Kisii University farm manager Peter Ondieki inspects tomatoes at the institution's wooden greenhouse demonstration farm at the Kisii Agricultural Society of Kenya Show Ground on July 15, 2016. Crop rotation in greenhouse farming quadruples yields. PHOTO BY LABAN ROBERT

Greenhouse crop rotation can help farmers utilise nutrients better besides raising crop yields by more than four times as compared to open field cultivation.

Harvests drop season after season when farmers repeatedly grow greenhouse’s commonest crops from the same family due to susceptibility to similar diseases and demand for same nutrients.

Tomatoes, capsicum, cucumber, pepper, are among the crops farmers prefer growing in greenhouse; they are in the solanaceae family.

But Embu County farmer Raphael Ngari has found out that intercropping with other vegetables such as spinach and kales can earn farmers profits by four-fold.

After harvesting capsicum and tomatoes from his 8m by 30m greenhouse, Ngari in October 2016 earned a gross income of Sh75,000 after selling 3,400kg from 1,000 bushes of spinach. Spinach is from the amaranthaceae family.

A similar population of the spinach in an open field had yielded 700kg, more than four times less than the greenhouse harvest.

“Greenhouses allow for micromanagement of climatic conditions in production. But rotation ensures utilisation of resources that were not used by the previous crop. Fruits have different mineral requirements from leaves-harvested crops,” the farmer, who is also an agronomist and a wooden greenhouse constructor, said.

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Greenhouses also protect crops against harsh weather condition like strong wind and UV rays from the sun.

Excessive rain leeches nutrients even before use by the crops, while strong wind causes withering due to high transpiration rates.

Ngari helps farmer set up affordable wooden greenhouses, besides offering free agronomic support up to the end of the first growing season.

A complete 8m by 30m kit costs Sh210,000 while that of 8m by 15m requires Sh135,000.

The 8m by 30m metalic greenhouse costs more than Sh300,000 in other agribusiness companies.

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The farmer’s desired starting crop, pesticides, folia and granular fertilisers, and complete drip irrigation equipment are included in the cost of the kit.

The 8m by 30m and 8m by 15m kits are accompanied by 1,000 litres and 500 litres water tanks for the drip irrigation.

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In helping farmers raise healthy crops, the farmer samples soils for laboratory testing to determine the nutrients content as well as the possible infections like bacteria wilt.

Although the skeleton is wooden, Ngari uses treated posts, which he also wraps with a 200 microns polythene sheet after treating them for durability.  His greenhouses last for at least five years.

Ngari can be reached on +254723387656.