The Importance of Testing Your Runoff: Why should I care? No matter what background you come from in the cannabis industry, we all have very important roles to play. Whether it be growing, selling or consuming what is put into our flowers from day 1 affects us all. Serene Green takes pride in making sure we make growing as easy as possible and to set every customer up for success; Think of us as your personal “synthetic chemists' '
Why Should I Test the TDS and Check my PPMs? PPMs stand for “parts per million” and is a unit of concentration. For example: let’s say there are 5 lbs of cannabis compared to 1,000,000 lbs of water, we could say that the concentration of cannabis is 5 ppm. When we are talking about PPMs we are referring to the Total Dissolved Solids (TDS). You may also come across growers who use Electrical Conductivity (ED) but the principle is the same. The more nutrients you add to your water (higher concentration, more PPMs), the higher
your EC.
When measuring PPMs, you are analyzing the amount of nutrients or salts in your water. This is important to ensure you add the correct amount of nutrients every feeding. Let’s say you measure on Monday and you get 1,400 ppm. You measure on Tuesday using the same feed and you get 2,000 ppms in your reservoir. This data can help you conclude that too much nutrients was added on one day vs the other and you can make corrections accordingly.
Although this information is helpful, it isn’t the other reason we measure PPMs. Testing the water stream that goes beyond the root zone (runoff water) can give you the edge to make corrections before problems occur, setting your plants up for success.
How to Measure your Runoff Treat every time you measure like a science experiment, whether you are checking for pH, ppm or something else, it should always be done properly. Measuring your water stream alone is useless if no other data is collected along with it. I recommend testing at minimum the pH and ppms (usually can be done with the same instrument). Both of these measurements should be taken from the original water solution (the sump) AND from your runoff water.
How to Read your Results: Situations you may come across and how to interpret the data Assuming you have collected your pH and ppms from both the sump and your runoff, here are a few situations you may encounter: No change in the PPMs between the sump and your runoff can suggest that your plant is not up taking the nutrients properly from the sump. This could be due to your pH range; certain ions can only be taken up by the plant in certain ranges
If your ppms is lower in the sump than usual, check for white precipitate (a solid). If you’re sure you added the correct amount of nutrients then one reason this might be the case is nutrient lockout. Not all the ions in your sump get long and can react with one another to form a solid that is not soluble in water, for example calcium phosphate. When your ppms are lower in the runoff than in the sump, you’re in the clear! This means your plant is up taking the nutrients as it should! If you monitor daily and notice a standard drop (ex: 1500 in 750 out) 5-6 days a week, your plant is up taking the same amount of nutrients each day and have a very consistent conditions. When it comes to pH, a little variation is normal but when you notice a large difference, look out for nutrient lock out. If your pH is drifting certain nutrients might not be readily available to your plant which can lead to nutrient lock out. You will notice yellowing when your pH is out of the ideal range, but continue to look for other deficiencies.
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