I purchased two soil sample/test kits from my state university’s extension program. It didn’t cost much but was very helpful and saved me money because I was adding supplement my soil didn’t need. Also, I can water less now that my grass and other plant roots are better developed. Despite the dry weather we have had this summer, my lawn has never been greener and with much less watering than in previous years. Potassium was the big deficiency. The results included suggested plans for soil improvement.