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ISLAND PERSPECTIVES University of the Virgin Islands Agricultural Experiment Station 1988-1989 Vol. 3 a ae nye ‘:. ilies Pal fi a j.7 chat eet es a om, Sest | fi, Stes anne - = oe hae 4 a age" ry ae aE i Sey = Ld 7," % ee Pin ten i = ee ee E eaten oa, er aaa a Se a “i Pa i ome o, at bike © & eine, ge -_ os —_s. ye *, it © Ge hey ¢* — #.. a ey r~ +p -8 Ri i a C te ed OM Ty = = ca RO = a . or a a a a =: LT) cal Ss i a a * a .* Fo om hd a — Sy — il <3 _ = 7 a fd —, ma “GS. aad = + L = i n oy Mer —_ a alt * ; = , t= fe _ Ce ply oe SS ue —_< = he — aah a Ne e =a. — x mt ee! - oe. ee ln lt = zy? P ee ali @ a = si oT i + of a a a el 4 5 (‘a f = = aft Pr =a a a ue <= a =” a a2 pa <3 id 8 rs in | sail aa ia 4 a a e rs a, 4:3 ~ an “a Pe O, ‘— ~e ro pe -? i 1, chad 7 Lt i [= “= +e = aan She: a = ey, 4 Z ~~" an L = els o ae, eel 7 a ae em a) a oe es i a9 - & if Sy a6 _ uJ —— wa Ais, ailtee emt = “4 Ie = =. Sh = A = . >. —_ ta a ee PL ? } = al Pa) SF — a = ra #s a} oi ie ate ae eo a Laie — La Ee is, ay Iz ay, si fe i = - al a J = 5 = = i. — moll Lane —_ ae ar “a =a Se rl mm Pon _ a be fai al ale .»_ a LT om - eG" yy =" id, ea “J a ae nae = i ant rs =F, er ae if i Te at —e = = _ 4 - he . a! . ee oy he eo = i pe . te = ow ae [— a" “5, je, = 2 wh a ea ais 1 A= ee se =a = - md Beat : fi a: = ab 4 es x te a. = aes =. 5 a é 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 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 Agricultural Experiment Station 1988-1989 Vol. 3 Hydroponic Lettuce Production in a Recirculating Fish Culture System .......... 5 James E. Rakocy Citrus Germplasm Evaluation Under V.I. Conditions ............... 00... eee 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. ................05- 24 Stephan Wildeus and Cyndi L. Wildeus Environmental Monitoring in the Salt River Submarine Canyon, St. Croix .......... ccc cee ceeeeees i CE KOR WOE 26 Mary Lou Coulston AES Personnel and Current Research Projects............... 200.0 eee eeee 30 Recent AES Publications « . 2.05 seu cecesce ceased ceeeeeeneenesneanenes 31 James E. Rakocy Carrol B. Fleming Associate Director Editor Editorial Board Members John Hargreaves Stephan Wildeus Arthur A. Richards Darshan S. Padda Published by the University of the Virgin Islands Agricultural Experiment Station RR2, Box 10,000 Kingshill St. Croix, U.S. Virgin Islands 00850 1990 President Vice President Ri) me tlh Teh i eit "a “hie ae i iF ii Pe Lie! Le sha. all "| jie i aH AT i Ww ot oe el Like te Lott i= ie tt hips I Ft i ave ei) I i jae 4 HF te: cai gall ate iE me ALG, +e y® ae ici) | | i) is ae 4 y WY hrs iM a “i Pi ark ie pete + ow al i te lal ate itt It He “he = A ila ds i * #,! ie) arf eo d i y “ong. Bi, as Pe y — ne ol _ ae C4 y ey ’ ie Et hati. ié i 1 “a, A / i Bt ad 4 ae Pie | vie af ré - 7 Hl a Ye a, o & “if ay x 2 yw "Pts “© hg eae: ad atta re Mi ton BS i # “dp oes ah a, ‘Py at aud é, one a’ aap te 4 aol if} Pe). fd, ail. |i a “| 7 Das Sn | 7 aif 5 Ha Me i" = cd) aly ee i, 144) rs a! the a il ri a t q 7 * | “SB. s 8, uae a ; ¥, i ‘iM ria < Mi a ts ‘ier By / ey ill mo S/. 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.” Hydroponic Lettuce Production in a Recirculating Fish Culture System 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-m°(3,300-gallon) fish rearing tank, a 1.9-m°* 500-gallon) settling tank (clarifier) for removal of solids, two, 2.1-m? (550-gallon) hydro- by James E. Rakocy ponic tanks with a total plant growing area of 13.8 m? (148 square feet), anda 1.4-m? (370-gallon) reservoir (Figure 1). The total system volume during oper- ation averages 17.8 m? (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 m? (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 (% 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 Water Inlet .