[hamil]

I recently bought a soil testing kit. It seems obvious to me that since after testing chemicals the color determines the concentration of nitrogen, phosphorus, and potassium. This must mean that with a given concentration of sample, some sort of pH determining chemical or other chemical must be used to determine the concentration. I would like to know the exact chemistry behind the soil test kit. That is what are the chemicals used, what concentrations, and etc. Can someone point me to the answer? Thanks a lot.

[Arkcon]

When you asked the question two years ago: http://www.chemicalforums.com/index.php?topic=79780.msg290631#msg290631 no one jumped in at the time, or since.  This question is a somewhat obscure one, its come up before, and no one really knows the answer.

Maybe its a trade secret, the kit makers don't want to share.  Seems odd to me, and likely to you too, but that's a guess we have to consider.

I don't think people try to study this topic because -- these tests aren't that good.  They seem to give some sort of answer, but if you're a government agency testing the soil to address a serious agricultural problem, there are likely better tests.  What you have is really a toy for home use.

[Arkcon]

If you search this forum for soil testing, you'll see how often this topic comes up.  Here's a technical reference I found that will teach you something about the accuracy of these tests:  http://horttech.ashspublications.org/content/17/3/358.full

[hamil]

Given the vast agricultural industry we have I would think that understanding soil analysis would be state of the art and very well understood. How can a commercial grower grow tomatoes or other vegetables without knowing all about soil analysis. I would think that the chemical reaction that make the various color would be well documented in the chemistry fields. Also, I would think that commercial growers would not use small test kits. They I am sure analyze their soil accurately and often. Actually, I would have thought this topic would make a good science fair project.

As to fertilizers, my wife tells me to just go and get 25 pounds of fertilizer and throw it on the dirt. This is probably why we seldom have and good produce :-)

[hamil]

The article you mentioned is a good one. Thanks