I use the one from the Biologic site only because it is convenience for me. I mail it to them and they e-mail the results within 36 hours usually. I don;t have a coop near me, so using the mail makes it pretty eay and straightforward. The biologic company send it to a lab i beleieve. They are also plant specific with the results, meaning if you tell them what you are going to plant, they will tell you how much lime and fertilizer you will need to add, as well as the fertilizer 'recipe', or numbers of nitgorgen, phosphorus and whatever the third number is.