Greenhouse Construction In Kenya

Greenhouse construction in Kenya for your crop is a key consideration in commercial greenhouse farming. The right structure guarantees yield, efficiency, and profitability.

Grekkon Limited makes daily field visits to farmers in Kenya training them on how to construct a greenhouse. Below, we share our key considerations when we visit grow

How many greenhouses per acre?

An acre can either be 4,048 meters square, or 4,900 meters square. In the former, the dimensions are 63.6M x 63.3M. So, assuming that each greenhouse unit is 63M long, and 8M wide, these are 8 units with a total area of 504 meters square. In the latter, assuming that each greenhouse unit is 70M long, and 8M wide, these are also 8 units, with a total area of 560 meters square

Co-joined vented type greenhouses

Greenhouse Construction In Kenya

There are 3 key considerations:

I. Budget

• A galvanized steel greenhouse lasts longer and is more expensive than an aluminum paint coated one
• The steel internal cop support structure makes it costly but provides good mature crop support

Cost of a greenhouse in Kenya

These are greenhouse construction in Kenya prices for galvanised metallic greenhouse tunnel type structures with a 1,000L tank, and a full irrigation system. Note that it does not include the internal steel crops support structure. This price includes all greenhouse materials

C. Large
From 800M square. Kes 850 per meter square. We customise our price according to size, and your greenhouse budget

These are prices for a various types of wooden greenhouse vented type structure

How To Construct Timber Greenhouses

i. Know the crop type to plant. This will guide on the greenhouse design and amount of material to use. For instance, a tomato greenhouse will take more material than one with herbs. This is because tomato will require training, and herbs won’t. It also guides on the greenhouse paper to cover with. You will have more light for fruiting crops like tomato, capsicum, chilli, cucumber, and strawberry, or bi/ multicolored flowers. Have a clear polythene for these. Mono-color flowers will have the yellow polythene cover

ii. Determine the plant population you need. This informs the area of the greenhouse

iii. Once you determine the amount of timber required based on the greenhouse area, treat it. This is to prevent weevils and termites from attacking the timber which reduces it’s lifespan. Do not apply motor oil on the timber as treatment. This is because it will contaminate food crops in the greenhouse

iv. Your construction design is the vented type. This is because, the tunnel type design is only possible with steel greenhouses

v. Cover the roof and side ventilation with an insect net. Select the high density gauge which is effective in keeping away white-flies

vi. Make the beds according to the crop type. Beds are important in managing drainage. For seedling production, set up the tables 1M high

vii. Set up the drip irrigation system on the beds. For seedling production, set up he misting or fogging system above. The misters or foggers are 1M apart

A wooden greenhouse by Grekkon Limited

II. Location

In the cool highlands, build a tunnel type to retain heat during the cold nights. In the warm lowlands, construct the vented type to moderately high temperatures during the day.

Vented type greenhouse is more expensive than tunnel types

III. Crop type

Mono color roses or other mono-color flowers will have yellow polythene covering. Multi-color flower crops and vegetables will have a clear polythene cover

Steps on greenhouse construction in Kenya

i. Choose your greenhouse size according to your budget

ii. Select your greenhouse type according to location

iii. Choose your polythene color according to your crop type

iv. Level the area where your greenhouse will stand

v. The 2 longer sides of the greenhouse will face eastwards and westwards. However, consider the wind direction too

vi. In the tropics, your greenhouse will be 5 meters tall or higher

Seedlings propagation in a greenhouse

Basic ‘Must Haves’ Treatments of a Greenhouse Polythene in Kenya

• It will be treated with anti-ultra violet (anti-UV) block to prevent the harmful UV sun rays from causing damage to the paper. Greenhouse polythene is made from polymers which photo-degrade easily under UV light exposure. The greenhouse paper changes color (yellowing), cracks, chalks on the surface which impairs transparency, and will have lower mechanical properties. Anti-UV treated paper lasts for a minimum of 36 months before replacement as a greenhouse cover. Without the treatment, the usable lifespan under equatorial climate is a few months. UV treatment reduces insect pest attacks such as; white flies, thrips, and aphids by making them less active. It controls some fungal diseases, thereby reducing overall pesticide application

Farmers growing crops that need external pollinators such as bees are advised to get a film that allows part of the UV light in. This is because these bees need it to move about

An illustration of UV damage on untreated polythene sheet over a 3 week period

• Anti-drip treatment. This prevents moisture condensation on the paper especially in the morning, otherwise known as ‘dew’. Dew droplets cause fungal disease growth when they fall on the crops leaf’s surface. In a solar dryer, dew on dried produce causes molding

Dew droplets on greenhouse crop foliage encourage formation of fungal diseases

How To Select The Right Greenhouse Cover For Your Crop

1. Crop type

Different crop types have different light requirements

1.1. Fruiting type. Tomato, pepper, strawberry, cucumber require more light to make food to support fruiting. Have a clear polythene greenhouse cover for more light

1.2. Vegetative crops. Leafy vegetables, herbs and spices will produce well in less light than in 1.1. above. Clear or yellow polythene works

1.2. Mono color flowers. Yellow polythene intensifies petal color for mono color roses and other flowers. This increases their marketability

1.4. Bi or multi color flowers. Construct with clear polythene for with this crop

Clear greenhouse polythene

Yellow greenhouse polythene

2. Disease incidence

Crops such as; tomato, pepper, strawberry, cucumber, roses, carnations, chrysanthemums and many others are susceptible to blight. This is when moisture remains on their leaves. For such, your greenhouse polythene sheet will have anti-drip treatment. Anti drip treatment prevents dew droplets from forming on the paper when moisture condenses. These drops cause fungal infections when they drip on the leaf surface of the crop. Anti-drip treatment is available for both clear and yellow paper types

3. Budget

The anti-drip treated greenhouse polythene paper more expensive. However, it saves the grower more money, as a result of less fungicide application

The paper choice applies to any greenhouse structure; wooden or steel. This is true also for any greenhouse size

How to Choose Greenhouse Nets

Greenhouse nets allow for ventilation of the crops, and personnel working in the unit. Below are the consideration made when deciding the choice of greenhouse net to install on the sides

1. Crop type. Some crop types require higher light intensity than others. In this case, a lower shade % net is appropriate for the former. Fruiting crops such as; tomato, strawberry, capsicums, and so on require more light than leafy vegetables. Examples are; cabbage, spinach, collards, kale etc.

2. Crop stage of growth. The shade net in the nursery will block out more heat, than the one for established crops in the field

3. Location of the farm. In the highlands where the heat intensity is less, a lower shade net will protect crops well. In the mid to low altitudes where it’s hotter, a higher shade net works best.

4. Latitude. Countries such as Kenya lie along the equator where solar radiation is high. Your choice of greenhouse net will have higher UV treatment than that of a temperate region

Greenhouse Construction In Kenya FAQs

a. What materials are needed to build a greenhouse?

• UV treated greenhouse polythene
• Steel pipes
• Insect netting
• Profiles and wires

b. Can I grow year-round in a greenhouse?

Yes because the crop is protected from the elements of weather

c. Do greenhouses make money?

Yes they do with a high-value crop

Growing herbs and spices in a wooden greenhouse