Testing Hydroponic Nutrients

Hydroponic systems use a formulated nutrient mix to fertilize plants.

Although nutrients are formulated in ratios that reflect the needs of the plant, transpiration and crop differences mean that nutrient levels can drift away from the optimal values. A system manager must manage the fertilizer in system water to maximize plant growth.

If you have a hydroponic system, that manager is you. There are several convenient ways to test a system. Let’s learn what those are.

Dr. Nate had Upstart Farmer Haydn Christensen, an experienced hydroponic farmer, walk us through the process of testing a hydroponic system. Haydn tests his system once a day. The frequency with which you test your system is especially important if your system is small, as smaller systems fluctuate more severely than large systems.

Key measurements: pH and EC

The two main measurements a hydroponic grower needs to make are pH and EC levels. Both of these can be done with meters.

pH is the measure of the acidity of a system, and determines how plants and other organisms interact with different nutrients. Every crop has a specific pH range, but most herbs and greens overlap within a range. Try to keep pH between 5.5 and 6.5 without changing more than .5 per day. (Drastic changes may shock plants.)EC is a measure of the salts in your system- that is, the level of nutrients in your system. EC should be kept between 1.2 and 2.0.

EC and pH meters are affordable and often come as one dual meter.

Adjusting pH is as simple as adding an acid or base solution

Unless you use an RO filter together with an acidic solution, rarely will you have to worry about raising pH. It’s more likely that you will have to lower pH. While lowering pH requires several steps in aquaponics, lowering it in hydroponics is simple. You can use a pH buffer like pH Down by General Hydroponics, added to your system in a certain quantity, which is decided by how far you wish to lower your pH.

If you do have to raise pH, you can use a base addition instead of an acid addition.

Quick Tip: If your pH is behaving strangely or giving you difficulty, you might have a carbonates problem. Check out what that means and how to fix it here.

The key to EC is dilution

You can easily lower EC by diluting your system with fresh water. Take measurements intermittently while adding water until it is mixed to the correction level.

You can raise EC by adding fertilizer.

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