Hey! So I'm having some difficulty finding information about the RapiTest soil test kit. I need to know if it can detect nitrate or ammonia in clay soil. Does the nitrogen test that comes with this soil test kit even really test for nitrogen? Or does it somehow detect the oxygens and hydrogens attached to the nitrogen? If someone could explain to me how this test works I would really appreciate it!

I believe it only tests for nitrate (NO3) nitrogen. There's an article about testing it for that here.

http://horttech.ashspublicatio...

Thanks so much!! I'll give it a read

So is there even ammonia present in clay soil? I read somewhere that clay particles are negatively charged and hydrogen is positively charged. So would that attraction between the clay particles and hydrogen prevent the ammonia from even being able to form?

Plants take up nitrogen primarily as ammonium and nitrate. Yes clay particles are negatively charged, ammonium is positively charged and nitrate is negative. That's why ammonium nitrogen doesn't leach like nitrate does. Ammonium should be present even in clay soil as part of the nitrogen cycle and then converts ultimately to nitrate, but nitrogen is the nutrient most likely to be deficient because it doesn't originate with mineral soil particles. However, a nitrate test will only tell you the amount of nitrate and not the amount of organic nitrogen or ammonium that has not yet been converted so you might expect there to be more nitrogen in the soil than a nitrate test would show. Hope this makes some sense!

Great answer, thanks so much for all your help!