Just wondering if I should be using some soil testing kit both from local hardware stores? They are not so expansive and they tell you the pH level along with the NPK ratio. I'm interested in knowing in what calculation form will it say the NPK? I never used a soil testing kit before but i'm planning on using some this year to know exactly if I need more nitrogen in the lawn or if it has to much potassium etc. How difficult is it to use?