I have found a source of Peat Lite 20-10-20 manufactured by J.R. Peters Co. at $15.50 per 25 lb bag. It is a water-soluble fertilizer. Please advise whether or not it can be used as a substitute for the Mittleider formula, and what, if any additions should be made.

I can’t answer for the usability of any other fertilizer, not having field-tested them. But water-soluble fertilizers are intended for use in a greenhouse or hydroponic growing environment, where feeding is done in the daily watering. So, for seedling production, it may work for you (with the caveats stated below), however, where we feed weekly in the garden, Pete Lite may leach beyond the plants’ root zone before the next feeding, and your plants could go hungry.

Nutrient Mittleider Magic % Pete Lite %
Nitrogen 13.0 20.0
Phosphate 8.0 10.0
Potash 13.0 20.0
Magnesium 1.3 0.25
Sulfur 6.4 0.00
Calcium 0.9 0.00
Boron 0.16 0.02
Manganese 0.15 0.05
Zinc 0.20 0.016
Iron 0.02 0.10
Copper 0.04 0.01
Molybdenum 0.03

 

0.01
Chloride 0.10 0.00

Dr. Mittleider’s worldwide experience has shown us that the high %’s of NPK are not needed. That may be why some folks are concerned with toxicity in many commercial fertilizers.

On the other hand, we almost always experience a need for higher amounts of the next three – or secondary – nutrients than are customarily applied. Notice we have 5 times the magnesium, and Pete Lite lists neither of the other two (in their defense, they recommend a separate calcium-source application, similar to our Pre-Plant Mix). Sulfur should be supplemented – especially in a low-rainfall/high pH area (sulfur lowers the pH).

And most of the micro-nutrients are substantially higher in Mittleider Magic – for good reason. Sometimes, however, the %’s of Micro-nutrients can be misleading. For example, if a chelated compound is used, the nutrient is more available than if a straight sulfate compound is used. This is the case with our Iron – and that’s why we use less than Pete Lite does. Perhaps they use chelated compounds of some of the others, whereas we do not.

All of that being said, you may have success with Pete Lite for some time, especially in the greenhouse, before you begin seeing serious deficiency symptoms.