when it comes to soil there all around the same,I have 2 of them 1 shows moisture ph and light the other shows ph and how fertile the soil is I use the ph and fertility one and I think its made by burpee the best thing to do is get a soil test kit this will tell you alot more about whats in or not in your soil,I allways use dolimite lime when mixing soil and is fairly foolproof to use,you could spend big bucks on a high end meter or a few bucks on a cheap one,I use the cheap one and the lime peace
