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Five key areas to look out for in a greenhouse

By George Mbakaya
For a healthy crop, good ventilation is critical in maintaining an optimal growing environment and improves the overall efficiency of a greenhouse. [File, Standard]

In spite of the advantages of greenhouse farming, many farmers face a lot of challenges. But, doing things differently can make greenhouse farming a likable venture.

Growing media

Soils are not recommended for production of plants in greenhouse because they do not provide the aeration, drainage and water holding capacity required. They also need to be pasteurised or fumigated to prevent development of diseases and germination of weed seeds. It is advisable to plant transplants in a variety of soilless ingredients such as peat moss, vermiculite, perlite, shredded coconut husks (coir), or composted materials plus starter nutrients and a wetting agent.

Handling soil

However, if soil is used, it must be treated to eliminate soil borne plant pathogens, insects and weed seeds. Afterwards, care must be taken to avoid re-infestation. Treatment of soil with steam is effective and safe compared to chemical fumigation. Portable steam generators can be used. Ideally, the temperature of the entire soil mass should be raised to 160° to 180°F for 30 minutes. Use several accurate thermometers placed in one or more corners and in the centre of the soil mass.

Water quality

Good water quality is also important in growing quality greenhouse crops, yet it is often taken for granted. There are many factors which determine water quality. Among the most important are soluble salts, alkalinity, and the sodium adsorption ratio. But there are other factors to consider, such as whether hard water salts such as calcium and magnesium, heavy metals or individual toxic ions are present. To determine this, water must be tested in a laboratory equipped to test water for irrigation. Poor water quality can lead to slow growth, poor aesthetic quality of the crop and, in some cases, gradual death of plants. High soluble salts can directly injure roots, interfering with water and nutrient uptake. Salts can accumulate in plant leaf margins, causing burning of edges. Water with high alkalinity can adversely affect the pH of the growing medium, interfere with nutrient uptake and cause nutrient deficiencies.

Good ventilation

Good ventilation is critical in maintaining an optimal growing environment and improves the overall efficiency of a greenhouse. It is essential for both good temperature and humidity management. Ventilation is also important for air circulation and replenishing carbon dioxide. Poor air circulation reduces plant activity and can lead to problems with humidity and disease management.

Feed programme

A constant feed programme may also be modified so that nutrients are applied at every other irrigation. This approach may be necessary under conditions of high soluble salts. The balance of plant nutrients is important in producing vigorous, efficient plants. In some cases, when nutrients are out of balance severe deficiencies or toxicities may occur. Therefore, it is important to consider the source and amount of fertiliser used.

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