As grow operations in the cannabis industry mature, more attention is being paid to water conservation. The first LEED-certified cultivation facility is currently being built in Ohio, and water reclamation is one of the several key infrastructure milestones needed to meet the coveted benchmark.

Industry-wide, there’s a general understanding that the ultimate goal is to reach full sustainability, and while the “perfect” grow-op might be years away, new methods are being employed today. Regulations also continue to play a larger role in how water is managed, pushing for both less consumption and less discharge, the two primary issues in reducing an operation’s environmental impact.

Many commercial grows employ dehumidifiers and air-conditioning. Dehumidification is essential to mitigate crop-destroying fungi and mildew, while air-conditioning controls excessive heat generation from grow lights. Combined, these two systems can generate hundreds, even thousands of gallons a day of condensate water, depending on the scale of the operation. And while that water is essentially distilled, some contaminants, pathogens and bacteria can still get into the water, so growers will typically just dump condensate instead of risking contamination by reintroducing it to plants.

Condensate water chemistry can vary considerably from system to system, as there are many factors that can influence its quality. Most condensate water contains dust and other suspended solids, accumulated through air ducts and picked up as liquid makes contact. A quick google search for “HVAC duct contamination” reveals many of the potential variables that can ruin what would otherwise just be distilled water. Examples include corroded metals, manufacturing oils, or any other contaminants the distilled water may encounter. Furthermore, the internal coils and other parts of these systems also contribute to contamination, as they are perfect breeding grounds for mold and organic pathogens.

Low mineral content in the condensate causes the water to absorb atmospheric CO₂, creating an acidic water profile. While this is not necessarily harmful to plants, acidic water acts like a vacuum, aggressively leaching metals as it comes in contact with coils, venting or other metal components. This is more of an issue with older equipment, although even trace amounts of certain metals such as lead should be considered as hazardous. The optimal pH for cannabis is a range from 6.0 to 6.5, and while condensate is usually closer to 5.0, dilution typically evens out any potentially harmful effects.

Condensate reclamation, while fairly new to the cannabis industry, is relatively easy to accomplish with specialized, off-the-shelf filtration systems. The investment is usually minimal and ensures a suitable irrigation formula for healthy plants. These systems should include:

1. UV sterilization to eliminate pathogens and bacteria
2. Re-mineralization for balanced pH
3. Sediment filters for dust and other suspended solids.

For grow operations dealing in high volume, the value gained in water savings alone is enough to warrant the relatively small cost of condensate reclamation systems.

Editor’s Note: Another common method of water purification is reverse osmosis, although there is more waste water from RO systems, and they tend to be pricier

Resources:

Want to get in touch with Hydrologic Systems? They can be reached via the following methods:

1. Website: https://www.hydrologicsystems.com/
2. Email: info@hydrologicsystems.com
3. Phone: (888) 426-5644

In many ways, taking care of plants is like tuning a guitar. Just like finding the harmony between notes that are too sharp or too flat, watering is about finding the harmony between too wet and too dry. Every grower has questioned themselves, “Did I water too much?” or “Is there enough water?”. Most can even recall a time or two when they accidentally damaged the health of one of their plants due to an enthusiastic watering schedule or simple forgetfulness.

Mild over-watering is rather hard to detect. It doesn’t generally cause leaf droop and often presents no outward signs in the canopy, placing it into the category of “If it ain’t broke, don’t fix it.” Imperfect hydration still allows for high-quality cannabis and excellent yields, but in the case of the world’s most lucrative cash crop, optimization is paramount. Even a 4% bump in yield can result in enormous additional revenue.

In the quest to increase quality and maximize yield, greenhouse conditions now approach environmental perfection. Ironically, this perfection creates liabilities for watering. For example, greenhouses maintain high humidity levels in order replicate a cool, humid morning for photosynthesis. This practice speeds growth, but plants end up locked into a metabolic moment in time that would only occur in nature for a relatively brief period. This environment out other points in the day such as the afternoon. The afternoon is a critical time for moisture regulation, presenting an opportunity to eliminate extra water in the soil or conserve water. A cool, humid greenhouse may interfere with these processes. Growers must be careful not to inhibit their plants’ natural desire to regulate themselves.

The canopy’s ability to regulate and release moisture is affected by the pressure differential between the inside of the leaves and the outside air. Specifically, a lack of water vapor pressure in the air, otherwise known as vapor pressure deficit (VPD), “pulls” moisture out of the leaves, and, in turn, out of the soil and through the plant. VPD is important to consider because it is directly tied to the plant’s transpiration rate, which, in turn, is directly linked to watering. Transpiration increases the moisture in the air, lowering the VPD and reducing the plant’s ability to transpire. In nature, this behavior balances out with the rest of the environment. But in the greenhouse, this compromises the plant’s ability to cool itself under hot grow lights, even though ample moisture is available in the soil.