° verflow Outlet 7 A harvest of tilapia cultured in a recir- culating system. Drain Line rs Reservoir Clarifier a —_ Lower Hydroponic Tank —a \f Zl Upper Hydroponic Tank : 1 meter : Valve O Valves a: --~ 1T~~~s_ Canopy az yt ~ “ i] ~ i! ‘ , Return yi \ inlet Vt Rearing . 1! Tan \ u ank ! waee™ i to Outlet 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/m? (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 7.5, 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/m?/m? 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 24 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 Stocking rate (fish/system) 44 Feeding rate (kg/day/system) 0.2 (g/day/plant) 0.6 (g/day/m*/m/?)? 0.8 Lettuce production (kg/week/system) 10.5 + 0.4 (kg/m?/crop)° 2.3 (g/head)< 98 + 4z Net fish production (kg/system) 20.5 3.8 2.5 1.9 1.5 1.2 88 132 176 220 264 0.4 0.6 0.8 1.0 1.2 1.2 1.8 2.4 3.0 3.6 1.6 2.4 3.2 4.0 4.8 11.8 + 0.7 12.3 + 0.7 14.1 + 0.9 13.1 + 0.9 11.2 + 0.8 2.6 ait 3.1 2.8 2.4 109 + 6yz 117 + 6xyz 131 + 8x 124 + 8xy 106 + 7yz 41.3 96.8 83.1 95.6 112.2 *Based on a system volume of 17.8 m° and a plant growing area of 13.8 m? with 23.9 plants/m*. ‘Each 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. 6 1200 E RATIO ew a 1050 ‘iomeccgy 48 Po ad v—v 1.5 s m 900 o—o 1.9 — oo yan aire rs : a-——Aa 3.8 ; v) e—e 7.5 ZO 600 ’ > 450 — ot 5 150 0 8 12 16 20 TIME (weeks) Figure 2. Accumulation of total dissolved solids during 20 weeks in 17.8-m 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 (m°*) and plant growing area (m?) or, specifically, grams/day/m?/m? for designated plant growing densities, which in this case was 23.9 plants/m?. The optimum feeding rate was 3.2 g/day/m?/m? 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 m?° (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 (%)? 88.2 (94.3) 87.7 (93.2) — Water use Quantity (m°) 24.1 13.7 19.3 Cost ($)° 255.04 144.88 71.57 Chemical use Quantity (kg)° 9.56 21.99 10.10 Cost ($) 43.30 47 .37 35.15 The 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. ‘Potassium 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 Ibs/100 gallons), magnesium sulfate (applied at 0.31 Ibs/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/m?/m?, 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 ae a ~_ in 3-week cycles. 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 m%; 6,370 gallons) than the hydroponic (13.7 m°; 3,620 gallons) or fish culture (19.3 m3; 5,100 gallons) sys- tems, but the combined water use (33.0 m’; 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/m°> 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/m? ($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 An experimental recirculating system integrating vegetable hydroponics with fish culture. Me TTT Libel AL i" He nate a i 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 J . ie inh —— SEs ce ait) aa 20; 7.5 Plente : Fish Lettuce Production (kg) 3.8 Plants : Flah 1.2 Pients : Fiah 012345 6 7 8 9 101112131415161718 012345 67 8B 8 101112131415161718 612345 6 7 B 9 1011 12131415161718 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 10 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. 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 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- Table 1. Percentage survivability of 21 citrus cvs. on 2 rootstocks over 5 years (1984-1989) Scion RootstockY % Survivability Ortanique orange Unknown 100% Valencia orange 5.0. 90% Navel orange 3.0. 100% Pineapple orange Cleo 100% Blood orange Cleo 50% Blood orange 5.0. 50% Murcott orange Cleo 80% Temple orange 5.0. 40% Parson Brown orange 5.0. 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 5.0. 