Water source alkalinity is a much more important number to look at than its pH. The pH is simply a onetime snapshot of how acidic or basic your water is; alkalinity is a measure of its long lasting pH effect. Once you know your water alkalinity, you can work with your local extension educator, fertilizer supplier or testing laboratory to select an appropriate fertilizer strategy. Depending on your alkalinity, you may need to choose a formulation with a greater proportion of acidic nitrogen forms (ammonium or urea) or add acid to neutralize the alkalinity and counter the pH rise.