• TABLE OF CONTENTS
HIDE
 Front Cover
 From the director
 Table of Contents
 Hydroponic lettuce production in...
 Citrus germplasm evaluation under...
 Reproductive performance of hairsheep...
 Improving agricultural marketing...
 Temperature build up and control...
 Production potential of buffelgrass...
 Environmental monitoring in the...
 Agricultural experiment station...
 AES publications
 Back Cover














Group Title: Island perspectives
Title: Island perspectives. Vol. 3.
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/CA01300009/00001
 Material Information
Title: Island perspectives. Vol. 3.
Series Title: Island perspectives
Physical Description: Serial
Language: English
Publisher: Agricultural Experiment Station, University of the Virgin Islands
Publication Date: 1989
 Record Information
Bibliographic ID: CA01300009
Volume ID: VID00001
Source Institution: University of the Virgin Islands
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 23201242
issn - 1072-0804

Table of Contents
    Front Cover
        Page 1
    From the director
        Page 2
    Table of Contents
        Page 3
        Page 4
    Hydroponic lettuce production in a recirculating fish culture system
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    Citrus germplasm evaluation under V.I. conditions
        Page 11
        Page 12
    Reproductive performance of hairsheep ewes following pre-breeding supplementation
        Page 13
        Page 14
        Page 15
        Page 16
    Improving agricultural marketing in the U.S.V.I.
        Page 17
        Page 18
        Page 19
    Temperature build up and control measures in container-grown plants
        Page 20
        Page 21
        Page 22
        Page 23
    Production potential of buffelgrass pastures in the V.I.
        Page 24
        Page 25
    Environmental monitoring in the Salt River Submarine Canyon, St. Croix
        Page 26
        Page 27
        Page 28
        Page 29
    Agricultural experiment station (AES) personnel
        Page 30
    AES publications
        Page 31
    Back Cover
        Page 32
Full Text




















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ISLAND PERSPECTIVES
University of the Virgin Islands Agricultural Experiment Station
1988-1989 Vol. 3


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From The Director .. .


The eye of Hurricane Hugo passed
directly over St. Croix just as the
fourth issue of this publication was
ready to go to press. The outcome was
catastrophic. The University of the Vir-
gin Islands Agricultural Experiment
Station (AES) did not escape Hugo's
devastation. Most of our research
projects sustained extensive damage.
In fact, very little remains of the aqua-
culture and plant science facilities.
While the Animal Science and Forages
Program suffered the loss of some
animals and fences, their field facilities
remained basically intact and they have
been able to reestablish their research.
The hurricane did dramatically show
us an overlooked advantage of root
crops. Although the winds stripped
away all of their vegetation, the tubers
survived and quickly resprouted. The
same cannot be said for vegetables, a
total loss, and fruit trees. The trees that
survived were badly damaged and will
require years to recover.
While Hugo has dealt the Station a
major setback, we are rebuilding. The
Aquaculture Program is erecting new
tanks and rebuilding fish stocks. New
greenhouses will be added to the Plant
Science Programs which have already
sowed the seeds for new experiments.
Although the research reported here is
now history, we still feel it is important
to document our past efforts as com-
pletely as possible as we continue the
recovery.
During this period of change we
would like to introduce our new for-
mat and new title-Island Perspectives.
We hope the larger size will give you a
better feeling-or quite literally-a bet-
ter picture of the exciting work done
here. With this issue, we have also
opened the publication to the staff of
all three research and extension divi-
sions of the University of the Virgin
Islands, in addition to the Agricultural
Experiment Station. Island Perspectives
will contain reports on the multi-
faceted research and outreach activities
at the Agricultural Experiment Station,
Caribbean Research Institute and
Cooperative Extension Service. We


Oak





think the inclusion of all three divi-
sions will give our clientele a broader
view of the many ways that researchers
in the areas of agriculture, forestry,
food and natural resources are work-
ing to develop and transfer new tech-
nologies to improve the quality of life
in the territory and the region.
Research findings presented in this
issue are immanently practical as well
as geared toward long-term technolog-
ical advances. For example, our hor-
ticulturist has found that ornamental
plants do not grow well in the black
plastic flower pots that are in common
use here. The tropical sun raises the
soil temperature over the plant's stress
threshold and eventually hampers its
growth. Light colored pots solved the
problem. This is just one example of
research that can be put to use on
many levels-from a few potted plants
on porches to the thousands of trans-
plants destined for commercial use.
Our first story highlights an aspect of
our nationally recognized aquaculture
program which is developing technol-
ogy for growing vegetables and fish in
a closed system. This system harvests


rainwater, conserves it through recy-
cling, and recovers nutrients from the
fish culture operation for vegetable
production. At the same time, nutrient
uptake by vegetables improves water
quality and enhances fish growth.
Although part of this facility was
destroyed, the systems are being
reestablished and new experiments are
planned.
A report on research done at our
sheep facility indicates that expensive
short-term food supplementation of
breeding sheep has very little effect on
subsequent lambing performance.
Although this type of feeding is a stan-
dard flock management practice in
northern locations, our results suggest
that it is unnecessary as well as
unprofitable under St. Croix con-
ditions.
We have also included some infor-
mation on marketing which will be of
interest to both farmers and con-

sumers. And, as part of UVI's com-
mittment to maintaining the quality of
the environment and the natural
beauty of our islands, we have
reported on an ongoing marine
monitoring program which may help
set up guidelines for keeping corals
healthy throughout the Caribbean.
The ability to evaluate Hugo's under-
water impact is another unanticipated
application for this project.
I would like to take this opportunity
to encourage all Virgin Islands resi-
dents to look through this publication,
make use of these findings, and feel
free to contact us for more information.
We look forward to our participation in
rebuilding St. Croix and the Virgin
Islands.
Darshan S. Padda
Vice President for Research
and Land-Grant Affairs










ISLAND PERSPECTIVES


University of the Virgin Islands


Hydroponic Lettuce Production in a Recirculating Fish Culture System .......... 5
James E. Rakocy

Citrus Germplasm Evaluation Under V.I. Conditions .......................... 11
Feiko Ferwerda and Chistopher Ramcharan

Reproductive Performance of Hairsheep Ewes Following
Pre-Breeding Supplementation ..................... 13 '
Stephan Wildeus

Improving Agricultural Marketing in the U.S.V.I. .........17 ,
Francois Dominique **

Temperature Build Up and Control Measures in Container-Grown Plants ..20
Christopher Ramcharan

Production Potential of Buffelgrass Pastures in the V.I. ................... 24
Stephan Wildeus and Cyndi L. Wildeus

Environmental Monitoring in the Salt River
Submarine Canyon, St. Croix ..................................... 26
Mary Lou Coulston

AES Personnel and Current Research Projects .......................... 30

Recent AES Publications ............................................ 31


James E. Rakocy
Associate Director


Carrol B. Fleming
Editor


Editorial Board Members
John Hargreaves
Stephan Wildeus


Arthur A. Richards
President


Published by the University of the Virgin Islands
Agricultural Experiment Station
RR2, Box 10,000 Kingshill
St. Croix, U.S. Virgin Islands 00850
1990


Darshan S. Padda
Vice President


Agricultural Experiment Station
1988-1989 Vol. 3








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Harvesting hydroponic lettuce involves separating the net basket from the peat cube. This removes most of the
roots, but some remain and the plant can be sold as "living lettuce."


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Hydroponic Lettuce Production in a


Recirculating Fish Culture System
by James E. Rakocy


Innovative methods are required to
expand food production on small
Caribbean islands where resources are
limited and most of the food supply is
imported. The University of the Virgin
Islands Agricultural Experiment Sta-
tion (AES) is taking a new approach to
growing more food by integrating
vegetable hydroponics with fish cul-
ture in water reuse systems. These
diverse agricultural enterprises are
being combined to increase production
while minimizing nutrient inputs and
the consumption of water, the major
limiting factor to agriculture in the U.S.
Virgin Islands. Fish culture water pro-
vides most of the nutrients required by
vegetables while nutrient uptake by
vegetables improves water quality and
may increase fish production. An
experimental system has been estab-
lished for studies on design, manage-
ment, and production. This is a report
on the results of two recent experi-
ments involving the production of leaf
lettuce and tilapia.
The integrated system at AES con-
sists of a 12.3-m3(3,300-gallon) fish
rearing tank, a 1.9-m3 500-gallon)
settling tank clarifierr) for removal of
solids, two, 2.1-m3 (550-gallon) hydro-


ponic tanks with a total plant growing
area of 13.8 m2 (148 square feet), and a
1.4-m3 (370-gallon) reservoir (Figure 1).
The total system volume during oper-
ation averages 17.8 m3 (4,750 gallons).
The hydroponic tanks, which are 6.10
m (20 feet) long, 1.22 m (4 feet) wide,
and 0.2a8 m (0.92 feet) deep, are co-
vered with floating sheets of polysty-
rene (3.8 cm thick; 1.5 inches)
containing 5-cm (2-inch) holes for the
support of lettuce plants in net baskets.
Biofiltration (ammonia removal) is
provided by a rotating biological con-
tactor (RBC) with 92 m2 (1,000 square
feet) of surface area located in the rear-
ing tank. The RBC is rotated by in-
fluent water striking a water wheel in
the center of the RBC. Water is circu-
lated by a submersible pump (1/6 hp)
at an average rate of 57 liters/minute (15
gallons/minute), and aeration in the
rearing tank is provided by an agitator
(1/3 hp) and a diffused air line. High-
quality water for the system is obtained
by harvesting rainwater from a vinyl-
lined catchment.
An experiment was conducted to
determine the optimum ratio of lettuce
plants to fish for maximum lettuce
production. Six identical systems were


A harvest of tilapia cultured in a recir-
culating system.


Valve O
1 meter
I I---


Figure 1. A closed recirculating system for integrating vegetable hydroponics with fish culture.






stocked with Tilapia nilotica at rates of
44, 88, 132, 176, 220, and 264 fish/sys-
tem. The fish, which averaged 113
grams at stocking, were fed a complete
diet for 21 weeks at a constant daily
rate of 200, 400, 600, 800, 1000, and 1200
grams, respectively, which was equal
to 4.5 grams/fish. The floating, pelleted
food contained 36% protein plus vita-
min and mineral supplements.
In each system, 330 leaf lettuce
plants (var. Summer Bibb) were grown
in 3-week, staggered production
cycles. On Monday of each week, 110
plants from each system were harvest-
ed and individually weighed after root
removal. An equal number of seed-
lings in peat pellets were then trans-
planted into the net baskets. The
seedlings were grown for 3 weeks in
flats prior to transplanting. Planting
density was maintained at 23.9
plants/m2 (2.2 plants/square foot) for a
total of 18 crops.
Six ratios were obtained by holding
the number of plants constant and
varying the fish stocking rates. The
ratios were 75, 3.8, 2.5, 1.9, 1.5 and 1.2
lettuce plants to 1 fish. The respective
feeding rates were therefore equivalent
to 0.6, 1.2, 1.8, 2.4, 3.0, and 3.6
grams/day/plant or 0.8, 1.6, 2.4, 3.2, 4..0,
and 4.8 grams/day/m3/m2 in terms of
system volume and plant growing sur-
face area.


