Introduction:
In recent years, crop steering has taken on a life of its own in the cannabis industry. You hear from growers etc. But what is it? How did we get here? Today let’s talk about crop steering: what it is, how to do it, why it’s important, and how you can benefit from it. this guide provides an overview of the concepts, methodologies,
WHAT IS CROP STEERING?:
Cannabis plants have hormonal systems that regulate their growth in response to external conditions and stresses. These reactions are a result of millions of years of evolution and the plant's adaptation to seasonal changes. Crop Steering is essentially the exploitation of these hormonal responses through the manipulation of a controlled environment. Using lights, climate, irrigation to encourage plants to grow a certain way. Next to light intensity, it’s the most important tactic you can use to manipulate yield.
Vegetative plants are in a state where most of their energy goes towards leaf growth and very little towards flower production. The opposite is true of generative plants, where the plants put most of their energy into flower growth and have little left to invest in new leaves or stem growth.
Plant Balance:
Growers must maintain proper plant balance, which is the balance between leaf and flower production. Plants that are growing overly generatively or vegetatively are considered to be out of balance. If the plant isn’t in balance, then it’s likely that production and quality will ultimately suffer.
In general, the intent in commercial cannabis production is to maximize yield by optimizing the time plants spend in vegetative growth to ensure they produce only enough foliage and stems to support vigorous flower production.
Vegetative v Generative Phases
Vegetative Growth
Vegetative growth is when stems and foliage are the predominant focus of the plant’s energy use and resulting growth. As plants grow vegetatively they increase their photosynthetic capacity by increasing their leaf area and mass.
Although cannabis vegetative growth is most notably associated with the phase between clone and flowering, it’s possible to use vegetative cues to nudge plants into vegetative growth at any point in their lifecycle. For instance, if you have compact, slow-growing flowering plants you can use climate and irrigation cues to inspire vegetative growth, stretch the plants out, and increase internode spacing. Some growers also use vegetative cues at points during the flowering growth phase to promote hearty bud growth.
Vegetative Steering Characteristics
To inspire vegetative growth you must simulate conditions similar to spring, which allows your plants to thrive and maintain vigor. Conditions that favor vegetative growth include lower electrical conductivity (EC), higher water content (WC), lower vapor pressure deficit (VPD), lower light intensity, and an overall stress-free environment.
The following ranges are examples of conditions that could induce vegetative growth. Actual conditions will vary by grow environment and cultivar. It’s critical that you adapt your climate and irrigation strategy to your specific environment and genetics by combining experimentation of steering actions with frequent crop registration.
Generative Growth:
In generative growth, the plant’s energy is directed toward creating flowers. With this focus on flower production, the plant slows down the growth of new foliage and reduces stretching.
Generative growth cues can be leveraged throughout the plant’s lifecycle, not just in the flowering period. For instance, if you have plants that are demonstrating signs of excessive vegetative growth, such as stretching too much with larger internodal spacing, then you can modify your climate and substrate to steer your plants to grow more generatively.
Generative SteeringCharacteristics
In contrast to the mild conditions that inspire vegetative growth, harsher summer-like conditions are the foundation of generative cues. Lower WC, higher EC, and higher VPD are all examples of ways to motivate generative growth in cannabis plants.
The following ranges are examples of conditions that could induce generative growth. Actual conditions will vary by grow environment and cultivar. It’s critical that you adapt your climate and irrigation strategy to your specific environment and genetics by combining experimentation of steering actions with frequent crop registration.
In generative growth, the plant’s energy is directed toward creating flowers. With this focus on flower production, the plant slows down the growth of new foliage and reduces stretching.
Generative growth cues can be leveraged throughout the plant’s lifecycle, not just in the flowering period. For instance, if you have plants that are demonstrating signs of excessive vegetative growth, such as stretching too much with larger internodal spacing, then you can modify your climate and substrate to steer your plants to grow more generatively.
Generative SteeringCharacteristics
In contrast to the mild conditions that inspire vegetative growth, harsher summer-like conditions are the foundation of generative cues. Lower WC, higher EC, and higher VPD are all examples of ways to motivate generative growth in cannabis plants.
The following ranges are examples of conditions that could induce generative growth. Actual conditions will vary by grow environment and cultivar. It’s critical that you adapt your climate and irrigation strategy to your specific environment and genetics by combining experimentation of steering actions with frequent crop registration.
WHAT IS CROP REGISTRATION?
