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Soil sensors - vital for crop steering & yield manipulation.

Tom Starley
September 22, 2021
9 min read
Tomatoes grown with soil probes for crop steering
Tomatoes grown with soil probes for crop steering
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Crop steering – an introduction.

Crop steering is a fairly new term that’s increased in popularity recently, but some growers have been using crop steering techniques for many years.

The phrase crop steering is most often used by cannabis growers in relation to commercial cultivation of medicinal cannabis plants, but is applicable to commercial cultivators across the board.

After all, cultivation businesses are always looking for ways to improve operations and efficiency.

There is a surprising shortage of information out there on the topic of crop steering, but it’s the main reason that we’ve decided to make an additional detachable soil probe available to purchase in conjunction with the Grow Sensor.

The environmental data collected by the Grow Sensor alongside the data provided by a soil sensor gives commercial growers a complete and detailed overview of their whole growing environment.

This enables cultivation businesses to utilise crop steering techniques for the most benefit.

In this post I’ll be giving an overview on key points relating to crop steering, but if you’re short of time skip ahead to the specific information you need about crop steering now:

  • What is crop steering?
  • Balance is key to crop steering.
  • Crop steering with climate.
  • Crop steering with irrigation.
  • Other crop steering methods.
  • When to steer in a different direction.
  • Slow & steady wins the race.
  • Crop registration & monitoring plant development.
  • Climate crop steering with the Grow Sensor.
  • Smart soil sensor for crop steering with irrigation.
  • Combining the Grow Sensor & soil probe for crop steering.
  • Takeaways.
  • Want to help test & shape our sensor hardware & enterprise solutions?

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What is crop steering?

Crop steering is a way of managing plant growth by manipulating the growing environment to encourage crops to grow in a specific way.

Commercial cultivators can influence or tightly control light, climate and irrigation at any stage of a plants’ life cycle.

A plants’ hormones govern and regulate its growth in response to the external conditions and stress they experience.

Crop steering taps into and cashes in on this mechanism, exploiting hormonal responses through the provision of a strictly controlled environment.

By providing plants with specially engineered environmental conditions growers can literally “steer” a plant’s growth towards either vegetative or generative growth.

During vegetative growth, plants use their energy to grow roots, leaves and stems, whereas during generative growth, energy is directed into developing flowers and fruits.

Balance is key to crop steering.

Commercial growers need to nurture balance. Both foliage and flower or fruit production are important and play their part.

A crop steered too far towards generative growth with the aim of producing higher yields will rapidly deplete its energy without the necessary balance of vegetative growth to facilitate continued growth and productivity.

An uneven balance tipped towards generative growth actually causes small, weak plants, susceptible to breakage, stress and disease.

Crops that are steered too far towards vegetative growth grow excessively. Too much of the plant’s energy goes into unproductive branches and leaves and not into flowers or fruit.

If plants grow either predominantly vegetatively or generatively, the lack of balance can impact the quality and quantity of the end yield, so it’s essential to observe and adjust as necessary.

Tomatoes grown using crop steering

Crop steering with climate.

Changes in the day/night cycle of some plants can be used to induce flowering.

Just like changing the photoperiod, there are additional climate factors that can be controlled and changed to steer plants either towards vegetative or generative growth.

Generally higher temperatures are more vegetative.

Lower temperatures slow plant growth and steer towards generative as it mirrors seasonal changes seen in nature that a plant would be experiencing towards the end of its life lifecycle.

Augmenting the difference between temperatures during the day and night also has the potential to control stretching.

Bigger differences in temperature can increase inter-nodal spacing, whereas smaller differences in day and night time temperatures can decrease it.

Crop steering with irrigation.

Carefully planned irrigation is an essential part of the crop steering puzzle.

How much, how often and when irrigation takes place all affect how the plant responds and therefore how growth can be steered.

Caution needs to be taken when crop steering with irrigation as the needs or preferences of one crop or variety of plant can be different from another.

The differences can be substantial enough that an irrigation strategy that promotes generative growth in one species or type of plant, may promote generative growth in another

Creating an irrigation strategy that is tailored specifically to the genetics, environment and stage of plant development of a particular crop will lead to greater quality, quantity and consistency of the final product.