Since the bilfiltration process (nitrifi-
cation) produces acid, pH was meas-
ured often. When the pH decreased to
less than 6.5, a strong base (potassium
hydroxide or calcium oxide) was added
to the system to raise pH. These addi-
tions also supplemented the system
with potassium and calcium, essential
plant nutrients that do not accumulate
in sufficient quantities in integrated
systems. The system was also sup-
plemented twice with chelated iron
and once at the beginning of the
experiment with phosphorus (as
dipotassium phosphate).
The highest lettuce production (14.1
kg/week/system; 31 pounds) and the
largest heads (131 grams; 0.29 pounds)
were obtained from a ratio of 1.9 let-
tuce plants to 1 fish (Table 1). At this
ratio the feeding rate was equivalent to
2.4 grams/day/plant. The plants obtained
most of their nutrition indirectly from
fish feed after it had been digested by
the fish. Nutrients were excreted
directly into the water by the fish or
released to the water after waste
products were broken down by bac-
teria. Lettuce production and head size
decreased at both higher and lower
ratios. At the higher ratios there was
less fish feed available to plants as a
source of nutrients, which led to nutri-
tional deficiencies and diminished
growth. Plants at the highest ratio even


exhibited chlorosis, yellowing of the
leaves. There was more fish feed available
per plant at the lower ratios, resulting in
an accumulation of nutrients that pos-
sibly inhibited plant growth (Figure 2).
Weekly lettuce yields were variable,
and only with the ratio of 1.9 plants to
1 fish was there a pattern of gradually
increasing yields (Figure 3). Yields did
not increase as nutrients accumulated
at the highest ratio (7.5) nor were initial
yields substantially higher before pos-
sible inhibitory effects occurred at the
lowest ratio (1.2). The nutrient dynam-
ics of integrated systems therefore
appear to be very complex and warrant
further investigation.
There was a direct correlation between
the stocking ratio (feeding rate) and
the accumulation of total dissolved
solids (mainly nutrient salts). Concen-
trations of dissolved salts increased
(Figure 2) with an increase in the feed-
ing rate. Most of the salt came from the
addition of bases (potassium hydrox-
ide, calcium oxide and dipotassium
phosphate) to neutralize the acid
produced by nitrification. Acid
production increased with higher
feeding rates, and therefore more base
was added to these systems. The other
major component of total dissolved
solids was generated from fish feed
and consisted of nitrate, phosphate
and sulfate ions. The initial sharp


Table 1. Fish (Tilapia nilotica) stocking rates, feeding rates and mean lettuce (Summer Bibb) and fish production during
21 weeks in integrated recirculating systems stocked at six ratios of plants to fish.
Stocking ratio (plants:fish)
Variable 7.5 3.8 2.5 1.9 1.5 1.2
Stocking rate
(fish/system) 44 88 132 176 220 264
Feeding rate
(kg/day/system) 0.2 0.4 0.6 0.8 1.0 1.2
(g/day/plant) 0.6 1.2 1.8 2.4 3.0 3.6
(g/day/m3/m2)a 0.8 1.6 2.4 3.2 4.0 4.8
Lettuce production
(kg/week/system) 10.5 + 0.4 11.8 + 0.7 12.3 + 0.7 14.1 + 0.9 13.1 + 0.9 11.2 + 0.8
(kg/m2/crop)b 2.3 2.6 2.7 3.1 2.8 2.4
(g/head)c 98 + 4z 109 + 6yz 117 + 6xyz 131 + 8x 124 + 8xy 106 + 7yz
Net fish production
(kg/system) 20.5 41.3 56.8 83.1 95.6 112.2
aBased on a system volume of 17.8 m3 and a plant growing area of 13.8 m2 with 23.9 plants/m2.
bEach crop was produced in 21 days from transplanting. Using staggered production, one crop was harvested weekly for a total of 18
crops.
'Means followed by the same letter are not significantly (P>0.05) different.








1200

1050

900

750

600

450

300

150


0' '
0 4 8 12 16 20

TIME (weeks)

Figure 2. Accumulation of total dissolved solids during 20 weeks in 17.8-m3 integrated
recirculating systems stocked at six ratios of plants to fish.


increase in total dissolved solids was
due mainly to the addition of bases
and nutrient supplements during a
period when three staggered groups of
lettuce were being established. After-
wards, salts increased at a relatively
low rate at 7.5, 3.8, and 2.5 plants:fish,
indicating that a large portion of
nutrient salts were being used for plant
production. The rate of salt accumula-
tion was substantially higher at 1.9
plants:fish, which suggests that the
nutritional needs of the plants had
been met and exceeded. Total dis-
solved solids reached 900 mg/liter in 20
weeks and increased at an average rate
of 135 g/kg of feed at 1.9 plants:fish,
which gave the highest lettuce yields.
Ratios of plants:fish that are intermedi-
ate between 1.9 and 2.5 should be
examined to determine if comparable
yields can be obtained while lowering
the rate of salt accumulation. High
accumulation rates will shorten
production cycles or necessitate more
frequent water exchanges or dilutions.
The ratio of plants to fish and the
equivalent feeding rate per plant are
inadequate terms for quantifying the
relationship between plants and fish in
integrated systems because they do not


consider volume. The system volume
is an important factor in determining
nutrient concentrations, which in turn
affects plant production. The relation-
ship is expressed more clearly by relat-
ing feeding rate (grams/day) to system
volume (m3) and plant growing area
(m2) or, specifically, grams/day/m3/m2
for designated plant growing densities,
which in this case was 23.9 plants/m2.
The optimum feeding rate was 3.2
g/day/m3/m2 in this experiment. This
feeding rate can be used as a design ra-
tio in determining optimal fish feeding
and stocking rates for a given level of
lettuce production or the optimum let-
tuce growing area for a desired level of
fish production.
Integrating vegetable hydroponics
with fish culture has been promoted as
a means of obtaining greater profitabil-
ity by reducing water and nutrient
costs. Vegetables are viewed as a by-
product of the fish culture operation
that would generate additional
income. But these are unproven
assumptions. Therefore, an experi-
ment was conducted to compare
chemical and water use in a integrated
system for tilapia and lettuce produc-
tion with a lettuce hydroponic system


utilizing synthetic nutrient salts. Tilapia
production in the integrated system
was also compared to tilapia produc-
tion in a recirculating system without
lettuce hydroponics. The overall objec-
tive of the experiment was to quantify
the likely advantages of integrated sys-
tems over traditionally separate produc-
tion systems where tilapia and lettuce
are grown independently.
Three of the systems used in the first
experiment were modified by creating
separate hydroponic and fish culture
systems. The hydroponic system,
known as a deep flowing system, con-
sisted of a reservoir and two hydro-
ponic tanks. Water was continuously
pumped from the reservoir to one of
the hydroponic tanks from which it
flowed by gravity through the second
hydroponic tank to the reservoir. The
fish culture system consisted of a clar-
ifier and fish rearing tank containing
an RBC. Water was continuously
pumped from the clarifier to the rear-
ing tank and returned by gravity to the
clarifier. The water volumes of the in-
tegrated, hydroponic and fish culture
systems were 17.8, 4.8, and 13.5 m3
(4,700, 1,270, and 3,570 gallons), respec-
tively. Each system was replicated
three times.













There was no significant

difference in lettuce

production or survival

between the integrated

and hydroponic systems.





Table 2. Mean tilapia (Tilapia nilotica) and lettuce (Summer Bibb) production,
and water and chemical use in an integrated fish culture/vegetable hydroponic
system, a vegetable hydroponic system, and a fish culture system after 14 weeks.
System
Integrated fish
culture/vegetable Vegetable Fish
Variable hydroponic hydroponic culture
Tilapia production
Net production (kg) 46.8 41.6
Mean final weight (g) 1008 968
Feed conversion ratio 1.68 1.89
Survival (%) 99.5 99.5
Lettuce production
Total weight (kg) 385.1 380.1 -
Mean weight (kg) 115.4 114.6 -
Total number 3337 3318 -
Survival (%)a 88.2 (94.3) 87.7 (93.2) -
Water use
Quantity (m3) 24.1 13.7 19.3
Cost ($)b 255.04 144.88 71.57
Chemical use
Quantity (kg)c 9.56 21.99 10.10
Cost ($) 43.30 47.37 35.15
aThe number in parenthesis is survival excluding the crop destroyed by Hurricane Gilbert.
bDelivered desalinated water for hydroponic plant production costs $40/1000 gallons.
Piped government water (a blend of well and desalinated water) for fish production costs
$14/1000 gallons.
cPotassium hydroxide, calcium oxide, dipotassium phosphate, and iron chelate were
added to the integrated system. Potassium hydroxide was added to the fish culture system.
Potassium hydroxide, calcium nitrate, magnesium nitrate and 8-15-36 (N-K-P) were added
to the hydroponic system.


Over a 14-week period, twelve crops
of leaf lettuce (var. Summer Bibb)
were cultured on 3-week staggered
production cycles in the integrated
and hydroponic systems. Each crop
consisted of 110 plants per system
with the exception of the first three
crops when fewer transplants were
available.
A commercial nutrient formulation
for lettuce was used in the hydroponic
system. It consisted of 8-15-36 (N-P-K)
with trace elements, calcium nitrate
(both applied at a rate of 0.5 lbs/100
gallons), magnesium sulfate (applied
at 0.31 lbs/100 gallons), and potassium
hydroxide (applied as needed to raise
pH). The hydroponic solutions were
discarded after weeks 4 and 10 and
replaced with fresh solutions to main-
tain a proper nutrient balance. Fish
feed was the main nutrient source in
the integrated system, although the
system was supplemented with potas-
sium hydroxide, dipotassium phos-
phate, calcium oxide, and chelated
iron. Potassium hydroxide was the
only chemical addition to the fish cul-
ture system. In the integrated and fish
culture systems, pH was measured
often and maintained at 6.5-7.0 by
adding base.
The integrated and fish culture sys-
tems were stocked with Tilapia nilotica
at a rate of 138 fish per system. The
fish had been used in the first experi-
ment and averaged 663 grams at stock-
ing. The fish in each system were fed
at a constant rate of 800 grams/day (5.8
grams/fish) for 98 days. The feeding
rate in the integrated system was 3.26
g/day/m3/m2, which was found to be
the best feeding ratio from the previ-
ous experiment for maximum plant
production.
There was no significant difference
in lettuce production or survival be-
tween the integrated and hydroponic
systems (Table 2). Total production
was 385.1 and 380.1 kg (847 and 836
pounds) in the integrated and hydro-
ponic systems, respectively. Lettuce
growth was the same with synthetic
nutrients or nutrients mainly from fish
feed.
The integrated system produced
12.5% more tilapia than the fish cul-
ture system alone (Table 2). Net tilapia
production and final mean weight
were 46.8 kg (103 pounds) and 1008






grams (2.2 pounds) in the integrated
system and 41.6 kg (92 pounds) and
968 grams (2.1 pounds) in the fish cul-
ture system. Significantly greater
production in the integrated system
resulted from more efficient feed con-
version (1.68 vs. 1.89). The lettuce
plants helped create a stable environ-
ment by inhibiting phytoplankton
growth, reducing suspended solids,
and absorbing toxic metabolites, which
thereby improved feed conversion and
fish growth.
The results clearly demonstrate the
quantitative advantages of integration
(Table 2). The amount of chemicals
(21.99 kg; 48.3 pounds) applied to the
hydroponic system was more than
twice of that (9.56 kg; 21.0 pounds)
used by the integrated system,
although the costs were similar due
primarily to the expense of iron chelate
in the integrated system. The advan-
tage of the integrated system is illus-
trated dramatically by combining the
chemical requirements and costs of the
hydroponic and fish production sys-
tems. The combined cost and chemical
requirement of the separate produc-
tion systems ($82.52; 32.09 kg or 70.6


