• TABLE OF CONTENTS
HIDE
 Front Cover
 Table of Contents
 Effluents from intensive tilapia...
 Promising bulb onion varieties...
 Sheep grazing pressure effects...
 Papaya ringspot virus, symptoms...
 Evaluation of trees for use as...
 An evaluation of two methods of...
 AES personnel and current research...
 Publications
 Back Cover














Group Title: UVI research
Title: UVI research. Volume 7.
ALL VOLUMES CITATION PDF VIEWER THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/CA01300008/00002
 Material Information
Title: UVI research. Volume 7.
Series Title: UVI research
Physical Description: Serial
Language: English
Publisher: Agricultural Experiment Station, University of the Virgin Islands
Publication Date: 1995
 Record Information
Bibliographic ID: CA01300008
Volume ID: VID00002
Source Institution: University of the Virgin Islands
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 31871075

Downloads

This item has the following downloads:

UVI research ( PDF )


Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Table of Contents
        Page 1
    Effluents from intensive tilapia tank culture as a nutrient source for pak choi production
        Page 2
        Page 3
        Page 4
        Page 5
    Promising bulb onion varieties for commercial production in the U.S. Virgin Islands
        Page 6
        Page 7
        Page 8
    Sheep grazing pressure effects on productivity of Guinea grass pasture
        Page 9
        Page 10
        Page 11
        Page 12
    Papaya ringspot virus, symptoms and control
        Page 13
        Page 14
        Page 15
    Evaluation of trees for use as hedgerows in alley cropping
        Page 16
        Page 17
        Page 18
    An evaluation of two methods of estrous synchronization in sheep
        Page 19
        Page 20
    AES personnel and current research projects
        Page 21
    Publications
        Page 22
        Page 23
        Page 24
    Back Cover
        Back Cover
Full Text


I F Ag


t f e V i Agr a En S o V m 7


a tir ll
Q:" 'I1


_ 1





*


T-


" %


rM "


.I


., C





























On our cover ..


1. A bountiful harvest of onions from a variety trial.
2. Antonio Rodriguez herds a flock of St. Croix White hair sheep in a rotational grazing study
on native pastures.
3. Joni Rae Collins feeds Barbados Blackbelly and St. Croix White hair rams which are used
in studies comparing these two breeds.
4. Jim O'Donnell measures the height of Leucaena leucocephala, a nitrogen-fixing shrub,
as part of a study in which vegetables are cultivated in alleys between hedgerow species.
5. Reinardo Vasquez, Nelson Benitez, Roger Southwell, Paulino Perez and Jacqueline
Kowalski (left to right) harvest a field of pak choi that were irrigated and fertilized in a study
to compare aquaculture effluent with conventional methods.
6. Kurt Shultz demonstrates the joys of fish farming to a group of Head Start children.








I~~ *V oo n Agriulur


2 Effuents From Intensive Tilapia Tank Culture as a Nutrient Source for Pak Choi Production
William Cole, Manuel Palada, Stafford Crossman, Kurt Shultz and Jacqueline Kowalski

6 Promising Bulb Onion Varieties for Commercial Production in the U.S. Virgin Islands
Manuel Palada, Stafford Crossman and Jacqueline Kowalski

9 Sheep Grazing Pressure Effects on Productivity of Guinea Grass Pasture
Martin Adjei, Terry Gentry and Robert Godfrey

13 Papaya Ringspot Virus, Symptoms and Control
Thomas Zimmerman and Jeanette Richards

16 Evaluation of Trees for Use as Hedgerows in Alley Cropping
Jim O'Donnell, Manuel Palada, Jacqueline Kowalski, Aberra Bulbulla and Stafford Crossman

19 An Evaluation of Two Methods of Estrus Synchronization in Sheep
Robert Godfrey, Joni Collins and Mark Gray

21 AES Personnel and Current Research Projects

22 Recent Publications



Orville Kean,
President, University of the Virgin Islands

Darshan S. Padda,
Vice President for Research and Land-Grant Affairs
and Experiment Station Director

James E. Rakocy,
Associate Director

Robin Sterns, Editor

UVI Research is published annually by the University of the Virgin Islands Agricultural Experiment Station, RR 2,
Box 10,000, Kingshill, St. Croix, USVI, 00850.
Contents of this publication constitute public property. The written material may be reprinted if no endorsement of a
commercial product is stated or implied. Please credit the authors, the University of the Virgin Islands Agricultural Experiment
Station and UVI Research.
To avoid overuse of technical terms, trade names of products are occasionally used. No endorsement of these products
or firms is intended, nor is criticism implied of those not mentioned.
The University of the Virgin Islands is committed to the policy that all persons shall have equal access to its programs,
facilities and employment without regard to race, religion, color, sex, national origin, age or veteran status.








Effluents From

Intensive Tilapia

Tank Culture

as a Nutrient

Source for Pak

Choi Production

William M. Cole,
Manuel C. Palada,
Stafford M.A. Crossman,
Kurt A. Shultz and
Jacqueline A. Kowalski


Shortage of freshwater resources limits both fish and
vegetable production in the Virgin Islands. Farmers rely
on irrigation in dry periods to maintain steady production.
Well water is the primary source of irrigation water,
although rainwater catchment is also used. Tanks or
plastic-lined ponds used for water storage may also be
used to culture fish, thus using the water for two crops.
High yields of fish per unit volume of water can be
obtained with intensive fish culture in tanks, which reduces
land and water requirements. An essential requirement of
these systems is the concentration of solid wastes (sludge)
by sedimentation or filtration before removal. Sludge,
which has a high concentration of organic matter, nitrogen
and phosphorus, is a good nutrient source for crop
production. A study was conducted at the University of
the Virgin Islands Agricultural Experiment Station to
compare rearing tank water and sludge from tilapia culture
with commercial fertilizer for the production of pak choi
(Brassica rapa L. Chinenses). The study also compared
tilapia production and water quality in outdoor tanks from
which solids were removed (SR) to those with no solids
removed (NSR).
All-male Florida red tilapia, originally derived from
a cross between Oreochromis urolepis hornorum and 0.
mossambicus, (initial weight = 16.5 g) were stocked at a
rate of 24 fish/m3 in six 31.2 m3 circular rearing tanks
and fed a 32% protein feed for 168 days. The initial feeding








Table 1. Fish production parameters for all-male Florida red tilapia... -..-
(initial weight = 16.5 g) cultured for 168 days in outdoor tanks with --
(SR) and without (NSR) solids removal. For each row, values .
followed by the same letter are not significantly different by t-test
analysis, (P>0.05). -


64Crop irrigation with nutrient-rich aquaculture effluents is an example of
sound resource management through the reuse of water and the recycling
of nutrients. ,


rate was 4% of biomass per day and
was gradually reduced to 0.8 or 1.4%
of biomass. All tanks were aerated
with a 1/20-hp vertical lift pump.
Each of three SR rearing tanks was
equipped with a 1.4-m3 cylindro-
conical, external clarifier (settling
tank) to facilitate settling of solids.
Water was drawn from the center
drain in the rearing tank to the clarifier
using an air-lift pump and then
returned by gravity at a rate of
approximately 22 L/min. Sludge from
each SR system was drained from the
clarifier twice daily, combined and
stored in a 2-m3 tank. Samples of
rearing tank water and sludge were
analyzed at 14-day intervals for total
ammonia-nitrogen (TAN), nitrite-
nitrogen (NO -N), nitrate-nitrogen
(NO3-N), total phosphorus (TP),
potassium (K), total suspended solids
(TSS) and chlorophyll a. Dissolved
oxygen (DO) in the rearing tanks was
measured weekly.
At the end of the experiment,
mean values for final weight, growth
rate, feed conversion ratio (FCR, total
feed administered : wet weight gain
of fish biomass), survival, yield and
final biomass were compared.
Treatment means for fish production
and water quality parameters were
compared by t-test analysis and were
considered significant at the 0.05 level
of probability.


Two sequential trials (experimen-
tal period = 42 and 37 days) were
conducted to evaluate the effect of
rearing tank water and sludge from
the tilapia tanks on the yield of field-
grown pak choi. Twenty-day-old seed-
lings were transplanted into 6.0 x 1.8
m plots. Each plot contained four
rows spaced 45 cm apart. Beginning
two weeks after transplanting, the
plants were drip irrigated or fertilized
with the following treatments:
1) Rearing tank water from which
sludge was removed (SR) and applied
using Hardie E-2 drip emitters.
2) Rearing tank water from which
no sludge removed (NSR) applied
using Hardie E-2 emitters.
3) Sludge applied via drip irrigation


using a 15-mm poly-ethylene (PE)
hose with 0.5 cm emitters spaced every
30 cm and applied once per week.
4) Sludge application similar to
treatment 3, but applied 2-3 times per
week.
5) Sludge applied once per week via
drip irrigation using 15-mm PE hose
with microtubing emitters spaced at
30 cm.
6) Liquid nitrogen fertilizer
(fertigation) applied through drip
irrigation using Hardie E-2 emitters.
The fertilizer was injected at a total
rate of 100 kg N/ha divided into eight
equal weekly applications. Granular
P and K were applied (50kg 1 ha each)
to plots one week after transplanting.
7) Granular fertilizer applied 10 cm


SR NSR
Final weight (g) 422.5a 363.8b
Growth rate (g/d) 2.4a 2.1b
Feed conversion ratio (FCR) 1.60a 1.61a
Survival (%) 88.3a 86.3a
Yield (g/m3/d) 51.2a 42.6b
Final biomass (kg/m3) 9.0a 7.6b


Culture Tank Clarifier (1.4 m3)
_-- ir Lift
1.1 m water vol. =31.3 m3
L I i -- Sludge

I 6.1 m -l


B ~I. ..:f:l~d








Table 2. Mean concentrations of water quality parameters analyzed at 14-day intervals over 168 days in which
Florida red tilapia were cultured in outdoor tanks with (SR) and without (NSR) solids removal. Within SR and NSR
rows, values followed by the same letter are not significantly different by t-test analysis, (P>0.05).
SR NSR Sludge

