Crop Steering Cannabis Plants to Maximize their Potential – Learn how implementing different crop steering techniques help cannabis plants achieve higher yields, greater cannabinoid levels, and overall performance.

Crop steering is hardly a new concept for many indoor agricultural commodities. Tomato growers, for instance, learned how to increase flower development in their plants by reducing water frequency in indoor greenhouse production years ago.

As science and technology are elevating cannabis cultivation practices in recent years, however, crop steering has become a popular phrase in the industry. Growers are now implementing several different tactics to steer their cannabis plants into producing higher yields, increased trichome development, and cannabinoid content.

Modern advancements in indoor growing environments offer cultivators more control over lighting, temperature, and irrigation systems. In addition, science continues to uncover more about cannabis plant growth development, helping growers understand how the plant functions. These innovations are the driving force for cannabis grow operations to implement crop steering techniques to maximize their plant's potential.

What is Crop Steering?

In simple layman's terms, crop steering is a method of tweaking environmental controls to activate a response from plants to change the way they perform. For example, many cannabis growers observe their plants happily praying with leaves opened wide each morning after going all night without watering. The dry-down time stimulates the plants to work harder to survive.

Science discovered the response is partly due to an internal system of phytohormones that signal the plant when a stressful situation exists. For example, auxins are important phytohormones that contribute to cellular activity, root formation, and overall plant development. When triggered in a drought response situation, stimulated auxin activity results in massive plant growth.

This scientific finding reveals how water intake reduction steers cannabis plants to grow bigger and thus, produce larger yields. However, the timing of a particular crop steering technique is essential for optimal plant health. Drying down too much, say in the seedling or cloning stage before a sound root system establishes, may result in a wilted stalk that cannot survive.

Let's look at some of the ways a grower can adjust the environment to bring out the best in a cannabis plant's performance.

Crop Steering Practices

Water Content

Young cannabis plants in the vegetative stage love their water. They like a warm, humid environment to expand their root system, develop leaves, and build their branching structure. Plants in the generative stage, also known as the flowering phase, need adequate water supplies also. However, limiting water intake during this growth period initiates a response within the complex system to bulk up the buds. Let's delve into science to understand this concept better.

Using nature's gift of photosynthesis, plants take in energy from the sun, water, and carbon dioxide (CO₂). Through a shuffling of electrons, the plant absorbs CO₂ and water, converting them into chemical energy to create carbohydrates that feed the plant.

Oxygen and water vapor are then released back into the atmosphere through tiny pores on the plant's leaves called stomata. Stomata are gatekeepers of gaseous exchanges, regulating the trade through guard cells that open and close in response to environmental conditions. In drought situations, stomata close up to conserve resources, pushing the plant to work harder using stored energy. 

During the flowering stage, cannabis plants continue photosynthesizing. However, energy focuses on flower development instead of growing leaves and stems. Lowering water content availability during the generative cycle drives plants to use their built-in reserves to push flower development.

Interestingly, a study in 2019 showed that lowering water content increased dry weight flower and secondary metabolite production in cannabis plants. The research utilized controlled plants receiving adequate water needs during growth stages, comparing results from other plants with frequent dry down periods. The data revealed substantial increases in cannabinoid outputs of tetrahydrocannabinol acid (THCA) and cannabidiolic acid (CBDA), terpene production, and plants' yields with controlled fertigation reduction. 

Crop steering water availability through different life cycles signals the plant to focus energy on the immediate development stage, promoting optimal growth in all phases. The drought stress response also increases oxygen levels in the root zone, which helps improve nutrient uptake and root growth while shielding root-borne disease invasions.

Electrical Conductivity (EC)

A good nutritional diet is vital for cannabis plants to thrive throughout their life cycles. Nitrogen, phosphorous, and potassium are the macronutrients responsible for most of the plant's development. However, other secondary nutrients such as calcium, magnesium, sulfur, and trace elements like boron, iron, and molybdenum also have substantial roles in plant growth.

While all of these nutrients are essential for optimal growth, different plant life stages require alterations in recipe formulations. For instance, nitrogen is the driving force for leaf and branch production during vegetative growth. As the plant matures into the flowering phase, however, backing off on nitrogen inputs while supplementing more phosphorous and potassium encourages bud formation and flower development.

Not only is a change in nutrient recipes necessary when flipping into the generative state, but an increase in the concentration of formulas is also essential to feed the maturing plants. To put it simply, young plants in veg don't need as much of these elements compared to when they advance into the blooming stage. An incremental increase in nutrient concentrations throughout the plant's life encourages healthy development.

One method of determining nutrient concentrations is by taking electrical conductivity (EC) measurements with special meters. Looking into science once again, EC is the electrical charge that flows through an aqueous solution. To further elaborate, all aqueous solutions have tiny ions in constant motion flowing within them. Some are positively charged, known as cations, while others carry a negative charge called anions.

Nutrient salts also have electrical charges depending on their formulas. When mixed with water, the solution creates massive ionic exchanges, which produce an electrical charge. The higher the salt concentration, the higher the EC measurement.

Typically, young clones don't need a high concentration of nutrients as their initial focus is on root development. As the cuttings flourish, however, incremental adjustments to increase EC levels supply the plants with adequate nutrition to sustain further plant growth. Higher EC readings supplement the hungry plants as they mature into the generative cycle.