When a surplus of water in the soil (hydrostatic pressure) pairs with a low VPD, the plant begins to “drown” because the process of transpiration can’t keep up. Water displaces the oxygen needed by the roots, stopping photosynthesis and potentially damaging the roots. Too much water can also drown beneficial soil microbes and spur the growth of other microbes that excrete alcohols and damage the roots. Once over-watering compromises the population of beneficial microbes, it may never recover, and nutrients that would have been provided by microbes are no longer available.

One unique method of controlling VPD is employed by a company called Blumat Watering Systems. It is possible to combat the “drowning” issue, by only water into the soil when the soil becomes dry. By taking advantage of hydrostatic pressure, the system only releases the amount of water that the plant pulls from the soil, without the need for electricity or computer monitoring. The dry earth creates a suction force that sucks water out of a ceramic sensor. Suction tension develops in the system, opening a flexible valve. Once the soil is moist enough, the sub-pressure in the sensor causes water to be sucked back into the cone, returning the valve to its original position, squeezes the drip tube closed. Blumats work as tension-meters with a ceramic tip, as you can see below.

That’s not to say that this is the only method for solving overwatering issues. Hygrometers, thermometers and soil moisture meters can help a grower manage VPD, but the time-intensive process is best handled by an integrated automation system. Controller technology has advanced to the point that an integrated automation system can handle VPD changes on the fly to stay within a set limit of environmental conditions. The downside to systems such as these is that they are often expensive to install and maintain, and require electricity.

In fact, the plant’s response to irrigation might be the only way the plant itself can provide growers with definitive feedback. Cannabis plants ultimately communicate via water. The language they speak is dry or soggy soil. By allowing plants to control the environment, they can regulate their own health, allowing them to better adapt to changes in grow room conditions.

Resources:

Want to get in touch with Brianna or Sustainable Village? They can be reached via the following methods:

1. Website: https://www.sustainablevillage.com/
2. Email: briannasustainablevillage@gmail.com

When most people think about using LEDs in horticulture lighting, the first thing that comes to mind is the purple glow being emitted from a fixture consisting of red and blue diodes. This purple glow may be the industry standard for horticulture LEDs, but have you ever wondered why red and blue diodes have historically been the semiconductors of choice by lighting manufacturers? Many manufacturers reference the absorption spectra of Chlorophyll A and B (which peak in the blue and red regions of the electromagnetic spectrum) as the main reason for providing a purple spectrum (Figure 1).

Figure 1. The absorption spectrum of Chlorophyll a and b measured in vitro.

At first glance, it makes sense to use red and blue light only, since chlorophyll drives photosynthesis.

But have you considered how the absorption spectrum of chlorophyll is measured? And have you considered whether chlorophyll directly correlates to plant growth, or indirectly? And finally, what happens if you only target a sole pigment and neglect other pigments responsible for plant growth and development? This article will discuss the differences between absorption spectrum and action spectrum, and (spoiler alert) dispel the myth that “plants don’t utilize green light” to promote plant growth and development.

The action spectrum of photosynthesis was created from research that was performed in the 1970s by Drs. McCree and Inada and this work was fundamental in defining the range of photosynthetically active radiation (PAR). Prior to this research, very little work had been performed to determine how varying wavelengths of light influenced photosynthesis and plant growth. These researchers utilized filters to determine the influence of light spectra on photosynthesis of single leaves using an assimilation chamber. If you see figure 2, you will notice that plants do in fact utilize green light for photosynthesis, and rather efficiently too (figure 2).

Figure 2. The action spectrum of photosynthesis as determined by Drs. McCree and Inada.

The next logical question to ask is why is there such a difference between the absorption spectrum and the action spectrum if chlorophyll is responsible for photosynthesis? The answer is simple: Chlorophylls are not the only photoreceptors that are responsible for photosynthesis. There are other types of antenna photoreceptors (mainly carotenoids) which also promote photosynthesis, and by utilizing narrow band red/blue LEDs in single-source lighting conditions these pigments are not able to optimize their light harvesting capabilities. Also, it should be noted that green light does in fact promote photosynthesis in chlorophylls. Recent work has shown that green light is able to penetrate deeper into leaf surfaces to drive photosynthesis in chloroplasts located towards the bottom surface of the leaf. As PPFD increases, light energy that is absorbed in the upper chloroplasts tends to be dissipated as heat, while penetrating green light increases photosynthesis by exciting chloroplasts located deep in the mesophyll (Terashima et. al., 2009). Additionally, green light penetrates through leaf surfaces much better than red or blue light to reach the lower canopy, which is extremely important in dense canopy production techniques which are common in controlled environment agriculture.