Dissolved oxygen (mg/L) 6.9a 6.5a
Total ammonia-nitrogen (mg/L) 0.32a 0.33a 0.78
Nitrite-nitrogen (mg/L) 1.96a 2.17a 4.70
Nitrate-nitrogen (mg/L) 71. la 46.4b 40.2
Total phosphorus (mg/L) 7.21b 15.24a 107.08
Potassium (mg/L) 52.3a 52.8a 52.8
Total suspended solids (mg/L) 227b 682a 11071
Chlorophyll a ( u/L) 655b 1029a 22197


from the base of the plants at a rate
of 100N-50P-50K kg/ha. The N was
equally applied in three splits at one,
three and five weeks after
transplanting. Plots were drip
irrigated using Hardie E-2 emitters.
To maintain similar levels of P
and K, all plots were fertilized with
50 kg P and 50 kg K per ha as basal
application. Tensiometers were
installed at a 15 cm depth in
representative plots to monitor soil
moisture tension which was
maintained at 20 kPa. All treatments
were replicated four times in a
randomized complete block design. At
the end of each trial, treatment means
for plant size and total yield were
compared and separated for
significant differences using Duncan's
Multiple Range Test.
Tilapia cultured in SR tanks had
a significantly higher final weight and
growth rate than fish cultured in the
NSR tanks (Table 1). Feed conversion
ratios and survival did not
significantly differ between the SR
and NSR treatments. Mean
concentrations of TAN, NO2-N and
DO were not significantly different
between the SR and NSR treatments,
but mean TSS was significantly lower
and mean NO,-N was significantly
higher in the SR treatment (Table 2).
Nitrate-nitrogen, the primary form of
inorganic nitrogen in the rearing
tanks, increased from approximately
10.5 mg/L to 161.9 mg/L and 94.3
mg/L in the SR and NSR treatments


respectively. Likewise, TP increased
from 0.1 mg/L in both treatments to
14.9 mg/L (SR) and 33.3 mg/L (NSR)
by the end of the experiment.
Potassium concentrations in the SR
and NSR tanks were similar
throughout the study and increased
over time (SR, 3.2-131.1 mg/L; NSR,
3.2-131.4 mg/L). By the end of the


Results from the
two pak choi trials
indicate that rearing
tank water and sludge
from tilapia tank
culture may be used to
obtain yields
comparable to
commercial fertilizer
application. ?

experiment, the TSS concentration in
the NSR tanks was 1250 mg/L
compared to 368 mg/L in the SR tanks.
The lowest concentrations of DO were
3.4 mg/L (SR) and 4.1 mg/L (NSR),
both observed on day 147. Mean
concentrations of TP, TSS and
chlorophyll a were approximately 15,
49 and 34 times higher in the sludge
than in the SR rearing tanks.
In the first trial, pak choi fertilized
weekly with sludge were significantly
larger than plants fertilized with


granular fertilizer or water from either
the SR or NSR rearing tanks (Table 3).
Similar results were observed in the
second trial. In both trials, yields ofpak
choi fertilized with rearing tank water
or sludge had total yields similar to or
higher than those fertilized with the
inorganic fertilizers.
Ammonia, the primary metabolic
waste product of most fish, is toxic to
fish at low concentrations and must be
removed from intensive fish culture
systems. Most recirculating aquaculture
systems rely on bacteria to convert
ammonia to nitrite, which is also toxic
to fish at low concentrations, and then
to nitrate, which is toxic only at high
concentrations. This process is called
nitrification and is usually accomplished
by recirculating the water through a
fixed-film biofilter. The biofilter is a
means of increasing surface area for
bacterial growth. Water quality results
from this study indicate that nitrification
occurred in the water column of both
SR and NSR systems as seen by the
increase ofNO3-N over time.
Relatively high concentrations ofTP,
TSS and chlorophyll a(algae) inthe sludge
compared with concentrations in the SR
fish rearing tanks indicate that the
clarifiers were effective in removing
these substances from the system. In
addition, the ability of the clarifier to
remove solids was demonstrated by
much higher concentration of TSS in
the NSR tanks compared to the SR
tanks. Fish production results show
that solids removal increases tilapia








Table 3. Mean size and yield of pak choi fertilized with waste water generated from tilapia tank culture and commercial
inorganic fertilizers. Within columns for each experiment, means followed by the same letter are not significantly
different using Duncan's Multiple Range Test, (P>0.05).


Size (g) Total Yield (t/ha)

Experiment 1
SR rearing tank water 288b 19.28b
NSR rearing tank water 300b 20.03b
sludge (0.5 cm once/wk) 393a 26.10a
sludge (0.5 cm 2-3x/wk) 353ab 23.38ab
sludge (adapter) 333ab 22.15ab
fertigation 320ab 21.23ab
band 300b 19.93b

Experiment 2
SR rearing tank water 614ab 41.03ab
NSR rearing tank water 653a 43.63a
sludge (0.5 cm once/wk) 791a 47.40a
sludge (0.5 cm 2-3x/wk) 662a 44.20a
sludge (adapter) 612ab 40.88ab
fertigation 674a 45.03a
band 527b 35.20b


production in outdoor tanks without
fixed-film biofiltration.
Results from the, two pak choi
trials indicate that rearing tank water
and sludge from tilapia tank culture
may be used to obtain yields
comparable to commercial fertilizer
application. In addition to providing
a nutrient source for crop production,
repeated application of aquaculture
effluents could improve soil fertility
by increasing organic matter.
As demand for fresh water
increases, particularly in arid and
semiarid regions, the development of
techniques for water conservation and
reuse are essential. Intensive
aquaculture systems conserve water by
increased yield per unit volume. As the
aquaculture industry grows and fish
farming practices intensify, the disposal
of effluents is becoming an
environmental concern. Crop irrigation
with nutrient-rich aquaculture effluents
is an example of sound resource
management through the reuse of water
and the recycling of nutrients.
This research was supported in
part by a special grant in tropical and
subtropical agricultural research,
CBAG Grant No. 92-34135-7289.


. :A*


4- -.
SrIts
"X,

--" -.- ,'~
i~+ Q-~'t.


. : L .. .


4As demand for
fresh water
increases,
particularly in arid
and semiarid
regions, the
development of
techniques for
water
conservation and
reuse are
essential.









Promising Bulb

Onion Varieties

for Commercial

Production in the

U.S. Virgin

Islands


Manuel C. Palada,
Stafford M.A. Crossman
and Jacqueline A. Kowalski


Onion (Allium cepa L.), one of the major vegetable
crops in the world, ranks fifth in terms of production area
and volume. In the U.S., onion ranks fourth in terms of
area of production and value. Although the U.S. is one of
the leading countries producing onions, imports have been
steadily increasing since 1970. This is because the per
capital consumption and demand for onions have been
increasing for the past two decades. Onion is also one of
the top ten vegetable imports of the U.S. Virgin Islands.
In 1993, a total of 3.8 million pounds of onion worth $3.3
million was shipped from the U.S. mainland to the Virgin
Islands. This value represents the second highest after
potatoes. In addition, the Virgin Islands also imported onions
from other regions outside the U.S. totalling $1.3 million.
Although the Virgin Islands is not self-sufficient in
vegetable production including onions, vegetable imports
can be reduced by encouraging local production. The
climate and soils of the Virgin Islands are suitable for
growing onions on a commercial scale provided growers
use improved production technology such as
microirrigation. However, successful onion production
depends on the type of cultivars being grown. Growing
onions for bulbs is mainly determined by the response of
cultivars to daylength and temperature. These factors in
turn determine the type of onion cultivars.
Daylength or photoperiod is an important factor which
influences production of bulb onions. The critical
daylength varies from 11-16 hours. Onion cultivars are
classified according to the approximate photoperiod
necessary to induce bulb formation. Based on bulbing


response to photoperiod, onion cultivars are grouped into:
short day (>12-13 hr); intermediate (>13.5-14 hr); long
day (>14.5-15 hr); and very long day (>16 hr). Bulb
formation occurs when the photoperiod is longer than the
minimum daylength characteristic for the cultivar.
Temperature also influences bulbing and interacts with
daylength. Onions require high temperatures to trigger
their reaction to the effect of long daylength on bulb
formation. Tropical onion cultivars can grow at
temperatures between 22-300C (72-860F). High
temperatures seem to shorten the time necessary for the
bulbing response, but very high temperatures can retard
bulbing. In contrast, cool temperatures and adequate soil
moisture favor early growth and establishment of onions.
This is essential in providing maximum vegetative growth
desired before bulb formation is initiated. Bulb size and
total yield are determined by plant size at the start of bulb
formation; hence, the bigger the plant the more likely that
good and excellent bulb yields will be produced. As the
plant matures and bulbs attain full size, hot and dry
conditions are preferred for ripening and harvesting.
Most onion cultivars are very sensitive to daylength
and temperature; therefore, their range of adaptation is
very limited. Consequently, cultivars should be developed
for a particular region, and, generally, shortday cultivars
are preferred for the tropics. Introduction of new cultivars
should be preceded by local checks to ensure that their
optimal growing temperature and photoperiod
requirements are compatible with local climatic conditions.
It is essential that cultivars be carefully tested under local








Table 1. Bulb diameter and height of onion cultivars in St. Croix, U.S. Virgin Islands, 1994-95.

Cultivar Bulb Diameter (mm) Bulb Height (mm)

1994 1995 Mean 1994 1995 Mean
Contessa 73.4a 80.1b 76.8 71.4ab 67.7c 69.6
Granex 33 69.6a 96.1ab 82.9 60.4b 70.8c 65.6
Granex 429 77.4a 88.9ab 83.2 64.8ab 72.2bc 68.5
Texas Grano 502 74.7a 89.3ab 82.0 76.0a 83.2b 79.6
Texas Grano 1015 74.3a 100.8a 87.6 74.8ab 95.2a 85.0
Texas Grano 1025 75.9a 87.2ab 81.6 72.6ab 76.6bc 74.6
Year Mean 74.2 90.4 82.3 70.0 77.6
For each column, means followed by similar letters are not significantly different (P>0.05) by Duncan's Multiple Range Test.


conditions to evaluate their
horticultural adaptation.
Short day onion cultivars are best
suited for the Caribbean region, and
seed companies are making progress
in breeding them. There are cultivars
adapted to tropical areas which
develop bulbs during increasing
daylight conditions of 11-13 hours, or
that are almost completely day-
neutral. Cultivars recommended for
the tropics include 'Granex' and
'Texas Grano'. The objective of this
study was to evaluate onion cultivars
suitable for commercial production in
the Virgin Islands.
Seeds of six onion cultivars
('Contessa,' 'Granex 33,' 'Granex
429,' 'Texas Grano 502,' 'Texas
Grano 1015' and 'Texas Grano
1025') were sown in speedling trays
(Speedling Mfg., FL) containing Pro
Mix BX (Premier Brands, PA) in
October 1993 and 1994. Seedlings
were transplanted into the field at 47
days after sowing for both trials. The
field trials were replicated four times
in a randomized complete block
design. Plots consisted of three rows
3.6 m (11.8 ft) long, with a spacing
of 0.3 m (11.8 in) both between plants
and rows. A drip irrigation system
was installed consisting of 1.27 cm
(0.5 in) poly-hose (Hardie Irrigation,
CA) as the submains and 15 mil
Hardie New Tape with laser drilled
orifices 0.3 m (11.8 in) apart as the
laterals. Soil moisture levels were
maintained at field capacity until the
crop approached maturity. Fertilizer
was band-applied at rates of 150 kg


N, 100 kg P and 200 kg K per ha (134
lb N, 89 lb P and 179 lb K per acre),
using ammonium sulfate, triple
superphosphate and sulfate of potash,
respectively. All plots were hand-
weeded as required and no pesticides
were applied, even though sporadic
infestations by defoliators were
observed during the growing season.

