Garlic is a high value horticultural crop in the onion family. Farmers in Kenya can be able to grow it and considerably increase their income because garlic has a good local market. It is mainly used as food flavouring and for medicinal purposes. Garlic has anti-feedant (insect stop feeding), bacterial, fungicidal, insecticidal, nematicidal and repellent properties.
Garlic is effective against a wide range of disease-causing pathogens and insects at different stages in their life cycle (egg, larvae, adult). This includes ants, aphids, armyworms, diamondback moth and other caterpillars such as the false codling moth, pulse beetle, whitefly, wireworm, beetle, mice, mites, moles, and termites as well as fungi bacteria and nematodes. Garlic can kill beneficial insects as well. Therefore it should be used with caution.
When growing garlic for pest control, it has been recommended avoiding use of large amounts of fertilizers. This is because heavy doses of fertilizer reduce the concentration of the effective substances in the garlic.
Not common crop
Very few farmers grow garlic mainly due to lack of knowhow and experience on its production. This is one of the reasons for the poor quality of locally produced garlic; another reason is the stiff competition from China. Very often, farmers sell the garlic even before it has matured and cured properly (hanging and drying in controlled light). Exploitation by middlemen is another big problem; farmers who grow garlic rarely sell it directly in the market; they have to rely on brokers.
Garlic can grow well at an altitude of between 500-2000 meters above sea level. The right temperatures for garlic are between 12-24 °C. Extremely high temperatures are not suitable for garlic production. Excess humidity and rainfall interferes with proper garlic development, including bulb formation. The crop is grown in low rainfall areas where irrigation can be practiced, especially in early stages when the plant requires enough water to growth. Adequate sunlight is important for bulb development. Garlic develops its flavour depending on sunlight conditions during growth.
Garlic requires a fertile, well drained, light soil. Clay soils should be avoided since they lead to poor bulb development. Soil pH should be between 5.5 to 6.8. Deep soil cultivation is important to ensure rooting depth. Farmers should seek for advice on the garlic varieties suited to local conditions to ensure they get good yields that meet market requirements.
Garlic is vegetatively propagated. That means that the farmer has to plant individual cloves separated from the main bulb. Very small cloves should not be used. The larger the cloves, the more the space required for planting. The cloves should be planted in upright position. The bulbs intended for use as seed should be stored at 10 ° C and a relative humidity of 50 -56 per cent. Stored bulbs should be fumigated and continuously inspected to ensure they do not rot.
The crop is grown on raised beds or on ridges at a spacing of 30 cm between rows and 15 cm between the plants, giving a plant population of 15,000 to 20,000 per hectare. The normal seed clove requirement is 500-700 kg per hectare. Closer spacing within the rows is possible; but disease risks are also high when garlic is planted too closely; bulb formation is also affected when the cloves are near each other. The cloves should be planted at 2.5 cm deep in well-firmed, but not compacted soils.
Kenyan farmers have devised their own method of determining whether their clove seeds are ready for planting: They cut a cross-section of a clove to see if the inner leaf is developing. Its colour and appearance help them determine if the cloves are ready for planting.
Garlic does well if well-composted manure is ploughed in before planting. Top dressing with liquid manure should be done regularly at the beginning of 6 – 8 weeks and increased during bulb formation. The field should be weed free to ensure garlic does not compete for nutrients with weeds.
The most common diseases are purple blotch, downey mildew, rust and bulb rot (white rot). They can be controlled through long crop rotation, improved drainage and use of copper based fungicides such as copper oxydchloride, which is accepted in organic farming.