kari mini-greenhouse ups yields by 2x to 6x
By Farmbiz | Thu 01 Mar, 2012

A door has been opened for small-scale farmers to farm all year round and maximize their yield, while using less farming space and pesticides, with the launch of a miniaturised green house developed by the Kenya Agricultural Research Institute (KARI).

Greenhouses have long been an icon of Kenya’s large-scale large scale horticultural and flowering companies. But the new model is set to bring the technology to urban and peri-urban users with some space to farm. “We found the need to tap the technology to help small-scale farmers,” said Paul Kahiga an Agricultural Engineer at KARI.

The country’s recent history of drastic climate changes, from drought to downpour, also drove the initiative to ensure farming continues in spite of the weather.

The more expensive and longer lasting small-scale metallic greenhouse mirrors the commercial ones and measures 8 by 15 metres, while the greenhouse made from locally sourced materials, including wood, net and polythene, measures 6 by 15 metres, but will only last for 4 or 5 years.

In an 8 by 15 metres greenhouse, a farmer can plant approximately 600 tomato plants.  Kahiga advises planting high value crops like Anna F1, money Maker, Marglobe tomato species, lettuce, cucumbers and the pepper dubbed “pilipili hoho”.

The controlled climate in the greenhouses delivers high yield and uniform maturity, with over 90 percent of yield guaranteed year round according to a Horticultural Development Authority report.

In rainy or cold seasons, crops grown in the open are vulnerable to destruction and pest attacks, leading to low yields for tomatoes, which can yield can be less than 10kg per plant in a whole season. However those grown in greenhouses like Anna F1 or Money Maker a farmer can harvest in a single plant 15kg to 20kg in the first harvest and by the time the plant completes its roughly one year full cycle it could have yielded 60kgs.

With the right conditions, maturity is also shorter. Greenhouse tomatoes can mature in two months while the minimum time taken for those farmed outdoors is three months. The quality of the crop after picking is better too, with greenhouse tomatoes enjoying 21 shelf life days compared to 14 for those grown in the open.

Depending on the demand in the market, a farmer can make from Sh40 a kilogram for the Anna F1 tomato variety. This minimum would see the investment in teh greenhouse paid for within 8 months.

When installing the greenhouses, they are built parallel to the wind direction to ensure plants inside are not ruined by rough winds. The outside has a translucent roll up polythene and the inside is padded with a net. The net, wards off pests or birds that can destroy the crop.

Kahiga advises that temperatures in the greenhouses range from 21 to 29 degrees, ideal for tropical crops. To regulate the temperature to that range the polythene is either rolled up when it’s too hot, or rolled down in cold spells.

But humidity must be kept under control. High humidity can lead to outbreaks of diseases and pests like germination of spores of powdery mildew, while low humidity can lead to dehydration.

For the crops growing in the greenhouse drip irrigation is recommended for watering. In addition to saving 50 percent or more of water, it’s cost effective to invest in and further aids yield. Soluble fertilizers can be distributed to each crop through the drip, disease is lower because the leaves are not directly watered, and the drip makes for uniformity of growth.   

The KARI-designed standard 6 by 15 metre greenhouses made from locally sourced materials costs around Sh46, 000 to construct. The metallic ones cost Sh140,000.

The lowest costing drip irrigation kit available from the Kenya Rainwater Association (KRA) costs Sh1750 and can water an area of 15 to 20 metres squared. The emitters’ drips have a spacing of 15cm to 30cm, connected to bucket of 20 litres.

The drip C can save up to 10 times the water used in other irrigation methods.

For More Information Contact or visit the Irrigation, Drainage and Problem Soils Research Programme at the National Agricultural Research Laboratories, Waiyaki Way, Nairobi. Tel: 4444250. Email; irrigation@iconnect.co.ke

Contact for greenhouse designs: Mathaiya Kahiga 0720-578636

Written By James Karuga for African Laughter

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