Controlled Environment Agriculture

What is Controlled environment agriculture?  Simply put, it is an approach to crop-growing where each facet of crop production is not merely met, but optimized.  That might sound simple, but there's a lot to it which doesn't immediately meet the eye.  So let's take a closer look.

Any given plant has multiple, and sometimes changing, requirements throughout the sprouting, growing, pollination and fruiting (if applicable), and maturation stages.  Those requirements can be vastly different not only between plants of different types, but even within the same plant type at different growth stages.  Furthermore, the qualities of the end product, the crop itself, may be dependent upon conditions which actually stress the parent plant in some way.  For instance, a red ripe juicy sweet tomato is the product of dramatically changing conditions over the lifetime of the plant.  The lighting, temperatures, humidity, nutrition, CO2, pH and air movement requirements for a tomato seedling are very different from that of a tomato putting out its first blossoms, versus a tomato vine in full fruit production.  Compare that to the needs of a lettuce seedling, versus a mature cut-and-come-again leaf lettuce plant, versus a head-type lettuce, versus a lettuce plant being raised for seed production.  And compare that to perennial herbs which have multiple years' worth of growth at any given time.  Each stage for each of those plants, and each product created from those plants, requires slightly different conditions.  Controlled environment agriculture (CEA) seeks to proactively provide those conditions.  Furthermore, controlled environment agriculture seeks to provide them not only efficiently, but profitably.  That's one heckuva goal.

Controlled Environment Agriculture: The Details

While the above description may start to sound like Mission Impossible, we have made great strides on accomplishing that goal for a wide variety of plants.  And other sections of this website are already addressing various elements of that goal, by providing details about topics such as lighting, growing media, nutrition, etc.  This particular section, however, will address those aspects of controlled environment agriculture which are not already addressed elsewhere.  To be specific, we'll look at the following:

  • season extension
  • temperature (in both the leaf zone and root zone)
  •  humidity
  • CO2 vs O2 concentrations
  • air movement (ie, calm vs breezy)
  • beneficial biological elements (insects, protective fungi, symbiotic root communities, etc)
  • weed, pest and disease monitoring, control and/or prevention
  • human worker comfort (work spaces, ergonomics, task efficiency, etc)
  • equipment and infrastructure maintenance, which must be integrated into crop growth cycles

Why Such A Big Net?

Some of the above items may seem only distantly related to hydroponics per se.  And in some cases, that's true.  However, all the above relate directly in some way to successful hydroponic crop production.  And that's the goal here, to provide a look at, and describe solutions to, all the different challenges which may come up for any given hydroponic operation.  Some of the above elements are taken from our own frustrations over the years as we worked to build comprehensive systems to provide everything our plants needed, only to discover after the fact that we'd missed something important.  Bottom line, we're hoping you can learn from our mistakes and discoveries, along with the mistakes and discoveries of others, so that you can reap all the rewards without re-inventing the wheel.  No matter what form of growing you're engaged in, or at what scale, at some level you're doing controlled environment agriculture.  So let's get started.

Season Extension

This is a huge topic in its own right, and covers any/all forms of providing protective shells around growing plants one or more stages of the growing cycle.  Greenhouses fit into this category, as do smaller hoop houses, hot frames, cold frames, soil heating cables, and germination cabinets.  It's tempting to say that season extension is merely a form of temperature control, but it's much more than that.  Putting a shell around a growing system will have important, and sometimes not-so-obvious implications for things like humidity, irrigation rates, pest/disease control, lighting options, and worker comfort/safety.  It also introduces a whole new level of complexity to any growing system, because it's one more thing to be managed.  So there are definitely trade-offs to consider.  We'll take a look at the more common forms of season extension, and how those forms of season extension impact all the other aspects of c0ntrolled environment agriculture.


Any given plant's surrounding temperature, in both the leaf and root zones, can have a profound impact upon the growth habits, health and productivity of that plant.  Controlled Environment Agriculture seeks to optimize temperatures in both zones in cost effective manners, often using a variety of techniques.  Thankfully, those techniques are usually relatively simple both in terms of approach and application, such that hobbyists and small-scale growers can use them too.  As the website expands, we'll take a look at specific methods for determining, then optimizing, leaf-zone and root-zone temperatures.


Humidity is a strange creature, not being a fixed thing in and of itself but rather always being linked to both temperature and atmospheric pressure.  Hence the term "relatively humidity".   Regardless of that complication, humidity is a critical element for plants because that plays a large role in how quickly the plant absorbs and loses internal moisture.  Extremely dry conditions can literally suck the moisture out of plants, even at relatively low temperatures, while extremely high humidity can become a breeding ground for fungal disease (damping off, early blight and late blight being among them).  We'll take a look at what relative humidity is, how it works, how it's measured, what plants need, and how relative humidity can be modified to create optimal conditions.

