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Monitoring critical to success in hydroponics

by Vicki Parsons

The reason that hydroponics can be so spectacularly successful is that growers provide the perfect environment for their plants, ensuring that the exact nutrients, pH and light levels and day lengths are available for optimum growth.

The downside to that equation, of course, is that it’s 100 percent up to the grower to make sure that everything is perfect – or at least within very clear limits of survival. The new nutrient solutions (see Garden & Greenhouse May and June 2007) make it much more likely that your plants are getting exactly what they need, but most experts still recommend regular testing.

Two measurements are critical, pH and nutrient levels. Not enough nutrients and your plants will stop growing, but if they receive too many nutrients they’ll die. pH is more complicated – simply put it’s a measure of the acidity or alkalinity of the water. Too much acidity burns plants (think vinegar) but too much alkalinity is just as bad (chlorine bleach is a good example.) While different plants may have slightly different pH requirements, most thrive in a slightly acid to neutral solution, about 6 to 6.5 on a scale of 15.

Even minor changes in either direction can cause problems, because nutrients begin to precipitate out of acid or alkaline solutions so they are no longer available to your plants.

Nutrient levels are measured two ways, either as total dissolved solids (TDS) which is often expressed as  parts per million (ppm), or electrical conductivity (EC). Understanding the science isn’t as important as knowing which numbers the plants you’re growing require. Small seedlings or green plants like lettuce typically require far fewer nutrients than heavy feeders such as fruiting tomatoes.

As you might expect, new technology has made monitoring much easier than the traditional test kits that required that you dip little pieces of paper into meticulously measured solutions and then compare colors on a chart to guess the results. Products like the Tri-Meter from Extreme Growing offer real-time monitoring of pH, EC, TDS and temperature with an incredibly easy setup and calibration recommended just once a month. A remote probe stays in the hydroponic reservoir and reports back to an easy-to-read display that plugs into an electrical outlet instead of requiring batteries.

If you’re not quite ready to make that investment, you should still plan on purchasing an inexpensive pH test kit. Even the simple paper strips can give you an idea of where your nutrient solution lies along that critical continuum.

And if you’re not monitoring, you should have a regular schedule to replacing all or part of your nutrient solution. But be careful – dumping nutrients into storm drains or creeks can cause algal blooms in nearby bodies of water. In fact, nutrients are generally considered to be the single most damaging contaminant in most US rivers and lakes. GG

An award-winning journalist with more than 20 years experience as a business, environmental and garden writer, Vicki Parsons is also a fifth-generation farmer who owns Neem Tree Farms in Brandon, Fla. You can visit her website at www.neemtreefarms.com