Education Guides

Getting to the root
of cannabis runoff

One of the biggest challenges growers face is finding the balance between the “old way” of doing things and the present realities of needing to be profitable. And not just with their practices, but also with the language used to define them. Take cannabis runoff, for example. Historically with runoff, cannabis cultivators looked to it as a gauge for nutrient buildup to make up for the lack of visibility inside the substrate. But now that growers have access to sensors that deliver precision EC and WC data, measuring runoff in cannabis is more about assessing the bigger irrigation picture. By adjusting our thinking beyond using it to determine the build-up of cannabis nutrients, runoff volume helps growers assess their approach to watering. When applied within the context of crop steering, runoff in cannabis can go a long way to help cultivators dial in their overall irrigation strategy – here are some things to consider…

Cannabis runoff isn’t just about nutrients

For lots of growers, runoff in cannabis has long been used as a marker for the uptake of nutrients – the higher the runoff pH, the more negatively-charged ions are being taken into the plant, and vice versa. But plants uptake water differently in rockwool versus coco, which means cultivators who rely solely on this data point to inform their overall nutrient program could be missing key information. That’s why we’re such big proponents of leaf tissue analysis, which gives growers a more detailed breakdown of each plant’s nutrient composition – distilling down to the specifics necessary to identify, and address, nutrient imbalances. Besides, at the end of the day, runoff has a much bigger role to play when it comes to irrigation.

Once a substrate has reached its maximum field capacity, adding more water will cause it to seep from the container – that seepage is known as leachate, aka runoff. When steering crops to achieve certain outcomes, understanding how much amount water the grow medium can take in before runoff occurs is crucial, because it tells growers how much water their plants need in other to achieve optional growth and nutrition. As a general rule of thumb, exceeding 30% runoff likely means you’re overwatering your plants. But it’s important to remember that everything from substrate type to the individual needs of the cultivar can impact runoff – and using data is your best tool for figuring out the benchmarks that make the most sense for your crops.


Benefiting from a birds-eye view of runoff

Let’s face it: growers work hard to cultivate success in an industry that’s highly regulated, yet lacking in centralized standards and practices. That’s why data holds the key – not only by expanding our knowledge but by helping to set universal standards that improve upon the “old way” of doing things. To go deeper into runoff, check out these segments from Episode 12 and Episode 42 of Office Hours.

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