4 The climate and
soils of the Virgin
Islands are suitable
for growing onions on
a commercial scale,
provided growers use
approved cultivars
and improved produc-
tion technology.

Onions were harvested when plant
leaves began to fall over (or necks
were broken). Two harvests were
performed in both trials because some
cultivars matured earlier than others.
Data collected were diameter, height
and weight of onion bulbs. All data
were analyzed using the GLM
procedures of SAS (SAS Institute,
Cary, NC).
The mean maximum daytime
temperatures during the 1994 growing
season ranged from 28.80C (83.90F)
in February to 30.10C (86.1F) in
April. Temperatures during the 1995
growing season ranged from 28.9C
(84.10F) in March to 31.30C (88.30F)
in May. During the 1994 trial, Granex


onion cultivars produced bulbs with
the largest ('Granex 429,' 77.4 mm)
and the smallest ('Granex 33,' 69.6
mm) diameters (Table 1). Bulb height
varied from 60.4 to 76.0 mm with
Texas Grano cultivars producing
bulbs which were higher than other
cultivars (Table 1). 'Texas Grano
1015' produced a yield (32.3 t/ha)
which was significantly higher than
'Texas Grano 502' (25.1 t/ha) and
'Granex 33' (18.7 t/ha) as shown in
Table 2. 'Granex 33' was the earliest
maturing cultivar, harvested at 81
days after transplanting. However,
this cultivar produced the lowest yield
and the smallest bulbs.
During the second year of study
(1995), 'Texas Grano 1015' (Table 1)
produced bulbs with a significantly
larger diameter (100.8 mm) than
'Contessa' (80.1 mm). 'Texas Grano
1015' also produced bulbs with a
height of 95.2 mm, and was
significantly higher than the other
cultivars (Table 1). Even though
'Granex 33' was harvested earlier
(127 days after transplanting) than the
'Texas Grano' cultivars, the bulb
diameter (96.1 mm) and yield (49.2
t/ha) of 'Granex 33' ranked second
among all cultivars.
All cultivars produced yields of
over 39 t/ha in 1995, with mean yields
ranging from 39.3 t/ha for 'Granex
429' to 53.2 t/ha for 'Texas Grano
1015' (Table 2). 'Texas Grano 1015'
produced the greatest yield of bulb
onions in both years with mean yield
of 44.3 t/ha (Table 2). Yields were
generally higher during the 1995








Table 2. Yield of onion cultivars grown in St. Croix,
U.S. Virgin Islands, 1994-95.

Cultivar Yield (t/ha) Mean Yield
(t/ha)
1994 1995
Contessa 27.6ab 39.4a 33.5
Granex 33 18.7c 49.2a 33.9
Granex 429 30.1ab 39.3a 34.7
Texas Grano 502 25.1b 43.8a 34.5
Texas Grano 1015 32.3a 53.2a 44.3
Texas Grano 1025 26.6ab 41.5a 34.1
Year Mean 26.7 44.4
For each column, means followed by similar letters are not significantly
different (P>0.05) by Duncan's Multiple Range Test.


Table 3. Days from planting to harvest of onion cultivars
grown in St. Croix, U.S. Virgin Islands.

Cultivar Cropping Season
1994 1995
Contessa 100 127
Granex 33 81 127
Granex 429 110 127
Texas Grano 502 110 154
Texas Grano 1015 110 154
Texas Grano 1025 110 154
Mean 104 141


4 The early maturity characteristic of 'Granex 33' can have a significant
economic benefit for commercial growers, since it will be available early
and can have a premium price until the other cultivars are ready for market.


season compared to 1994. Average
yield was 26.7 t/ha in 1994 compared
to 44.4 t/ha in 1995. The difference
in yield between years can be
attributed to the length of the cropping
season (Table 3). The average number
of days from transplanting to harvest
in 1994 was shorter (104 days) than
in 1995 (141 days). Higher rainfall
in 1995 from January to March (165
mm) compared to 127 mm for the
same period in 1994 may have
extended the growing season and
maturity of the crop in 1995.
Harvesting was therefore delayed
during 1995, since it took longer time
for onions to dry in the field because of
relatively high moisture.
Onions are sensitive to small
environmental changes which can
affect a cultivar's performance not
only from location to location, but
also within the same location from


year to year. Yields obtained from
these trials are comparable to yields
from other Caribbean countries.
Bulb appearance and characteris-
tics of some onion cultivars are
shown in Figure 1. 'Contessa' is a
white-skinned cultivar, and, as such,
can be marketed as a specialty on-
ion. 'Granex 33' produced very good
yields in 1995, compared to low yields
in 1994. The performance of this
cultivar in 1995 merits further evalu-
ation regarding its potential as a rec-
ommended cultivar. It is the earliest
maturing of all the cultivars tested,
harvested one month earlier than
Texas Grano cultivars in both years.
The early maturity characteristic of
'Granex 33' can have a significant
economic benefit for commercial
growers, since it will be available
early and can obtain a premium price
until the other cultivars are ready for


market. Other advantages in growing
the early maturing cultivar are less
labor, especially for weeding, required
to produce the crop and less water use
for irrigation. Furthermore, early har-
vest will leave the land available for the
grower to produce another crop.
These evaluation studies have
clearly demonstrated the potential for
commercial onion production in the
Virgin Islands. Growers will have the
option of producing early or late
maturing cultivars depending on their
overall production and economic
goals. Both Granex and Texas Grano
cultivars are ideal and suitable for
growing, and adopting these cultivars
will help growers realize their goals
for successful onion production.
This research was supported in
part by the U.S. Department of
Agriculture under Hatch Grant No.
0158036.


i. R \ r \. u1


II .\ l


S l -AV \ 3.B I IR\,, -







Figure 1. From left, bulb appearance and characteristics of onion cultivars 'Contessa, 'Granex 33, 'Texas Grano 1015,' and
'Texas Grano 1025 'from the 1994 cropping season.


I ;! \ >-









Sheep

Grazing

Pressure

Effects on

Productivity

of Guinea

Grass

Pasture


Martin B. Adjei,
Terry J. Gentry
and Robert W.
Godfrey

The ruminant livestock industry
in the Virgin Islands and the
Caribbean at large is supported
primarily by grazing native pastures.
These pastures are dominated by
guinea grass (Panicum maximum)
and the browse legume leucaena
(Leucaena leucocephala) in
productive sites. Native pastures also
usually contain some herbaceous
legumes such as desmanthus
(Desmanthus virgatus) and teramnus
(Teramnus labialis), and can, if
properly managed, satisfy much of the
nutritional requirement of ruminant
livestock. However, guinea grass is
not drought tolerant and its inability
to produce forage in a cyclic dry
season is perhaps its chief limitation.
Pasture overgrazing, especially during
the dry season, has resulted in
widespread range deterioration in the


K 4
I, ,.. ..
*..., q


j't I 1,/,
4A i~ :I-.i-


:-r~f *^\^ '^ ^^,,i~u; ":\
-' 'az ^ru ^ .

Optimum post-graze guinea grass stubble


Virgin Islands to less productive
associations of hurricane grass
(Bothriochloapertusa) and the spiny
woody legume casha (Acacia spp.).
Under conditions of extreme
overgrazing, a number of broadleaf
weeds such as maran (Croton
astroites), side (Sida carpiniifolia),
man-batter-man (Achyranthes
indica), thistleroot (Argemone
mexicana), physic nut (Jatropha
curcas), hollow stalk (Leonotis
nepetoefolia), castor bean (Ricinus
communis), stinging nettle (Tragia
volubilis) and even bare ground
become dominant.
This experiment was conducted to
determine the carrying capacity of
native, predominantly guinea grass,
pasture for sustainable sheep
production in the Caribbean based on
an evaluation of (1) dynamics of
pasture botanical composition and (2)
animal performance.
The experiment was conducted at
the sheep research facility of the
University of the Virgin Islands
Agricultural Experiment Station.
Each of four levels of herbage
allowance (HA) [4, 7, 10 and 13 kg
DM 100-kg-' body weight (BW)] were


height should be approximately 0.3 m.


assigned to three 0.2-ha fields of
renovated native pasture in a
randomized complete block design.
Each pasture replicate was subdivided
into three 0.07-ha paddocks that were
grazed in rotation of 14 days of
grazing, followed by 28 days of rest
to give a grazing cycle of 42 days.
Two tester weaned lambs
(approximately 16 kg initial BW) and
additional grazer animals, to meet
prescribed HA, were allowed to graze
a pasture 24 h d-', beginning in
February, 1992. All sheep were
weighed at 14-day intervals in order
to make adjustments in grazers to
meet prescribed HA. Animals were
given free access to shade,
mineralized salt and water. Testers
were replaced when their BW reached
approximately 30 kg and grazing was
continued rotationally through 1993
and 1994. There were nine grazing
cycles in each season (378 d). Weight
changes of testers were used to
calculate average daily gain (ADG)
for each 42-day grazing cycle and also
for the entire season. Stocking rate (kg
BW ha-' d-') was calculated using
both tester and grazer animals. Gain
ha-' was calculated as the product of









Figure 1. Annual stocking rate
associated with grazing native
pasture at different levels of herbage
allowance.
850
8 '92-93 season
800- M '93-94 season
S750- -
700-
0)
1650
2600
1 550
S500i
4 7 10 13
Herbage allowance, kg DM 100-kg-' BW d-1


