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Greenhouse vs open field: Which is greener?

By George Mbakahya | May 7th 2016

Many young farmers towing with the idea of starting tomato farming always ask me “should I go the greenhouse way or the open field?” I can confidently, say greenhouse is more superior though it must be adopted with more caution and care. The discussion will therefore focus more on greenhouse technology.

Greenhouse production is often perceived as an artificial process, characterised by low nutritional quality of the final product and the heavy use of chemical inputs. Moreover, large areas covered with greenhouses create a big visual impact. In contrast, open-field cultivation is perceived as an ‘eco-friendly’ activity, and one that has a much smaller visual impact.

Setting aside these ‘apparent’ perceptions of the two cultivation systems, I will dwell on the facts. Growing under greenhouse conditions, instead of an open field, can enhance quality, quadruple production and enable growers cultivate their crop over a longer window of time.

When carried out correctly, it can significantly increase yields over what is possible under open field production. For example, greenhouse tomato yields four to five times more than openfield.
Greenhouse extends your growing season as harvests can last up to eight months compared to one month in the open fields. Any gardener or farmer knows planting crops outside depends wholly on weather patterns and conditions that must be suitable for seeds to take root and thrive. With a greenhouse, many different techniques can be used to keep temperatures stable, causing less stress to the plants and promoting strong growth much earlier in the year. Some popular techniques involve creating thermal solar mass by using natural materials that readily absorb, store and release thermal heat, and using man-made heaters and heating fans.
Expand the variety among your produce by using greenhouse.

As vegetables come in and out of season, prices fluctuate accordingly based on availability, demand, and production methods among many others. Investing in a greenhouse gives your operation the opportunity to provide a variety of different produce on the “off season” creating greater availability for your customers in times of low supply and having the ability to grow new produce or flowers that do not typically thrive in your climate.

Not having to worry about external elements gives you almost complete control to provide the best growing environment for your crops.
Minimise external threats to your crops.

There’s nothing worse than coming out to your newly sprouted seedlings to find that a furry little bunny made a tasty salad out of the dainty leaves that once occupied your defenseless new stems.

While rabbits aren’t the worst of your worries when it comes to your crops, in your greenhouse, you control what comes in and goes out. Besides providing shelter from threatening weather, this control allows you to minimise introduction and spreading of diseases, troublesome varmints waiting to snatch up your delicious greenery and to control temperatures to keep your plants from getting too chilly.

Yield and volume:

Crops from green houses are protected from pests, diseases and other hazards in the open field. The closed nature of the greenhouses reduces the risks of soil borne tomato diseases. For instance, diseases spread when wet soil is splashed onto tomato leaves while it rains (or when using overhead irrigation systems). By use of drip irrigation, the amount of moisture on the tomato leaves, further reducing the risk of fungal tomato diseases that thrive on wet foliage. Pest control is also easier in a greenhouse than with outdoors tomato farming. Birds are a huge nuisance for outdoor tomato farmers this can be minimised through adoption greenhouse.
Minimum water wastage is another advantage of greenhouse. Drip irrigation systems that are mostly preferred in greenhouses have no surface run-off since the water is delivered directly to the root area of the plants. Water is distributed uniformly, which prevents clogging.

Weed management

Management of weeds in the greenhouse is easier, tomatoes grown in small scale greenhouses consume less space but produce more fruits per acre. The planting of tomatoes in a concentrated space makes weeding easier. Moreover, use of drip irrigation denies weeds the water they need to thrive. Good space utilisation in small scale greenhouse farming means there is less distance to cover when tending to your tomatoes. Tomatoes need staking to support the weight of the fruits and to grow upright. It is easier to stake your tomatoes withgreenhouse.

Minimal theft cases

Stealing of farm produce is a big problem in most regions in Kenya and that can be minimised by use of greenhouse. Would-be thieves cannot know when the tomatoes are ripe and ready for harvesting.
The need for pesticides is thus reduced, which lowers costs and risk of harmful residues on the crop.

As a result of this, higher quality produce is possible. For consistent quality, good agricultural practices such as optimal plant population, irrigation, plant nutrition and vigilant crop protection (must still be maintained).

Open field cultivation

Tomatoes grown in the open field are exposed to all insects and diseases in the open environment. Greenhouses are covered with mesh screen to keep most of these pests and diseases they carry, away. However, strict monitoring for breaks in the mesh and proper use of entrance doors, is necessary. The plastic roofing materials also reduce the level of some diseases, by controlling the type of light entering the house.

Notwithstanding these huge benefits, several challenges exist. Ecological, physical and socio-economic conditions call for modifications to this introduced technology. For example, some regions of the country experience higher temperatures. This poses challenges for more appropriate design and construction to reduce heat buildup.
High upfront and operating expenses. In order to utilise a greenhouse to the best of its ability, you’ll need to invest in a kit or supplies that will have a good lifespan and proper characteristics for the plants you want to grow. For example, cheaper film plastics may provide sufficient conditions to retain heat, but more expensive glass windows will last longer and may help ventilate the greenhouse if able to be opened.

With maximum climate control, comes the potential for a high operating cost. If you choose to heat your greenhouse via electronic heaters or by way of gas, you’ll see a serious increase in your monthly bills.
Troublesome pests and lack of pollination.

While having a greenhouse can help you control most of what your plants come in contact with, one or two plants carrying pests like white flies or other diseases can quickly spread to the rest of your plants, sabotaging your entire crop. Careful precautions must be taken to eliminate any pests or diseases to make sure your next crop won’t be affected.
Implementing greenhouse growing can be an excellent investment when carefully planned, built, and maintained, creating the potential for an increase in revenue or a means of saving on your monthly grocery bill. Make sure to research all of your options before committing to one style or method.

The writer is an expert/consultant on agricultural solutions and innovations

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