The $20 pH meter from Lowes works fine for me. You can mix ferts in a gallon of water, then add lime as necessary to bring the pH somewhere around the low 6s. Meter also has a fert gauge, which I think is useless. The catch is you have to strip the oxidation off the prongs if it's been sitting for a few days. It comes with a little scouring strip to do that, but it wears out pretty fast. Gotta see if I can find some more or maybe use something else to scour.