Factors To Consider For Successful Production In Controlled Environments

Factors To Consider For Successful Production In Controlled Environments

Editor’s Note: This is the first of a two-part series from Merle Jensen, professor emeritus, Plant Science, at the University of Arizona. Part one focuses on marketing, variety selection, location, management, and environmental control. Part two offers pointers on growing systems, pest control, harvest, and more.

Jensen is a speaker at the University of Arizona’s 2015 Greenhouse Crop Production & Engineering Design Short Course, which is slated to be held March 22-27 in Tucson, AZ. 

 

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Growing greenhouse vegetables is one of the most exacting and intensive forms of all agricultural enterprises. Hydroponics, in combination with greenhouses, requires high technology, is capital intensive, and highly productive. For success, a grower must have a clear understanding and knowledge of the following critical factors:

Marketing and Distribution

Most greenhouse crops are of high value, perishable, and must have a market quality advantage over open field production. A thorough knowledge of markets, both national and international, and the ability to produce high-quality products on schedule, preferably year-round, is important.

Merle Jensen

Merle Jensen

Identifying and selecting a market will be key to the success of a greenhouse vegetable operation. One can market direct to the consumer, on or near the location of the greenhouse – either through a store located on the farm or at farm markets near the site of production. Marketing through farm markets is probably the most common in newly established enterprises. One can build a tremendous following if growing procedures produce a quality product over and above any products brought in from long distances.

Today, the consumer places tremendous trust in locally produced vegetables. This buy local phenomenon, along with high-quality products can result in local supermarkets wanting to sell your product as well as featuring the products as locally grown.

Local growers can receive two to three times the price over products coming from long distances, grown in large greenhouses, which are often termed “factory tomatoes” in the tomato world.

Vegetable Type and Variety

Select a reputable seed dealer with a wide selection of high-quality greenhouse vegetable varieties. Make sure the seed dealer can provide knowledge and instruction on cultivation, pest control, and marketing.

The quantities and types of vegetable varieties are offered to the greenhouse industry by seed companies today are absolutely incredible. Tomatoes of all shapes are available, along with peppers and eggplant. Long and short cucumbers with extraordinary flavor are available as well as leafy greens –full head or mini-head lettuces. There are early, mid- and late-season varieties of green leaf, red leaf, green Romaine, Romaine hearts, and green and red butterheads.

Today, a salad mix of many colors, harvested at the baby or immature leaf stage is becoming very popular, as well as a new, innovative, salad mix called Salanova which produces 40% greater yields with better flavor and texture. All of these, along with spinach, kale, sprouts, and microgreens are becoming increasingly popular as are herbs, which are now being grown in pots and sold as edible houseplants.

Location

A good building site is crucial to the function and operation of a greenhouse. The location is greatly dependent on customer access, the availability of good light, and a constant supply of good water.

The site should be free of high winds and unshaded by trees and mountains. The location must have good drainage of surface water and subsurface drainage. It is important to have access to labor, all-weather roads for transport to market, and the availability of dependable and economically efficient energy such as electricity and fuel for heating and mechanical cooling, if needed.

Location is extremely important if you envision direct marketing to the consumer from your farm. If this is the case, make sure your customers have an opportunity to see the produce growing area. It is important that you build near a highway that is well-traveled, especially by city people, but avoid hills or curves, and allow easy access to enter or exit. Another consideration is a location close to populations of medium- to high-income residents.

You should evaluate your market based on how it may be seen by your customers. Know all the laws and regulations regarding the marketing of food products and food services, if a restaurant is to be part of your market. Be aware of any future developments that might have a bearing on your market in the future such as zoning, potential road widening projects, travel counts, and competition.

Management

Excellent management skills in greenhouse production are not enough. A successful manager/grower must have a thorough knowledge of horticulture, plant physiology, growing media, plant pathology and entomology as well as computer and labor relations skills, and the engineering capability to provide an environment best suited for plant growth.

Management must have leadership qualities, be honest, timely, have vision, and treat employees as they wish to be treated. The management must be willing to “pitch in,” no matter what the job, the situation, or occasion.

Greenhouse Design

A greenhouse has basically one purpose and that is to provide and maintain a growing environment that will result in maximum crop yields and quality. In general, there is no one best greenhouse. The structural design must provide protection from wind, rain, heat, cold, insects and diseases. The structural members and covering must permit maximum light transmission to the crop.

If tall, high-wire crops such as tomatoes, peppers, and cucumbers are to be grown, the greenhouse must have a gutter height of 14 to 16 feet to allow plant support cables/wires to be 12 to 14 feet off the greenhouse floor. If high pressure fog/mist cooling systems are used, the system must be 6 feet above the plant support cables so that any moisture from the cooling system evaporates before it reaches the plant canopy; in which case the gutter height will need to be 18 to 20 feet or higher if shade/heat curtains are installed above the cooling system. It is not uncommon for gutter height to be 22 to 24 feet, especially for the Venlo glasshouse designs that have a low peak above the gutter. All structures must be installed with butterfly vents to enable ample cooling.

Environmental Control

High light and temperature control are central to high-quality products. While a greenhouse can be expensive to heat, it can be profitable if high-quality, cost-competitive products are grown.

For example, tomatoes require a temperature range of approximately 60 to 78 degrees F. Greenhouse temperatures lower or higher can greatly hinder optimum growth and fruit quality.

The environmental control system will vary greatly depending on location of the greenhouse. In the Northwestern part of the U.S., roof vents are normally enough to achieve ample summer cooling while in the desert Southwest, both roof vents and evaporative cooling are advisable.

Double roof vents must be used rather than a single vent. A double vent, often termed butterfly, will provide cooling up to 14 to 15 degrees cooler greenhouse temperatures during hot summer days. The efficiency of evaporative cooling will depend on outside humidity levels. Heating is required in all regions of the U.S.

If you are not fully educated on greenhouse environment requirements, be sure to work with a reputable greenhouse supplier and/or consultant. It is absolutely imperative that a correct environmental system be installed in order to achieve high yields and quality products.