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کشاورز ایرانی (مرکز ارائه خدمات جامع آموزش کشاورزی) - مطالب دی 1390

کشاورز ایرانی (مرکز ارائه خدمات جامع آموزش کشاورزی)

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پنجشنبه 29 دی 1390

Cucumber

نویسنده: مهندس علیرضا شعاعی   طبقه بندی: گلخانه، 


Planting

Cucumbers generally grow more rapidly than tomatoes and produce earlier. They also require higher temperatures, which means they are generally grown as a spring or early summer crop. Daytime temperatures should be 80-85°F (nighttime 65-75°F). Soil temperatures should be at least 65°F. Lower temperatures will delay plant growth and fruit development.

Cucumbers are heavy feeders requiring 300-400 lb/a of P205. Similar quantities of potassium are required. Weekly feedings with a balanced fertilizer (20-20-20) will be required for maximum production. Never stress seedlings for water or nitrogen.

Plants are best started in individual containers. As seed are often very expensive, sow one seed per container (1/4 to 1/2 inch deep) in a sterile potting mix with the spiked end of the seed up (root will emerge facing down). Water, cover pots with clear polyethylene, and place in the shade. Plants will emerge in two to three days at 80-85°F. Remove plastic coverings when plants emerge and place them in full sun.

After plants have formed at least two true leaves, transplant them to their permanent location in the growing bed. Cucumbers will require 6-8 square feet of space per plant. Plants are generally spaced 2 feet apart in rows 3 to 4 feet apart.
Training

Cucumber vines can be trained on plastic twine supported from horizontal support wires running the length of the rows (7-8 feet above top of bed). The base of the string can be anchored loosely to the base of the stem with a non-slip noose.

As the stem develops, it can be fastened to the string with plastic clips. Allow one stem to develop, removing all laterals and tendrils as they develop. Fruit buds should be removed from the first five leaf nodes. Thereafter, fruit can be allowed to develop, but continue to remove all laterals and tendrils.

After the stem reaches the horizontal support wire, it can be trained along the wire and then down another string suspended from the horizontal wire between the two plants in the row. The stem is then allowed to follow the string downwards to within 18 inches of the bed. It is then trained back up the original string with the stem forming a circle. Remove old leaves on the older part of the stem ahead of the developing stem terminal.

ادامه مطلب

پنجشنبه 29 دی 1390

Tomato

نویسنده: مهندس علیرضا شعاعی   طبقه بندی: گلخانه، 


Planting

One or two tomato crops can be planted in the greenhouse during the year. Planting, transplanting, and harvest dates will vary depending on location. As most tomato varieties will begin to ripen 100 days after planting, seed should be planted so the fruit begin to ripen soon after first frost for fall crops.

In cooler areas of New Mexico, tomato crops are generally planted in early July and transplanted to greenhouse beds in mid-August. Harvest will begin in October and may continue until early March. Harvesting may be terminated at an earlier date if heating costs become extreme. Late spring harvest can be accomplished by delaying planting until late fall or early winter. Planting dates in southern New Mexico should be delayed until mid-August or later due to hot weather in mid-summer.

Plants are best started in individual containers (plastic pots, peat pots, or cubes) to reduce labor costs and reduce transplanting shock. Use of commercial sterile potting mixes will decrease the incidence of seedling disease problems. Custom soil mixes can be used, but must be pasteurized to eliminate insects, diseases, and weed seed. Heating the moist soil mixture to a temperature of 160°F for 30 minutes will kill most pests.

Sow two to three seeds per pot (1/4-inch deep) and water. Then cover pots with clear polyethylene and place in the shade (70°F) until seedlings emerge. Plastic should then be removed and the pots moved into full sun. Thin the seedlings to one plant per pot.

If possible, seedlings should be grown at daytime temperatures of 58-60°F (nighttime 52-56°F) for the first 10-14 days. This initial cold treatment should help seedlings develop larger cotyledons and thicker stems. Plants should also set more early fruit, increasing both early and total yields. Thereafter a daytime temperature of 70-75°F (nighttime 60-62°F) should be maintained. After the initial cold treatment, temperatures should not fall below 55°F, which may cause rough, irregularly shaped fruit and stunted plant growth. Temperatures can be reduced slightly during cloudy days.

Irrigation water may have to be heated in the winter before use. Water less than 50°F will chill the roots, causing poor growth. Plants should be fertilized weekly with a starter solution (1/2 ounce of 21-53-0 per gallon of water) in the irrigation water. As plants become larger, feeding can be increased to twice a week.

Transplants should be established in the ground beds approximately four to six weeks after seeding. Set transplants in the soil 1 inch deeper than previously grown. Space plants 15-18 inches apart in rows 3-3.5 feet wide. Water immediately after transplanting.
Training
Plants should be trained as single (main) stems by removing all side shoots or suckers that develop between leaf petioles and the stems. Remove shoots by snapping them off, not cutting, as diseases can be transmitted on the knife blade. Vines can be supported by plastic or binder twine loosely anchored around the base of the plants (non-slip loop) and to overhead support wires (11- to 12-gauge) running the length of the row. Overhead wires should be at least 7 feet above the surface of the bed and be firmly anchored to support structures.

