Since many growers of greenhouse lettuce also plant other crops, they should consider the requirements of these crops in planning the cons...
Since many growers of greenhouse lettuce also plant other crops, they should consider the requirements of these crops in planning the construction of new greenhouses. Lettuce, tomatoes, and cucumbers are important vegetable-forcing crops, and many growers plant all three at different seasons.
Since lettuce is grown chiefly during the winter, when the days are short and there are many hours of dull, cloudy weather, it is important that greenhouses be constructed so as to afford the maximum of light.
It is important that the temperature be properly controlled and that drafts be reduced to the minimum consistent with good ventilation. Efficient heating equipment is essential.
Some important points to be considered in selecting a location for a vegetable-forcing greenhouse include
1) nearness to market,
2) availability and cost of labor,
3) supply and cost of fuel
4) soil suitable for the crops to be grown
5) water supply, and
6) freedom from smoke and fumes from industrial plants
The type of lettuce grown in greenhouses is not very well adapted for long-distance shipment as the hard-headed type grown in the field. It tends to wilt quickly unless it is kept moist and cool. The delicacy of the product makes it imperative that the crops be grown fairly near the market
Labor is a major item in the cost of almost all commodities, agricultural as well as industrial Capable, well-trained help is often diff,-cult to obtain. The available labor supply should be kept in mind in selecting a location for a vegetable greenhouse.
The cost of fuel has always been a large item of expense in greenhouse maintenance, and it has risen sharply in recent years. Soft coal was historically the chief source of fuel for greenhouse heating, but oil, gas, and now solar are more modern alternatives.
Although the sod used in greenhouses can be made to suit the crop to be grown by adding fertilizer organic matter lime, and other soil amendments, it is highly desirable that the range be located where the soil is naturally suitable for the crops to be grown. The lighter types of soil are preferred for greenhouse-vegetable production.
There should be an adequate and constant supply of water free of materials that may be toxic to plants or that may corrode the heating system. Highly chlorinated water is not desirable. Avoid a high concentration of salts.
Smoke from industrial plants reduces light intensity through its presence in the air and form a film on the glass, which greatly reduces the intensity of the light that reaches the plants. Avoid reducing the light of dull winter days by smoke or fumes. Do not locate greenhouses near industrial plants because of the smoke and also the fumes, which may be toxic to certain plants.
Most of the newer greenhouses built for growing lettuce are evenspan structures of steel, aluminum, or steel and aluminum. Wood is used much less than in the past. Although the original cost of wood construction may be low, the upkeep in painting, glazing and other repairs over a period of years adds greatly to the total cost.
Lettuce can be grown in almost any type of greenhouse in which the lighting is good, except the lean-to type, which is not suitable for commercial lettuce growing.
The ridge-and-furrow type of construction is widely used to enclose a large area under one roof. This kind of structure permits an almost unlimited area to be enclosed with a minimum of obstruction to interfere with cultural operations and the entrance of light.
Large even-span metal-frame greenhouses are being widely used for vegetable forcing. The use of steel and aluminum in the framework adds greatly to the strength and life of these greenhouses, and they afford better lighting than the old-style wood-frame buildings.
Most greenhouse lettuce is grown on ground beds. In large ranges, the entire greenhouse floor is fertilized, plowed, and tilled in much the same manner as a Held.
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