However, in another development, recent chatter on internet cannabis grow forums present a radical approach to this method, particularly when taking clones from a mother plant. The argument addresses the fact that the mother plant is receiving a higher EC due to her maturity. Thus, the clones will quickly adapt to the same elevated nutrient concentration. Some growers are experiencing bigger plants with higher yields using this method.

While side-by-side comparisons from growers who have experimented with this idea may substantiate their argument, more scientific research is needed to validate the theory.  

Fertigation Frequency

Many cannabis growers implement a daily irrigating technique that floods the substrate, allowing the excess to drain out the bottom of the pot. This feeding technique is also easy to check EC and pH levels from run-off to determine plant nutritional needs. The drain to waste method produces healthy plants with good cannabinoid profiles. However, a lot of nutrient solution leaches away with this process.

In recent years, technological advancements in automatic drip irrigation systems, complete with specialized dosing equipment, prove a better alternative in fertigation applications. These schematics save growers the costs associated with labor-intensive hand watering without wasting nutrients.

In addition, growers learned that root ball saturation was not necessary for optimal plant health. In fact, going back to the dry down tactic, cannabis plants respond better with small injections of fertigation several times a day. As the substrate dries out in between shots of nutrient dosing, the plants kick in their natural responses.

Of course, young plants in the vegetative stage need good moisture content to develop their structure. During this phase, frequent injections with some dry back time train the plants to accept the fertigation method. However, many growers stop fertigating mid-afternoon to induce a full dry back overnight.

Dialing down the frequency of shots during the generative stage sets the plant up for superior results. Growers will reduce the number of injection times during this stage to pack on the buds in the flowering cycle. Training cannabis plants with this crop steering technique increases size, bud formation, and cannabinoid production.  

Vapor Pressure Deficit (VPD)

Vapor pressure deficit plays a critical role in indoor cannabis cultivation facilities. Growers looking to maximize the potential of their crops use VPD as a measurement to control the environment. However, recent developments in crop steering take that control a step further as growers learn to dial in temperature and relative humidity to bring out the best from their plants in all life cycles.

While VPD seems like complex analysis, it's actually pretty simple. To better understand how VPD works, let's first learn how a cannabis plant distributes water throughout its system.

Through a process called transpiration, water and nutrients are transported from the root system to supply foliage and flowers with their essential needs. When the plant is satisfied, it releases excess moisture in the form of water vapor through the stomata on the leaves.

Transpiration is affected by temperature, and relative humidity in a grow room. In controlled environments with pleasing temperatures, plants move the moisture in and out, creating a steady flow of vapor pressure emitted from the plants.

However, as we've learned above, stomata react differently in stressful situations. For example, if temperatures get too high, stomata close the doors to hold moisture in the plant. Likewise, with relative humidity, if it becomes too muggy in the room, the plant cannot transpire due to excess water vapor in the air – the rate of evaporation reduces. Think of transpiration as the evaporative mechanism in water transfer through plants.

Vapor pressure deficit determines the difference between the vapor pressure emitted from the cannabis plant's leaf surfaces and the atmospheric vapor pressure in the surrounding air. A mathematical calculation with data gathered from temperature and RH readings in the grow room, and leaf surface temperatures determine VPD. However, technological advancements in Controlled Environment Agriculture (CEA) facilities now provide state-of-the-art sensors which determine VPD levels and control the environment.

Tweaking VPD at certain times in cannabis plants' life cycles can steer them to maximize their performance. For example, lower VPD levels in the vegetative stage provide a delightful environment for massive plant structuring. The rate of transpiration fuels the plants to grow prolifically during this developmental stage.

On the other hand, the stress of higher VPD levels during the generative phase causes the plants to work harder, elevating phytochemical levels. Lowering the moisture evaporation from the plant during the flowering cycle also discourages mold spores from harboring inside the stacked buds.

Crop Steering Strategies

As with everything related to cannabis cultivation, growers are still learning new concepts to achieve higher yields and increased cannabinoid production. While the above crop steering techniques explain how the plants respond when applied, every grow environment is different.

Cultivators use these techniques in various manners to achieve their own success stories. Some growers initiate generative steering when the plant is flipped into the pre-flowering stage during reproduction to boost plant response.

Others keep the vegetative training practices to within a few weeks before harvest and then hit them hard with the generative steer to finish off. Others go back and forth depending on the health of the plants. Perhaps a strain begins performing poorly after switching to generative training. Simply going back to veg steering helps the plants overcome the stress.

Crop steering is a balancing act of learning to manipulate environmental controls. Too much or too little can make or break the whole grow room. In addition, each cultivar may react differently to a stress-induced situation.

Accurate data recording and analysis when initiating crop steering techniques ensures success. Fortunately, many high-tech CEAs with full automation capabilities provide real-time data availability for growers to consider. Technology is certainly elevating the playing field in cannabis cultivation.

On the other hand, old-school growers know the importance of keeping good records of changes in their grow rooms as they learn by trial and error. On a positive note, as the cannabis industry continues to evolve, compiling data and sharing experimentation knowledge sets future cultivators up for success in the coming years.