Mixing fertilizer and sulfuric acid

marc5(6aOH)November 1, 2012

I recently discovered this wonderful forum, and have spent hours reviewing some great threads led by Al, with contributions by many experienced growers. Thanks Al, for sharing your knowledge. A short intro: I'm interested in propagating native deciduous trees, mostly pawpaws. I've been experimenting with starting them from seed in different containers and mixes. From threads here on the forum I've already gained some insights on mixes, watering, and fertilizer. I now see where I've gone wrong at times! I've got plenty of questions, but I'll start out now with one.

Next spring I will be watering hundreds of containers, so I need to be efficient. New containers will be filled with 5-1-1, or something similar (thanks, Al). The alkalinity of my water is very high (260 ppm, and ph is 7.4) so I must add sulfuric acid to it. With plenty of calcium and mag, I don't need to add those elements. For fertilizer I have used some controlled release; I have also used some water soluble with fertigation. I am shopping for water soluble with Al's ideal 3:1:2 ratio without Ca and Mg. I will be purchasing a Dosatron injector to inject fertilizer and acid. My question: what about mixing the acid and the fertilizer in the same stock tank? I have read here of possible problems with precipitants (thanks redshirtguy). Short of a jar test, is there any way of knowing of potential mix problems before I buy a bag of fertilizer? Peters and Plantex are available around here.

Many thanks for sharing your knowledge,


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The best thing to do is call and ask, as it's very likely they can give you exact recommendations based on the product you want to use. The conventional wisdom is to use separate injectors, because the interactions between acid stock solutions and fertilizer stock solutions are complicated and likely to cause problems.

Even jar tests may not give you all the information when you're using a micro-irrigation system.. even small amounts of insoluble precipitates can build up and clog nozzles, creating a huge headache.

If citric acid is an economically practical choice, you may want to consider it. It's relatively complication free, even with respect to micronutrients.

    Bookmark   November 1, 2012 at 12:47PM
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