ADG, stocking rate adjusted for the
average tester BW and the number of
grazing days.
Herbage mass (HM), an
instantaneous measure of total weight
of herbage per unit area of ground at
the start (pre-graze) and end (post-
graze) of each grazing in a paddock
was estimated by clipping forage in
six 0.5 m2 randomly selected plots to
7.5 cm stubble height. Subsamples
were dried at 60 oC to constant weight
for dry HM ha-'. Pre-graze and post-
graze herbage canopy heights were
measured for guinea grass and
leucaena from six random spots in
each paddock. Dried pre-graze
herbage was composite across
paddocks within a pasture for each
42-day grazing cycle, ground and
analyzed for crude protein (CP) and
in vitro organic matter digestion
(IVOMD), but these data are not
presented here.
Frequency of plant species
(guinea grass, hurricane grass,
leucaena, desmanthus, teramnus,
casha and broadleafweed) occurrence
was measured at the beginning of the
trial and then annually (June-July),
using a modified line transect and
point method. The point consisted of
a 0.325 m square quadrat. Lines were
laid at 5.0 m intervals across the width
of a paddock and quadrat was
dropped every 1.0 m along the line,
making 1.0 x 5.0 m2 grids on each
paddock. Plants with canopy falling


Figure 2. Pre- (a) and post- (b) graze guineagrass; and pre- (c) and post- (d)
graze leucaena canopy heights as affected by levels of herbage allowance.
1.0 *'92-93season 1.0
0.9- (a) *'93-94 season 0.9- (b)
0.8- 0.8-
0.7- 0.7-
z 0.6- 0.6-
S0.5- 0.5-
0.4 0.4-
O 0.3- 0.3-
0.2- 0.2-
0.1 0.1
0.0 -I 0.0


4 7 10 13 4
Herbage allowance, kg DM 100-kg-' BWd-1


-- I -- IU.U I ---
10 13 4
Herbage allowance, kg DM 100-kg-1 BWd-


1.U
).9- (c)
3.8-
0.7-
0.6-
0.5-
0.4-
0.3-
0.2- /


4 7


within the quadrat were recorded as
present. Bare ground was also
recorded when it covered more than
50% of the quadrat.
Carrying capacity (stocking rate
at optimum herbage allowance) of the
native pasture was determined by
regressing HA separately on ADG
and botanical data using the REG
procedure of SAS.
The two-year mean seasonal
stocking rate associated with
prescribed levels of herbage
allowance ranged from 540 to 775 kg
BW ha-' d-' (Figure 1). Given that an
average mature St. Croix White sheep
weighs approximately 35 kg, these
values corresponded with 15 to 22
mature sheep ha-' for the highest and
lowest HA, respectively. This
represented a linear (P<0.0001)
decline in SR with increasing HA.


7 10 13


7 10 13


Both the pre- and post-graze
guinea grass canopy heights were
positively related to HA. Pre-graze
guinea grass canopy height increased
in a curvilinear pattern (P<0.001)
from 0.35 m to 0.65 m as HA was
increased (Figure 2a). Post-graze
grass canopy height increased from
0.2 m to 0.45 m with increasing HA
(Figure 2b). In both cases, the
greatest increase in canopy height
occurred between the 4 and 7% HA,
followed by marginal increments as
HA was increased further.
Changes in leucaena canopy
height were characterized by
significant linear (P<0.0001),
quadratic (P<0.01) and cubic
(P<0.03) effects of HA (Figure 2c and
2d). Analysis conducted using
orthogonal contrasts showed no
statistical difference in pre- or post-


(d)








+/x /



























4Although short-term hi
is obtainable with high st
results from this experim
evidence of rapid guinea
deterioration to undesiral
under that type of manag


graze canopy height between the 7 and
10% HA for any season.
Pre- and post-graze herbage mass
provided the best overall relationship to
HA across all grazing cycles (seasonal
R2 =0.61, P<0.0001). Pre-graze
herbage mass increased linearly from
1.0 to 2.5 Mg ha' as HA was increased
from 4 to 13% (Figure 3a). Post-graze
herbage mass increased curvilinearly
from 0.7 to 2.0 Mg ha-' with no
statistical difference between values for
the 7 and 10% HA (Figure 3b).


Figure 3. Forage dry matter on-offer
affected by herbage allowance.
3.5
(a) *'92-93 season
( 3.0- '93-94 season
S2.5
o 2.0-
g 1.5-
1.0-
0.5-
S0.0- i
4 7 10 13


oc
gr
95
pr
du
He
gr
fol
at
at
co
pr


at


0)
0
0
4)


0
a.


Herbage allowance, kg


-- ',," '-'' decreased by 20-30% after two-year
grazing, regardless of HA (Figure 4b).
.' A Visual observation indicated selective
leucaena grazing by sheep and greater
"'"''" grass competition at the higher HA
4 treatments which probably
, ,j contributed to the lack of response of
leucaena frequency to HA. Of the
.. i ', other important pasture legumes, the
." frequency of teramnus, which initially
<"- was 12%, decreased to 2.5-7% in an
inverse linear relationship to HA after
two-year grazing (data not shown).
Desmanthus also showed increased
^ frequency of occurrence under heavier
-'<~ grazing pressure. Its initial frequency
prior to 1992 grazing was 26%.
igh animal production Desmanthus frequency at the end of
two-year grazing was 23, 31, 29 and
rocking rates, the 39% for the 13, 10, 7 and 4% HA
ent provide direct treatments, respectively.
irass pasture Among the pasture weeds, the
original frequency of hurricane grass
3le plant species occurrence was 3%. At the end of
ement. two-year grazing, the incidence of
hurricane grass on pasture had
increased to 15-24% (Figure 5a).
Guinea grass frequency of However, the effect of HA on
currency prior to initiation of hurricane grass population dynamics
azing in 1992 was approximately was not clear-cut. This was partly due
%. This frequency remained to the confounding effect from a large
actically unchanged under all HA shade tree (Swietenia mahagoni) in
ring the first year of grazing, one replicate of the 10% HA
)wever, the frequency of guinea treatment. Sheep congregated in
ass occurrence decreased to 75% shaded areas and also in areas
allowing two-year rotational grazing adjacent to alleyways which created
the 4% HA compared with 85-95% pockets of overgrazed sites even at the
the remaining HA (Figure 4a). By higher (7-13%) HA treatments.
ntrast, the proportion of leucaena Therefore, whereas the sixfold
esent in the original pasture increase in hurricane grass incidence
at the liberal HA was restricted to
overgrazed microenvironments, the
pre- (a) and post- (b) grazing as increase at the 4% HA was widespread
3.5 throughout the entire pasture.
3.0 (b) Casha (Acacia spp.) frequency of
occurrence, which initially stood at
2.5- 1%, increased independently of HA
2.0- to 1.5-3% after two-year grazing
1.5. (data not shown). However, HA had
1.o0 a negative linear effect on other
broadleaf weed (BLW) incidence
0.5- following two-year grazing. The
0.0 7 1 1 initial 1992 pregrazing frequency of
DM 100-kg-' BWd-' BLW occurrence was 17%. That









Figure 4. The frequency of occurance of guineagrass (a) and leucaena (b) relative to their initial 1992 pregrazing
occurances (95% and 45%, respectively) as affected by levels of herbage allowance.


1.4 (a) End '92-93 season
0 End '93-94 season
1.3- 8
1.2-
1.1- 0
1.0 0 95% |
0.9-
C"
0.8-
0.7- cc
0.6-
n. .


I.U -
0.9-
0.8- -
0.7-
0.6
n (; --- --- --- --- ---


4 7 10 13
Herbage allowance, kg DM 100-kg-' BWd-'


7 10 13


Figure 5. The occurance of hurricane grass (a) and broadleaf weeds (b) relative to their initial
occurances (3% and 17%, respectively) as affected by levels of herbage allowance.
12- 12
11- (a) End'92-93 season 11- (b)
8 10- U End '93-94 season 10-
( 9- 9-
8- 8-



S4- 4-
_U 3- 3-
a 2- 2-
1- 3% 1
0- 1
4 7 10 13 4 7 10
Herbage allowance, kg DM 100-kg-1 BW d-'


45%


1992 pregrazing


value remained constant under 13%
HA treatment but increased linearly
to approximately 100% as HA was
reduced to 4% (Fig 5b).
Sheep average daily gain ranged
between 0.071 and 0.076 kg and the
effect of HA was not significant.
However, as a result of major
differences in animal stocking rates,
sheep seasonal (378 d) liveweight
gain increased from 660 kg ha-' with
13% HA to 845 kg ha-' with 4% HA
treatment.
Although short-term high animal
production is obtainable with high
stocking rates, the results from this
experiment provide direct evidence
of rapid guinea grass pasture
deterioration to undesirable plant


species under that type of
management. Minor differences in
botanical parameters between the 7
and 10% HA treatments seem to
indicate the locus of an optimum
range. For a rotational grazing
management system, this optimum
will correspond with varying the
stocking rate between 575 and 690
kg BW ha-' d-' depending on the
rainfall situation. The concentration
of hurricane grass weed on
repeatedly grazed pockets even at
liberal HA suggests a lower carrying
capacity for a continuously grazed
system. Further experiments are
being conducted to compare pasture
performance under a faster rotation
with a continuous grazing system.


This research was supported in
part by the U.S. Department of
Agriculture under Hatch Grant No.
0159522.


Figure 6. Annual sheep liveweight
gain per hectare as affected by
herbage allowance.
900
90 '92-93 season
850- '93-94 season
800-

750-

0700-
650-
600
4 7 10 13
Herbage allowance, kg DM 100-kg-1 BW d-








Papaya Ringspot


Virus, Symptoms


and Control


Thomas W. Zimmerman and
Jeanette A. Richards


Papaya (Carica papaya) production throughout the
world has been devastated by the papaya ringspot virus
(PRV). This viral disease costs the papaya industry
millions of dollars each year and can be a limiting factor
to growing papaya in areas of Hawaii, Guam, Florida,
the Caribbean, Africa, Australia and the Far East.
The Daily Gleaner newspaper from Jamaica last year
reported that the Agriculture Ministry had ordered the
destruction of 81 ha of papaya, valued at $600,000, that
were suspected to have PRV. Each year in southeastern
Mexico, 90% of the papaya in plantations die from PRV.
Papayas are now grown only as an annual crop, and
production cannot meet local demand. The Virgin Islands
was an exporter of papayas until the early 1980's.
Papaya production in the Virgin Islands is presently
sporadic with few fruits being sold at local markets or
roadside stands. However, the demand for papaya is high,
both at the local markets and at the hotels and restaurants
that cater to tourists.
Infection and Symptoms
Papaya ringspot virus is a member of the potyvirus
group and multiple strains of PRV exist from varying
tropical regions around the world. Papaya ringspot virus
is closely related to PRV-W, which is also known as
watermelon mosaic virus 1. The host range for PRV
includes papayas, cucurbits such as pumpkin, squash,
cucumbers and melons and relatives of beets in the
Chenopodiaceae family. The virus is principally
transmitted by aphids but can also be transmitted through
wounds from contaminated tools or equipment. The virus
spreads rapidly once it occurs in an orchard.
Symptoms of the virus include: water-soaked streaks
or lesions on the stems and leaf petioles (Figure 1);
ringspots on the fruit (Figure 2); mottled and distorted
leaves (Figure 3); premature ripening and reduced flavor;
reduced plant vigor, low fruit set and smaller fruits; and,
finally, death of the plant.
Any plant stress caused by drought or the cooler
temperatures experienced from December through
February will amplify the development of the viral


