a easy way to test the soil is by watering with water that u know the PH already. then water ur plants untel water starts to drip. empty it into another cup. then PH test the water in the cup. compare to the water u started with. pridy easy. example. u feed R/O water (PH7) it comes out of the soil with a PH of 6 u know now that ur soil is alittle acidic. understanding ur soils PH will make ur grow