This describes the acidity or alkalinity of water. The PH of the soil can affect the growth of plants, irrigation equipment, pesticide efficiency, and the quality of drinking water. Water that has a PH that is below 7 is acidic and that which has a scale above 7.5 is alkaline in nature. Most of the natural waters that exist are between PH 5 and 8. The accepted PH for farm water is 6.5-7.5.