Figure 1. Papaya stem and petioles with watersoaked streaks
or lesions that are visible symptoms of PRV.


symptoms. Once introduced, PRV has never been
successfully eradicated from a production region.
Control of PR V
Presently, 100% control of PRV is not possible.
However, certain factors can delay the outbreak of the
virus in a papaya orchard. First, locate the papaya field
in an isolated area away from other established or
diseased papayas. Planting a windbreak around the
orchard can act as a natural barrier in isolating the orchard
from the insect vector.
Do not grow other PRV host plants such as squash,
melons, cucumbers or beets near the papaya. Inspect the
orchard weekly for signs of the disease and remove
infected plants. Fruit set on plants prior to infection with
PRV will not develop the istotion or ringspot symptoms
on the fruit.
Pest Control
Routine pest control will inhibit the aphid vector and
delay the viral disease outbreak. Maintain a regular spray
program for disease-carrying insects and pests. Apply
adequate fertilizer for maximum growth and production









in a short period of time. Growing
strong healthy plants that have not
been subjected to stress can delay
disease symptoms in a papaya
planting.
Varietal Selection
Natural resistance to PRV has not
been found in Carica papaya after
screening large collections of papaya
lines and cultivars. Presently, there
are no commercial papaya varieties
that are resistant to PRV. However,
some varieties, such as 'Cariflora,'
have been developed with increased
tolerance to PRV.
Papaya varieties that were
screened at the Agricultural
Experiment Station of the University
of the Virgin Islands on St. Croix
have indicated varying levels of
tolerance to PRV (Table 1). The most
tolerant varieties, after nine months
in the field, include '356-3,' 'PR6-
65' x 'Cariflora' and 'Cariflora.' An
advantage found in planting
'Cariflora' is that flowering may
occur within three months after
planting while 'Sunrise' and
'Kapoho' took five and six months,
respectively. The variety 'Kapoho'
became infected with PRV prior to
flowering. The solo 'Sunrise' related
varieties are very susceptible to PRV
(Table 1) with limited production
potential for PRV infested areas.
Growers should plant the most
tolerant papaya varieties available
and avoid the most susceptible
varieties. The use of ground covers
in the papaya field can influence the
spread of PRV. The papaya ringspot
virus spread more quickly through a
papaya field when mowed grass was
used as a ground cover, as compared
to a chipped wood mulch or tilled soil
(Table 2). The grass may harbor the
aphids that spread this viral disease.
The wood chip mulch provided the
greatest deterrent to the spread of PRV
and also preserved the soil moisture.
Control of PRV through Cross
Protection
Cross protection is a system in
which plants infected with one strain


Table 1. Progression of PRV infection through a field of twelve papaya
varieties over time.

PRV Infection
Total 5 mo 7 mo 9 mo
Papaya Varieties Plants Plants % Plants % Plants %
Cariflora 65 1 2 17 26 28 43
SS x CFL F2 41 7 17 16 39 27 66
Washington 39 0 0 7 18 19 49
PR 6-65 35 1 3 6 17 15 43
PR 6-65 x CFL F2 32 0 0 6 19 11 34
Solo 64 25 2 8 7 28 18 72
Barbados Dwarf 23 0 0 10 44 15 65
Kapoho 23 2 9 16 70 20 87
Tainung-2 20 2 10 6 30 10 50
Yeun Nong-1 20 2 10 7 35 11 55
356-3 20 2 10 2 10 2 10
Exotica 18 0 0 9 50 17 94
Sunrise 13 0 0 5 39 13 100
Total 374 19 5.1 114 30.5 206 55.1


Figure 2. Developing papaya fruit with ringspots that are associated with PRV.


of a virus are protected from the
severe effects of a second related
strain of the same virus. Under warm
conditions, above 25 C, papayas
inoculated with the mutant PRV
strains grow well and do not show
conspicuous symptoms. The fruit of
some plants had a few ringspots that
became less apparent at maturity and
did not affect the quality of the fruit.
However, when temperatures drop
below 20 oC, or during rainy and
cloudy conditions, chlorotic spots
appear on the leaves and small


ringspots appear on fruit. As the
temperatures rise above 25 C, new
developing leaves and fruit have less
apparent viral symptoms. The mild
symptoms may be repressed by
applying more fertilizer to the trees.
Cross protection can only delay
expression of severe symptoms;
superinfection by persistent PRV
strains can still occur. If cross
protection breaks down before
flowering, no economic benefit is
gained. Cross protection, when tested
in Puerto Rico, was not effective in








Table 2. The influence of ground cover in a papaya field and the spread of PRV infection over time.

Total 5 mo 7 mo 9 mo
Treatment Plants PRV % PRV % PRV %
Grass 118 18 15.3 52 44.1 78 68.1
Mulch 120 6 5 28 23.3 61 50.8
Tilled 136 11 8.1 34 25 67 49.3



... UVI-AES, in cooperation with the
University of Puerto Rico and
'' Cornell University, is working to
bioengineer resistance to a local
PRV strain into papaya cultivars
grown in Puerto Rico and the
Virgin Islands.


Figure 3. Mottled and distorted papaya leaves: signs of PRV.


reducing or controlling the Caribbean strain of PRV.
Genetically Engineered Viral Resistance
Genetic engineering or transformation involves the
transfer of genetic information for a specific trait or
characteristic from one type of organism to another in a
way that permits stable incorporation and expression of
the foreign genes in the recipient organism. Researchers
have demonstrated that the transfer of a gene for the viral
coat protein (CP) into virus-susceptible plants can cause
resistance to the viral disease. The presence of the
Hawaiian PRV-CP gene in transgenic papaya plants has


provided resistance to the Hawaiian strain of PRV.
However, these transgenic papaya plants are susceptible
to strains of the PRV found in other regions of the world,
including the Caribbean.
Through a 1994 Caribbean Basin Administrative
Group grant, UVI-AES, in cooperation with Dr. Bryan
Brunner from the University of Puerto Rico and Dr.
Dennis Gonsalves from Cornell University, is working
to bioengineer resistance to a local PRV strain into papaya
cultivars grown in Puerto Rico and the Virgin Islands.
Zygotic embryos, developing seeds from green fruit
90-114 days after flowering, are placed into a plant tissue
culture system. A special tissue culture medium
formulation has been successful for somatic
embryogenesis on 16 papaya cultivars. Somatic
embryogenesis is the regeneration of embryos or seed-
like structures from unorganized cell clusters. Depending
on the papaya cultivar, somatic embryos form within 4
to 8 weeks. After 8 weeks, somatic embryos are matured
and germinated as a normal seed.
The first phase of the study has been completed with
the successful tissue culture regeneration of 16 papaya
varieties. The second phase of inserting the PRV
resistance gene into papaya has begun. The final goal of
having locally-grown papaya cultivars that are
immunized against the Virgin Islands strain of PRV, by
bioengineering transgenic papayas with the coat protein
gene from PRV, is now on the horizon. The future for
papaya production looks bright with the development of
disease resistance in the local papaya varieties.

This research was supported in part by a special grant
in tropical and subtropical agricultural research, CBAG
Grant No. 94-34135-0280.








Evaluation


of Trees


for Use as


Hedgerows

in Alley


Cropping


J. J. O'Donnell,
Manuel C. Palada,
Jacqueline A.
Kowalski, Aberra
Bulbulla and
Stafford M.A.
Crossman

Alley cropping is an agroforestry
system in which trees and crops are
combined in a systematic manner in
order to maintain a stable, sustainable
environment for crop production.
There are two main components in an
alley cropping system: the hedgerow
formed by trees or shrubs, and the
alleys between the hedgerows. The
main crop is planted in the alleys. The
hedgerows, being deep-rooted, can
take up nutrients from the subsoil and
cycle them back to the soil surface
through their prunings for use by the
main crop.
In most alley cropping systems in
the tropics, the hedgerows are
continuously pruned and the prunings
incorporated into the soil or applied
as mulch to the soil surface. The
prunings increase the organic matter
content of the soil and provide
nutrients to the crop, while decreasing


A e.'


competition between the hedgerow
and crop.
Alley cropping may be an
alternative to traditional vegetable
farming practices in the U.S. Virgin
Islands for a number of reasons. The
application of prunings to the soil
could reduce the use of expensive
fertilizers. The incorporation of the
leaf material in the soil would build
up the soil organic matter, thus
increasing soil fertility and water-
holding capacity. Use of pruning as a
mulch would reduce evaporation of
soil water and decrease the soil
temperature resulting in more efficient
water use. And hedgerows could serve
as windbreaks to protect the crops
from the damaging effects of the wind.
On the other hand, hedgerows may
compete with the crop for light, water,
nutrients and land, possibly reducing
crop yields.
As part of a long-term study of
vegetable alley cropping systems for
the USVI, the University of the Virgin
Islands Agricultural Experiment
Station has been evaluating the
performance of four hedgerow
species. The species being evaluated
are gliricidia (Gliricidia septum),
leucaena (Leucaena leucocephala),
moringa (Moringa oleifera) and
pigeon pea (Cajanus cajan). Some of
the criteria used to evaluate hedgerow
trees for alley cropping are ease of


establishment, rate of growth,
biomass production and the ability to
withstand heavy pruning.
The four species were seeded in
polyethylene bags (approximate
volume 2.25 L) and grown for 19
weeks prior to planting in the field
plots. Hedgerows were planted in
December, 1992, using a randomized
plot design with three replicates. Each
plot consisted of three hedgerows 12
meters in length with 5 meters
between hedgerows. Trees were
planted 30 cm apart within
hedgerows. The plants were drip-
irrigated for four weeks to ensure
good establishment.
During the establishment phase
hedgerows were measured for height
growth every four weeks with initial
measurements made at 8 weeks after
planting. At the end of the establishment
period measurements of total plant
height and diameter at 50 cm above
ground were taken. The initial cutting
of the hedgerows was at 40 weeks
after outplanting. All four species
were cut at 50 cm above ground.
Prunings (except for pigeon pea) were
separated into leaves and stem, and
fresh weight for both components
taken. Subsamples were taken from
both components, weighed and then
dried at 800C until a constant weight
was obtained. The dried samples were
ground and analyzed for nitrogen (N),


*I .,








Figure 1. Hedgerow height growth
establishment phase.
3.5 1 I


3.0-

2.5-

E 2.0-

.2'1.5-
0J
I


8 12 16 20 24 28 32 36 40
Weeks after Planting
Leucaena HT=0.19+0.03x+0.001x2 R
Moringa HT=0.45+0.13x-0.001x2 R2=
A Gliricidia HT=0.01+0.02x+0.001x2 R2
V Pigeon Pea HT=0.23+0.14x-0.002x2


phosphorus (P) and potassium (K). After the
hedgerows were pruned periodically in p
planting the alleys or, as needed, to lessen ti
with the vegetable crop. At each pruning
were cut to 50 cm height and weight dai
described previously. Moringa, gliricidia
were pruned seven times, and pigeon pea
were collected from the middle hedgerow.
Pigeon pea had the fastest rate of gro\
first two measuring periods. Pigeon pea gro,
to slow and in the later measurements


Figure 2. Annual biomass production
hedgerow species. Bars for each year
letter are not significantly different. (Dun
Range Test, P=0.05).