Crop registration, which is the collection of detailed observations about your crop, is arguably the most important aspect of crop steering. Through this method of diligent data collection, you can track how steering actions are driving changes in your plants. Each cultivar is unique, and as a result, you should experiment to see how growth cues impact the various genetics you grow.
What Should You Track?
Crop registration should occur frequently to ensure you’re effectively tracking the impact of steering cues on your crop. By collecting data on these key performance indicators (KPIs) at a regular frequency for each round, you can begin to make correlations about the cause and effect of various steering actions. This historical data becomes a powerful tool in predicting plant performance and enables you to optimize crop yields by making changes to your operational processes and steering techniques.
COMMON CROP OBSERVATIONS
• Plant height
• Root development
• Stem diameter
• Internodal spacing
• Leaf color / Stem color
• Flower circumference
• Trichome attributes
• Plant vigor
DEVELOPING AN IRRIGATION STRATEGY
Irrigation is a fundamental aspect of cannabis crop steering. In order to successfully steer plants with irrigation, growers must have the ability to sufficiently manage the root zone. Selection of substrate and irrigation equipment, in addition to volume, frequency, and timing of irrigation events, are key considerations during the development of an irrigation strategy.
Considerations for Different Substrates
When attempting to apply irrigation steering techniques to different substrates, it is best to check with the manufacturer or supplier to see if there are any special considerations to take into account. In general, Rockwool is considered a more steerable substrate since it has a low cation exchange, meaning it has less influence on the pH and nutrients being applied, thus requiring less runoff than other substrates. Rockwool also has a higher holding capacity and water is more readily available to the plants, allowing for larger swings in water content.
Coco, soils, and other “organic” substrates have higher cation exchange, so there is more competition for nutrients with the plant and buffering of pH. Thus requiring more runoff to maintain ideal growing conditions. Additionally, the composition of these substrates can vary, changing the watering holding capacity and dry back speed.
Container size and height also play a significant role in the steerability of the root zone. Taller containers, or stacking of Rockwool blocks, will create larger differences in water content over the height of the medium. In some cases, there can be more than a 30% difference in water content over the height of the container. Growers should take this into account when drying back after initial transplant or when attempting to achieve large dry backs during the late growth stages since this can induce high stress on the plants and potently build up EC in the higher parts of the media.
Calculating Substrate Irrigation Volumes
Calculating ideal irrigation volumes is simpler than it sounds. The amount of solution you apply to irrigation is a product of how much growing media you have per plant and whether you would like to steer more generatively or vegetatively. For example, if you had 3.5 liters of growing media, to determine shot volume you multiply by the desired shot size.
Crop registration, which is the collection of detailed observations about your crop, is arguably the most important aspect of crop steering. Through this method of diligent data collection, you can track how steering actions are driving changes in your plants. Each cultivar is unique, and as a result, you should experiment to see how growth cues impact the various genetics you grow.
What Should You Track?
Crop registration should occur frequently to ensure you’re effectively tracking the impact of steering cues on your crop. By collecting data on these key performance indicators (KPIs) at a regular frequency for each round, you can begin to make correlations about the cause and effect of various steering actions. This historical data becomes a powerful tool in predicting plant performance and enables you to optimize crop yields by making changes to your operational processes and steering techniques.
COMMON CROP OBSERVATIONS
• Plant height
• Root development
• Stem diameter
• Internodal spacing
• Leaf color / Stem color
• Flower circumference
• Trichome attributes
• Plant vigor
DEVELOPING AN IRRIGATION STRATEGY
Irrigation is a fundamental aspect of cannabis crop steering. In order to successfully steer plants with irrigation, growers must have the ability to sufficiently manage the root zone. Selection of substrate and irrigation equipment, in addition to volume, frequency, and timing of irrigation events, are key considerations during the development of an irrigation strategy.
Considerations for Different Substrates
When attempting to apply irrigation steering techniques to different substrates, it is best to check with the manufacturer or supplier to see if there are any special considerations to take into account. In general, Rockwool is considered a more steerable substrate since it has a low cation exchange, meaning it has less influence on the pH and nutrients being applied, thus requiring less runoff than other substrates. Rockwool also has a higher holding capacity and water is more readily available to the plants, allowing for larger swings in water content.
Coco, soils, and other “organic” substrates have higher cation exchange, so there is more competition for nutrients with the plant and buffering of pH. Thus requiring more runoff to maintain ideal growing conditions. Additionally, the composition of these substrates can vary, changing the watering holding capacity and dry back speed.
