The competitive cannabis marketplace has necessitated the development of precise cultivation methods. Central to the success of these methods is data collection, which offers multiple benefits to the cultivator.
Foremost, accurate data collection – and real-time monitoring – allows for any operational errors to be corrected before irreversible damage is done to the plants. Secondly, helpful trends often emerge from historical data, inspiring experiments or ‘tweaks’ which can further improve the desired characteristics of the strain. Third, data collection allows for the creation of recipes: specific growing conditions and practices ensure consistency from one harvest to the next.
These three benefits can be achieved by collecting the right data, presented in the categories below.
One additional point of attention worth noting is the tolerance of any environmental measurement device. Cannabis demonstrates high sensitivity to its environment, some strains more than others. Recommended tolerances are included for each category.
Environmental Parameters
Day and night temperatures (+/- 3C)
Temperature measurements should be taken at intervals no greater than one hour. Temperature measurements should be read from multiple points within the grow space, with the exact number of sensor points determined by the size of the room. In general, measure temperature at the center of the room, within the canopy at several locations, and closer to the perimeter of the crop.
These measurements can be used to detect any discrepancies between the intended temperature schedule of the grow room, and the actual grow room temperature.
There is also a variety of handheld IR (infrared) monitors available, which can be useful in diagnosing plant stress as well as any hotspots within the cultivation space that may be caused by suboptimal installation or operation of HVAC equipment.
The following image shows a cannabis plant under an IR camera, courtesy of Black Dog LED:
Relative humidity (+/- 3% RH)
Relative humidity can spike much more rapidly than temperature, and cannabis is much less resilient to changes in humidity. Measurements taken every 15 minutes are recommended. Humidity sensors should be placed at similar locations to temperature sensors.
Light levels (+/- 5% uncertainty)
A portable spectrometer should be on-hand to measure PPF output of all grow lights, and to ensure a consistent spectrum – as the spectral output of any luminaire will degrade over time. This spectrometer should have a nanometer range encompassing that of the grow lights used. Test each luminaire at the canopy, a minimum of once a month and before any new crop is started. Expired grow lights should be replaced with an equivalent model to ensure consistency.
Supplemental CO2 levels (+/- 5% CO2)
CO2 should be measured at the plant canopy and compared with the expected levels based upon what was supplied to your system. Mass transfer is a complex process, influenced by air movement within the room; this may affect how much CO2 is actually delivered to the plants. Take note of the time of day supplemental CO2 is provided.
Plant Parameters
Watering schedule
For traditional, soil cultivation, the total daily volume of water delivered to plants should be measured along with the rate of delivery. Plants respond differently to ‘tiny drinks’ of water vs. long soaks; this data can help uncover ways to improve your watering schedule.
Nutrient dosing
Measure the type and quantity of nutrients delivered, as well as the time of day.
This data above must be collected over several harvests, using a consistent collection methodology, to develop a complete cultivation ‘recipe’ to which subsequent crops can adhere.
Data Analysis
Effectively analyzing the data is an entirely different matter. As each parameter does not exist in isolation, the interactions between each variable and the subsequent influences on crop quality can be complicated.
A horticultural specialist would be useful to have available to look at the data and make recommendations. Alternatively or in conjunction, many control systems do offer their own automated data analysis package to take the guesswork out of making sense of cultivation data.
Central Control System
Optimally, these components critical to a successful indoor grow would be regulated with the same central control system. A central control system should have the option of remote monitoring, providing the ability to see the environmental conditions of the grow at any time, from any location, on multiple devices.
Additionally, this system should be redundant, able to operate continuously in the event of a power outage. Appropriate data storage should be included – on-site with an optional cloud backup – based upon the size and demands of the grow.
Having a centrally-integrated data collection and control system can be more time- and cost-intensive at the outset, but saves much of both during the lifetime of the grow.
