Horticultural News January - February issue

ONIONS
Onions are important horticultural crops in Kenya. They can be grown for subsistence
or commercial farming. The choice of onion variety matters a lot when it comes to
commercial farming / agribusiness. This is because a farmer has to calculate the input
costs verses the output costs in order to maximize profits.
Open Pollinated Varieties are normally grown for subsistence and small scale farming.
For instance, Onion Red Creole, Bombay Red and Texas Grano. The choice of variety
depends on the farmers’ market preference. i.e. On the other hand, Hybrid onion
varieties are good for commercial / large scale farming. This is because of their high
yield returns.
New hybrid varieties have been released and are recorded to produce very high yielding
and quality onions.
These onions are Red Passion F1 and Red Nice F1.
Insect pests
Important insect pests that attack onions include; Thrips, Whiteflies and Aphids and
would require insecticide applications. Thrips are more severe in dry seasons. Hence one
should keep the plants well irrigated at such seasons. One can reduce pests’ populations
by pulling out weeds since they act as alternate hosts for the pests. Chemical applications
can also be made i.e. insecticide. Plants extracts have also been used and prove to be
effective. I.e. Neem and Garlic extracts. These are sprayed on attacked plant parts. The
plants extracts should be tested for phytotoxicity before any applications are made.
Chemical Applications
Fungicides; this can be classified as curative or protective fungicides. Protective
fungicides are chemicals which have the Active Ingredient Mancozeb e.g Milithane,
Oshothane, Dithane, e.t.c. This is applied when weather conditions would likely to favor
development of the disease. Curative fungicides are applied to plants that are already
infected by the fungal diseases e.g. Pink Rot, Purple blotch and blights (early & late
blight). In this case, applications are made on the infected regions i.e. bulbs, stems.
Foliar feeds;
This is applied mainly at the vegetative stage of the plant especially foliar high in
Nitrogen. Foliar feeds applications results in vigorous growth of plants. In onions, a
balance foliar feed enhances bulb formation and hence quality grade onions. Example
of a balanced foliar feed is Omex, Mastargro. A Calcium spray makes bulb compact. This
is because Calcium is crucial for structural development of the bulbs as the cell wall
gets tightened such that the fungal spores ( sporangia) don’t penetrate easily; hence
improving its tolerance to diseases.. An example of calcium spray is Citicalmag.
Harvesting
Harvesting can be done as from 90 to 150 days after sowing. The onions are ready for
harvest when the leaves collapse. The necks can be twisted and its leaves bent over and
left to dry for 10 to 12 days or less depending on whether conditions. The crop is pulled
out by hand and kept for some days in the field with bulbs covered with leaves. This is
called windowing/curing process. Leaves are then cut off and the mature bulbs stored.
Nutritional value of onions.
High in Niacin; It promotes good digestive system, healthy skin and nerves. It is also
important for converting calories from protein, fat and carbohydrates into energy
through the effect of Niacin.
It also contains a vegetable hormone-glycoqune that gives onion effects on reducing
blood sugar. The hormone stimulate gastrointestinal juices hence promoting digestion.
Rich in Flavonoids; blocks the oxidation of fat in the blood hence prevent hypertension,
improve blood circulation and prevent cardiac problems.
RED CREOLE
• A purple red onion.
• Flat round/ rounded squat in shape.
• Easy to manage.
• Yield ; 6000- 7000kg/acre.
TEXAS GRANO
• Straw coloured outer skin and white
inner flesh.
• Mild tasting. Ideal for salads.
• Easy to grow and widely adapted.
• Yield ; 6000-7000kg/acre.
BOMBAY RED
• Deep red onion.
• Globular in shape.
• Provides good grade onions.
• Its neck dries/cures well.
• Yield ; 6.000 - 7,000kg/acre.
RED PASSION F1
• Deep red hybrid onion.
• Very good drying and keeping quality.
• Tolerant to Pink Rot and Purple blotch diseases.
• Produces good grade onions.
• Less incidences of splitting/sprouting.
• Uniform and early maturity.
• Easy to manage.
• Can store for upto 6 months.
• Has good cooking qualities/ very pungent.
Yield ; 15 - 22,000kg/acre
H O R T I C U LT U R A L N E W S I j a n u a r y - F E B r u a r y 2 0 1 2 11