20% Ponderosa lemon Cleo 0% Persian lime Cleo 20% Lakeland lime Cleo 0% Pumelo S 100% Kumquat S 20% YS.O. - Sour orange rootstock; S - seedling Cleo - Cleopatra mandarin rootstock 75 replicate trees/combination T1 Choosing the proper citrus variety for local conditions is the first step... yi a, 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 di His outperformed some of the recom- Ortanique orange produced high yields under Virgin Islands conditions eeed warleties te peed, Dart thet : fruit quality was inferior. High night temperatures and the low altitude of the experimental site may be contribut- —— _ ing factors. Table 2. Yield data of selected citrus cvs. on2r rootstocks Variety Rootstock Av. No. fruit Av. Wt./ Although the W.I. lime, which is tree/harvest —_ fruit (Ibs) used locally as a beverage and in many a aC SASONCCCCCCCS—SsCiSheess, thrives under most local condi- Valencia orange S.O. 98 0.46 tions, the limes in this experiment per- Pineapple orange Cleo 81 0.54 formed poorly. The reason is Navel orange S.O. 47 0.61 unknown, but poor quality of original Parson Brown orange 5.0. 93 0.39 planting stock is suspected. The Ortanique orange Seedling 78 0.63 Pumelo, a vigorous disease-resistant Orlando tangelo Cleo 128 0.38 citrus, could have some future poten- Ruby Red grapefruit S.O. 28 0.760 tial with the proper introduction of its Thompson Pink grapefruit 5.0 29 0.903 uses to local growers. The Kumquat Marsh grapefruit 5.0. 21 0.842 can be grown as a potted plant and S.O. - Sour Orange rootstock serve a dual purpose as a fruit and a Cleo - Cleopatra manderin rootstock 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- 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 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 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 13 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 Ibs/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 14 Oo——Otreatment ®——@ contro! Body condition score (1—9) { ~ 0 — 95 + o! _ as. pt \f- “” Bodyweight (Ibs) 75 + \ 7 . / “~e A/ 70 + A A start flushing end flushing 65 joy 0 10 20 30 40 50 60 70 280 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. Table 1. Body weight and condition, and reproductive performance between ovulation and lambing rate is (mean+SEM) in mature ewes fed pasture (control) or pasture with supplement not readily apparent, but may be prior to breeding. partly the result of the surgical interfer- TO — - ence due to laparoscopy. This decline _ Supplemented* Control in lambing rate was the result of ewes Beginning of flushing: not lambing according to their project- Weight (Ibs) 83.04+4.1 80.9+3.4 ed ovulation rate, as well as ewes fail- Condition (1-9) 3.89 + .26 4,444.17 ing to lamb. The number of lambs born After flushing: per ewe lambing in this experiment Weight (Ibs) 87.343.9 74.24+2.9 (1.5) was lower than the value gener- Condition (1-9) 4.11+.26 2.66+.24 ally observed (1.7) in mature ewes End of breeding: lambing on pasture at the Sheep Weight (Ibs) 89.0+4.1 76.24+2.1 Research Facility. However, both con- Condition (1-9) 4.44+ .50 3.00+ .24 trol and supplemented ewes were Days to estrus 2.6+0.8 8.9421 equally affected by this decrease. Ovulation rate 2.00+0.19 1.78 +0.22 Gestation length was similar in control No. of lambs/ewe lambing 1.50+0.18 1.57+0.18 and supplemented ewes. No. of lambs/ewe exposed 1.3340.23 1.22+40.28 In the second experiment body Gestation length (days) 149.0+0.7 148.4+0.7 weights of control and supplemented ‘supplemented with 2 lbs/head/day of cracked corn 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 Table 2. Body weight and reproductive performance (means+SEM) in hairsheep __ no longer evident at the end of the ewes lambing for the first time fed pasture (control) or pasture with supplement. —_ breeding season (Figure 2). The weight -_- eS at conception was 1.1 lbs lower in the Ee _ CE __ control. group, Pre-feeding weight (Ibs) 66.7 + 1.94 67.8+1.70 In the young ewes pre-breeding sup- Post-feeding