So, what does this all mean for the grower? While we are still in the early-stages of understanding how plants use light and we are still working to understand how different photoreceptors function and interact with one another, the bottom line is that plants absolutely do utilize green light. If your horticulture lighting system is delivering a spectrum which neglects photoreceptors that absorb light in the 500-600 nm region (especially in sole-source lighting applications) you will not be optimizing your growing environment. If you would like to learn more about the spectra that Fluence Bioengineering includes in their lighting fixtures, click here.

Resources:

Want to get in touch with Fluence? They can be reached via the following methods:

1. Website: https://fluence.science/
2. Email: info@fluencebioengineering.com
3. Phone: 512-212-4544

Repotting your cannabis plants is an essential part of the growing process. One of the major misconceptions about repotting cannabis plants is that it’s simple and doesn’t require a lot of thought and effort. This could not be further from the truth. It’s not as simple as transfering your plants from one pot to the next, especially if you haven’t had a lot of experience with growing. Here are some of the do’s and dont’s for repotting your cannabis plants.

Why do we even bother with repotting our cannabis plants? The short answer is that this makes them grow faster, and who doesn’t want that? The vegetative stage is not as exciting as the flowering stage, but it is no less important. Repotting your cannabis plants during the vegetative stage can actually stimulate new growth. This means a bigger crop in a shorter period of time!

Editor’s Note: There’s a multitude of reasons why this occurs, but essentially the plant’s roots will recognize that they are no longer bound by the sides of the pot when they are given more room to grow.

When you first start your grow it’s important that you don’t plant in a container that’s too large. This is a mistake that a lot of people make when they first start growing. They think that planting in a large container will encourage more growth. The truth is that your plants will have trouble getting sufficient amounts of nutrients and water if they are planted in a container that’s too large.

This is of course only for when your plants are in the beginning stages. When you go to repot your cannabis plants, you’ll want to make sure that you plant them in a much larger container; this will encourage them to grow much larger when they reach their final form.

Image Source: growweedeasy.com

If you wait too long to repot your cannabis plants, you run the risk of allowing your plants to become rootbound, which is another expression for when the roots begin to choke each other out. This may occur when you wait too long to repot your plants. Obviously this can hinder your plants’ growth and actually end up killing them.

On the flip side, transplanting too early can also be detrimental to your plants. Your plants are far more likely to end up with a nutrient deficiency if you do this. So, when is the right time for repotting your cannabis plants? Typically a good rule of thumb is to repot your plants once the leaves have reached the outer edges of the container. For example, if you’re starting out with a plastic Solo cup (hey, they make excellent growing containers!), then you’ll want to repot them when they’ve reached the lip of the cup.

You’ll know that you’re ready to repot your plants once more when they’ve doubled in height. This is usually pretty easy to tell, but it will come about quickly, and then you need to immediately start repotting your cannabis plants

Do you know how big your next container should be? You don’t want to go too small or too big. When repotting your cannabis plants for the first time, you’ll want to move them to a new container that ranges from 1-3 gallons in size. This will ensure that your plants don’t end up rootbound.

Resources:

Want to get in touch with ILGM? They can be reached via the following methods:

1. Website: http://www.ilovegrowingmarijuana.com/
2. Contact Form: https://shop.ilovegrowingmarijuana.com/pages/contact-ilgm#contact

Hi everybody! Welcome to this installment of Dr. NPK! This post is dedicated to the unsung heroes: the secondary elements! If you’re a football fan like me, this is the “O-Line” tribute for cannabis science.

A lot of focus is placed on the primary macronutrients (nitrogen, phosphorous, and potassium, a.k.a. N-P-K), but these elements can’t do their job without the right supporting staff. I’m talking about the secondary macronutrients:

1. Calcium (Ca)
2. Magnesium (Mg)
3. Sulfur (S)
4. Iron (Fe)

I want to make one important distinction: many people categorize iron as a micronutrient and thus would not be consider it a secondary macronutrient; I make a personal choice to incorporate iron into my list of secondary macronutrients for two reasons:

1. Iron is typically used at a higher treat rate than many other micronutrients
2. Iron deficiencies often present the same symptoms as those of secondary macronutrient deficiencies.

By a mile, calcium is the most commonly discussed secondary nutrient. Calcium plays an important role in any plant, not just cannabis. When you think of calcium, you should think of the cell wall. Calcium ions (Technically Ca²⁺ if you really want to get into it) helps plants develop their cell walls. Cell walls prevent diseases as well as to ensure proper and even growth. Calcium deficiencies tend to manifest in the growth of younger leaves; calcium ions are immobile in the plant, so a deficiency in calcium will affect the younger leaves.

