Monday, September 20, 2010

Nutrient Mixing and Monitoring

The following tools have been purchased to provide maximum growing nutrients for the plants:

First thing's first, calibrating the meters.

Pour some of the pH 7.0 buffer solution into a cup. Remove the cap and submerge the pH meter. It should be around 7.0. Mine was a 6.4 so it needed some calibration with the included flat head screw driver.

To calibrate the TDS meter you should probably also pour some solution into a small container. I don't have too much buffer, so I calibrated for the first time directly in the container. I know this is a big no-no, but the meter was fresh from the case and perfect accuracy may not be so important. It was close enough to be calibrated for my purposes.

Now that calibration is complete, we need some baseline measurements.

I got a half gallon of tap water then mixed in the appropriate amount of Pure Blend Pro Grow as recommended for seedlings (1.5 teas / gal so 0.75 teas/half gal). Using the TDS meter, I measured 243 ppm. Using the pH meter I measured 6.5. This was the perfect pH! All my plants grow best between a pH of 6.0-7.0.

Next I measured the ppm and pH of the nutrient solution that has been in use the last 2-3 weeks while the plants have been sprouting. The pH was 6.1 which indicates that as the plants use the solution, the pH goes down and some pH UP may be needed. However much to my dismay, the ppm was 362. I think this is likely caused by either plant waste or dust from the clay pellets. The only solution is to replace the entire batch of nutrients to get a good reading. To avoid this problem in the future, I will potentially add an internal filter; probably one designed for an aquarium. This regulator is needed so that I can use the lowering of ppm to determine how much nutrient solution to add as time goes on.

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