6

' 5
r-
4
-

3
a
S-


1993 1994
Year


1995


h during the moringa had the fastest rate of growth (Figure 1). Overall,
leucaena had the greatest height growth (341 cm), followed
by moringa and pigeon pea (287 cm). Moringa had the
largest stem diameter (3.8 cm) at the end of the
establishment period. Mean plant survival for all species
was 97%.
In the initial cutting of the four hedgerow species,
leaf biomass ranged from 3.7 t ha-' for pigeon pea to 0.6
t ha' for moringa. Leucaena produced the largest amount
of total (leaf+ stem) biomass (8.5 t ha-'). Leucaena also
produced the greatest stem biomass (5.4 t ha ').
Leucaena and gliricidia consistently produced the
greatest amount of leaf biomass annually from pruning
(Figure 2) Leucaena responded well to pruning, although
its yield was suppressed somewhat due to defoliation by
the leucaena psyllid (Heteropsylla cubana). Gliricidia was
slower to establish and required a longer recovery time in
2.7 the early prunings. In the later prunings gliricidia produced
0.61
=0.71 as much leaf biomass as leucaena or moringa. Moringa
R2=0.71 produced the largest amount of total biomass from the
prunings (23 t ha-'). Moringa also produced the greatest
stem biomass from the prunings, 15 t ha-' compared to a
initial cutting, mean of 5.25 t ha-' for gliricidia and leucaena. It also
reparation for responded well to pruning and in the second and third
he competition years produced as much leaf biomass as leucaena and
the hedgerows gliricidia. Pigeon pea did not respond well to pruning,
ta recorded as produced the smallest quantity of total biomass (1.5 t ha')
and leucaena and died out after its second pruning.
twice. All data Total leafbiomass production from all cuttings (initial
cutting + prunings) over the three-year time period ranged
Nth during the from 13.6 t ha-' for leucaena to 5.2 t ha-' for pigeon pea
wth then began (Figure 3). Leucaena and moringa produced the largest
leucaena and total biomass (Figure 4). Moringa also produced the
greatest amount of stem biomass (17.3 t ha-'). There were
no differences in the foliar-N concentration of leucaena,
by the four gliricidiaand moringa(mean=37.5 gN kg-'). Pigeonpea
ith te same foliar-N concentration (26.3 g N kg-') was lower than the
can's Multiple r
Other species. Leaf concentrations of K and P varied
between species. Concentrations of K in the leaf biomass
were highest in gliricidia (20.5 g K kg-') and lowest in
pigeon pea (9.9 g K kg-'). Moringa had the highest
concentrations of foliar-P (2.3 g P kg-'). Calculated from
leaf nutrient concentrations and biomass production, the
incorporation of prunings or their application to the soil
as mulch resulted in the equivalent nutrient yield of 558,
I 26 and 236 kg NPK ha-' for leucaena, 389, 20 and 220 kg
Pigeon Pea NPK ha-' for gliricidia; 301,16 and 158 kg NPK ha-' for
L a moringa; and 138, 10 and 52 kg NPK ha-' for pigeon pea,
over the 36-month study period.
a Although the hedgerow species are still being
Gliricidia
evaluated, it appears that the two species to be
Moringa recommended for use in alley cropping systems on St.
Croix are leucaena and gliricidia. Leucaena can establish
a hedgerow quickly, produces large quantities ofhigh-N









Figure 3. Leaf biomass production from hedgerow
species for all cuttings over the three-year time period.
Bars with the same letter are not significantly different.
(Duncan's Multiple Range Test, P=0.05).
16

14-
,12 a

6


2 -b
.2' 8






0
Leucaena Gliricidia Moringa Pigeon Pea
Hedgerow Species


Figure 4. Total hedgerow biomass (leaf + stem)
production for all cuttings over the three-year time period.
Bars with the same letter are not significantly different.
(Duncan's Multiple Range Test, P=0.05).
n .


25-

r20-





S5-


Leucaena Gliricidia Moringa Pigeon Pea
Hedgerow Species


leaf biomass and withstands frequent
prunings. The variety used in this trial
(St. Croix Native) proved susceptible
to attack by the leucaena psyllid,
which reduced yields. This variety
also has a tendency to flower and
produce seed early, although by
weeding and soil cultivation we were
able to keep it from spreading.
Gliricidia required a longer time to
establish, but proved a good biomass
producer once established. It is
tolerant of frequent prunings, is high
in N and its low spreading form
lessens competition for light with the
vegetable crop. Moringa's foliar-N
concentrations were equal to both
gliricidia and leucaena, which is
surprising since moringa does not fix
N as do gliricidia and leucaena. This
may indicate that moringa is an
efficient scavenger of soil nutrients.
The greater stem production for
moringa resulted in a much higher
stem-to-leaf ratio for this species (1.9)
as compared to gliricidia (0.48) and
leucaena (0.56). Moringa's rapid
growth and upright form caused
excessive shading of the vegetable
crop. Pigeon pea initially grew the
fastest, produced a hedgerow rapidly
and in the first cutting had the greatest
leaf biomass. But, its inability to


withstand pruning makes it a poor
choice for use as a hedgerow.
Although these four species were
evaluated for use as hedgerows in
alley cropping, the biomass data are



Although the
hedgerow species
are still being
evaluated, it appears
that the two species
to be recommended
for use in alley
cropping systems
on St. Croix are
leucaena and
gliricidia. ??


indicative oftheir production potential
for other uses. It is possible that under
a more intensive pruning regime
biomass production would be greater.
Both leucaena and gliricidia could be
used for cut and carry forage
production and as a high protein
supplement for livestock. These two


species could be planted on marginal
land for use as a biomass bank for
mulch and green manure for crop
production. Leucaena stems can be
used for tomato and yam stakes,
firewood and charcoal production.
Gliricidia also produces stakes which
can be used for cuttings and posts for
live fences. The rapid growth and
upright form of pigeon pea and
moringa would make them excellent
for windbreaks along the margins of
farm plots and fields. Pigeon pea
hedgerows may be beneficial in cases
where a quick windbreak is needed to
protect a crop. It also produces a
secondary crop (peas and pods) which
can be harvested during hedgerow
establishment and while the main crop
is maturing. Moringa stems root
readily if planted directly in the
ground and it makes an excellent live
fence. Depending on the desired use
and end product, all four of these
species have potential as hedgerows.

This research was supported in
part by a special grant in tropical and
subtropical agricultural research,
CBAG Grant No. 92-34135-7299,
and the U.S. Department of
Agriculture under Mclntire-Stennis
Grant No. 0162363.









An Evaluation of Two


Methods of Estrous


Synchronization in


Sheep


Robert W. Godfrey, Joni R. Collins
and Mark L. Gray


Estrous synchronization of sheep
can be accomplished using several
methods. Prostaglandin F2ca (PGF)
has been used successfully to
synchronize estrus in sheep when
given as two injections 10 days apart.
Another method of synchronizing
estrus involves the administration of
progesterone by injection, as a feed
additive or intravaginal sponges. The
length of time the progesterone needs
to be administered makes the injection
method less desirable: ewes need to
be injected daily for up to 10 days.
Progesterone can be fed to
animals for a period of time, and after
the treatment is stopped the ewes will


exhibit estrus. One drawback to this
method is that it is difficult to control
the amount of progesterone each
animal consumes unless the animals
are fed individually, which is not
practical on most farms. The
development of alternative methods of
administering progesterone such as
vaginal sponges has made the procedure
less labor intensive.
Recently a new device for
administering progesterone for
estrous synchronization has been
developed. The controlled internal
drug release (CIDR) device is a nylon
core surrounded by silicone that has
been impregnated with progesterone.


The CIDR is placed in the vagina of
the ewe for 12 days, and after it is
removed the ewe will come into estrus.
Presently C1DRs are only available
for research purposes in the U.S., but
it is hoped they will be commercially
available in the near future.
The objectives of this study were
(1) to evaluate the efficacy of CIDR
devices to synchronize estrus in hair
sheep and the fertility of the
synchronized estrus, and (2) to
compare CIDRs and PGF for
synchronizing estrus in hair sheep.
Two trials were conducted using
St. Croix White, Barbados Blackbelly
hair and Florida Native wool ewes.
In Trial 1 all three breeds were used.
One group of ewes (n = 27) were
treated with CIDRs for 12 days, and
29 ewes were not treated (CON-
TROL). The CIDRs were removed on
the same day that intact rams of the
same breeds, equipped with marking
harnesses, were placed with the ewes.
Ewes were monitored three times a
day for estrus (day 0). On day 6,
laparoscopies were performed on one
half of the ewes in each treatment
group to count the number of ovula-
tion sites on the ovaries.
In Trial 2, 14 St. Croix White
ewes were treated with CIDRs the
same as in Trial 1 and 14 St. Croix
White ewes were given 2 i.m.
injections of 15 mg PGF 10 days
apart. Intact rams, equipped with
marking harnesses, were placed with
the ewes on the day of CIDR removal
or the second PGF injection. Estrus
detection was conducted in the same
manner as in Trial 1.
Ram breeds used in Trial 2 were
St. Croix White, Florida Native and
Suffolk. The wool breed rams were
being used to produce crossbred
lambs for another study. In both Trial
1 and Trial 2 ajugular blood sample
was taken from each ewe on day 10
and assayed for progesterone
concentration to monitor the function
of the corpus luteum formed after the
synchronized estrus.
Time to estrus after ram introduc-








Table 1. Interval to estrus, ovulation rate, conception rate, number of lambs
born and progesterone on day 10 of ewes after estrous synchronization
with either CIDR or PGF. Within rows, means followed by the same letter
are not significantly different using Student-Newman-Kuels multiple range
test or chi-square, (P<0.05).

