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Coldwater, Michigan | Jon,
Many of the green phos acids are simply reacting sulfuric acid with rock phosphorous, giving the byproduct gypsum. That's a toxic waste in many of the areas where the mining and processing is done. Spent acid is in this case Phos acid that has been used for something prior to becoming fertilizer. Many times in the past (probably still) Phos acid was used to etch steel and aluminum ( didn't have to be white acid), then sold to the fertilizer companies as Phos acid fertilizer. Much the same way some of our micro-nutrients come to us. Anyway, in the past when Phos was short the products came directly to us, and tended to be black acid. In recent years the product usually is filtered, or reprocessed, before being returned to fertilizer grade. Since it has been used at least once it is referred to as "Spent acid. Not all of the "green" phos acid is spent acid, but you would have to know the products history to know for sure. Many purists believe if it is green, it is spent acid, not so. White acids go thru a purifying process in addition to the normal reaction described at the beginning of this paragraph above. That process is often described as "Furnace grade" which would be among the more pure "White" acids that are used in food production. Most premium fertilizer companies no longer use "furnace grade" acids because of the disconnect between food and the production of food from a cost standpoint. They may still use "White" acid, but usually not "furnace grade".
What some people, fertilizer companies, and farmers, can't get thru their heads is that absolute purity does not necessarily convert to yield. I believe in reasonable purity of a product, especially if it is to be placed with the seed, but a 80/20 6-24-6 with a good set of micros will do the job nicely, thank you!
The past company I worked for at the time, called off testing it's own product against any other product they produced because the less pure one was winning the yield trials. In 17 tests of their 6-24-6 (80/20 ortho/poly) vs their 9-18-9 (100% ortho - pure), the 9-18-9 only beat their 6-24-6 one time. At that time they decided they were going to declare the 2 products equal, or that one of the products was as good as the other. No further testing was to be done between the products, or any other product they produced. So, if a product is performing and not of absolute purity, it doesn't bother me a whole lot here. I believe in selling, and recommending what works, not some theory that is unproven. I will however say that most of the people at fertilizer plants have no clue whether they are recommending the best product for the particular situation at hand, or not, because they have never tested their ideas (or someone else's). They might know it is a good total fertility recommendation, but have little experience with whether that recommendation is the best paying recommendation for the farmer, or not.
Wow! That got long-winded!
Edited by Bill Moyer 4/6/2010 10:36
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Liqui-grow fertilizers