pounds) are approximately two and
three times greater, respectively, than
that of the integrated system ($43.30;
9.56 kg of 21.0 pounds) to produce the
same amount of lettuce and slightly
less fish.
The integrated system utilized more
water (24.1 m3; 6,370 gallons) than the
hydroponic (13.7 m3; 3,620 gallons) or
fish culture (19.3 m3; 5,100 gallons) sys-
tems, but the combined water use (33.0
m3; 8,720 gallons) of the separate
production systems was 37% higher
than that of the integrated system (Ta-
ble 2). The water cost ($255.04) for the
integrated system was higher than the
combined water cost ($216.45) for the
separate production systems because
the fish culture system used less
expensive water ($3.70/m3 or
$14.00/1,000 gallons for piped govern-
ment water, a blend of well and desali-
nated water). The integrated and
hydroponic systems require either
desalinated water at a cost of $10.57/m3
($40.00/1,000 gallons) or rainwater.
Groundwater is generally unsuitable
for hydroponics in the Virgin Islands
due to high levels of dissolved salts.
The cost of desalinated water was used


for comparison, but less expensive
water can be obtained by rainwater
harvesting.
The frequency of nutrient solution
exchange was a key factor in determin-
ing nutrient and water costs in the
hydroponic system. In recirculating
hydroponic systems it is common prac-
tice to replace nutrient solutions every
four weeks to ensure proper nutrient
balance. Different batches of the
nutrient solution were used for the
first 4 weeks, the next 6 weeks, and the
final 4 weeks of this experiment. There
was no clear trend of declining
production during the 4-week or
6-week periods. If nutrient solutions
could be used for longer periods
without a decrease in production,
nutrient and water costs would
decline, and the comparative econom-
ics of the integrated and separate
production systems would change
slightly. Nevertheless, integrated sys-
tems would still compare favorably
with separate production systems.
The concept of growing vegetables in
fish culture water has been envisioned
for many years, but there have been
few quantitative experiments. The ratio


An experimental recirculating system integrating vegetable hydroponics with fish culture. Lettuce production is staggered
in 3-week cycles.












70 75 Plant : Fbh

4
2


4
2
0


10

4
2
8
4
2
0


S1.9 Planta : Fi


3.8 Plant: Fh





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LFF


1.2 Plants: F


0 1 2 3 4 5 6


0 1 2 3 4 5 6 7 9 1011 12131415


Ti]


[hi


7 8 B 101112131415181718


Figure 3. Lettuce production for 18 crops in integrated recirculating systems stocked at six ratios of plants to fish.


experiment demonstrated that a large
quantity of lettuce plants can be grown
from the nutrients of a relatively small
amount of fish or a low feeding rate.
Extrapolating from the results of this
experiment, just one pound of feed
per day, enough to feed 33 lbs of tilapia
fingerlings, can sustain 189 lettuce
plants and produce nearly 3,300 heads
of lettuce annually. A much larger area
would be needed for the plants than
the fish. Growing lettuce also involves
much more time and labor than cultur-
ing fish. Fish culturists originally con-
sidered vegetables to be a by-product
of the fish culture operation, but the
emphasis in integrated systems falls on
the plant production component.
An objective comparison of integrat-
ed systems to individual production
systems for lettuce and tilapia is
problematic, and the results may be
more reflective of system design and
experimental procedures than realistic
economics. The deep flowing hydro-
ponic system, which integrates well
with fish culture, may consume more


4rsi


water and chemicals than sand culture
or the nutrient film technique, which
are industry standards. Nevertheless,
significant reductions in chemical and
water consumption were achieved
through integration for comparable
production; and as more efficient
management procedures are deve-
loped, inputs (e.g., nutrient sup-
plementation) may be reduced.
Two commercial-scale systems are
currently being established to eval-
uate annual production capabilities,
develop an enterprise budget, and
gauge the comparative resource
requirements and profitability of
integrated systems for fish culture and
vegetable hydroponics.

This research was supported by Virgin
Islands Hatch Project #082.

James E. Rakocy is Associate Director of
AES and a research aquaculturist.


0
V

J1


2.5 Pot: Flmh


II~hiILM






Citrus Germplasm Evaluation


Under V.I. Conditions

by Feiko Ferwerda and Chistopher Ramcharan


Citrus of all species are widely grown
in tropical and subtropical regions. The
fruits are used mainly as a dessert or
breakfast fruit and for making juices
and other citrus products. Citrus is in
great demand in the Virgin Islands by
local residents and the increasing num-
ber of visitors. However, almost 100% of
all citrus products used here are
imported from the U.S. mainland or
neighboring Caribbean Islands. This is
partly due to the limitations imposed
by soil, water and climatic constraints in
the V.I. Due to these limitations, plants
are often stressed, making them more
susceptible to disease and insect pests.
Choosing the proper citrus variety for
local conditions is an essential first step
for successful cultivation. A long term
study at UVI-AES evaluated 21 citrus
rootstock scion combinations. The
results of the first five years of this
investigation indicate a number of
differences in the success of various
citrus species.
The trial was conducted at the UVI-
AES between 1984 and 1989 on
Fredensborg clay soil with a pH of
8.0-8.5. The field was ploughed, disced
and banked into 8-10 feet wide ridges,
20 feet apart. Plant spacing within the
rows was 10 feet. The citrus plants
were obtained from a certified nursery
in south Florida and shipped bare-
root. The trees were planted in the
center of the ridges to ensure proper
drainage. Weed control was accom-
plished using Round-up@ herbicide (1
qt/ac.) around the trees and mowing as
required between the rows. Trees were
drip irrigated at 1 gallon/plant/day at
25 psi.
The major disease problem, foot and
root rot caused by Phytopthora spp.,
was controlled by drenching the root-
zone with a Ridomil@ at 0.05 oz/gallon.
Scale insects, aphids and mealy bugs
were controlled by a periodical spray
with Diazinon@ (1 lb/acre) plus Volck
oil, as needed. This insecticidal treat-
ment also eliminated the formation of
black mold on fruits and leaves. Plants


received a monthly fertilizer applica-
tion of sulfur coated 16-4-4 (N-P-K) at
0.25 lbs/tree. Micro nutrients
(Nutrileaf) was applied as a foliar
spray at a rate of 2 lbs/100 gallons.
Yields were determined from hand-
harvested mature fruits. Survival and
yield data are illustrated in Table 1 and
2 respectively.
Ortanique, valencia, navel and
pineapple oranges were the most
environmentally tolerant orange trees
(Table 1). Ortanique orange trees
produced the highest yields per tree,
while valencia produced the largest
number of fruits per tree (Tables).
Orlando tangelos produced abundant
juicy fruits, even under the relatively
dry conditions. The tangerines, kum-
quats, lemons and surprisingly the
limes showed poor survivability.
Thompson Pink and marsh grapefruit

Table 1. Percentage survivability of 21
(1984-1989)z


trees withstood local conditions very
well. However, the number of fruits
per tree were relatively low. Thompson
Pink yielded both the highest number
of fruit per tree and the highest weight
per grapefruit (Table 2). Pumelo
thrived well under local conditions
and trees were up to 12 feet high with
excellent disease resistance.
Overall results from this trial indicate
that large-scale commercial production
of citrus is generally not feasible in
areas of St. Croix with calcareous
Fredensborg soil types. The underly-
ing soft, marl limestone limits the root-
zone to the top 10-15 inches of soil
profile. Although this characteristic
tends to dwarf the growth habit of
citrus trees, it does not necessarily
affect fruit quality. The high pH-
deficiencies can be overcome by strict
fertilizer schedules. These trees, how-

citrus cvs. on 2 rootstocks over 5 years


Scion RootstockY % Survivability
Ortanique orange Unknown 100%
Valencia orange S.O. 90%
Navel orange S.O. 100%
Pineapple orange Cleo 100%
Blood orange Cleo 50%
Blood orange S.O. 50%
Murcott orange Cleo 80%
Temple orange S.O. 40%
Parson Brown orange S.O. 84%
Robinson tangerine Cleo 20%
Ponkan tangerine Cleo 20%
Orlando tangelo Cleo 100%
Ruby Red grapefruit S.O. 90%
Thompson Pink grapefruit S.O. 80%
Marsh grapefruit S.O. 100%
Meyer lemon S.O. 20%
Ponderosa lemon Cleo 0%
Persian lime Cleo 20%
Lakeland lime Cleo 0%
Pumelo S 100%
Kumquat S 20%
Y S.O. Sour orange rootstock; S seedling
Cleo Cleopatra mandarin rootstock
z 5 replicate trees/combination




































Ortanique orange produced high yields under Virgin Islands conditions.


Table 2. Yield data of selected citrus cvs. on 2 rootstocks
Variety Rootstock Av. No. fruit Av. Wt./
tree/harvest fruit (lbs)
season
Valencia orange S.O. 98 0.46
Pineapple orange Cleo 81 0.54
Navel orange S.O. 47 0.61
Parson Brown orange S.O. 93 0.39
Ortanique orange Seedling 78 0.63
Orlando tangelo Cleo 128 0.38
Ruby Red grapefruit S.O. 28 0.760
Thompson Pink grapefruit S.O. 29 0.903
Marsh grapefruit S.O. 21 0.842
S.O. Sour Orange rootstock
Cleo Cleopatra manderin rootstock


Choosing the proper

citrus variety for

local conditions is

the first step .


ever, produce relatively fewer and
smaller fruit than citrus grown on ideal
soil types.
For the small farmer and home
gardener in the Virgin Islands with
similar soil types we would recom-
mend the following varieties. Valencia
orange for its prolific bearing, good
tasting fruits and its drought tolerance.
Orlando tangelo performed well and
produced sweet easy to peel fruits.
Thompson Pink and Ruby Red
grapefruit produced fruit with a well
blended sweet and sour taste.
Parson Brown, pineapple, ortanique
outperformed some of the recom-
mended varieties in yield, but their
fruit quality was inferior. High night
temperatures and the low altitude of
the experimental site may be contribut-
ing factors.
Although the W.I. lime, which is
used locally as a beverage and in many
dishes, thrives under most local condi-
tions, the limes in this experiment per-
formed poorly. The reason is
unknown, but poor quality of original
planting stock is suspected. The
Pumelo, a vigorous disease-resistant
citrus, could have some future poten-
tial with the proper introduction of its
uses to local growers. The Kumquat
can be grown as a potted plant and
serve a dual purpose as a fruit and a
unique ornamental crop.

This research was funded by Virgin
Islands Hatch Project #085.

Feiko Ferwerda is a former research
specialist in the Horticulture Program.
Chris Ramcharan, Research Assistant
Professor, is the leader of the Horticulture
Program.