CO2 and O2 Concentrations

Plants are often called the lungs of the planet, because they are responsible for creating the oxygen (O2) we rely on for our own respiratory needs.  However, plants themselves need carbon dioxide (CO2) for their respiratory needs.  For plants being raised outdoors, the ambient atmosphere provides plenty of CO2.  However, any plant growing in a closed/controlled environment will quickly use up the available Co2, at which time it begins to suffocate.  While plants can survive for much longer without CO2 than we could survive without O2, productivity is definitely impacted by lower CO2 levels.  We'll take a look at what CO2 does for the plant, how a plant absorbs it, what concentrations are optimal, and how various growers have supplemented their plants with CO2.

Air Movement

One of the most interesting comments I ever read about controlled environment agriculture is that the air within a greenhouse needed to be "buoyant".  What in the world does that mean?  It means that plants do best when the air is moving around them at least slightly.  Humidity, temperature, CO2 and O2 measurements are all impacted by moving air.  There are exceptions to this rule too, such that even subtle changes in air movement rates can result in dramatic differences in conditions such as frost damage, disease progression, pollination and plant structural strength.  We'll take a look at how air movement affects all these issues, and how best to supply just the right amount of air movement at any given time.

Beneficial Biological Elements

Growers are realizing something that Mother Nature has realized for years: a rich mix of beneficial organisms within a growing environment can boost production and minimize disease issues.  Soil-based growers have capitalized on this for generations, but hydroponic growers have only recently begun to explore this aspect of controlled environment agriculture.  Beneficial insects, beneficial fungi, compost tea and other organisms can be proactively introduced into hydroponic systems to capture those same benefits.  We'll explore how this is being done, and where to get more information.

Weed Control and Prevention

Many folks believe hydroponics will completely eliminate weed pressures, and many hydroponic systems drastically reduce weed pressures.  However, weeds are extremely opportunistic, and they do still make their impact on hydroponic systems over time.  We'll take a look at how to ensure that all your hard work goes into your valuable plants, instead of into weeds.

Pest Control and Monitoring

Controlled Environment Agriculture, while providing optimum conditions for plants, also often provides optimum conditions for bugs.  Destructive insect populations can explode almost overnight in greenhouses and other protected environments, and overwhelm all your efforts to nurture your plants.  We'll take a look at how to monitor for destructive insect populations, how set up hydroponic systems and environmental conditions to minimize their occurrence, and how to deal with outbreaks when they occur.

Disease Control and Monitoring

Everything we said about insect pests is true for disease organisms as well.  One day your plants can look great, and the next day you might have row after row of dead or dying plants.  It is not unheard of to lose an entire greenhouse of valuable plantings within 48 hrs, if disease precautions are not taken.  Thankfully, growers have a variety of tools in the arsenal to help prevent or minimize this nightmare scenario.  This is definitely a case where "an ounce of prevention is worth a pound of cure."

Agricultural Ergonomics (Human Worker Efficiency)

One part of controlled environment agriculture is to help ensure that various tasks can be done in timely ways.  While this is usually a time to focus on the task itself and how to fold it into the busy schedule, there are also logistical concerns.  For instance, tomatoes can't be effectively harvested if the vines have climbed too high to reach.  Irrigation is difficult to accomplish if the hoses have to be dragged from one end of the greenhouse to the other, crushing or tangling in plants along the way.  And slick footing can do all sorts of plant and human damage.  Few things put as big a crimp in daily operations as an unexpected injury.  We'll take a look at how to minimize chores risk, and make various tasks as efficient as possible.

Equipment and Infrastructure Maintenance

Let's assume for the moment that you've successfully tackled all the above topics (in which case, wow!  Congratulations!)  There remains one large topic which you'll have to keep tabs on, and fold into your ongoing operations: maintenance.  This could be as simple as clearing filters and irrigation lines, or as involved as replacing all the lights or the greenhouse film itself.  We'll take a look at how to plan for these events well in advance, so that they can be scheduled in a way that is as minimally disruptive as possible.

Some Assembly Required

The above list is ambitious; we do not know of any other website which covers all these topics in any sort of comprehensive, organized, inter-linked way.  We're working to build all these pages and it'll take awhile.  We ask that you have patience with us as we do that work.  If you have specific questions about any of the above, Contact Us and let us know what's on your mind.  We'll weave that into our coverage.  As always, thanks for your interest!

Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.