The difference is in the extractant used to mix with the soil sample and which one is used is critical. I'd suggest you contact your state's extension service to find out which extract and methoe is best for your soil, they will want to know where you live in order to determine your soil type. State universities have spent decades and a great deal of money developing various extractants and methodologies for testing soils TO ACCURATELY PREDICT plant response to both no action and adding specific fertilizers in very specific amounts in different ways. I'm going to guess that the Morgan method has not been through such vigorous testing on a wide variety of crops in a wide range of soils for all parts of the country. BTW, there is also a Mehlich II, not to confuse you more.

Not to toot my horn but, I have spent many years of my life in vegetable crops nutrition research at a university and know what I'm talking about. If you want to go with the private lab that is touting their own method, that's your call, if you do, submit a portion of the sample both to the Morgan lab and another to the lab your extension service aims you to, the results may prove to be illuminating if you try the recommendations for both in your garden, side by side.

Here's a link to a lab that uses the Morgan extract, some folks here like Dr. Reams' philosophy, I want to see the science to back claims, kind of a pain in the rear that way.

Here is a link that might be useful: IAL

Thank you, that was very helpful. I had begun looking at IAL, but got turned arund in my research (I use this word loosely).