weight (Ibs) 71.141.79 70.64+1.96 plementation also failed to improve Weight at conception (Ibs) 73.34+1.67 72.2+1.80 reproductive and lambing perfor- Days to estrus 11.24+2.27 7.9+1.43 mance (Table 2). Supplemented ewes Ovulation rate 1.27+0.18 1.42+0.15 displayed estrus slightly later during No. of lambs/ewe exposed 1.07+0.21 1.27+0.17 breeding (3.3 days) and had lower ovu- Amount of lamb born (Ibs) 8.42+0,59 7.81+0.74 lation and lambing rates, but differ- Gestation length (days) 146.3 +0.60 145.7+0.38 ences were not statistically significant. The amount of lamb born and gesta- — tion length were also not affected by ‘supplemented with coconut/molasses mixture at 0.75 Ibs/head/day. I he) Hairsheep ewe with twins. 85 -- O—Otreatment 80 + @—-@control a o = | O-——O F- od Oo 75+ a @ O & A fo ff © pes a a | e—e 70 g-<—e A A [ss flushing end flushing 65 | t 1 0 10 20 50 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). 16 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 Ibs/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 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 Ibs.) far exceeds the outlets’ demand (197,078 Ibs.), 67% of their purchases are imported (Table 1). Of the approximate 300,000 Ibs. 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%) in the U.S.V.I. 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/Ib.) 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/Ib.). 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 7 Quantity in Ibs. (mill.) "" @ AVOCADO BANANA GRAPEFRU T | I [__] Production Demand LLLLL 1 CAT EP PPP PPOPPPOT TELE: | LILES ILA LALA AI AL LANA LLL AD La WITZZ. BUZZ Po d y, 150 125 Quantity in Ibs. (thou.) sw ° on ro S hm cn [__] Market spoilage Unsold production To the detriment of their operations, local farmers tend to use retail prices to wholesale their produce. 290 200 Production 3 Quantity sold = 150 2 = rey = 100 N , \ G S 50 \ \ TL IN [1 |S os 0 © AVOCADO BANANA GRAPEFRU LIME MANGO ORANGE [_] Imports Local Purchases 100 SSJ_ 90 | 80 + - 70+ | 60 + 4 30 + - Percentage 40+ + 30 + 4 20 + “ 10 F- - i A L 0 AVOCADO BANANA GRAPEFRU LIME §$MANGO ORANGE Figure 1. Aspects of fruit crop production, marketing and consumption in the U.S. Virgin Islands in 1987. 18 Table 1. Marketing survey of imports vs. local fruits purchased. Fruit Quantity Source Purchased Import Local (Ibs.) (%) (%) 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 79 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/Ib. Retail/Ib. Wholesale/ Retail Ratio Banana $ .38 $ .57 1.50 Orange 34 79 Ze Lime a0 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) (Ibs) (Ibs) (%) ($) 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 reseach was supported by Smith Lever Cooperative Extension Project #031. Francois Dominique is a former Program Supervisor for the CES Community and Rural Development Program. 19 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 20 | ‘alt |e, 4 SH ll 5 ~ : Root-zone temperatures in container-grown plants vary with the color, design and = a 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 O—O East _—A—A 45 + 4—A West = ™ OoO—oO North va ] © 35+ 4 - 30+ 3 S 25+ 20+ St. Croix, May 23, 1986 Time (hrs) Figure 1. Mean diurnal temperature of media in black plastic containers. 2.000 site O—o 5 | 's 1.500+ \o 3 ‘Noo E 1.000 + \ © O oO— ~ o0s00t 9 ° \ oO 3 2 O St. Croix, May 25, 1986 0.000 +—+—__+_+#_ +++ j—finng 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (hrs) Figure 3. Diurnal solar radiation. 90 45+ 5s ate Pot—to—Pot spacing A—A East & © 35+ 2 5 30+ on 3 Z 2 25+ 207 St. Croix, October 30, 1986 ————_—— 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. 6 7 8 9 10 11 12 13 14 15 16 17 18 50 7 Western Exposure 4A—A Black Container _—A 45 + O——D White Container tA ©— © Poly Bag in Container pr > 40+ we © 354 : . 