Reproductive Performance of Hairsheep Ewes


Following Pre-Breeding Supplementation
by Stephan Wildeus
Increasing the level of nutrition prior
to and during the early stages of breed-
A... ing ("flushing") has successfully
increased the lambing rate of sheep in
temperate environments. Flushing can
be accomplished by either moving the
ewes to a pasture with high quality
forage, or by supplementation with
harvested feed, starting approximately
2-3 weeks before breeding. The benefi-
cial effects of flushing have been
observed in breeds of wool sheep
under range conditions, but it has not
been established if this management
tool is useful under Virgin Islands con-
ditions. Two experiments were con-
ducted to examine the effects of
different types of supplementation
(energy and protein) on the reproduc-
tive performance of young and mature
hairsheep at the Sheep Research Facil-
ity of the Agricultural Experiment Sta-
tion on St. Croix.
In the first experiment 20 mature
ewes (over 2 years of age), nursing
4 -lambs, were divided into control and
treatment groups stratified by weight 4
weeks before the beginning of breed-
ing (September 9, 1987). All ewes were
grazed on the same Guinea grass
(Panicum maximum) and tan-tan (Leu-
caena leucocephela) pasture during the
day and were separated in the eve-
ning. The treatment group then
received a cracked corn supplement
(8 % crude protein, 3% crude fiber and
3% crude fat) at a level of 2.0
lbs/head/day. After 4 weeks, at breed-
ing, supplementation was terminated
S ,and the lambs were removed from
their dams. During the 34-day breed-
ing period all ewes were mated to a
ram that was painted daily on the
brisket with colored oil to mark ewes
that had been bred. Within 5 to 10 days
following their respective breeding
dates all ewes were examined by
laparoscopy to determine ovulation
rate. During the supplementation and
breeding period, body weight and
condition (estimate of fat cover over
the ribs and vertebra) were recorded
weekly. At lambing, the number of







ewes lambing and the number of
lambs per ewe were recorded.
In a second experiment, a similar
protocol was repeated with a group of
young (6 to 12 months of age) ewes
(n=26) to be bred for the first time.
Ewes were allocated to a control and
treatment group stratified by age,
weight and type of birth (single, twin).
In this experiment a mixture of coco-
nut meal and molasses was fed at a
level of 0.75 lbs/head/day. The supple-
ment was prepared fresh every day by
mixing coconut meal, molasses and
water in a ratio of 2 : 1 : 1.5 (12% crude
protein, 7% crude fiber and 0.5% crude
fiber fats on an as fed basis.) For this
study the supplementation period was
reduced to 3 weeks, but the remainder
of the protocol was similar to the first
experiment. Ewes in this second
experiment were bred starting January
28, 1988 and lambed between June 26
and July 15, 1988.
In the first experiment supplement-
ed ewes gained 4.3 lbs during the
flushing period, while the control
ewes lost body weight (6.7 lbs) and
condition (Table 1). Most likely this
loss in body weight and condition can
be attributed to the lactation stress ex-
perienced by these ewes, while not
receiving an adequate level of feeding
to satisfy nutritional requirements.
Although there was some fluctuation,
both groups generally maintained the
body weight and condition established
during the flushing period throughout
breeding (Figure 1).
Reproductive measurements indi-
cated no significant advantages in sup-
plementing with corn (Table 1).
Supplemented ewes tended to breed
earlier in the breeding season (6 days),
but this difference would not result in
a major economic benefit, since ewes
in both groups conceived during their
first estrous cycle (15-17 days). Ovula-
tion rate was higher in the supple-
mented group, but was of no signifi-
cance during subsequent lambing. In a
separate study (unpublished data)
mature ewes on a high plane of nutri-
tion achieved ovulation rates of 2.0 on
a year round basis, suggesting that
non-supplemented control ewes had
ovulation rates slightly below the bio-
logical optimum of the breed on St.
Croix. The reason for the difference


6-



5-



4-
0

E 3-

-
0 2-


o-Otreatment
--- control


S

V


*1 r--1- I~ I-- I- I- I


95



90



S85
.0






75



70



65


0 10 20


30 40 50 60 70 80


Time on study (days)


Figure 1: Body weight and condition changes in mature ewes during and after
supplementation with corn (treatment).












This lack of response due
to "flushing" may be
partly due to the absence
of a photoperiod
on St. Croix.


-i !


Ewes waiting for feed.


Table 1. Body weight and condition, and reproductive performance
(mean+SEM) in mature ewes fed pasture (control) or pasture with supplement
prior to breeding.


Supplemented"


Beginning of flushing:
Weight (lbs)
Condition (1-9)
After flushing:
Weight (lbs)
Condition (1-9)
End of breeding:
Weight (lbs)
Condition (1-9)
Days to estrus
Ovulation rate
No. of lambs/ewe lambing
No. of lambs/ewe exposed
Gestation length (days)


83.0+4.1
3.89+ .26

87.3+3.9
4.11+.26

89.0+4.1
4.44+ .50
2.6+0.8
2.00+0.19
1.50+0.18
1.33+0.23
149.0+0.7


Control


80.9+3.4
4.44 +.17

74.22.9
2.66+ .24

76.2+2.1
3.00+ .24
8.9+2.1
1.78+0.22
1.570.18
1.22+0.28
148.4+0.7


supplemented with 2 lbs/head/day of cracked corn



Table 2. Body weight and reproductive performance (means+SEM) in hairsheep
ewes lambing for the first time fed pasture (control) or pasture with supplement.
Supplemented Control
Pre-feeding weight (lbs) 66.7 +1.94 67.8+1.70
Post-feeding weight (Ibs) 71.1 +1.79 70.6+1.96
Weight at conception (lbs) 73.3+1.67 72.2+1.80
Days to estrus 11.2+2.27 7.9+1.43
Ovulation rate 1.27+0.18 1.42+0.15
No. of lambs/ewe exposed 1.07+0.21 1.27+0.17
Amount of lamb born (lbs) 8.42+0.59 7.810.74
Gestation length (days) 146.3+0.60 145.7+0.38

supplemented with coconut/molasses mixture at 0.75 lbs/head/day.


between ovulation and lambing rate is
not readily apparent, but may be
partly the result of the surgical interfer-
ence due to laparoscopy. This decline
in lambing rate was the result of ewes
not lambing according to their project-
ed ovulation rate, as well as ewes fail-
ing to lamb. The number of lambs born
per ewe lambing in this experiment
(1.5) was lower than the value gener-
ally observed (1.7) in mature ewes
lambing on pasture at the Sheep
Research Facility. However, both con-
trol and supplemented ewes were
equally affected by this decrease.
Gestation length was similar in control
and supplemented ewes.
In the second experiment body
weights of control and supplemented
groups were not significantly affected
by the feeding regime (Table 2). After
three weeks of feeding, supplemented
ewes were only slightly heavier (1.5
lbs), but the difference in weight was
no longer evident at the end of the
breeding season (Figure 2). The weight
at conception was 1.1 lbs lower in the
control group.
In the young ewes pre-breeding sup-
plementation also failed to improve
reproductive and lambing perfor-
mance (Table 2). Supplemented ewes
displayed estrus slightly later during
breeding (3.3 days) and had lower ovu-
lation and lambing rates, but differ-
ences were not statistically significant.
The amount of lamb born and gesta-
tion length were also not affected by




































Hairsheep ewe with twins.
85-




0-0 treatment
80
---* control




75

O /
0 0---0
M Z


A
end flushing


0 10 20 30 40 50 60
Time on study (days)
Figure 2. Body weight changes in young ewes bred for the-first time during and
after supplementation with coconut meal/molasses (treatment).


pre-breeding supplementation.
However, gestation length was 2.5 to 3
days shorter in these younger ewes
compared to the mature ewes in the
first experiment.
The results from the first experiment
suggest that short-term supplementa-
tion, at least at the level and for the
duration practiced here, was able to
generate a difference in body weight
and condition, but failed to have an
impact on the lambing performance of
hair sheep on St. Croix. Though there
was an indication of slightly higher
ovulation rates following supplemen-
tation, this effect did not materialize in
subsequent lambing rates. In the
younger ewes no significant body
weight changes were associated with
pre-breeding supplementation at 0.75
lbs/head/day, and it is not clear if the
lack of a response to supplementation
is an indirect effect of the insufficient
body weight change or a failure of the
supplement to directly affect reproduc-
tive function.
At this point the data suggest that
short-term supplementation prior to
breeding will not result in an improved
lambing performance in ewes in
moderate to good body condition.
This lack of response to "flushing"
may be partially a result of the absence
of photoperiod-induced seasonality in
breeding of sheep on St. Croix.
However, the benefits of a long-term
improvement in the level of nutrition,
either through supplementation or
improved pastures, cannot be ruled
out and deserve further investigation.

The author acknowledges the tech-
nical assistance of Ms. K.T. Traugott,
Ms. J.R. Fugle and Mr. A. Schuster in
animal handling and data collection.

This research was supported in part
by the U.S. Department of Agriculture
under CSRS Special Grant No.
86-CRSR-2-2816 managed by the Carib-
bean Basin Advisory Group (CBAG).

Stephan Wildeus, Research Assistant
Professor, heads the Animal Science and
Forages Program.






Improving Agricultural Marketing


in the U.S.V.I.


Fruit production has been an alter-
native form of agriculture in the U.S.
Virgin Islands from the beginning of
the twentieth century. As the basis of
the local economy changed from
agriculture (sugar cane) to heavy
industries and tourism, fruit produc-
tion became the dominant crop farm-
ing activity. A 1986 study showed
notable production increases of avo-
cado, banana, lime, and mango from
1930 to 1982. During the same era
sugar cane cultivation declined from
8,685 acres in 1917 to 3,676 acres in 1960,
and by 1982 cultivation was down to
three acres. Apparently, the high labor
cost and competition for labor in the
more lucrative tourism and industrial
sectors has forced farmers into less
labor intensive fruit crops production.
Presently, V.I. fruit growers are con-
fronted with many adverse marketing
conditions. According to the UVI
Cooperative Extension Service market
survey in 1987, the factors which
impede trading between retailers and
local producers ranked as follows: (1)
dependability of supply; (2) high
prices; (3) low production volume; (4)
fragmented supply system; and (5)
poor quality control. Over 80% of
tropical fruits are imported to the
island and 17% of that volume spoils
(Figure 1).
Supermarkets are the largest retailers
of food items. Of the 46 marketing out-
lets surveyed, six (6) or (13%) were
supermarkets, and with the exception
of mango, these outlets control the
largest share (52%) of the fruit market.
The major marketing outlets import an
average of 82% of these commodities
and, even in the case of mango were
domestic production (219,510 lbs.) far
exceeds the outlets' demand (197,078
lbs.), 67% of their purchases are
imported (Table 1).
Of the approximate 300,000 lbs. of
fruits produced, 138,000 lbs. (46%)
generated farm income (Table 1). Most
(76%) of this volume was marketed
through direct distribution to con-
sumers and only 33,142 lbs. (24%)


by Francois Dominique
were sold to supermarkets, grocery
stores, roadside vendors, hotels, and
restaurants. Table 2.
The V.I. market absorbs 84% of the
banana production and this makes it
the best seller, and the second largest
cash crop ($10,121/yr.). Although it
fetches the highest wholesale price
(0.38/lb.) among the selected crops, the
retail/wholesale price ratio of
$0.57/$0.38 or simply 1.5:1 has the
lowest retail markup price ($0.19).
From the standpoint of farmers, such a
low markup makes bananas a good
wholesale crop. On the other hand,
mango represents the largest quantity
sold (101,628 lbs.) and yields the
highest cash returns ($56,925) but has
the lowest wholesale price ($0.15/lb.).
The high price differential of 54 cents
from the retail/wholesale ratio of 4.6
makes it a good retail crop (Table 3).
The domestic market has the capac-
ity to absorb all the local fruits
produced, and the surplus mangoes
could become an export crop. But
though both producers and buyers
recognize the importance of volume,
quality, dependability, regularity,
prices, and an organized market struc-
ture, the two entities have different
ranking priorities for these trade
barriers.
In the Virgin Islands, the structure of
marketing channels for domestic food
crop production is quite simple
because the system does not include
processing and exporting. The two tier
distribution system for fruit markets
are 76% direct to consumers, and 24%
through other marketing channels.
To the farmer, the strategic function-
ing of a marketing system is to offer a
convenient outlet for produce, and to
the commercial sector and the con-
sumer, assurance of a steady supply is
the vital service. Improvement of the
marketing system then depends on the
ability of willingness of producers to
develop and capitalize on higher prices
obtained by direct distribution, and to
increase production and improve post-
harvest techniques so as to sustain