Container size and height also play a significant role in the steerability of the root zone. Taller containers, or stacking of Rockwool blocks, will create larger differences in water content over the height of the medium. In some cases, there can be more than a 30% difference in water content over the height of the container. Growers should take this into account when drying back after initial transplant or when attempting to achieve large dry backs during the late growth stages since this can induce high stress on the plants and potently build up EC in the higher parts of the media.
Calculating Substrate Irrigation Volumes
Calculating ideal irrigation volumes is simpler than it sounds. The amount of solution you apply to irrigation is a product of how much growing media you have per plant and whether you would like to steer more generatively or vegetatively. For example, if you had 3.5 liters of growing media, to determine shot volume you multiply by the desired shot size.
ROOT ZONE MANAGEMENT
Management of your irrigation strategy on a daily basis is critical to successfully steering with irrigation. Utilizing root zone monitoring sensors and measuring drain volumes empowers growers to tailor their irrigation strategy to different plants under changing environmental conditions. By monitoring and adjusting water content (WC), total drain achieved compared to irrigations applied, electrical conductivity (EC), as well as dry back overnight, and between irrigations each day, you can steer your crop to the desired result.
Daily IrrigationSchedule
Many growers utilize a multi-phase irrigation schedule that was initially popularized by Grodan. When utilizing this methodology there are four distinct phases.
IRRIGATION PHASES
Phase 0: Lights On to First Irrigation
Phase 1: First Irrigation to run off
Phase 2: Runoff to Last Irrigation
Phase 3 : Last Irrigation to Lights On
Management of your irrigation strategy on a daily basis is critical to successfully steering with irrigation. Utilizing root zone monitoring sensors and measuring drain volumes empowers growers to tailor their irrigation strategy to different plants under changing environmental conditions. By monitoring and adjusting water content (WC), total drain achieved compared to irrigations applied, electrical conductivity (EC), as well as dry back overnight, and between irrigations each day, you can steer your crop to the desired result.
Daily IrrigationSchedule
Many growers utilize a multi-phase irrigation schedule that was initially popularized by Grodan. When utilizing this methodology there are four distinct phases.
IRRIGATION PHASES
Phase 0: Lights On to First Irrigation
Phase 1: First Irrigation to run off
Phase 2: Runoff to Last Irrigation
Phase 3 : Last Irrigation to Lights On
Phase 0: Lights On to First Irrigation
After the lights are on in your room (sunrise), you should wait until your plants are actively transpiring before beginning irrigation for the day. You can verify that they’re transpiring by monitoring the water content (WC) in your substrate. As the plant's uptake water, the WC in the substrate will decline. You can use varying amounts of dry back from sunrise to your first irrigation in order to steer your plants vegetatively (1 - 4% dry back) or generatively (4 - 6% dry back).
Phase 1: First Irrigation to Runoff
Once your plants are actively transpiring, your plants are ready for the first irrigation of the day. The goal for this irrigation phase is to reach peak water content (WC) for the day and achieve runoff 1 - 3 hours after your first irrigation.
The number of irrigations required to produce runoff will vary depending on substrate size, starting WC, shot size, and irrigation frequency. Achieving a minimum of 1% dry back between each irrigation is ideal to ensure you’re not seeing runoff too quickly. If you’re steering more generatively and are applying a larger irrigation shot (6%+), you should aim for a longer dry back of 2% - 3% between feedings to avoid hitting peak WC too early and creating excess drain.
Phase 2: Runoff to Last Irrigation
During this phase the goal is to reduce EC to its lowest daily value while light intensity and temperature are at their highest, These conditions require your plants to work their hardest and typically correspond with the midpoint of the day.
Since you’ve already achieved your desired WC and first drain in Phase 1, during this phase you can tailor the volume and frequency of irrigations to hold WC consistent in your substrate. You can do this by reducing your shot size and adjusting the dry back between shots. You should aim for at least 1% to 3% dry back between each shot if steering more vegetatively. If steering more generativity you should target 3%-6% dry backs during this phase.
Phase 3: Last Irrigation to Lights On
It’s important that you time the last irrigation of the day so that you allow adequate time for proper overnight dry back. Depending on the stage of growth, you should aim to achieve 2% to 6% dry back between the final irrigation and lights off (sunset). If steering vegetatively, you should target dry back from the last irrigation of the day until the first irrigation of the following day between 10% to 15%. For generative, aim for 20 - 30% or more.
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