Types of Greenhouses
1. Post and Rafter Greenhouse
2. Quonset
3. Gothic
4. A-frame
Material options for greenhoause Framework
Aluminium, Steel, plastic,wood, combination
Site selection for the technology
- Flat to Gently sloping
- Adequate lighting from the sun
- Accessible and reliable water source
- Well drained site
- Stable and workable soils/use tubes where the situation is not practical
- Safe from lines of strong winds
- Access to source of heat in the temperate zones
- Proximity to storage/processing area
Greenhouse design Considerations
- Accessibility to cost effective materials
- Ability to achieve optimum temperatures
- Structural stability-shape,height, length, width,footing and wind,
- Roof drainage- slant slope 22-28 degrees
- Air circulation-10% of wall area is left for netting
- Desired flexibility in crops to be grown
- Expected level of mechanization
Materials for Greenhouse Covers
1. Plastic films-clear or green/yellow
2. Glass
3. Fibre glass
4. Rigid double wall plastics
Note:The
polythene covers scatter light(diffuse)which is beneficial to the upper
leaves .The polythene cover is also cost effective to the small scale
farmer compared to all other covers for the technology.
Green House Farming Technology
This technology is widely practiced in Israel, due to scarcity of water and land aiming at increasing the incomes of
rural households. In most African countries adoption of Greenhouse
farming is in the initial stages, and it is increasingly becoming
popular. This technology has several benefits as below:-
- The system increases agricultural output
- Economizes on space
- Saves irrigation water
- Improves farming income
- Improves food security
- The technology reduces crop pest and diseases incidences
- Allows growing of crops not suited to the region due to climate modification.
When operated correctly a greenhouse can give fresh produce throughout the year regardless of the season. The capacity to carefully control the temperature and humidity are important advantages of this farming system. Greenhouse system enables the use of modern technology such as hydroponics which involves growing plants in soil-less media, in a liquid which can be water infused with specialized nutrient mixes. This allows plants to grow larger and faster than normal, helping to maximize efficiency. The main disadvantage of greenhouse farming is high cost of buildings construction and maintenance, which in Africa and developing countries can be addressed by organizing smallholders into green house farming groups, in order to pool resources.
While this technology offers numerous advantages,
proper techniques are necessary to avoid the pitfalls of the
technology. If you manage your project well all the year round, you'll
need to prepare for the hazards of each season.
In hot season cross-ventilation system is required. Passive ventilation
with exhaust openings cut both high and low on the walls may provide
sufficient air circulation for small structures. However, some
greenhouses require a system of fans to keep the air circulating during
the hot season due to high temperatures.
In cool weather the circulation will be unnecessary in most cases. Soil fertility management practices are vital and they include crop rotation, regular application of compost, mulching, leaving the soil fallow to improve and maintain fertility. Apply fertilizers according to the soil requirements and the crops to be grown following soil analysis report. Fumigation or entire change of soil may be required before planting to clear crop pests and diseases. Fumigation involves saturating the greenhouse soil with pesticides like Dioxysan which releases fumes of Chlorine dioxide, (CL2) to control soil pest and diseases. In conclusion this is a farming technology whose time is ripe in Kenya.
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