GREENHOUSE ONIONS FARMING IN KENYA

Greenhouse onion farming is the current method of growing onions in enclosed polythene sheeting structure. Generally, onions farming are best recommended to be done in the green houses. Greenhouse provides good climate and conditions necessary for the growth of onions.

THE BENEFITS OF GROWING ONION CROPS IN A GREENHOUSE

Over time, farmers have come to realize that there are plenty of benefits of growing plants in a greenhouse, especially with the uncertainty in climate change lately.

However, before you carry out your greenhouse farming in Kenya, you have to conduct adequate research to ensure that you will reap some of the following benefits.

1. A greenhouse delivers an extended growing season
2. There are consistency and reliability in food production
3. You can plant a variety of crops in a greenhouse
4. It allows you to control the growth environment, humidity levels, and soil easily
5. A greenhouse makes it easy for you to control insect and animal infestation

 Factors to consider for greenhouse onion farming

1. The variety of the onion crop.
2. The climatic conditions of the onions.
3. Agronomist practices required by onions.
4. Irrigation method.
5. Availability of the market.
6. Pests and disease management

1. The variety of onions

The variety of onions depends mainly on the type of climatic and the soil factors. The commonly used varieties may include;

• Super Yali for lowland regions
• Neptune F1 variety
• Bombay red.
• Red coach F1
• Russet F1

Quantifying onion seed for greenhouse onion farming

Quantifying seed required for planting depends on land availability by the farmer. The standard seed required by a greenhouse of 8 meters by 30 meters is approximately 250mg.  This quantity is good enough to plants six beds of one meter each with a running length of 30 meters.

The numbers of seedlings that can accommodate in a single bay of a greenhouse is roughly 50,000 seedlings thus the 3 months output in terms of kilogram are 3000kgs-5000kgs. These kilograms when translated into Kenyan shillings per kilograms comes to about ksh150, 000 to ksh250, 000

Irrigation methods of greenhouse onion farming

1. Drip irrigation system

The commonly used method of irrigation of onion farming is the drip irrigation. Drip irrigation system commonly used for onion farming are drip line of 10 centimetres, 15 centimetres and 20 centimetres.

These spacing dictate the onion spacing along the rows and the column. The GAP ( Good Agricultural Practices) in Kenya recommends these spacing from plant to plant and 30 centimetres from one line to another.

Benefits of best drip irrigation system

• The drip irrigation system is the most efficient method of irrigation. Through emitters, water is directly delivered to the plant root zone hence economical on water usage.
• In the best drip irrigation system, there is a constant benefit of water supply in small quantities to the plants. This creates an ideal moist condition for proper growth of most plants.
• The best drip irrigation system minimizes weed growth since water is only supplied to a particular crop root.
• The best drip irrigation system helps in the control of fungal diseases which grow very fast under moist conditions.
• Timeliness and labor-saving. In the best drip irrigation system, the control valves can be managed by one personnel. One person operates the whole system thus minimizing the labor costs. This minimizes production cost.
• Ease in fertilizer application. , method of liquid fertilizer application (Fertigation) is very easy and fast. Since water emitters are used to directly distribute fertilizers to particular crop/plants

2. Over head irrigation system

For large greenhouses the onion farming can be done by over head irrigation system. The commonly used method of irrigation is the sprinkler irrigation system is yet another common irrigation system that you could install on your farm to compensate for the low rains that Kenya has been experiencing for quite some time. Actually, a sprinkler irrigation system can be termed to be the opposite of a drip irrigation system.

This type of irrigation system, supplies water from an overhead position. The sprinklers rotate, distributing water to the plants on your farm from above. However, rest assured that you will find a variety of sprinkler irrigation systems from major irrigation equipment suppliers in Kenya.

Sprinkler irrigation system is used for many crops like maize, beans, vegetables like onions and other types of plants that require much water on different types of soils in various types of land slopes.

The system is best suitable for irrigating sandy soils at different slopes. This is because sandy soils have high filtration rates thus much water is needed to irrigate the land.

Sprinkler irrigation  system is best suitable for shallow soils that do not require proper leveling, areas with steep slopes with high washing of soil .i.e. erosion and high valued crops.

• Disease and pest management and agronomy practices

Thrips are tiny insects that have onions as most preferred host crop on hot and dry weather conditions. They feed by sucking the plant sap hence opening the onions to attack by diseases like purple blotch.

They mostly cause great damage to younger onions when bulbs are forming than older ones hence control measures should be undertaken during early stages of growth. Thrips can cause economic loss by reducing yields by up to 60% if not controlled timely.

Symptoms:

They cause silvery streaks or patches on the leaves while severe infestation and feeding can result in minute black “tar” like sports on leaves.

Younger plant leaves show brown tips and eventually a white color as a result of feeding by thrips. This reduces ability of plants to make food thus resulting in small undeveloped bulbs.

The presence of thrips can also be indicated by the black dotted patches of thrips fecal materials produced during their feeding on the onion plant.

Cultural/ prevention measures of thrips in green house onion farming

Control of thrips is problematic since they reside in the inner leaves especially during bulb formation.

• Avoid transplanting infected seedlings and if noted discard them appropriately.
• Remove weeds and volunteer onions (those that show up by themselves and were not planted) to avoid infecting healthy ones.
• Scout and monitor field margins to detect early infestation as it start at field edges and margins and take actions to avoid further spreading.
• Scout by sampling at least five plants from different locations in the field. Inspect leaf base and areas under leaf folds for feeding damage and larvae presence. More than 3 thrips per leaf calls for insecticide use.
• Use yellow or while sticky traps to catch adult thrips which will indicate infestation and decide on control method.
• Practice crop rotation by avoiding fields where onions had been planted before or other vulnerable crops like maize.
• Plant resistant or tolerant varieties like Neptune F1, Texas Grano or Red Sanga F1 among others. White onions are more tolerant than red onions.
• Use overhead irrigation as it suppresses thrips population by washing them down.
• Avoid using broad spectrum insecticides to preserve beneficial predators like predaceous mite which feed on thrips and minimize their number.