Twine should be wrapped clockwise around the vine as it develops, with one complete swirl every three leaves. The vine should be supported by the twine under the leaves, not the stems of the fruit clusters. Also wrap twine in the same direction, using clips or tape to keep vines from slipping down the twine. Do not try to wrap the twine around the growing tip because the tip may break.

ادامه مطلب

پنجشنبه 29 دی 1390

Greenhouse Vegetable Production

نویسنده: مهندس علیرضا شعاعی   طبقه بندی: گلخانه، 



Greenhouse vegetable production has traditionally been located near population centers, primarily in the northeastern United States. Improved transportation and high energy costs have forced the industry south. With light being one of the most important factors in greenhouse vegetable production, the Southwest has become an ideal area for future development of this industry, particularly in the winter months when tomato and cucumber prices are at a premium.
Location of Greenhouse

The ideal location for a greenhouse has high winter light intensity, moderate winter temperatures, low humidity, and easy access to markets. The easy availability of existing utilities will help reduce establishment costs and will affect ongoing fuel costs. Avoid trees or buildings that may shade the greenhouse, although windbreaks will help reduce heating costs if properly located. Be sure to leave sufficient room for future expansion and parking.

While superhighways have made transporting greenhouse-grown vegetables easier, locating greenhouse-grown tomatoes near large population areas is still important. High quality tomatoes should be vine ripened; as ripe tomatoes are hard to transport, the closer they are to the retail market the better.

Greenhouses using native soil for vegetable production should be constructed on level sites with deep, well-drained soils. Sandy loams are best. A source of good quality water also is important. High salt concentrations in either the soil or water can significantly reduce yields. Where soils are not suitable, growers may consider bringing in a better soil or using a soil-less production system.
Greenhouse Construction

When considering greenhouse designs, three major factors should be considered: load limitations, light penetration, and cost. The primary load considerations include snow and wind. Roof slopes of at least 28° and heated air in the greenhouse should prevent snow accumulation on the roof. Bracing along sides of the greenhouse and roof should be sufficient to withstand wind, particularly in the spring. Bracing along the roof also should be sufficient to withstand crop loads if tomato or cucumber vines are to be supported by twine attached to the bracing. A concrete footing is preferred for a permanent greenhouse. A wide door at one end of the greenhouse will ensure easy access for equipment.

Without sacrificing strength, support structures should be kept to a minimum to maximize light penetration. Glazing materials should be highly transparent. Overhead electrical lines, irrigation systems, and heating ducts should be kept to a minimum. Support structures should be painted with a reflective, light-colored material for maximum light reflection.

Most greenhouse crops grow best in light whose wavelengths range from 400 to 700 nanometers. This range of wavelengths is called photosynthetically active radiation (PAR). Most greenhouse coverings will accommodate these short waves of visible light. Polyethylene and fiberglass tend to scatter light, while acrylic and polycarbonate tend to allow radiation to pass through directly. Scattered or diffused light tends to benefit plants by reducing excess light on upper leaves and increasing reflected light to lower leaves.

Plastic glazed greenhouses have several advantages over glass greenhouses, the main advantage being cost. Plastic also is adapted to various greenhouse designs, generally resistant to breakage, lightweight, and relatively easy to apply.
Types of Plastic Coverings
Acrylic is resistant to weathering and breakage and is very transparent. Its ultra-violet radiation absorption rate is higher than glass. Double-layer acrylic transmits about 83 percent of light and reduces heat loss 20-40 percent over single-layer. This material does not yellow. Its disadvantages are that it is flammable, very expensive, and easily scratched.
Polycarbonate resists impact better and is more flexible, thinner, and less expensive than acrylic. Double-layer polycarbonate transmits about 75-80 percent of light and reduces heat loss 40 percent over single-layer. This material scratches easily, has a high expansion/contraction rate, and starts turning yellow and losing transparency within a year (although new varieties with UV inhibitors don't yellow as quickly).
Fiberglass reinforced polyester (FRP) panels are durable, attractive, and moderately priced. Compared to glass, FRP panels are more resistant to impact, transmit slightly less light, and weathering over time reduces light transmission. This plastic is easy to cut and comes in corrugated or flat panels. It provides superior weatherability only when coated with Tedlar. Fiberglass has a high expansion/contraction rate.
Polyethylene film is inexpensive but temporary, less attractive, and requires more maintenance than other plastics. It is easily destroyed by ultraviolet radiation (UV) from the sun, although film treated with UV inhibitors will last 12-24 months longer than untreated. Because it comes in wider sheets it requires fewer structural framing members for support, resulting in greater light transmission. Using a double layer of 6 mil polyethylene on the outside and 2 mil as an inner barrier will help conserve heat; this inner layer also will help reduce water condensation. The inner layer should be 1-4 inches from the outside layer with layers kept separated by a small fan (creating an insulating dead air space) or wood spacers. Two layers reduce heat loss 30-40 percent and transmit 75-87 percent of available light when new.
Polyvinyl chloride film has very high emissivity for long-wave radiation, which creates slightly higher air temperatures in the greenhouse at night. UV inhibitors can increase the life of the film. It is more expensive than polyethylene film and tends to accumulate dirt, which must be washed off in winter for better light transmission.

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