30+ E s 25+ 20 + St. Croix, May 23, 1986 7 7 7 Uy 7 T 7 7 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (hrs) Figure 2. Mean diurnal temperature in western quadrant. 50 45+ cs Near 18 inch 0.C. spacing A—A East =~ 40+ o—o South [é) o—9> a iA 2 A 5 «304 ° a. E v2 2 29+ 20+ St. Croix, October 30, 1986 15 ee 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 O—O 1,500 + Oo” \ & 0” Q § 1.0007 / 5 5 fe) E Oo” . 0.500+ Oo i fe) ” St. Croix, October 30, 1986 O 0.000 ? ' : i—t+- + t +— 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (hrs) Figure 6. Diurnal solar radiation. 21 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’ BRP4 66.5b* 61.5a 25.7¢ 10.2b WPRP 74.5a 55.2a 37.1a 15.2a BPBP 70.2ab 65.2a 31.1b 12.6a Ixora Chinensis ‘Maut’ 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. “ 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.4 65.2¢ 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 78a 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 2 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 ¥ means within columns for each species followed by the same letter are not significantly different at the 5% level. 22 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. l oe mi: If ae = 14 HE ti gi ity Fa all alt! Wi ite | oe ity, aoe 9 = Mh The traditional er il -:- ~ le hail La aH Ya i. fey, inh, a black plastic ey ta i, ai ‘lis » eS, a containers he —_ 7 ea¥) ¥roe a al Lass i, dar 2 aed Si >. oa reduced overall i af rs a TE a %\," .-— . 2 oo Pn jal! plant growth «a _ tn. » A\ oe ._ aff" ™ . tn fS F. dae in most species. nie =e \:=as ~~ 4 Y aioe ‘; »s 4 x Se — a BA \ a ao ~* = Sali — > a aN 2 ig se Wz: -.* i Ni ~_ = \ =f Sie ‘g” ~ 24> (Ge = era 1 Pt =_™ a All aon Sh. = . —_— : —— a ny ee = al ew ° Sn <_<" a Ther ut, ~ re oe < = ~ —@ ® | Xa Optimum growth and quality of ie Gee _ — al “<-* yA =~" ars ga = — container plants in the USVI can be al ee — or achieved when cultural practices main- we ™ <o ee a ‘= yO Teles V4 Vie 5a, —. | @!! tain media temperatures below 40 C. = 4 The feasibility of importing and using ~~ a &, 1, plant containers other than the tradi- ii ls: te 7 a a Se / 7. a. * _ tional black plastic or black poly bags hla FF ns should be seriously considered by — pT ait nursery plant growers in the USVI. & x ers we 1H, »* i = ~~ This research was supported in part by the U.S. Department of Agriculture rine a Le a é. under CSRS Special Grant No. I) 9 a wn 84-CRSR-2-2482, managed by the wy i tlk £4 <7 HH stash * 7 * + J. 2 al... os ® Caribbean Basin Advisory Group 1 te, alll -, (CBAG). laa Bs .> Dts ty & Christopher Ramcharan, Research Assis- ia? S*. eo, i = > tant Professor, is the leader of the Horticul- dl a os aw ture Program. Production Potential of Buffelgrass 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- 24 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. Pastures in the V.I. by Stephan Wildeus and Cyndi L. Wildeus 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 4; 8- or 12-week intervals. The yield of each plot was determined and samples (0.75 Ibs) dried in a forced air oven at 140°F 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 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 3.27 461 409232 1.54 2.68 4,21 409359 1.19 3.07 4.38 BxBW37? 1.16 23 3.24 _ *buffelgrass x birdwood hybrid O e O—O 4 wk harvest interval S 44 A—A 8 wk harvest interval 3 O—DO 12 wk harvest interval 0 T & ra) an 3+ _ ne ger ~ Y — > 27 5 3 OUT 5—0 0-0-9 E o—O— 3 4 & | 0 J F M A M J J A S 0 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 Cultivar Llano consistently produced the highest dry matter yield. 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 ayvalues 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 1n- 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. 