We recently reviewed some indoor growing tools of the trade and how they help control your growing environment. Let’s dive deeper into the field of environmental control. – Enabling Environmental Control


1. Laser (infrared) thermometers


Incorporating a laser thermometer into your toolkit is recommended, as it will provide a multitude of data. It can quantitatively measure the surface temperatures of hard-to-reach places, or surfaces with temperatures outside the range of a typical thermometer or hygrometer. It also can provide the user with a qualitative measurement of transpiration.


Transpiration is the process by which plants transfer water from their roots, up the stems or stalks, and out of small holes in the foliage called stomas. Similar to evaporation, it is a cooling mechanism that occurs as water molecules are broken down and released as a gas. A plant regulates this process by opening and closing their stomas.


Increasing the air temperature, air movement or amount of light a plant receives will increase levels of transpiration. Decreasing the humidity while other factors remain constant will also lead to an increase of transpiration. There are limits to these factors, as extremely high air temperatures, high wind speeds, high levels of light and extremely low levels of humidity all will hinder the ability of the plant to transpire. Most of the water a plant takes up is transpired into the atmosphere surrounding it, while only a small portion of the water is retained by the plant and used for growth.


In essence, healthy transpiration leads to healthy growth. Depending on the type of crop, transpiration can allow foliage to maintain a temperature up to 9 degrees Fahrenheit cooler than similar non-transpiring foliage, which can be a huge difference if the plant encounters other environmental stressors. So, by monitoring the leaf temperatures and comparing them with air temperatures and humidity readings, we can infer a relative level of transpiration.


2. Magnifying lens/jeweler’s loop


A magnifying lens or jeweler’s loop will provide an inexpensive way to monitor the produce’s growth and health beyond what we can see with the naked eye. A magnification power of 20 to 60 is suggested. Many loops come with a light source to facilitate better views and some can work in conjunction with a smartphone to capture pictures. Many insects, fungi as well as nutrient deficiencies can be discovered by the use of this device long before being noticed by our natural sight. The early identification of these threats, before they can spread or decimate a crop is vital to formulate a solution and mitigate the problem.


3. Brix meter


A Brix meter is a refractometer, which will measure the solids (sugars, minerals) in a solution by determining how much light is bent as it passes through a drop of the liquid (juice). If leafy greens are being measured, use a press to generate a sample. Generally, the higher the sugar and mineral content, the better the produce will taste. It is also relevant to note that plants with a higher Brix value are healthier and more resistant to insects. Each degree of Brix on the scale indicates the presence of one gram of sucrose (and other minerals) per 100 grams of solution. Most refractometers have a range of zero to 32. However, Brix values differ significantly among crop types. For example, a reading of 12 would indicate excellent sugar and mineral contents in tomatoes, bell peppers or blackberries. Conversely, a reading of 20 is required to indicate excellent sugar and mineral contents of most grapes, nectarines and oranges. Not only is a brix meter useful for determining the differences among strains or types of a crop, it is often used for benchmarking the development of the crop within a cycle.

Enabling Environmental Control


4. Exhaust fans and charcoal filters


The use of exhaust fans and charcoal filters is integral when confronting excessive temperatures in your growing environment, a common theme in controlled environment agriculture.


The most efficient way is to incorporate ventilation into your light reflectors. Many reflectors are ductwork ready and include a glass cover to close off the heat source (the bulb). Use of a charcoal filter is almost a necessity because you don’t want to pull dust or any other contaminants into the reflector and onto the bulb. The exhaust fan will pull air through the charcoal filter, then push this “clean air” through the light reflector, and finally carry the hot air out of the building. This will create a vapor pressure deficit, which is to say that the air pressure inside the facility is slightly less than the air pressure outside the facility. Since air will move from areas of higher pressure to areas of lower pressure, cooler replacement air will find its way into your environment. Because of this inevitability, it is best to create vents with intake filters that will expedite this process as well as keep insects at bay.


5. Ozone generators


The use of an ozone (O3) generator can help sanitize and sterilize the air in the growing area by eliminating bacteria and spores. It works by generating O3 molecules, known as triatomic or activated oxygen molecules, which is an allotrope of oxygen (O2). The O3 molecules quickly react with the bacteria and spores by losing the extra oxygen atom and reverting to its natural state of O2. This extra oxygen atom combines with the organic matter, causing a molecular change in the structure of the spores or bacteria, therefore eviscerating their cells and eradicating them as a threat. It should be noted that a large excess of O3 molecules in your environment could hurt your crop as well as contribute to health problems if excessive exposure occurs. To avoid this, always follow the manufacturer’s recommendations, and purchase an ozone monitor to place at the canopy height of the plants. If O3 levels exceed 15/100 of a part per million (.15 PPM), it is approaching levels that could cause negative effects. O3 levels should never exceed 3/10 of a part per million (.3 PPM) unless it is for a specific purpose, like mold remediation, and even then should only be maintained for a short period of time.


6. Choosing a structure


No discussion of environmental control would be complete without taking a quick look at the barriers that separate the external environment (outside) from your growing environment (inside). The choice of building material is critical. The upfront construction costs can be exclusionary, but the ability of your facility to maintain a fairly consistent environment could lead to the relative success or failure of your crop. The size of your operation, type of crop, lighting and ventilation requirements, outdoor climate and geographical location are all factors that will influence building material selection. Although any environment can be modified to meet the needs of a specific crop, it is much harder to create an indoor rainforest in an outdoor desert, in terms of structural requirements, energy, costs and effort.


Read more: Indoor Gardening Tools and Enabling Environmental Controls