Mangoes yield high cash returns.

regular supplies and to meet the qual-
ity requirements of wholesalers. At the
current level of domestic production,
direct sales are the preferred marketing
method because the consuming public
poses less stringent demands on
producers in terms of regularity, quan-
tity, and quality as required by
wholesalers. Many farmers discount
the economic cost of retailing because
of the higher prices obtained for their
produce through this distribution
method. Thus an effective marketing
system should be geared towards
expanding the range and types of con-
sumers served, and this should offer
producers expanding outlets.
Even a low production level and an
organized delivery system would
benefit producers, wholesalers, and
consumers. Ideally, producers, retail-
ers, and consumers could trade at one
center through an intermediary agency
such as a marketing board. To the con-
trary, because prices of direct market-
ing are better, vendors are scattered
along the road from Christiansted to
Frederiksted where some have estab-
lished permanent locations, while
others make occasional appearances at










1.2


1.0
i

- 0.8 -
E
n
0.6-


a 0.4
0-


0.2 -


0 AVOCADO BANANA GRAPEFRU LIME MANGO ORANGE


I Market spoilage N
SUnsold production











0 AVOCADO BANANA GRAPEFRU UME UANGO ORANGE


To the detriment of their

operations, local farmers

tend to use retail prices

to wholesale their produce.

n


-L J..A.I


) AVOCADO BANANA GRAPEFRU UME MANGO ORANGE



SI Imports Local Purchases




-1\-1


MANGO ORANGE


0 AVOCADO BANANA GRAPEFRU UME


Figure 1. Aspects of fruit crop production, marketing and consumption in the U.S. Virgin Islands in 1987.


I Production
K Quantity sold


n


F"i







Table 1. Marketing survey of imports vs. local fruits purchased.
Fruit Quantity Source
Purchased Import Local
(lbs.) (%) (%)
Avocado 225,120 85 5
Banana 1,104,764 97 3
Grapefruit 205,643 99 1
Lime 128,522 45 55
Mango 197,078 67 33
Orange 1,110,313 99 1

Mean 495,240 82 18




Table 2. Percentage of market share.
Fruits Supermarket Wholesale Grocery Roadside Restaurant
Avocado 58 8 27 5 2
Bananas 75 6 15 2 2
Grapefruit 53 30 11 4 2
Lime 35 26 29 6 4
Mango 23 22 24 31 1
Orange 68 22 10 1 1

Mean 52 19 19 8 2




Table 3. Price structure of fruit crops.
Fruit W/Sale/lb. Retail/lb. Wholesale/Retail
Ratio

Banana $ .38 $ .57 1.50
Orange .34 .79 2.32
Lime .35 1.09 3.10
Grapefruit .32 1.04 3.20
Avocado .20 .73 3.65
Mango .15 .69 4.67




Table 4. Farm survey of fruitcrop production, sales and cash value.
Produce Quantity Quantity Quantity Percent Cash Value
Grown Produced Sold Sold of Sales
(trees) (lbs) (lbs) (%) ($)

Avocado 143 21,450 3,395 16 2,046
Banana 1,254 22,920 19,300 84 10,121
Grapefruit 47 4,116 2,805 68 2,432
Lime 140 20,440 1,182 6 1,078
Mango 813 219,510 101,628 46 56,952
Orange 73 12,050 9,781 81 6,671


various points. The largest number of
vendors gather in the area of the
Sunny Isle Shopping Center on Satur-
day, the traditional market day in the
Caribbean. The Hendrick's Market in
Christiansted operates with 90%
imports but the Frederiksted Market is
totally abandoned.
Beyond the current level of produc-
tion farms should operate as a true
business enterprise (Table 4). Produc-
tion should be planned, post-
harvesting techniques should be
improved, farmers should be aware of
the competition from the mainland
and other Caribbean islands, and mar-
keting intelligence and linkages with
buyers should be established.
One factor which has not received
adequate attention is pricing. To the
detriment of their operations, local
farmers tend to use retail prices to
wholesale their produce. A recent sur-
vey of the Christiansted Market by
UVI students revealed that retailers
preferred purchasing imported rather
than domestic tomatoes because
returns on the former were higher
even with higher spoilage rate. This
statement seems to concur with the
findings of this study. Given the
spoilage rates of many of the imported
fruits, domestic prices could be set to
clear local production.
The St. Croix Dairy Products and
Good Farm of St. Croix (sprouts farm-
ing) are two examples where
producers have used spoilage factor to
penetrate the market. Realizing that
they could produce quality items on a
regular basis and at competitive prices
with imports, longevity of product
shelf life became the main promotional
strategy.

This research was supported by Smith
Lever Cooperative Extension Project #031.

Francois Dominique is a former Program
Supervisor for the CES Community and
Rural Development Program.





Temperature Build Up and Control


Measures in Container-Grown Plants

by Christopher Ramcharan


Many tropical fruit and ornamental
plants destined for field planting or the
landscape are started in containers.
Although this production method
offers many advantages, high growth
medium temperature build up under
local conditions can reduce plant
growth and quality. Temperatures
above 50C have been recorded in con-
tainer media and temperatures above
40C are commonly attained for more
than 4 hours daily. Heat injury to plant
roots can result in plant starvation
effects and biochemical lesions or the
accumulation of toxic byproducts.
Research at the Agriculture Experi-
ment Station of the University of the
Virgin Islands was conducted to deter-
mine critical root-zone temperatures
(RZT) for selected tropical species and
to evaluate cultural practices aimed at
reducing heat stress in container-
grown plants. The objectives were to
evaluate the effects of plant-container
type and container spacing on RZT
fluctuations and growth of two com-
monly used ornamentals Dracaena
marginata 'tricolor, and Ixora chinen-
sis 'maui' and three economic fruit
species 'Carrizo' citrange citrus,
'Grande Naine' banana and Barbados
solo papaya.
Containers used were 2 gallon black
rigid plastic, 2 gallon rigid plastic
painted white and 2 gallon black poly-
ethylene bags inserted into black rigid
plastic containers 3 inches greater in
diameter than the poly bags. Metro
mix growth medium (W.R. Grace, Inc.,
Cambridge, MA, USA) was used for
transplanting.
Plant height, width and shoot and
root dry weights were recorded. Diur-
nal RZT and solar radiation intensity
fluctuations were recorded monthly in
four regions of four replicated contain-
ers of each container type using a
microdatalogger (Model 21X, Camp-
bell Scientific, Logan, Utah, USA).
In a second study, plants in black
rigid containers were either spaced at


.A



Root-zone temperatures in container-grown plants vary with the color, design and
spacing of the containers. Elevated temperatures can cause heat injury to plant
roots, reducing overall growth.


18 in. on center, pot-to-pot for the
entire experiment or spaced pot-to-pot
for 8 weeks then spaced to 18 in. on
center for the remaining 12 weeks of
the experiment. A row of border plants
were maintained at the same spacing
around the plants from which data
were collected.
Dracaena height and root and shoot
dry weights were significantly greater
in plants grown in the white container
compared to the black rigid container
(Table 1). The black poly bag inside the
rigid plastic container resulted in inter-
mediate height and root dry weight.
Measured parameters of 'Carrizo'
citrange and papaya were not
influenced by container type. Ixora
final height was reduced by the black
rigid plastic container compared to the
poly bad in the rigid container and
shoot and root dry weight was lowest
in plants in this treatment. The black
containers therefore reduced overall
plant growth in most species com-
pared to the other treatments. See-
dling growth variability in 'Carrizo'


citrus and papaya could have masked
their response to the container
treatments.
The Maximum media temperature
recorded was 45.5 C and temperatures
above 40 C were maintained for four
hours in the black rigid container
(Figure 1). The maximum temperature
was recorded on the western exposure
of the black rigid container and tem-
peratures in this treatment were gener-
ally 5 to 10 C higher than in the other
treatments (Figure 2). Data from this
experiment are consistent with growth
room and laboratory research on the
response of these plants to elevated
container temperatures.
'Grande naine' banana height was
greatest when plants were initially
spaced pot-to-pot and than spaced
after 10 weeks, with the continuous
pot-to-pot treatment resulting in
greater plant height than the 18 in.
spacing (Table 2). Shoot dry weights
did not reflect these differences in
plant height, but root dry weight was
greatest in plants spaced pot-to-pot. A
similar trend was noted in papaya with












50 -


304+


0-0 East
A-A West -A --
0-o North
0-0 South 0-








St. Croib, May 23, 1986


15 11 I l I 1
6 7 8 9 10 11 12 13 14 15 16 17 18

Time (hrs)
Figure 1. Mean diurnal temperature of media in black
plastic containers.


ou
Western Exposure
A4 -A Black Container
45 -- White Container
0--0 Poly Bag in Container/
. 40 4

, 35 -

30-

S 25

20 St. Croix, May 23, 1986

15I I I I I I
6 7 8 9 10 11 12 13 14 15 16 17 18

Time (hrs)
Figure 2. Mean diurnal temperature in western quadrant.


2.000 -


1.500-


1.000-


0.500-


( -0
O \







0-0-0
S
St. Croix, May 23, 19


0-O0



86 0

86 0


0.000- 1 1 i
6 7 8 9 10 11 12 13 14 15

Time (hrs)
Figure 3. Diurnal solar radiation.


n-- West
0-0 North
A-A East
o-0 South


16 17 18


Pot-to-Pot spacing


25-

20
20 St. Croix, October 30, 1986

15 I I I I
6 7 8 9 10 11 12 13 14 15 16 17 18

Time (hrs)
Figure 5. Mean diurnal temperature of media in black
plastic spaced pot-to-pot.


0-0 West
45- o-o North 18 inch O.C. spacing
A-- East
S 40 0--0 South

S 35-

I4 30 /

4 25-

20- St. Croix, October 30, 1986

15 1i I i I 1 I
6 7 8 9 10 11 12 13 14 15 16 17 18

Time (hrs)
Figure 4. Mean diurnal temperature of media in black
plastic spaced at 18 inches.