25 Environmental Monitoring in the Salt by Mary Lou Coulston A diver uses a Stanley hydraulic impact-twist drill operated by a 15-hp. hydraulic supply from the surface to provide a hole for a permanent stake. Photo by M. Herko 26 River Submarine Canyon, St. Croix 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 Park Service (NPS). The Aquarius habitat is located in 60 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 mL E. 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 27 Aquarius Habitat ea] East wall tank rack West wall tank rack Center canyon tank rack A - E Excursion lines radiating from the habitat Cross canyon excursion line © ORT) i ye se a < uy “y Lt | 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. 28 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 established 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: O. 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. 29 Agricultural Experiment Station (AES) Personnel Administration Datshian S, Page wsscscvesss ca toa qusaa es a4 Merwe WS oe HOO E ess Vice President for Research & Director JANES RAKOCH: a cowsiascrnamaaw 09 vewrmerseare ee KURR ROE IAeINNe Oo RM ea ERIE EN en ecermCeleemmER OEE Associate Director Carrol Fleming ee cicnencsiee ua cesemegemenes ts uammesiemeda 6 Ke USEDOSS SS He Ch ER RACATORSS 1 RRNA Editor Raquel Santiago causes we us peewee es se vem eemese oa meee we aera Administrative Specialist II AUGLCY VALTIONE: ccccisisnacace vie ve wemeeegwns ao Heme SRSA Eo HEUER ERR He oR Administrative Assistant III Yvonne Horton «..00ce gece oe eee cee didi soe oe eealeaele Oa ae He Ke SEWED EEN IS POSSESS Administrative Assistant II Coreen Highest s: 3:50 se oe wwaseemawas os vewerneesen 0 wees os ee Administrative Assistant II GO ATO 'iccs ws vie srcaeneracenss a0 mee euecne om MaRS MANE Oe KHORMLSECRTELE Om RUREMEELAONLES He Trade Worker II VACHOR VASQUEZ . co cccncey nee dG 4 tie be WORSE EG UG ETFOSERTRSG 36 HE VENEERS Oe Ho NSROMeRER Agricultural Aide III Animal Science and Forages Stephani Wes i 63 ca eecccccacan crcwenewes te cesT RAS HE MAA eS on Research Assistant Professor CORE VICES esc cammsaccncemumeiens me KemameOeR ce eoOAREERAEEOR meaUMmeMUMIE NaF goReANONE Research Analyst Ill Jord Rae Fugles 2.65 is os io Se esas ee Ae os SORSRRWEN ES Ua ROU NE NUER & EERE EN eG Re CaR eR Research Analyst II Rigi THAGORE seissceiss ce csarerarecanreianaim arn 6% SNR RNNERS ANE me REM NRRERNCLTO ROU ois RK MTRMAOR NON Kee aKOCACeieE Research Analyst II Angela Belardo ......... 222 cece ccc eee nent eee e etn nn eeees Research Assistant II Allan Schuster jis. is c4 s2 s2cas@was os 85 Oe eS REREWOS Us He ENEOROTES Te US HOVE TENOR IN Hs WWE Research Assistant II Victor Callag- This x6 ti sieownnas os taswecew wee oa in KaWE Es Oe WaKEROWELTEN Re KmaremETER 6 Agricultural Aide II Ramiro GomeZ..... 0.2 nee eee e ene e een tense een eee e tee eeeeee Agricultural Aide II Antonio BOGHSUES & saxccscwxed sp SOR WEWEeN US te MRO CERET EY GI EE UewenseED i ee Koes Agricultural Aide II Aquaculture JaitteS RACY vcscsescencnsisaca va smeeseee we MRMREIIRRRINR Rie MaLeTEECTUNEMESe Bu BiaerETRERATNARINE Research Aquaculturist John Hargreaves ..... 2.2... ccc cece rece cece cece teeter e eee e ese nee esse eens eeneee Research Specialist II Donald Batley scaceseu vs sc ceveeesawss ts eerwacsewey ee eorewea ewes 96 ge crew en os ea Research Analyst II BSiCh Re6tO? wcesccanaacars a scoceancemnnes necro ecateceiemene ecw suenermteRelN ane ema IN Oe ON ene eoRe Research Analyst I Ezekiel Clarke. ice ne cenanee awe ne genre dance d6 08 te ae Teeeh, Je KE SOMERS REM SN 8 Tea Agricultural Aide II Vegetable and Root Crops Adriane Navatie swsseess ci couacesew oe ca ewan ee sewees a eoeE Research Assistant Professor Stafford Crossman ...........