Whether in a greenhouse, glasshouse, or indoors, cultivating in a protected environment is all about controlling the surrounding conditions. Out of all the various climate parameters, humidity is often overlooked. The lack of attention is understandable because just like light, humidity isn't always visible -- or immediately felt.
But no matter how unintuitive humidity may be, its effects on crops are dramatic and often detrimental. This has led to the current state of humidity control in agriculture, which is under-informed, inaccurate and is usually either under or over-invested in.
There are several reasons for these shortcomings. The first is the shallow understanding of this complex subject. The second --and possibly the most critical reason-- is a lack of accurate monitoring. The last reason leaves growers struggling to compensate for local microclimates, rapid fluctuations and the need for a certain degree of foresight.
As a result, growers invest a lot into dehumidification efforts that leave them unsatisfied with the results.
The Effect of Humidity on Nutrient Transport
The effects of humidity are a huge deciding factor when it comes to plant health, growth, and quality.
Nutrient transport isn't usually the first thing growers think of when faced with the word “humidity." But, it is one of the major factors determining the overall quality and quantity of the end product.
As humidity levels rise, the rate of plant transpiration begins to do gown, eventually halting altogether once the relative humidity reaches 100%. By that point, it means that the air is completely saturated and the water can no longer evaporate.
Transpiration from the leaves creates a “pull” through the plant, all the way to the roots. In turn, the roots then begin to take water from the ground. This water is what contains the nutrients plants require to operate and grow.
When humidity rises, nutrient uptake slows down. This leads to the diminished growth and health of the plant. But this isn't an on/off situation. Think of it instead as a range in which plant performance is optimal.
Reducing Humidity-Related Diseases
With nutrient transport covered, another aspect that requires humidity control is disease. It's also another major problem that growers need to deal with on a regular basis.
Humidity-related diseases such as botrytis and powdery mildew, are found worldwide, infecting an extremely wide variety of crops around the globe. This is one of the major initial reasons for the development of humidity control technology for agriculture.
The peril of these diseases is much greater than suboptimal nutrient uptake. An outbreak can lead to anything from reduced quality output to the elimination of an entire crop cycle.
But all humidity-related diseases do have one thing in common. They share a dependency on water for their development. Most of them, at one point or another in their life cycle, require the presence of free water (as in liquid water that isn't in the form of vapor).
Many of these diseases develop quickly when these conditions appear, but do not disappear once the water dries up.
Avoiding Dew Point Condensation
In a properly irrigated and covered greenhouse, the main source of water appearance is humidity. When water vapor that has been emitted by the plants reaches saturation in the air, liquid water begins to appear.
This point is known as the dew point.
The best way to avoid water presence in the growing space is by simply avoiding the dew point. In fact, many of the ailments associated with humidity, are barely affected by the actual relative humidity level.
Instead, they just need water. One instance of water appearance may be enough for them to develop. Using various techniques to reduce humidity, many growers already abide by this method to avoid dew point condensation. But, as humidity is neither felt nor seen like other climate parameters, it is often treated in a relatively inefficient manner.
Most grow operations either under-treat or over-treat humidity. This is due to the simple fact that it’s very difficult to get an accurate gauge of the actual humidity levels in the space.
Increasing the Effectivity of Humidity Control
The secret to efficiently avoiding dew point condensation is effective monitoring. The same is true for tweaking humidity ranges to promote optimal nutrient transport.
Humidity levels constantly fluctuate and differ from area to area. Microclimates with higher humidity develop in denser foliage and the risk of condensation increases with proximity to the exterior walls or covers, where outdoor conditions have a greater effect.
Well-placed, real-time monitoring throughout the grow room, offers the most precise image of the present conditions. With a better understanding comes increased control.
When growers deal with the issue of humidity without the proper understanding, they exhaust excess efforts, energy, and spend far more without achieving the desired results.
Imagine working without a thermostat or a feeling for the temperature in the space. The chances are good that heating would be ineffective and would often lead to underheating.
A real-time understanding of the processes taking place in the greenhouse allows growers to push the boundaries without risking dangerous moisture buildup or dew point condensation. Plant placement can become denser, while still keeping an eye on the developing microclimates. Yields can then be increased without seeing a compromise in quality.
Energy consumption also has a lot to gain from this knowledge. Dehumidifiers do not need to operate during hours when they aren’t necessary. On the other hand, heating can be cut down a good measure, as it is often used as a method of relative humidity reduction.
This allows growers to cut back drastically on costs, just by gaining a better understanding of the inner-workings of their space. Growers can also benefit from a boost in quality and yield by providing the precise conditions plants require, avoiding disease outbreaks in the process.