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The Caribbean region is one major source of most herbs and spices consumed in the U.S. Although the U.S. Virgin Islands (USVI) is part of the Caribbean, local production of herbs and spices does not contribute significantly to exports into the U.S. market. Nevertheless, culinary herbs area” important horticultural crop in the USVI and their sale provides income for many small-scale growers. Little research has been done to improve field production in the USVI. Inefficient cultural practices used by growers result in low yields. Lack of information on fertilizer rates, irrigation and pest control methods is a major constraint to high yields. In 1988, the Agricultural Experiment Station initiated a project to improve field production of herbs and spices in the USVI. Use of drip irrigation, mulching and fertilizers has improved yields of basil (Ocimum basilicum) and thyme (Thymus vulgaris). This paper will discuss crop management studies to improve culinary herb production in the USVI. Increasing production may help reduce U.S. imports of these specialty crops from other Caribbean island nations.
Small-scale herb growers in the U.S. Virgin Islands traditionally water their crops with sprinkler cans and garden hoses. This method is inefficient and consumes large amounts of water, a scarce resource in the islands. Introduction of drip irrigation has reduced water use in vegetable production. Integrating this system with mulches may further cut water use, making herb production more profitable. Basil (Ocimum basilicum) was grown in plots with organic (compost or straw) and synthetic (black plastic or weed barrier) mulches. A no mulch control plot was also included. All plots were drip irrigated to maintain soil moisture at -30 kPa. Total plant fresh weight and leaf fresh and dry weights were highest in the compost mulch treatment. Fresh and dry basil yields in black plastic mulched plots were almost identical with those in compost mulch, but did not differ from other treatments. Black plastic mulch reduced water use 46% compared with 27% for compost or straw mulch. All mulch treatments resulted in increased water use efficiency. Organic mulches reduced surface soil temperature, while synthetic mulches increased soil temperature 2-5°C.
Chive (Allium schoenoprasum) is one of the most popular culinary herbs in the Virgin Islands, and local demand is always high throughout the year. However, local production is not sufficient to meet increasing demands. Chive production is constrained by insect pests, weeds, and high cost of irrigation water. A study was conducted to compare the influence of organic and synthetic mulches on yield and economic returns from chive production. The study also evaluated the effect of mulch on weeds and water use. Chives were planted in plots consisting of three rows 3.6 m long. Plants were spaced 20 cm within rows 41 cm apart. The plots were mulched with grass straw, wood chips, shredded paper, and white plastic. A control plot (no mulch) was also planted for comparison. Plots were arranged in randomized complete-block design with four replications. All plots were drip-irrigated and soil moisture tension maintaned at 30 kPa. Chives grown with grass straw mulch produced taller plants and higher number of tillers (slips) than all other mulch treatments. Total fresh yield of plots with grass straw mulch was superior to all other mulch treatments including the control. On the average, plots with grass straw mulch produced 1203 g/m2 of fresh chives. All mulches resulted in reduced weed population compared to the control (no mulch). Due to high rainfall during the growing season, differences in irrigation water use were not significant. Economic comparison indicated that the net return above mulch costs was 50% higher with grass straw than with other mulch treatments. To improve production and income, herb growers should consider using grass straw and realize other benefits, including weed control and improved soil fertility.
Four tropical leaf vegetables commonly used as pot herbs for “kallaloo,” a local West Indian dish, were grown in replicated plots during the fall season of 1996 to determine growth and productivity. Leaf vegetables included green malabar spinach (Basella alba L.), red malabar spinach (Basella rubra L.), sweetpotato (Ipomoea batatas L.), and bush okra or jute mallow (Corchorus olitorius L.). Plants were harvested periodically and data on number of stems or vines, fresh weight of stems and leaves, leaf area, and leaf area index (LAI) were recorded. Except for leaf fresh weight, cultivars or species did not differ significantly in all parameters measured. Leaf fresh weight ranged from 27 g for jute mallow to 198 g for red malabar spinach. LAI was highest for sweetpotato (2.90) and lowest for jute mallow (0.86). Among the species, productivity (fresh weight) was highest (6.78 g/m2 per day) for green malabar spinach and lowest (3.22 g/m2 per day) for jute mallow.
Abstract
Cultivars of heading and loose-leaf types of Chinese cabbage (Brassica campestris L. Group (Pekinensis) were field-planted in the spring (25 Mar., 18 Apr., and 5 May) and fall (19 Aug. and 10 and 30 Sept.) to determine optimum dates for early and extended production in the northeast. All cultivars of heading Chinese cabbage developed flower stalks (bolting) in 25 Mar. and 18 Apr. plantings when mean minimum temperatures were −1.7° and 3.9°C, respectively. Bolting was virtually absent in fall planting for both types. Optimum dates for early spring planting were 5 May for heading types and 25 Mar. for loose-leaf cultivars. Late fall plantings (10 and 30 Sept.) resulted in no head formation and reduced yields for heading Chinese cabbage. For both types, marketable yields were generally higher in spring than in fall plantings.
Using fish culture waste water may benefit vegetable production by reducing the need for high quality irrigation water. Fish waste water also contains nutrients, reducing the need for chemical fertilizers. A study was conducted to integrate fish (tilapia) culture with field production of bell pepper (Capsicum annuum L.). Waste water from low and high fish stocking densities and variable water exchange rates were applied to bell peppers 2 to 3 times weekly. These treatments were compared with fish sludge. cow manure and commercial N fertilizer. Fish waste water and sludge were applied by hand in the first year. A modified irrigation system was used in the second year. All other treatments were drip irrigated. In 1992 marketable yield was highest (9.0 t/ha) in plots with N fertilizer (drip fertigation) followed by plots applied with sludge (5.0 c/ha). Lowest yield (2.0 t/ha) was obtained from plots applied with fish waste water. In 1993 plots applied with fish waste water had a slightly higher yield (7.0 t/ha) than N-fertigated plots. Marketable yield was highest (10.4 t/ha) in plots treated with sludge.