+4-- Le cee cee ene eee tence eet e eee eee ee eens eeeeees Research Specialist I] Chatles Collingwood «ci cco se eeeeses 0665 MWONOTENER KE RENRES RUN oR Os ROE SEEN WS Ee ews Research Analyst II Pranes Dial sc scewrssesy a6 ce ees os oe tee OF Ea as ee Be ERNOTE RE AZ was cere Research Assistant I Paulino Perez 2.0.0... eee ee ee ee ee ee eee e nent ene e een e ee eeees . Agricultural Aide III WelsOi: BOREZ:...<c005 ce KETETOTES ES LA IG AORTA CRNG HG HE RESET Mh MONSON ewEA ce MOLE ER Agricultural Aide I ReiMAIdo Vasque? sack ia cosrwcwcnss es ca mmemenies see oe ea see REE we see mO Agricultural Aide | Horticulture and Forestry Christopher Ramcharan ............ 0 cece eee eect eee t eee e ee enennes Research Assistant Professor Feito Per werd oes iissieu 55 5S oe HO RAUIENEE O8 UDRURETEIEN oe EER AeRE EY i Ee EURO om OX Research Specialist I Elizabeth GIEHRORN: ciisccscass as ca ccmenanoas nn ee Ke Ree Ow RUN aRe ENA Eee Research Analyst II Osvaldo Lopez ...... 6. ccc teen e eee teen nent tenn ete eee ee nnnnees Agricultural Aide III Jereriiah Hassall scenes cs csawwscsewen me oweeeRcewE se veCeNeeED 8s oa wee Oe Dee Agricultural Aide II ABUSUNRYIZ: siecccccis 6s ce meeaiins ws me RRNA ae SER RENORD 4 SRA TEIN oF OES Agricultural Aide II Current Research Projects A study and analysis of management systems for native grass- lands in the U.S. Virgin Islands. Efficiency of hair sheep production in the Virgin Islands. Epidemiology and control of parasitic gastroenteritis of sheep on St. Croix. Evaluation of reproductive potential of tropical V.I. sheep. Increasing prolificacy in sheep and its impact on nutritional needs. Strategic supplementation of sheep grazing native, tropical pastures. A commercial-scale recirculating system for vegetable hydro- ponics and intensive tilapia culture. Cage culture of tilapia in the Virgin Islands. Evaluation of the culture potential of selected Caribbean marine finfish. Survey of biofouling control methods for V.I. mariculture. Improving field production of herbs and spices. 30 Performance of yam, cassava, and sweet potato in the U.S. Virgin Islands. Trickle irrigation in humid regions. Vegetable variety evaluation for adaptation and horticuotural characters. Water use in small farming systems in the tropics. Use of saline water for urigating vegetable crops. Evaluation of the effects of tissue culture on somatic variation and propagation of breadfruit. Improvement of fruit production in the Virgin Islands. Iron sources application evaluations and propagation analysis on selected pineapple varieties. No chemical control of disease of tropical food crops. Study of mango flowering to reduce erratic behavior. Phenological and physiogical study of mahogany in the Virgin Islands. Biological control of nutsedge with fungal pathogens. 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, 5.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.SV. 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 DJ. 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. Végetable 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 Agricul.ural 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 5. 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 grazin 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, 5. 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, DW., 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. 31 University of the Virgin Islands Agricultural Experiment Station RR2, Box 10,000 Kingshill St. Croix, U.S. Virgin Islands 00850 Disclaimer Statement Island Perspectives is published annually by the University of the Virgin Islands Agricultural Experiment Station. 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 University of the Virgin Islands Agricultural Experiment Station. Trade names of products occasionally are printed. No endorsement of products or firms is intended, nor is criticism implied of those not mentioned. 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