Other crop steering methods.

In addition to climate and irrigation, there are several other factors that can help to drive plant growth in one direction or another. These include:

  • How quickly temperatures change from both day to night and then from night to day.
  • Raising or reducing humidity.
  • How many air exchanges are present in the growing environment.

Again, it’s important to note that the needs and preferences of different crops can vary greatly.

Grower taking crop registration notes

When to steer in a different direction.

As mentioned above, it’s a plant’s hormonal response to conditions (stress or lack thereof) that it experiences that influences its growth.

Commercial growers usually focus on vegetative growth entirely until a given marker, i.e. until the plant is a certain size or until the first fruit has arrived.

Once this milestone is reached, the focus becomes to maximise yields via generative growth.

Whilst there are specific ways to steer each individual species of plant, generally the more stress that is placed on a plant or crops, the more growth will steer towards generative.

Steering from vegetative to generative growth.

Examples of environmental changes that generally increase stress and therefore steer away from vegetative and towards generative growth include:

  • Raising the average temperature.
  • Increasing the amount of time between irrigating (making the dry-back time longer.)
  • Raising the EC of soil through fertilisation.
  • Or adjusting the type or composition of fertiliser used.
  • Widening the gap between daytime and nighttime temperatures.
  • Increasing the rate at which the temperature drops at night.
  • Pruning suckers, leaves, flowers and fruit.

Changes such as these that subject plants to stress force the plant to put more energy into flower and fruit production.

Steering from generative back to vegetative growth.

Removal of environmental conditions that stress a plant or crops steer towards vegetative.

Reasons for needing to steer a crop back towards vegetative growth could be; plant growth slowing, nutrient deficiencies, smaller fruit, reduced fruit sets or if a growers decides that they need to improve crop density.

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Slow & steady wins the race.

Having determined that it’s time to start steering a crop, it’s crucial to do so gradually, gauging how the plants react.

This gives commercial growers the opportunity to steer back the other way if necessary.

The more a crop is steered in one direction, the harder it will be to go back the other way if needed.

Crop steering by manipulating plants’ functions is a delicate operation. It requires commercial growers to keep a very close watch on their plants at all times.

This is because the greater understanding that a grower has of their crop, the more likely they are to be able to successfully and repeatedly control its growth.

This level of care and attention requires a lot of time and effort, but crop steering done well can have massive impacts on yield quality, quantity and consistency.

Woman grower testing the soil EC

Crop registration & monitoring plant development.

Crop registration is a term used to describe how commercial growers monitor plant development, and it’s an important part of crop steering.

Taking detailed measurements of specific metrics across a sample of plants in each different growing environment lets commercial growers know how their crops are behaving and reacting to their specific lighting, temperature and irrigation conditions.

Measurements often taken weekly can include:

  • Weekly growth.
  • Number of leaves.
  • Plant quality.
  • Plant height.
  • Stem diameter.
  • Leaf and stem colour.
  • Inter-nodal spacing.
  • How long flower development takes.
  • How fast the roots develop.
  • Rootzone WC and EC measurements vs climate conditions.

Measurements often taken daily can include:

  • Day time, nighttime and average temperature over 24h.
  • Day, night and average humidity over 24h.
  • 24h average, day and night VPD.
  • CO2 levels.
  • Light spectrum.
  • Substrate moisture.
  • Substrate temperature.
  • EC drip measurements.
  • EC drain measurements.
  • When irrigation starts and stops.
  • Irrigation rates.

The more growers know, the better they can grow.

Taking measurements of the above (and often more) data points helps commercial growers know when and how to steer their crops and in which direction.

These data points and observations also help to inform the optimum climate and irrigation strategy for a growers particular crop, at each stage of growth, which helps to optimise each subsequent grow.

Having quantitative data regarding the yield from a completed crop cycle AND information on exactly how those results were achieved is essential.

Which is why it’s so beneficial to have smart sensor equipment that continually monitors and logs key environmental data 24/7.

You can read more about crop steering here.

Climate crop steering with the Grow Sensor.