2.000


0-0
1.500- -

o/ o
S1.000- -
.2 O


- 0.500-
-0 O
En St. Croix, October 30, 1986
O
0.000 1 I I I I I I
6 7 8 9 10 11 12 13 14 15 16 17 18

Time (hrs)
Figure 6. Diurnal solar radiation.


crt







TABLE 1. Effects of container type on growth of Ixora, Dracaena and citrus plants
produced in St. Croix, USVI.
Final Final Shoot Dry Root Dry
Container Height Weight Weight Weight
Treatment (cm) (cm) (g) (g)
Dracaena Marginata 'Tricolor'
BRPz 66.5bY 61.5a 25.7c 10.2b
WPRP 74.5a 55.2a 37.1a 15.2a
BPBP 70.2ab 65.2a 31.1b 12.6a
Ixora Chinensis 'Maui'
BRP 46.3b 49.3a 26.6b 8.6b
WPRP 53.2ab 43.0a 40.2a 11.2a
BPBP 59.4a 52.0a 42.7a 12.6a
Carrizo Citrange
BRP 130.7a 85.7a 60.8a 54.5a
WPRP 131.3a 65.0a 55.2a 36.8a
BPBP 122.0a 74.7a 60.8a 39.9a
Papaya
BRP 25.0a 31.0a 31.8a 26.1a
WPRP 26.6a 30.3a 36.4a 32.2a
BPBP 27.9a 32.8a 43.8a 32.5a
Y means within columns for each species followed by the same letter are not significantly
different at the 5% level.
z BRP = Black rigid plastic, WPRP = White painted rigid plastic, BPBP = Black poly bag
in black rigid plastic.

TABLE 2. Effect of spacing treatments on growth of container grown plants in St.
Croix, U.S. Virgin Islands.
Plant Plant Shoot Dry Root Dry
Spacing Height Weight Weight Weight
Treatment (cm) (cm) (g) (g)
'Grande Naine' Banana
18 In. O.c.z 65.2c 76.2b 20.4a 22.2b
P/P-18 In. O.C. 85.9a 85.6a 28.1a 16.5b
P/P 76.2b 84.9a 31.2a 30.8a
Papaya
18 In. O.C. 55.0b 74.2a 27.8a 9.0a
P/P-18 In. O.C. 85.5a 81.5a 31.5a 7.8a
P/P 62.5b 78.0a 32.2a 11.6a
Ixora Chinensis 'Maui'
18 In. O.C. 53.5b 56.5a 48.0a 34.6a
P/P-18 In. O.C. 65.0a 56.6a 47.9a 25.4a
P/P 68.1a 61.9a 50.5a 32.0a
Dracaena Marginata 'Tricolor'
18 In. O.C. 64.0a 62.4a 35.0a 22.8a
P/P-18 In. O.C. 66.6a 57.9a 32.0a 13.8b
P/P 65.1a 58.9a 33.8a 18.5ab
'Carrizo' Citrange
18 In. O.C. 57.5a 20.0a 11.6a 9.2a
P/P-18 In. O.C. 60.6a 18.8a 10.9a 7.5a
P/P 61.8a 16.9a 12.1a 8.1a
z O.C. = on center spacing, P/P 18 in. O.C. = pot-to-pot then shifted to 18 in. spacing,
P/P = pot-to-pot
Y means within columns for each species followed by the same letter are not significantly
different at the 5% level.


the tallest plants produced in contain-
ers spaced pot-to-pot, but dry weights
were not affected by treatments.
Dracaena shoot dry weight and plant
width and height were not influenced
by treatment, but plants grown on 18
inch centers had slightly more root dry
weight than plants grown pot-to-pot
then shifted to 18 inches. 'Carrizo'
citrange were not affected by treat-
ments. Ixora height was reduced in the
18 inch spacing but other measured
parameters were not influenced by
spacing treatments.
Although solar radiation in October
(Figure 1) did not differ much from
that recorded in May (Figure 3), tem-
peratures in October were generally
lower than those recorded during the
summer months. Maximum tempera-
tures were generally found on the
southern exposure in containers
spaced 18 in. on center (Figure 4), and
in October, did not exceed 40 C (Figure
4,5). Maximum temperatures were
generally 5 to 8 C higher in plants
spaced 18 in. on center (Figure 4) com-
pared to plants spaced pot-to-pot
(Figure 5). The same trends in
temperatures were noted in data col-
lected during other months of this
experiment (data not shown).
In summary, growth medium tem-
perature fluctuations in container
plants differ with time of the year in
St. Croix, U.S. Virgin Islands. The
western quadrant of the container
medium appear to attain higher tem-
peratures than the rest of the container
in summer while the southern section
heats up most later in the year. White
containers or containers within shield
containers decreased absorption of
solar radiation and reduced the maxi-
mum attainable temperature in growth
media. Cost factors might therefore-
determine which container method is
best for nurseries in the V.I. Incre-
mental spacing strategies particularly
pot-to-pot spacing decreased container
temperatures somewhat, but not
nearly to the extent that container
treatment did during summer months.















The traditional

black plastic

containers

reduced overall

plant growth

in most species.








Optimum growth and quality of
container plants in the USVI can be
achieved when cultural practices main-
tain media temperatures below 40 C.
The feasibility of importing and using
plant containers other than the tradi-
tional black plastic or black poly bags
should be seriously considered by
nursery plant growers in the USVI.

This research was supported in part by
the U.S. Department of Agriculture
under CSRS Special Grant No.
84-CRSR-2-2482, managed by the
Caribbean Basin Advisory Group
(CBAG).

Christopher Ramcharan, Research Assis-
tant Professor, is the leader of the Horticul-
ture Program.






Production Potential of Buffelgrass


Pastures in the V.I.
by Stephan Wildeus and Cyndi L. Wildeus


Buffelgrass, together with Pangola
grass, is the most widely used
introduced grass species for pasture
improvement in the Virgin Islands.
Buffelgrass can currently be found in a
number of pastures on St. Croix and is
used for both grazing and hay making.
Its desirable characteristics include
good drought tolerance, persistence
under grazing and the ability of
pasture establishment from seed.
Buffelgrass (Cenchrus ciliaris) has its
ancestry in Africa and was introduced
to the U.S. as early as 1917. Cultivars
most widely used today were derived
from "Common" buffelgrass, in-
troduced into the U.S. in 1946 from
northern Kenya. An official release of
this cultivar followed in 1949 as T-4464.
Initially, only different morphological
types with no variability were availa-
ble, but sexually reproducing plants
were found later that made the
hybridization and development of new
cultivars possible. Subsequent
research on buffelgrass indicated that
it responds well to fertilization and
irrigation. Studies measuring animal
production on buffelgrass pastures
showed good intake and animal
growth, but stocking rates need to be
adjusted to season and rainfall. In con-
trast, buffelgrass is ill-suited for heavy
clay soils and salinity and does not
withstand freezing temperatures.
Earlier studies on St. Croix by
Oakes, published in 1969, reported
that different cultivars of buffelgrass
varied greatly in their annual dry mat-
ter yield. In a more recent experiment
several new buffelgrass cultivars and a
buffelgrass x birdwood grass hybrid
were evaluated on St. Croix and their
production measured at three different
harvesting intervals. The seed for the
study was obtained from the Forage
Program of the Texas Agricultural
Experiment Station.
To establish the test plots, seeds were
germinated in flats in a greenhouse
and transferred to styrofoam cups to
allow a mature root system to estab-
lish. The seedlings were fertilized dur-


Buffelgrass (collar and infloresence
shown here) is originally from Africa.

ing root system development. Fol-
lowing root development, seedlings
were transplanted into a Fredensborg
clay loam soil. Plantings were done in
one row plots with a 40 inch spacing
between rows. Each row was 40 feet
long and contained 38 plants consist-
ing of three different cultivars. Each
cultivar by harvesting interval combi-
nation was replicated only twice due to
the limited amount of seed available.


?A


Table 1. Total dry matter yield (tons/acre) of 6 buffelgrass cultivars and one buffelgrass
x birdwood grass hybrid harvested at three intervals over 10-month period.
Harvest interval

Cultivar 4 weeks 8 weeks 12 weeks
Llano 2.30 4.84 6.05
Nueces 1.89 4.34 5.14
Common 1.41 3.27 4.63
209268 1.26 3.27 4.61
409232 1.54 2.68 4.21
409359 1.19 3.07 4.38
BxBW37a 1.16 2.33 3.24
abuffelgrass x birdwood hybrid


'V


Plots were initially irrigated and hand
weeded to ensure the establishment of
the seedlings, but received no fer-
tilization.
Following a 7-month establishment
period the plots were harvested with a
sickle bar mower at either 47 8- or
12-week intervals. The yield of each
plot was determined and samples (0.75
lbs) dried in a forced air oven at 1400F
for 48 hours to determine dry matter
percentage. All yield data were then
converted to total dry matter yield
(tons/acre) for analysis. Plots were har-
vested over a 10-month period.
Cultivar Llano consistently
produced the highest total dry matter
yield at all harvesting intervals (Table
1). Nueces was the second highest
producer with a reduction in yield of
10-18% over Llano. The more recently
developed cultivars #209268, #409232
and #409359 performed much like
Common buffelgrass, a cultivar that
has found wide spread application.
These latter cultivars produced only 60
and 70% of the yield of Llano and
Nueces, respectively, at the 4 and 8
week harvest intervals and 73 and 86%
at the 12 week harvest interval. There
was no interaction between cultivars
and the harvesting interval and culti-
vars had similar rankings at all three
harvesting intervals.
The buffelgrass x birdwood grass
hybrid produced the lowest amount of








0-0 4 wk harvest interval
A--A 8 wk harvest interval
--0 12 wk harvest interval


Cultivar Llano

consistently produced

the highest

dry matter yield.


J F M A M J J A S O N D
Figure 1. Accumulative dry matter yield of buffelgrass cultivars at three harvest-
ing intervals over a 10-month period.


total dry matter at all three harvest
intervals (Table 1). This hybrid was
developed with a compact bur for ease
of planting and to avoid problems
generally associated with the planting
of buffelgrass seed. However, total dry
matter production was only half that of
Llano at all harvesting intervals.
The accumulative dry matter yield
increased markedly with an increase in
the harvesting interval from 4 to 12
weeks (Figure 1). Extending the cutting
frequency from 4 to 8 weeks resulted
in a 122% increase and exending it to
12 weeks in a 200% increase in total
yield. The relative improvement in
yield due to the extended cutting fre-
quency varied between cultivars and
was highest for #209268 (160 and 266%)
and #409359 (158 and 269%).
The dry matter percentage of the
forage samples at individual harvests
was inversely related to the prevailing
rainfall at this time of the year (Table
2). During July, the driest month in the
year of the study, the dry matter per-
centage of the buffelgrass exceeded
50%. Dry matter percentage of the
buffelgrass samples was also higher
with an increase in the length of the
harvest interval. As a result, the buffel-
grass samples harvested every 12
weeks had generally the highest dry
matter percentage, reflecting the
increased maturity of these stands.
The results obtained in this study
confirm studies in Texas that ranked
Llano over Nueces and both of these


Table 2. Dry matter percentage of buffelgrass harvested at three intervals over a
10-month period
Harvest interval
Month Rainfall (in) 4 weeks 8 weeks 12 weeks
February 0.25 28.1
March 1.02 33.3 38.2
April 4.80 29.5
May 6.44 25.2 29.6
June 1.71 26.4
July 0.95 53.7 48.6 55.1
August 3.15 39.7
September 2.65 31.6 32.4
October 2.45 30.1 39.3
November 8.35 29.1 30.4
December 3.45 21.4 24.4 28.8
values are means of all cultivars


cultivars over Common buffelgrass.
The annual dry matter yield of unferti-
lized pastures at that location ranged
from 6.02 ton/acre for Common to 6.57
ton/acre for Llano. Although differ-
ences were evident in the performance
of the buffelgrass at the two locations,
the relative ranking in terms of dry
matter yield was similar regardless of
environment and management, sug-
gesting that Llano is the most promis-
ing cultivar for use under Virgin
Islands conditions.
The extension of the harvesting in-
terval to 12 weeks resulted in a sub-
stantial increase in dry matter yield,
but the longer interval was also asso-
ciated with a higher dry matter percen-


tage of the buffelgrass at harvest. This
increase in the maturity of the forage is
related to a decline in crude protein
content and thus a reduction in forage
quality. Therefore harvesting intervals
shorter than 12 weeks, possibly
around 8 weeks, seem more beneficial
when forage quality rather than total
dry matter production is the primary
production goal.