Water-soluble calcium is usually found in the highest concentrations in fertilizer formulations that include the secondaries. Calcium is typically listed as “water-soluble calcium” on the back of fertilizer bottles; for some organic products, it is a suspension in water what is usually derived from dolomite, a calcium/magnesium carbonate. The most commonly used source for fully water-soluble formulas is calcium nitrate. Elite CalMag and Elite Base Nutrient A both contain high concentrations of fully water-soluble calcium.

One final note: Have you ever added your total nutrient regiment into you tank and notice some white solid show up out of nowhere, quickly? Don’t worry, that’s likely not something biological (don’t you wish that was the news you always got?), it’s a sign of nutrient lockout. In all likelihood, you are forming one of a few insoluble salts: calcium phosphate, calcium sulfate, or maybe even calcium silicate. These salts are practically insoluble, but also harmless to the plant.

Following behind calcium on the secondary nutrient totem pole is magnesium. Water-soluble magnesium typically runs in smaller concentrations (Approximately 1-3%). Sources of magnesium in liquid nutrients include magnesium nitrate, magnesium sulfate (commonly called Epsom salt), or magnesium acetate. Elite CalMag and Elite Base Nutrient B contain high concentrations of water soluble magnesium.

I used to work at Rite Aid when I was in high school/college. I had a rude customer ask me one time where our chlorophyll pills were. I replied that perhaps he should go outside and eat a plant. Yes, I was formally disciplined and probably should not have been so snappy (hindsight is 20/20), but I promise you that this leads me to my next point: magnesium!

Magnesium is an important element in photosynthesis. Magnesium is believed to be a key contributor in converting sunlight to actual energy within the plant, likely due to its influence on chlorophyll (Yang et al, The Crop Journal 4 2016, 83–89). Thus, insufficient magnesium means fewer chlorophyll and therefore crappier photosynthesis.

Magnesium deficiencies tend to present themselves in older leaves as magnesium is a mobile nutrient. The plant will direct what little magnesium it has to new growth, leaving older leaves magnesium deficient.

Epsom salts may be great for tub soaking… but they’re also a great source of nutrients for cannabis!

Sulfur is an interesting element. The crux of my Ph.D. is based on this element. My wife isn’t a fan: sulfur compounds usually smell of rotten eggs (or for the less mature of you, farts). Regardless of the smell, plants absolutely need sulfur. Sulfur can be provided to the plant in a variety of ways:

1. Elemental sulfur (as a milky-yellow suspension)
2. The sulfate (SO₄^2-) ion (such as in magnesium sulfate) which is also the most plant-available form.
3. Bisulfite/sulfite (SO₃^2- and HSO^3-, respectively) in sodium bisulfite.

Sulfur is important in plants for a variety of reasons. Although it is important in catalytic processes and chlorophyll production, one of its hallmark attributes is its role in amino acid production. Amino acids are the building blocks of proteins, and proteins play a pivotal role in the strength of your plant as well as your yields. Sulfur is also important in essential oil production. Thus, insufficient sulfur means fewer amino acids and a reduced yield and droopy plants. No one likes droopy plants!

High concentrations of water-soluble sulfur are found in Elite Base Nutrient B, via magnesium sulfate, which is the most plant-available form of sulfur available on the market. Oh yeah, and it doesn’t smell like rotten eggs, so that’s a plus.

Although needed in significantly smaller concentrations, iron is still a vital element for cannabis growth. I will go into significantly more detail about iron in a later post, so a broad overview will suffice here. Iron is an ion that can be attacked by many other ions (Editor’s Note: “Attacked” is chemistry-speak for a redox reaction); to avoid this in your reservoir, iron should be supplied in chelated form; this protects the iron ion. The most commonly supplied form of plant-available iron is iron EDTA. Iron is found in Elite Base Nutrient A and Elite CalMag.

Iron serves a variety of functions in the plant, mostly involved with chlorophyll and chloroplasts. Iron, like magnesium, plays an important role in the development of chloroplasts, which are a key component of chlorophyll (Rout, G.; Sahoo, S. Reviews in Agricultural Science 2015, 3, 1–24). This is why iron deficiencies are categorized by the browning of leaves. No iron means no chlorophyll, which means no green, therefore you make no green, in the bud sense.

Although used in lower quantities, secondary macronutrients play a pivotal role in the plant growth. If you don’t pay attention to them, your plants will suffer. Elite Base Nutrient A and B provide all the secondary nutrients you may need. If you’re using RO water, Elite CalMag will provide the right supplement to your water to make sure you’re getting all those important secondaries!

Resources:

Want to get in touch with Elite Garden Wholesale? They can be reached via the following methods:

1. Website: https://www.elitegardenwholesale.com/
2. Email: info@elitegardenwholesale.com