Trial 1 Trial 2
CONTROL CIDR CIDR PGF
Time to estrus (days) 6.3 .7a 1.7 .8b 1.4 .4b 2.9 4c
Ovulation rate 1.61 .2a 1.4 + .2a --
Conception rate (%) 76a 72a 100a 86a
Lambs born 1.4 .2a 1.2 .2a 2.2 + 2b 1.9 2b
Progesterone (ng/ml) 8.4 .7a 6.8 .6a 10.8 .8a 10.4 .8a


From left, CIDR-G device, prostaglan-
din F2 a and progesterone sponge.


tion in Trial 1 was four days shorter
in CIDR treated than CONTROL
ewes (Table 1). Within three days of
ram introduction 100% of CIDR ewes
but only 37.9% of CONTROL ewes
had been in estrus. Conception rate
at the first estrus after ram introduc-
tion was 74.1% overall, and was not
different between treatments, but days
to conception after ram introduction
was shorter in CIDR-treated than
CONTROL ewes (3.6 + 1.3 vs 12.2
1.3 days, respectively).
Neither ovulation rate, determined
by laparoscopy, nor number of lambs
born, were different between CIDR
and CONTROL ewes (Table 1). The
CIDR ewes lambed earlier in the
lambing season than CONTROL
ewes (9.5 1.3 vs 15.1 1.3 day of
lambing, respectively).


In Trial 2, the CIDR ewes
exhibited estrus 1.5 days earlier than
PGF-treated ewes (Table 1). The time
to estrus after ram introduction was
similar between CIDR-treated ewes
in both Trials 1 and 2. Synchrony
response was higher in CIDR than in
PGF ewes (100% vs 71.4 % in estrus
within three days of ram introduction,
respectively). The conception rate at
the synchronized estrus was not
different between CIDR and PGF
ewes. Progesterone concentration on
day 10 after synchronized estrus was
not different among CONTROL,
CIDR and PGF-treated ewes.
These results show that estrus
synchronization can be used
successfully in hair sheep breeds in the
tropics. The shorter time to estrus and
the higher synchrony response of the
CIDR-treated ewes, when compared
to the PGF group, indicates that the
CIDR devices may be a more
efficacious method to use. The higher
level of synchrony would be critical
if the sheep were being bred by
artificial insemination or used in an
embryo transfer program.
There was no detrimental effect
of either CIDRs or PGF on fertility at
the synchronized estrus as shown by
the conception rates in Table 1. In
fact, all of the CIDR ewes in Trial 2
became pregnant at the synchronized


estrus. Even though there was no
treatment effect on the number of
lambs born, the ewes in Trial 2 had more
lambs/ewe than the ewes in Trial 1. This
may have been due in part to the fact
that the ewes in Trial 2 were on a
slightly higher plane of nutrition prior
to breeding than the ewes in Trial 1.
The progesterone levels on day 10
indicate that none of the treatments
had a detrimental influence on ovarian
function after estrus.
Even though sheep on St. Croix
can breed year round, it is still
advisable to manage the animals in a
way that imposes designated breeding
and lambing seasons. By doing this,
the breeding and lambing seasons can
be scheduled to take advantage of
seasonal variations in forage
availability or the demand for lambs.
Through estrous synchronization,
the ewes will be bred within a short
period of time (2-3 days), and the
subsequent lambing will also take
place over a short time period. This will
allow producers to plan for labor input
and feed resources and provide a more
uniform lamb crop for sale to the
consumer. Another benefit of estrous
synchronization is that it will allow
producers to utilize other advanced
breeding techniques, such as artificial
insemination or embryo transfer.
By using these procedures, sheep
producers in the U.S. Virgin Islands
will have the opportunity to access
genetic material from sheep breeds not
found locally without having the
expenses associated with importing
live animals. Subsequent studies are
being conducted by the Animal Science
Program at UVI to use these results to
develop procedures for artificial
insemination of sheep in the tropics.
This research was supported in
part by U.S. Department of Agriculture
Regional Grant No. NC-111.


"By using these procedures, sheep producers in the U.S. Virgin Islands will
have the opportunity to access genetic material from sheep breeds not found
locally without having the expenses associated with importing live animals."


L







Personnel


Administration
Darshan S. Padda....Vice President for Research and
Land Grant Affairs & Director
James Rakocy....Associate Director
Raquel Santiago Silver....Executive Assistant to the
Vice President for Research and Land Grant Affairs
Yvonne Horton....Administrative Assistant III
Audrey Valmont Schuster....Administrative Assistant III
Francis Diaz....Trades Leader

Agronomy
Martin Adjei....Research Assistant Professor
Paul Flemming....Research Analyst I
Antonio Rodriguez....Agricultural Aide II
Louis Lawrence....Agricultural Aide I

Animal Science
Robert W. Godfrey....Research Assistant Professor
Joni Rae Collins....Research Specialist II
Victor Callas....Agricultural Aide II
William Gonzales...Agricultural Aide I

Aquaculture
James Rakocy....Research Professor
William Cole....Research Specialist II
Donald Bailey....Research Specialist II
Kurt Shultz....Research Analyst II
Ezekiel Clarke....Agricultural Aide II
Donna James....Agricultural Aide I

Biotechnology
Thomas Zimmerman....Research Assistant Professor
Jeanette Richards....Research Analyst I

Horticulture-Vegetables
Manuel Palada....Research Assistant Professor
Stafford Crossman....Research Specialist III
Jacqueline Kowalski....Research Analyst I
Paulino Perez....Research Assistant I
Nelson Benitez....Agricultural Aide II
Reinardo Vasquez....Agricultural Aide II

Horticulture-Ornamentals, Fruits and
Forestry
Christopher Ramcharan....Research Associate Professor
James O'Donnell....Research Specialist II
Aberra Bulbulla....Research Analyst II
Agustin Ruiz....Agricultural Aide II


Current Research Projects


Evaluation of Forage Conservation Systems in the
Caribbean.
Evaluation of Integrated Mechanical and Chemical
Control of Casha (Acacia spp.) on Native Pasture.
Improving Forage Feeding Value by Urea Treatment.
Breeding and Biotechnology for Forage Yield, Quality
and Persistence of Pennisetums.
Evaluation of Native Pasture and Agro-By-Product-Based
Systems for Market Lamb Production.
Herbage Allowance and Pasture Rotation Systems for
Animal and Forage Production on Tropical Pasture.
Developing an Integrated Forage-Livestock Feeding
System for the Caribbean.
Increased Efficiency of Sheep Production.
Reducing Effects of Heat Stress on Reproduction in Dairy
Cattle.
Studies on the Production of Tilapia in Marine Cages.
Evaluation of the Culture Potential of Selected Caribbean
Fishes.
Integration of Tilapia and Hydroponic Vegetable
Production in Recirculating Systems.
Economic Analysis of Integrated Recirculating Systems.
Integrating Tilapia Culture in Tanks with Field Production
of Vegetable Crops.
Micro-Irrigation of Horticultural Crops in Humid Regions.
Horticultural and Economic Evaluation of Vegetable
Varieties in the U.S. Virgin Islands.
Alley Cropping Systems for Sustainable Vegetable
Production in the U.S. Virgin Islands.
Improving Crop Management Systems for the Production
of Culinary Herbs in the U.S. Virgin Islands.
Evaluation of Horticultural Practices for Enhancing Root
Crop Production in the Virgin Islands.
Evaluation of Cultural Practices for Sweet Potato Weevil
Control.
Evaluation of Integrated Production Methods for Tropical
Fruit Crops.
Evaluation of Minor Tropical and Subtropical Fruits and
Nuts for Production in the U.S. Virgin Islands.
Evaluation of Trees for Agroforestry in the U.S. Virgin
Islands.
Potential for Ornamental Pot Crops in the Virgin Islands
Using Growth Regulators.
Bioengineering Plants with the Role gene to Improve Water
Use Efficiency and Drought Tolerance.
Bioengineering Papaya Ringspot Virus Resistance in
Caricapapaya for the Caribbean.
Transformation and Regeneration of Hibiscus and
Bougainvillea.
Effects of Bioherbicides on Competitive Ability of
Nutsedge.
Biochemical Basis of Resistance of Nutsedge Biotypes
and Species to Nutsedge Rust.








Recent Publications


Adjei, M.B. 1995. Productivity of guineagrass pasture as
influenced by sheep grazing pasture. Agronomy
Abstracts:46. (abstract).

*Adjei, M.B. 1995. Component forage yield and quality of
grass-legume cropping systems in the Caribbean. Tropical
Grasslands 29:142-149.

Adjei, M.B. and T.J. Gentry. 1995. Forage growth performance
of lablab bean in the semi-arid tropics. Proceedings of the
Caribbean Food Crops Society, Christ Church, Barbados,
West Indies. 31:(in press).

Adjei, M.B. and T.J. Gentry. 1995. Forage growth performance
of lablab bean in the semi-arid tropics. Agronomy
Abstracts:31. (abstract).

*Adjei, M.B., W.F. Brown and T.J Gentry. 1994. The effects
of moisture, urea level and method of application on the
chemical composition and digestibility of native grass hay
in the Caribbean. Proceedings of the Caribbean Food Crops
Society, St. Thomas, U.S.V.I. 30:186-198.

*Adjei, M.B., T.J. Gentry, S.C. Schank and A. Sotomayor-
Rios, 1994. Forage yield, quality and persistence of
interspecific Pennisetum hybrids in the Caribbean.
Proceedings of the Caribbean Food Crops Society, St.
Thomas, U.S.V.I. 30:163-172.

Adjei, M.B. and T.J. Gentry. 1994. Improving guineagrass
forage feeding value by urea treatment. UVI Research,
Agricultural Experiment Station, University of the Virgin
Islands, 6:18-21.

Adjei, M.B. and S. Josephat. 1994. Preservative characteristics
of guineagrass/leucaena silage compared to sorghum
silage. UVI Research, Agricultural Experiment Station,
University of the Virgin Islands, 6:15-17.

Bailey, D.S., W.B. Peter, J.E. Rakocy and R.W. Moore. 1995.
Marketing locally-produced tilapia products on a
subtropical semiarid island: the St. Croix case. World
Aquaculture Society, Book of Abstracts:53.

Brown, W.F. and M.B. Adjei. 1995. Urea treatment to improve
the nutritional value of tropical forages. Proceedings of
the International Conference on Livestock in the Tropics.
IFAS, University of Florida, Gainesville, Florida, 71-77.