This research was supported by Virgin
Islands Hatch Project #044.


Stephan Wildeus is leader of the Animal
Science and Forages Program. Cyndi
Wildeus is a research analyst.






Environmental Monitoring in the Salt


River Submarine Canyon, St. Croix

by Mary Lou Coulston

As coastal development accelerates
throughout the Caribbean, scientists
and local government planners are
recognizing the need to establish base-
line data for coastal resources. Baseline
data will help assess changes occurring
in nearshore marine communities
(whether changes are the result of
natural processes or due to human
activities).
The importance of long-term
monitoring is well illustrated by a
study conducted at Kaneohe Bay in
Hawaii where dramatic differences in
community structure were recorded
before and after termination of sewage
discharges. These differences provided
evidence of the usefulness of long-
term monitoring to evaluate eutrophi-
cation and sedimentation, processes
which can adversely affect bottom
communities. In the same study indi-
cator species of organic pollution were
identified. Because of the value shown
by such long-term monitoring, many
such studies are now in progress. In
the Salt River study, changes in com-
munity structure are being docu-
mented along with water quality
measurements to provide clues to the
causes of change.
In April of 1989 a team of environ-
mental specialists established perma-
nent stations to monitor coral, a variety
of other marine organisms, and sea-
weed populations in the Salt River
Submarine Canyon. The Salt River
program began with a 10 day undersea
"saturation diving" mission in the
Aquarius Habitat, operated by the
National Oceanographic and Atmos-
pheric Administration (NOAA) under
the National Undersea Research
Center at Fairleigh Dickinson Univer-
sity (NURC/FDU). Participants
included staff from the University of
the Virgin Islands, the Virgin Islands
Department of Planning and Natural
Resources (DPNR) and the National
A diver uses a Stanley hydraulic impact-twist drill operated by a 15-hp. hydraulic Park Service (NPS).
supply from the surface to provide a hole for a permanent stake. The Aquarius habitat is located in 60
Photo by M. Herko feet of water in the center of the sub-






marine canyon. The underwater
accommodations allow divers to work
long hours in the water without com-
ing to the surface. This avoids decom-
pression. It is possible to work nine
hours below 50 feet (but above 95 feet)
within a 24 hour period; below 95 feet,
diver time is reduced as depth in-
creases. Divers can be inside or outside
the habitat at the 50 feet level in-
definitely. During the 10 days spent in
Aquarius, six divers spent a total of 268
hours working in the water at an aver-
age working depth of 88 feet. Only this
type of "saturation diving" allows the
necessary bottom time to set up
monitoring stations at the depths
studied. Surface diving was used to set
up a 30 foot site in June, 1989.
During the April, 1989 mission,
seven monitoring stations were estab-
lished. Each consisted of six 10 meter
transects (width of the transect is equal
to the width of transect line) running
parallel along depth contours at 60, 90
and 120 feet. At each station, seven
numbered, copperplated stakes were
secured with epoxy in holes drilled
into dead coral substrate at 10 meter
intervals along each transect. An addi-
tional station was established in June,
1989 at 30 feet with ten 10 meter tran-
sects utilizing eleven stakes. The loca-
tions of these transects are shown on a
submarine canyon map (Figure 1).
Three methods were used to evalu-
ate species composition and percent of
live coral cover. The first was a linear
transect method. Lines, marked off in
meters, were tied between each stake.
A chain with 1.3 centimeter links was
spread across the reef under each line.
The length of the moveable chain was
unspecified, but divers seemed to
prefer 1 to 1.5 meters. The type of bot-
tom under each link was identified
and recorded. This method provides a
three dimensional profile of the reef
rather than the two dimensional sur-
face view provided by photographs.
Calculations can be made of percent
live coral, abundance of coral, percent
cover of algae and other invertebrates,
as well as coral species diversity, spe-
cies evenness, species richness and the
spatial complexity of the reef.
The second method involved pho-
tographing permanently marked 0.50
square meter quadrants. A quadrapod


__ __ __ __ __ -
This permanent photo quadrant will be analyzed and compared to future photos
of the same quadrant using computer image processing.


with a fixed Nikonis camera with a 15
millimeter lens and two strobes was
placed on a premarked site. Two cor-
ners of the site were marked with 4
inch cut nails and numbered tags so
that the mount can be placed on the
exact same site each visit. This long-
term photographic monitoring pro-
gram will allow documentation of
growth, mortality, recruitment, and
competition of reef building corals.
The photographs will be computer
analyzed using automatic image
processing. The computerized tech-
nology for this process is being refined
by a number of researchers using simi-
lar techniques for reef monitoring.
Successive photographing may prove
useful in recording events such as coral
bleaching, algal overgrowth, disease,
and physical breakage. In this study a
total of 116 permanent photoquadrants
were established.
The third technique explored was
the use of 8 millimeter video camera to
record all areas along each transect.
Visually noted alterations on each tran-
sect can be used in evaluating major
changes in reef structure.


Photo by C. Kesling

Sediment damage is probably
responsible for the majority of coral
damage of local reefs. Sediments can
stress corals by reducing the light avail-
able for photosynthesis, thus decreas-
ing growth and reproductive activity.
Coral growth rates are also reduced be-
cause energy is utilized by corals in the
sediment removal process. This diverts
this energy from other natural reef
building processes. Sediment particles
also can cause corals to die by
smothering and scouring them. Sedi-
ment levels for the canyon were
recorded during the 10 day Aquarius
undersea mission by measuring tur-
bidity and total suspended solids.
Water samples were taken at the 60
foot sites and at the surface above
these same sites. Sampling and analy-
sis of canyon waters will be continued
on a regular basis.
Turbidity, the light scattering proper-
ties caused by particles in the water,
was measured using a Hach Model
2100A turbidimeter. Readings were
expressed in Nephelometer Turbidity
Units. Total suspended solids were
measured following an Environmental
Protection Agency procedure whereby

























LEi Aquarius Habitat
() East wall tank rack
West wall tank rack
0 Center canyon tank rack
A E Excursion lines radiating from the habitat
SCross canyon excursion line


Figure 1. Map of Salt River Submarine Canyon floor accessible from the Aquarius Habitat. Marked on the 30, 60, 90 and
120 foot contours are the eight stations showing the locations of the number stakes marking individual transects.






the samples were filtered through a
glass fiber filter and residue contained
on the filter was dried to a constant
weight at 103-105 degrees C.
Few studies actually quantify
amounts of sediment that are
detrimental to various species of
corals. However, data continually is
being gathered on sediment measure-
ments and its relationship to coral
cover. Researchers have found that 1-2
mg/liter of total suspended solids is
relatively normal, whereas reduced
coral cover is found where sustained
rates reach 3-5 mg/liter. However, short
term effects of 10-30 mg/liter following
storm-induced runoff with increased
current speeds have been shown to
cause little damage to corals. During
this study, mean total suspended
solids averaged 20.26+ 4.64 mg/liter
(range 8.76-31.34) and the mean for tur-
bidity averaged 0.26+ 0.12 NTU's
(range 0.11 0.83) with no significant
difference between surface water and
samples taken at 60 feet. The results
indicate that Salt River Submarine
Canyon does experience periods of
naturally high suspended solids with
low turbidity. However, inter-
relationships of total suspended solids,
turbidity, current and organism stress
in this study and from other studies
are too preliminary for speculation on
their meaning at this time.
A current meter was deployed in
center canyon in approximately 60 feet
of water. For the 10 day period the
mean current speed was 4.53 cm/s
(range 0 11.3) at a mean direction of
224.75 degrees. The meter also record-
ed a mean water temperature of 26.1
degrees C (range 25.5 26.7).
The results of this project, as well as
other long-term studies being con-
ducted in the territory, should allow
the formation of a biological monitor-
ing network to standardize data col-
lecting techniques. Biologists from the
National Park Service, West Indies
Laboratory, Virgin Islands Department
of Planning and Natural Resources,
Division of Environmental Protection
and Division of Fish and Wildlife Ser-
vice and private consultants are estab-
lishing permanent monitoring sites at
significant coastal areas throughout
the territory to document variability


Divers use a quadraped with camera and strobes to photograph the permanently
atse published half-meter quadrants.


and degradation of marine resources.
Only when these changes are
documented and evaluated with stan-
dardized techniques can possible
causative agents be identified and
management action effectively
initiated.
In summary, a long-term program
was established in Salt River subma-
rine canyon to monitor the bottom
community. Fifty-two 10 meter tran-
sects were established at 30, 60, 90 and
120 feet with 116 permanent photo-
quadrats. Baseline data was collected
for bottom cover using photographic
techniques and linear transects along
with water quality measurements.
Data collection will be repeated after
one year, or after significant ecological
or meteorological events, to allow for
the first evaluation of changes. Long
term management objectives include
the establishment of limits to man-
made sediment loading and the regu-
lation of activities that contribute to
threatening levels of sediment in
marine waters.


Photo by M. Herko

The author acknowledges the assis-
tance of her environmental monitoring
team: 0. Hewlett, C. Kesling, Z.
Hillis, M. Taylor, R. Simms and M.
Herko.

This research was supported in part
by the NOAAs Undersea Research
Center at Fairleigh Dickinson Univer-
sity Contract No. NA88AA-H-UR020
Subcontract No. 83-9 and managed by
the Caribbean Research Institute at the
University of the Virgin Islands.

Dr. Mary Lou Coulston, a research asso-
ciate professor is the coordinator of the
Environmental Research Center at the
Caribbean Research Institute.







