues at the Tropical Research
and Education Center in Homestead
demonstrated that the timing and rate of
nitrogen fertilizer significantly affected
soil and leaf nitrogen status High
nitrogen concentrations in the leaves
.,ere associated ,with .egetati..e flushing
and reduced flo.,ering and yield
Vegetati -e flushes in late fall can be
presented by restricting nitrogen in
summer Thus, through proper nitrogen
fertilization gro...ers can achieve
abundant flo:,ering and ultimately
increase yields

For additional information contact i Li
I yunli@'maii ifas ufl edu)

PAGE 7 1

Nutrient Management for Sustainable Productivity and Water Quality

The need for solutions as we strive to balance nutrient management for economical as
well as environmental sustainability has never been greater. The SWSD Nutrient
Management extension program takes a preventive and proactive posture by offering
soil testing services, developing educational material and offering training to IFAS county
faculty, consultants, and stakeholders. The role of nitrogen, phosphorus and several
trace metals as plant nutrients on the one hand and as major soil and water
contaminants with potential health and quality risks on the other, poses a challenge to
scientists and regulators alike. The extension program packages state-wide SWSD
research for the benefit of the clientele, starting with sustainable crop production to
minimize nutrient-impacts on the environment and fragile ecosystems of Florida.

The Extension Soil Testing Laboratory is the flagship of the SWSD nutrient management
extension program, a critical diagnostic service, analyzing over 12,000 soil, water and
tissue samples yearly for commercial producers and homeowners of Florida, including
IFAS extension faculty. The SWSD extension faculty plays a pivotal role in taking up field
demonstration projects such as the Suwannee 319 project at the crop production, dairy
and poultry sites, P-studies on potatoes in calcareous marl soils of Homestead and
vegetables in southwest Florida, P- leaching studies in south Georgia and north central
Florida, nitrate studies on potatoes in the St. Johns River Basin, P-retention studies in
the Lake Okeechobee Basin, etc. The SWSD faculty provided significant technical
support to the development of the Florida P-Index, a multi-agency effort led by the

Our extension faculty is also taking a major lead in the development of commodity and
region specific 'Best Management Practices' (BMPs) for Florida agriculture. Such efforts
include BMPs for Indian River Citrus Production, Forage Production, Row Crop and
Vegetable Crop Production, Landscape and Turfgrass Production, Ridge Citrus
Production, Nursery Production, and Beef Cattle Production. A major grant contract was
secured from FDACS by the SWSD and the Agricultural and Biological Engineering
extension faculty in collaboration with the NRCS to provide the required training for
nutrient management certification to third party vendors and others in Florida. The first
training session is scheduled for June 4-6, 2002 in Okeechobee. The SWSD faculty have
been taking a lead role in the Certified Crop Adviser training programs. For additional
information contact R.S. Mylavarapu (raom@mail.ifas.ufl.edu).

Anon0 i Arhu 0 G Honb Exeso P Oes O

Arthur G. Hornsby, professor of Soil and Water
Science, Institute of Food and Agricultural
Sciences (IFAS), University of Florida, with wife,

After a distinguished career of 30 years
(11 years with U. S. Environmental
Protection Agency and 19 years at the
University of Florida), Dr. Hornsby

retired from professional service. In
recognition of his professional
contributions, UF-IFAS is establishing
an endowment from private
donor funds to support the Arthur G.
Hornsby Extension Professorship.

The Art Hornsby Extension
Professorship program is a faculty
recognition program named in honor of
Dr. Art Hornsby. The program bestows
an honorary title for an outstanding
extension faculty member contribution
to protection of our soil, water and
other natural resources in Florida.

Contributions to the fund would be fully
tax deductible. Your contributions can
be mailed to Office of Development-
SHARE, P.O.Box 110170, Gainesville,
Fl. 32611-0170.

Production Bed Model
con't from page 7

Environmental impact of agrichemicals
applied during intensive management of
high-value crops growing in systems of
mulched soil beds is incompletely known.
Many factors including the hydrothermal
status of the soil affect the fate and
transport of these agrichemicals in soil bed
systems. With current and future
environmental issues concerning TMDL's
and protection of water quality, the ability to
predict what the fate of applied
agrichemicals would be under different
management scenarios would very
beneficial for planning and avoiding those
practices which contribute to groundwater

A mechanistic 2-dimensional model for
coupled water-heat and chemical transport
for non-isothermal conditions has been
used to numerically simulate the diurnal
dynamics of the hydro-thermal environment
within raised soil beds covered with plastic
mulch. This model has also been used to
investigate fumigant (methyl bromide) fate
and transport in soil beds during
fumigation. The development of this model
was supported by resources from the Lake
Manatee Watershed Demonstration Project
(USDA Water Quality Initiative). Faculty
members Craig Stanley and Bob Mansell
with graduate students Arne Olsen and Ha
Wonsook are collecting experimental field
data at the Gulf Coast Research and
Education Center in Bradenton to be used
to validate the present model and to add a
plant water uptake component and user-
friendly interface. It is expected that this
improved model will be useful in simulating
different management scenarios that will
provide information for improving
management decisions concerning nutrient
and other agrichemical applications made
by the vegetable producer. For additional
information contact C. Stanley at

Com ent/Sugesion plas sen to S S Nesetr Bo 1150 nvriyo*lrdG ievle lrd 21

PAGE 8 1

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