The Grow Sensor has the environmental monitoring needs of commercial indoor, greenhouse and tunnel growers covered by measuring CO2 levels, humidity, temperature, VPD and light spectrum.

Grow sensors link together to give growers a detailed picture of their environment and are able to detect and highlight undesirable and damaging microclimates.

The detailed environmental data provided by the grow sensor allows commercial growers to crop steer with climate by:

  • Informing necessary changes in light intensity and photoperiod for the appropriate stage of growth.
  • Allowing monitoring and implementation of temperatures to either promote vegetative or generative growth.
  • Giving growers visibility of and the capacity to alter the difference between day and nighttime temperatures,
  • Informing growers how fast those changes need to take place to promote or improve vegtative or generative growth or encourage plants to grow in the desired way.

It was always our intention to swiftly follow up the Grow sensor with a smart soil probe.

But understanding that measuring light, climate and irrigation together, in relation to one another provides the ideal solution to help commercial growers steer their crops to success is what drove us to offer our Grow Sensor in conjunction with soil probe sooner.

Smart soil sensor for crop steering with irrigation.

Both irrigation and climate are fundamental. Growers need to be able to measure and manage both environmental conditions above the substrate and at the root zone.

The addition of a detachable soil sensor to the Grow Sensor enables commercial growers to fine tune crop root zones in the following ways.

Track fertiliser movement with accurate EC values.

Generally decreasing EC in the root zone steers towards vegetative whereas increasing EC in the rootzone steers generative.

Measure soil moisture.

Higher water content (WC) at the root zone promotes faster vegetative growth, whilst decreasing WC in the root zone slows growth, steering towards generative.

Determine dry back.

Grow faster by ensuring smaller dry backs between irrigations and overnight to steer towards vegetative.

Slow growth down by Increasing dry backs between irrigations and overnight (by delaying the first irrigation of the day and stopping irrigation before night time) to steer towards generative.

Inform smart watering schedules.

Water less at high frequencies for faster vegetative growth and increase water volume at lower frequencies to steer towards slower, generative growth.

Measure substrate temperature.

Raise growing media temperature to increase plant growth rates and steer towards vegetative or lower it to decrease plant growth rates and steer towards generative.

The features that our precision wireless sensor equipment and accompanying software provides enables commercial growers to:

  • Easily monitor environmental climate data and uncover damaging microclimates.

  • Determine irrigation volumes, shot sizes and effectively manage crop root zones.

  • Discover, monitor and manage atmospheric or root zone extremes or fluctuations that waste plant energy and reduce yields.

  • Simply determine the optimal climate and irrigation strategy to enable effective automation.

  • Steer towards vegetative growth to grow strong, healthy, vigorous plants, faster and more efficiently.

  • Steer towards generative growth to optimise product quality, quantity and consistency.

  • Minimise waste, save costs and improve sustainability by using the optimum amount of lighting, heating, cooling, irrigation and fertilisation, no more.


Whether or not commercial growers know the term crop steering by name, or are instead just familiar with the optimisation required in modern day growing, it is undoubtedly the future of modern farming.

Crop steering helps commercial growers formulate strategies and chart a course to follow to grow the best produce, consistently.

Collecting the data required to inform and adapt plant growth management practises can be daunting.

Luckily smart agri-sensors that measure both the atmosphere and substrate simultaneously simplify the task.

Grow Sensor’s custom built software designed specifically for commercial indoor, greenhouse and tunnel growers provides all the data growers need about their growing spaces 24/7.

The user-friendly desktop, Apple and Android apps give growers the granular information to enhance crop steering capabilities, achieve desired outcomes and scale their business.

Want to help test and shape our sensor hardware and enterprise solutions?

The Grow Sensor is now available with an accompanying soil sensor to give growers like you a complete picture of your environment.

Get all the actionable data you need for successful crop steering!

As detailed in this post, we’re now ready to begin collaborating with a select few businesses to test our sensor hardware and enterprise software solutions.

We want to work with businesses that are looking to use intelligent technology to help them scale and optimise operations, (minimise waste and improve ROI.

Reach out to us on hi@growsensor.co and let’s get the conversation started… We can’t wait to hear from you!

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Tom Starley
September 22, 2021
9 min read

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