Agricultural Experiment Station (AES) Personnel
Administration
Darshan S. Padda ................ ............................. Vice President for Research & Director
James Rakocy .................... ................. ................... Associate Director
Carrol Fleming .......... ............................ ........................ .......... Editor
Raquel Santiago ................................. ....................... Administrative Specialist II
Audrey Valmont ........................................................... Administrative Assistant III
Yvonne Horton ................................. ........................ Administrative Assistant II
Coreen Hughes. ............................................................ Administrative Assistant II
Hector Arroyo ....................................................... ......... Trade Worker II
Victor Vasquez ................................................................... Agricultural A ide III
Animal Science and Forages
Stephan Wildeus ................... ................................. .... Research Assistant Professor
Cyndi Wildeus .................. ................. ................... Research Analyst III
Joni Rae Fugle ................... ....................... ......... . Research Analyst II
Kim Traugott ..................... ................ ................... Research Analyst II
Angela Belardo ....................... ................... ........... Research Assistant II
Allan Schuster .................. .................. ................... Research Assistant II
Victor Callas, Jr. .................. ................. ................... Agricultural Aide II
Ramiro Gomez .................... ................. ................. Agricultural Aide II
Antonio Rodriguez ................................................................ Agricultural Aide II
Aquaculture
James Rakocy ................... .... ................... ........... Research Aquaculturist
John Hargreaves ................... ....................... .......... Research Specialist II
Donald Bailey ................... ................... ................ Research Analyst II
Erich Kuster .................... ................. ................... Research Analyst I
Ezekiel Clarke .................. ................ ................... Agricultural Aide II
Vegetable and Root Crops
Adriano Navarro .................... ................... .. ....... Research Assistant Professor
Stafford Crossman .................. ................... .......... Research Specialist III
Charles Collingwood ...................... ................... ........... Research Analyst II
Francis Diaz ................... ...... ................... ....... .Research Assistant I
Paulino Perez .............. ..................................................... A agricultural A ide III
N elson Benitez .................................................................... Agricultural Aide I
Reinardo Vasquez .................................................................. Agricultural Aide I
Horticulture and Forestry
Christopher Ramcharan ............... .................................. Research Assistant Professor
Feiko Ferwerda ................................................................... Research Specialist I
Elizabeth Glennon ................... ................... ....... .. Research Analyst II
O svaldo Lopez .............. ................................................... Agricultural Aide III
Jerem iah H assan ........................ ................... ........ Agricultural Aide II
Agustin Ruiz ....... .... ..................................................... Agricultural Aide II

Current Research Projects
A study and analysis of management systems for native grass- Performance of yam, cassava, and sweet potato in the U.S. Virgin
lands in the U.S. Virgin Islands. Islands.
Efficiency of hair sheep production in the Virgin Islands. Trickle irrigation in humid regions.
Epidemiology and control of parasitic gastroenteritis of sheep on Vegetable variety evaluation for adaptation and horticuotural
St. Croix. characters.
Evaluation of reproductive potential of tropical V.I. sheep. Water use in small farming systems in the tropics.
Increasing prolificacy in sheep and its impact on nutritional Use of saline water for irrigating vegetable crops.
needs. Evaluation of the effects of tissue culture on somatic variation
Strategic supplementation of sheep grazing native, tropical and propagation of breadfruit.
pastures. Improvement of fruit production in the Virgin Islands.
A commercial-scale recirculating system for vegetable hydro- Iron sources application evaluations and propagation analysis
ponics and intensive tilapia culture. on selected pineapple varieties.
Cage culture of tilapia in the Virgin Islands. No chemical control of disease of tropical food crops.
Evaluation of the culture potential of selected Caribbean marine Study of mango flowering to reduce erratic behavior.
finfish. Phenological and physiogical study of mahogany in the Virgin
Survey of biofouling control methods for V.I. mariculture. Islands.
Improving field production of herbs and spices. Biological control of nutsedge with fungal pathogens.

30







Recent AES Publications


Allison, M.J., W.M. Cook, A.C. Hammond, W.R. Getz and S. Wil-
deus. 1989. Test for dihydroxypuridine-degrading rumen bac-
teria from animals in the U.S., Haiti and the Virgin Islands.
Proceedings of the Third International Symposium on
Poisonous Plants, Logan, Utah. (in press).
Bailey, D.S., J.A. Hargreaves and J.E. Rakocy. 1989. Enterprise
budget analysis for three stocking densities of caged Florida
red tilapia. Proceedings of the Gulf and Caribbean Fisheries
Institute-42, Ocho Rios, Jamaica. (in press).
Collingwood, C.D., A.A. Navarro and S.M.A. Crossman. 1989.
Effect of black plastic mulch on cucumber yield, water use and
economic returns. Proceedings of the Caribbean Food Crop
Society-25, Guadeloupe, French West Indies. (in press).
Crossman, S.M.A. 1989. Status of sweet potato weevil problems in
the U.S. Virgin Islands. Proceedings of the International Con-
ference on Sweet Potato Pest Management, Miami, Florida. (in
press).
Hargreaves, J.A., J.E. Rakocy and A. Nair. 1988. An evaluation of
fixed and demand feeding regimes for cage culture of
Oreochromis aureus. Pages 335-339 in R.S.V. Pullin, T.
Bhukaswan, K. Tonguthai, J.L. Maclean, editors. The Second
International Symposium on Tilapia in Aquaculture. ICLARM
Conference Proceedings 15, 623 p. Department of Fisheries,
Bankgkok, Thailand, and International Center for Living
Aquatic Resources Management, Manila, Philippines.
Hargreaves, J.A. 1989. Cage culture research in the U.S. Virgin
Islands. Alternative Aquaculture Network 8(3)1-3.
Hargreaves, J.A. 1989. The Virgin Islands longline fishery. Virgin
Islands Agriculture and Food Fair Bulletin No.4:35-36.
Hargreaves, J.A., J.E. Rakocy and D.S. Bailey. 1989. Effects of
diffused aeration on growth, feed conversion, and production
of Florida red tilapia in cages. Journal of the World Aquacul-
ture Society 20(1):42A.
Hargreaves, J.A., J.E. Rakocy, D.S. Bailey and D.J. Miller. 1989 An
evaluation of three cage designs and two tilapias for maricul-
ture. Proceedings of the Gulf and Caribbean Fisheries
Institute-42, Ocho Rios, Jamaica. (in press).
McGinty, A.S. and J.E. Rakocy, 1989. Cage culture of tilapio.
Southern Regional Acquculture Center Publication No. 281.
Delta Branch Experiment Station, Stoneville, Mississippi.
Michaud, M.W., C.L. Wildeus and W.D. Pitman. 1989. Desmanthus
germplasm responses to clipping on St. Croix. Proceedings of
the American Society of Agronomy, Las Vegas, Nevada. (ab-
stract).
Munoz, A.E., S. Farinas, M.W. Michaud and W.D. Pitman, 1989.
Evaluation of Desmanthus germplasm in the Western Llanos
of Venezuela. Proceedings of the American Society of Agrono-
my, Las Vegas, Nevada. (abstract).
Navarro, A.A. and C.D. Collingwood. 1988. Response of tomatoes
to varying rates of urea applied via a trickle irrigation system.
Proceedings of the Caribbean Food Crops Society-24, Ocho
Rios, Jamaica. (in press).
Navarro, A.A. 1989. Water: a key to agricultural productivity. Vir-
gin Islands Agriculture and Food Fair Bulletin No. 4:17-18.
Navarro, A.A. and J. Newman. 1989. Two drip irrigation rates and
two emitter placements on tomato production. The Journal of
Agriculture of the University of Puerto Rico. 73(1):23-29.
Padda, D.S. 1988. Senepol research symposium: a team effort on
V.I. cattle. Virgin Islands Agriculture and Food Fair Bulletin
No. 3:1-2.
Padda, D.S. 1989. From programs to issues new directions in
agricultural research and extension. Virgin Islands Agriculture
and Food Fair Bulletin No. 4:1-4.
Rakocy, J.E. 1989. Aquaculture production systems. Proceedings of
the Virgin Islands Water Resources Conference, St. Thomas
and St. Croix, U.S. Virgin Islands. (in press).


Rakocy, J.E. 1989. Mariculture potential in the Caribbean. Virgin
Islands Agriculture and Food Fair Bulletin No. 4:37-38.
Rakocy, J.E. 1989. Tank culture of tilapia. Southern Regional Aqua-
culture Center Publication No. 282. Delta Branch Experiment
Station, Stoneville, Mississippi.
Rakocy, J.E. 1989. Vegetable hydroponics and fish culture: a
productive interface. World Aquaculture 20(3):42-47.
Rakocy, J.E. and A.S. McGinty. 1989. Pond culture of tilapia.
Southern Regional Aquaculture Center Publication No. 280.
Delta Branch Experiment Station, Stoneville, Mississippi.
Rakocy, J.E. J.A. Hargreaves and D.S. Bailey. 1989. Effects of hydro-
ponic vegetable production on water quality in a closed recir-
culating system. Journal of the World Aquacultue Society
20(1):64A.
Rakocy, J.E. A. Nair and D.S. Bailey. 1989. Performance of cage-
cultured Tilapia nilotica, T Aurea, and three varieties of red tila-
pia. Journal of the World Aquaculture Society 20(1):64A.
Ramcharan, C. 1988. A low-cost chemigator for the irrigation of
fruit crops. Proceedings of the Caribbean Food Crops
Society-24, Ocho Rios, Jamaica. (in press).
Ramcharan, C. 1988. Potential of using Christmas Snowflake (Eu-
phobia leucocephala. Lotsy) as a Christmas pot crop using
growth retardants. Proceeding of the Caribbean Food Crops
Society-24, Ocho Rios, Jamaica. (in press).
Ramcharan, C. 1989 Some nutritional facts about tropical fruits and
vegetables. Virgin Islands Agriculural and Food Fair Bulletin
No. 4:53-54.
Traugott, K.T. 1989. Puberty in livestock. Virgin Islands Agricultural
and Food Fair Bulletin No. 4:31-32.
Wildeus, C.L. M.W. Michaud and S. Wildeus. 1989. Yield of buffel-
grass (Cenchrus ciliaris) cultivars at three cutting frequencies in
the Virgin Islands. Proceedings of the Caribbean Food Crops
Society-25, Guadeloupe, French West Indies. (in press).
Wildeus, S., J.R. Fugle and K.T. Traugott. 1988. Effects of breed, age
and season on bull reproductive function under tropical con-
ditions. Journal of Animal Science, Supplement 1, 66:83.
Wildeus, S., K.T. Traugott and J.R. fugle. 1988. Age of puberty in
ewe and ram lambs of the St. Croix breed under native, trop-
ical conditions. Journal of Animal Science, Supplement 1,
66:448.
Wildeus, S., K.T. Traugott, C. Wildeus and L.R. McDowell. 1988.
Growth and lambing performance of hair sheep grazing
native pastures during the dry season on St. Croix. Proceed-
ing of the Caribbean Food Crops Society-24, Ocho Rios, Jamai-
ca. (in press).
Wildeus, S., 1989. Barbados Blackbelly sheep in the Caribbean.
Pages 37-42 in K. Erskine, editor. Proceedings of the World
Congress on Colored Sheep, Eugene, Oregon.
Wildeus, S. 1989. Rapporteur's report: animal and livestock sys-
tems. Pages 161-162 in D.L. Ingram, editor. Proceedings of the
Workshop on Alternative Agricultural Enterprises for the
Caribbean and Pacific Basins, Ocho Rios, Jamaica.
Wildeus, S., J.R. Fugle and K.T. Traugott, 1989. Age, body weight
and scrotal circumference at puberty in Senepol bulls at two
locations on St. Croix. Journal of Animal Science, Supplement
1, 67:439.
Wildeus, S., K.T. Traugott and J.R. Fugle. 1989. Effects of pre-
breeding supplementation on body weight and reproductive
characteristics in multiparous and nulliparous St. Croix ewes.
Proceedings of the Southern Section of the American Society
of Animal Science, Nashville, Tennessee. (abstract).
Wright, D.W., C.J. Brown, S. Wildeus, Z.B. Johnson, H.D. Hupp
and S.A. Lakos, 1989. Non-genetic sources of variation in
weaning weights of Senepol cattle. Proceedings of the
Southern Section of The American Society of Animal Science.













University of the Virgin Islands

Agricultural Experiment Station

RR2, Box 10,000 Kingshill
St. Croix, U.S. Virgin Islands 00850









































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