Brown, W.F. and M.B. Adjei. 1995. Urea ammoniation effects
on the feeding value of guineagrass (Panicum maximum)
hay. Journal of Animal Science 73:3085-3093.

*Brown, W.F., M. Gray, M.B. Adjei and R. Godfrey. 1994.
Growth response of hair sheep fed urea-ammoniated
guineagrass (Panicum maximum) hay. Proceedings of the
Caribbean Food Crops Society, St. Thomas, U.S.V.I.
30:173-179.


Cole, W.M. and K.A. Shultz. 1994. Evaluation of three
indigenous Caribbean finfish for culture potential. UVI
Research, Agricultural Experiment Station, University of
the Virgin Islands 6:6-9.

Cole, W.M., J.E. Rakocy, K.A. Shultz and J.A. Hargreaves.
1995. The effects of four formulated diets on the growth,
feed conversion and condition factor of palometa
(Trachinotus goodei). World Aquaculture Society, Book
of Abstracts: 87.

Crossman, S.M.A., M.C. Palada and J.A. Kowalski. 1995.
Irrigation affects yield and sweet potato weevil [Cylas
formicarius elegantus (Summers)] infestation on sweet
potato. HortScience 30:829 (abstract).

Crossman, S.M.A., M.C. Palada and 1.A. Kowalski. 1995.
Germplasm evaluation of onion for growth and yield
characteristics in the Virgin Islands. Proceedings of the
Caribbean Food Crops Society, Christ Church, Barbados,
West Indies. 31 :(in press).

*Crossman, S.M.A., C.D. Collingwood, M.C. Palada and J.A.
Kowalski. 1994. The effect of varying rates of nitrogen
and irrigation on yam (Dioscorea alata L.) production.
Proceedings of the Caribbean Food Crops Society, St.
Thomas, U.S.V.I. 30:65-72.

Crossman, S.M.A., C.D. Collingwood, M.C. Palada and J.A.
Kowalski. 1994. Strategies for increasing yam production
in the Virgin Islands. UVI Research, Agricultural Experiment
Station, University of the Virgin Islands, 6:22-24.

Gloger, K.C., J.E. Rakocy, J.B. Cotner, D.S. Bailey, W.M.
Cole and K.A. Shultz. 1995. Contribution of lettuce to
wastewater treatment capacity of raft hydroponics in a
closed recirculating fish culture system. Pages 272-300 in
M.B. Timmons, ed. Aquacultural Engineering and Waste
Management, NRAES-90, Northeast Regional Agriculture
Engineering Service, Ithaca, New York.




























Gloger, K.C., J.E. Rakocy, J.B. Cotner, D.S. Bailey, W.M.
Cole and K.A. Shultz. 1995. Waste treatment capacity of
raft hydroponics in a closed recirculating fish culture system.
World Aquaculture Society, Book of Abstracts: 126.

Godfrey, R.W., J.R. Collins and M.L. Gray. 1995. Lamb
growth and ewe milk production of hair and wool sheep
in a tropical environment. Journal of Animal Science 73
(Suppl. 1):245.

Godfrey, R.W., J.R. Collins and M.L. Gray. 1995. The effect
of ambient temperature on sexual behavior of rams in a
tropical environment. Journal of Animal Science 73
(Suppl. 1):132.

Godfrey, R.W., M.L. Gray and J.R. Collins. 1995 Estrus
synchronization of sheep in the tropics using either
controlled internal drug release (CIDR) dispensers or
prostaglandin F2 o (PGF). Journal of Animal Science 73
(Suppl. 1):232.

Godfrey, R.W., M.L. Gray and J.R. Collins. 1995. Lamb
growth and milk production of hair and wool sheep in a
semi-arid tropical environment. Small Ruminant Research
(in press).

*Godfrey, R.W. and P.J. Hansen. 1994. Effects of coat color
on production and reproduction of dairy cattle on St. Croix.
Proceedings of the Caribbean Food Crops Society, St.
Thomas, U.S.V.I. 30:180-185.

Godfrey, R.W. and P.J. Hansen. 1994. Environmental
influences on reproduction and milk production of Holstein
cows in St. Croix. UVI Research, Agricultural Experiment
Station, University of the Virgin Islands, 6:10-12.

Kowalski, J.A., M.C. Palada and S.M.A. Crossman. 1995.
Germplasm evaluation of snap beans for growth and yield
characteristics in the Virgin Islands. Proceedings of the
Caribbean Food Crops Society, Christ Church, Barbados,
West Indies. 31:(in press).


*Kowalski, J.A. and M.C. Palada. 1994. Response of selected
vegetable crops to saline water in the U.S. Virgin Islands.
Proceedings of the Caribbean Food Crops Society, St.
Thomas, U.S.V.I. 30:232-246.

O'Donnell, J.J., M.C. Palada and A. Bulbulla. 1995. Canopy
growth and light interception by three hedgerow species
for alley cropping in St. Croix. Proceedings of the
Caribbean Food Crops Society, Christ Church, Barbados,
West Indies. 31:(abstract, in press).

O'Donnell, J.J., M.C. Palada, J.A. Kowalski, A. Bulbulla and
S.M.A. Crossman. 1995. Productivity and nutrient content
of hedgerow species for alley cropping in St. Croix.
Agronomy Abstracts, 44.

O'Donnell, J.J. 1994. Mahogany response to water stress. UVI
Research, Agricultural Experiment Station, University of
the Virgin Islands, 6:13-14.

*O'Donnell, J.J., C. Ramcharan and A. Bulbulla. 1994. The
minor tropical and sub-tropical fruit project on St. Croix.
Proceedings of the Caribbean Food Crops Society, St.
Thomas, U.S.V.I. 30:385-386.

*Palada, M.C., S.M.A. Crossman and C.D. Collingwood.
1995. Improving vegetable production using microirrigation
in the Virgin Islands. pp. 502-509 in Freddie Lamm, ed.
Microirrigation in a Changing World: Conserving Water
Resources/Preserving the Environment. Proceedings of the
Fifth International Microirrigation Congress, Orlando,
Florida. American Society of Agricultural Engineers 4-95.

Palada, M.C., S.M.A. Crossman and J.A. Kowalski. 1995.
Organic and synthetic mulches affect yield of basil under
drip irrigation. Proceedings of the Caribbean Food Crops
Society, Christ Church, Barbados, West Indies. 31 :(in press).

Palada, M.C., S.M.A. Crossman and J.A. Kowalski. 1995.
Water use and yield of basil as influenced by drip irrigation
levels and mulching. Proceedings of the Caribbean Food
Crops Society, Christ Church, Barbados, West Indies.
31:(in press).




ROF THE VIRGIN ISLANDS

i3 318 illll0191
3 3138 00191 8050


Palada, M.C., W.M. Cole, S.M.A. Crossman, J.E. Rakocy and
J.A. Kowalski. 1995. Fish culture water and sludge applied
via drip irrigation improves yield of pak choi (Brassica
rape L. Chinensis). HortScience 30:885 (abstract).

*Palada, M.C., S.M.A. Crossman and J.A. Kowalski. 1994.
Growth and yield response of thyme (Thymus vulgarus
L.) to sources of nitrogen fertilizer. Proceedings of the
Caribbean Food Crops Society, St. Thomas, U.S.V.I.
30:58-64.

*Rakocy, J.E. 1994. Aquaponics: the integration of fish and
vegetable culture in recirculating systems. Proceedings of
the Caribbean Food Crops Society, St. Thomas, U.S.V.I.
30:101-108.

Rakocy, J.E. 1995. The role of plant crop production in
aquacultural waste management. Pages 349-364 in M.B.
Timmons, ed. Aquacultural Engineering and Waste
Management, NRAES-90, Northeast Regional Agriculture
Engineering Service, Ithaca, New York, U.S.A.

Rakocy, J.E., D.S. Bailey, W.M. Cole and K.A. Shultz. 1995.
Effect of continuous light on the growth of Oreochromis
niloticus using demand feeders. World Aquaculture
Society, Book of Abstracts: 193.

Rakocy, J.E., J.A. Hargreaves and D.S. Bailey. 1995. Tilapia
culture in small cages. World Aquaculture Society, Book
of Abstracts: 193.

Ramcharan, C., J.J. O'Donnell and A. Bulbulla. 1995.
Preliminary trials with two FHIA banana cultivars on St.
Croix, U.S.V.I. Proceedings of the Caribbean Food Crops
Society, Christ Church, Barbados, West Indies. 31 :(in press).

Ramcharan, C. 1994. Bird pepper growth and fruiting
response to uniconazole sprays. Proceedings of the
Interamerican Society for Tropical Horticulture,
Campeche, Mexico: (in press).

Ramcharan, C. 1994. Growth and flowering responses of
culantro (Erynguim foetidum L.) to Pro-Gibb sprays.
Proceedings of the Caribbean Food Crops Society, St.
Thomas, U.S.V.I. 30:384.

Ramcharan, C. 1994. New ornamental pot crops. UVI
Research, Agricultural Experiment Station, University of
the Virgin Islands, 6:2.

*Ramcharan, C. 1994. Potential for pot crop production using
growth retardants in the USVI. Proceedings of the
Caribbean Food Crops Society, St. Thomas, U.S.V.I.
30:380.

Zimmerman, T.W. 1995. Effect of Timentin for controlling
agrobacterium tumefaciens following cocultivation on
select plant species. In Vitro Cellular and Developmental
Biology 31:70A.


Zimmerman, T.W. 1995. The effect of papaya ringspot virus
on production and future means of possible control.
Proceedings of the Caribbean Food Crops Society, Christ
Church, Barbados, West Indies. 31:(in press).

Zimmerman, T.W. and C. Ramcharan. 1994. A preliminary
investigation into breadfruit micropropagation. Tropical
Fruits Newsletter 13:5.

*Zimmerman, T.W. 1994. Effect of exposure to plant growth
regulators on cellular differentiation. Proceedings of the
Caribbean Food Crops Society, St. Thomas, U.S.V.I.
30:377.

*Zimmerman, T.W. 1994. Priming papaya seeds reduces seed
germination time. Proceedings of the Caribbean Food
Crops Society, St. Thomas, U.S.V.I. 30:329-332.

Zimmerman, T.W. 1994. Rapid and uniform papaya
emergence with primed seeds. UVI Research, Agricultural
Experiment Station, University of the Virgin Islands, 6:3-5.

*An asterisk in front of an entry indicates that it has been
previously listed, but was in press. Now the entry is
complete.



































































S1962.
96 '


University of the Virgin Islands
Agricultural Experiment Station
RR 2, Box 10,000 Kingshill
St. Croix, USVI 00850
1995




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs