Winter Growing & Season Extension

Changes to Greenhouse Crop Production, by Merle Jensen, PhD

Controlled Environment Agriculture (CEA)

Above: US-NSF South Pole Food Growth Chamber, ANTARCTICA
Photos: Courtesy University of Arizona Controlled Environment Agriculture Center (UA-CEAC)

Key Considerations for Beginning & Intermediate Growers

by Merle Jensen, PhD
Professor Emeritus, Plant Life Sciences
Founder, University of Arizona Controlled Environment Agriculture Center (UA-CEAC)
Dramatic Changes in Greenhouse Crop Production

Today, advanced technologies have dramatically increased vegetable, fruit, and flower yields, with a whole new array of varieties available to the greenhouse industry. Growing greenhouse crops is one of the most exacting and intensive forms of all agriculture enterprises. Hydroponics / soilless growing systems, in combination with greenhouses, require high technology, and can be capital intensive and highly productive. For success, a grower must have a clear understanding and 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. This knowledge base, plus management skills in greenhouse vegetable production, is a must.

Greenhouse Design & Environment Control
Large CEAC Greenhouse undergoing maintenance
One of the greenhouses at UA-CEAC, undergoing routine maintenance

Aspiring new growers must seek the correct greenhouse design that will provide and maintain a growing environment that will result in maximum crop yields and quality.

While 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. This, along with excellent temperature control, is central to high-quality products.

Growing Systems
Hydroponic Growing System
Soilless technology + greenhouse structures =
Controlled environment agriculture (CEA)

While growing in soil has been the standard for generations, major challenges with soilborne diseases and the lack of control over mineral nutrition and fruit quality require major changes moving forward.

Hydroponic/soilless technology, in combination with greenhouse structures (better termed controlled environment agriculture) have been developed to provide precise control over air and root temperatures, irrigation, plant nutrition, humidity, carbon dioxide, and even light. Newly available growing media, such as coco coir, are rapidly becoming popular. Today, such growing systems provide little root volume to reduce costs and maximize control over mineral nutrition, root aeration, diseases, and fruit flavor.

Irrigation & Mineral Nutrition
Fertigation workshop at UA-CEAC
Fertigation workshops offered at UA-CEAC address both the basics, as well as more advanced fertigation systems

A technological revolution occurred with the advent of drip irrigation, which offers the only means of applying uniform water and fertilizer to the plant. Such systems have assured maximum yields while conserving fertilizer nutrients, and controlling costs associated not only with fertilizer but also water, labor, and machinery costs.

Fertilizer formulas, while quite similar, will differ according to the crop grown. Today, a whole new and exciting future in mineral nutrition is evolving for growing organic vegetables using systems of growing that are providing remarkable success.

Biological Controls
Integrated pest management
Integrated pest management (IPM)

Today, pests and pathogens are best managed through an approach that is termed integrated pest management (IPM). In general, IPM is a multilayered approach involving the use of biological controls, plant genetics, and cultural practices, as well as chemical inputs, where necessary. Pesticides are avoided if at all possible because they are expensive and will reduce the potential for maximum yields.

A thorough knowledge of all diseases and insects, along with their control, is extremely important if one is to succeed.

Important for New Growers: Location, Location, Location!
Choose your location carefully
Light, water, shade, wind, grade, drainage, labor, transportion, fuel… these factors and more may have a bearing on where you site your growing operation

A good building site is crucial for the proper function and operation of a greenhouse.

A constant supply of good water is imperative, and it must have good drainage of surface water and subsurface drainage. The location should additionally be free of high winds. If natural light is to be the primary source, the availability of good light is critical, and unless you have an overabundance of natural light, the site should also be unshaded by trees and mountains.

One must also have access to good labor and all-weather roads to markets, as well as availability of dependable and economically efficient energy, such as electricity and fuel for heating and mechanical cooling if needed.

Fresh-market flavor speaks volumes
Fresh-market flavor speaks volumes

Greenhouse crops are high in value and perishable, and must have a market quality advantage over imported products coming from long distances, whether it be nationally or internationally.

One must be able to produce high-quality products under a label that indicates the products are Locally Produced. Provenance, together with freshness, visual appeal, aroma, and flavor, constitute an irresistible combination in the marketplace.

Crop Suitability & Seed Quality
Crop variety & quality for protected culture
Select varieties and source your seed with the utmost care

It is extremely important to select a reputable seed dealer that provides a wide selection of greenhouse vegetable varieties of the highest quality — a company that works with seed companies and plant breeders worldwide in the selection of the most suitable varieties for greenhouse vegetable production.

Growers producing fruit and flowers under protected culture must apply the same precaution in sourcing seed and plant material.

Workshops/Continuing Education
Murat Kacira, PhD: sensors & controls
Murat Kacira, PhD, presenting on sensors and controls in CEA

It is important not only for new growers to gain firsthand knowledge on the new technologies of controlled environment agriculture, but for existing growers also to gain up-to-date information on developments that are rapidly changing in today's industry. Companies and growers that don't pay attention to these new developments will have technology pass them by, decreasing their competitive edge.

As communities throughout the world are growing, their access to fresh, affordable, safe food becomes increasingly critical and so, too, does the role of the direct-market grower in association with protected environment agriculture. We encourage continuing education, networking, and hands-on workshops to keep abreast of rapidly advancing developments in this exciting field.

Controlled Environment Agriculture

To learn more, visit the University of Arizona's Controlled Environment Agriculture Center (CEAC). The CEAC hosts a series of short courses consisting of lectures and hands-on workshops that cover the many aspects of controlled environment agriculture (CEA).

Their Greenhouse Crop Production & Engineering Design Short Courses provide a firm knowledge base for beginning and intermediate growers. Participants of the Short Courses are presented the most current and innovative strategies used in developing and maintaining successful CEA greenhouse systems.

As past attendee and Senior Johnny's Trial Tech Andrew Mefferd states:

There is no other school like the University of Arizona, with the combination of research and educational programs in greenhouse growing. In particular, their programs that are open to growers and the public offer a unique opportunity to share their extensive knowledge in the field of controlled environment agriculture.
Learn More about UA-CEAC…

Professor Merle Jensen
Merle Jensen, PhD

Dr. Merle Jensen has served as an academician and consultant to industry for over 40 years, developing agricultural systems for businesses, communities, and aerospace application. He was one of the early pioneers in the development of agricultural plastics for greenhouses and brought one of the first Dutch Venlo glasshouses to the U.S. Early in his career, he did extensive research on tomato viruses and mineral nutrition for both horticultural and agronomic crops. He developed many of the cultural systems for controlled environment agriculture used in over 50 countries, including drip irrigation, growing media, solar energy, energy alternatives and conservation for greenhouse vegetable production. His programs of research served as a prototype for food support systems for aerospace application.

Through his fund-raising efforts, he was able to establish the Controlled Environment Agriculture Center at the University of Arizona, which serves today as the only such research/education center of its kind for students in the U.S.