Optimize Irrigation Water pH for Better Crop Yields

By Blake Jackson

Maintaining the correct pH in irrigation water delivers some of the best returns a produce grower can earn better fruit quality, fewer fertilizer pounds, and higher overall yields. Because pH is logarithmic, a single‑point shift changes acidity ten‑fold, meaning even “small” adjustments have outsized impacts on nutrient uptake.

Take tomatoes, Pennsylvania’s highest‑value crop: they extract nutrients most efficiently when the soil solution stays between pH 6.2 and 6.5.

Slide above that range and potassium uptake plummets, setting the stage for yellow shoulder, gray wall, internal white core, blossom‑end rot, and cracking. No amount of late fertilizer can rescue fruit formed under those imbalances.

Across the Mid‑Atlantic, most wells, springs, and surface supplies flow through limestone aquifers, so their water arrives both alkaline (pH > 6.5) and buffered by significant alkalinity bicarbonate that resists pH change.

High alkalinity water may demand far more acid than a quick pH check alone suggests, so test for both pH and alkalinity (report alkalinity in parts per million bicarbonate, not grains per gallon).

Organic growers typically dissolve powdered citric acid; seven to nine ounces per 100 gallons usually drop well water by one pH unit. Conventional operations lean on sulfuric acid, most commonly 35 percent strength because the 93-96 percent grade has become difficult to procure.

To dial in an exact dose, enter your water’s pH, alkalinity, and the target pH into the University of New Hampshire’s AlkCalc, then verify the result with a temperature‑compensating, two‑point‑calibrated digital pH meter (use pH 4 and 7 standards). Skip litmus strips; they simply are not precise enough.

Install the acid injector as the first station in a series of proportional injectors so every drop reaching the root zone is already balanced. Fertilizer itself shifts pH, so recheck whenever you fertigate and rebuild the injector annually for accuracy.

Field tomato and pepper acreage can benefit too, though the larger volumes require acid‑compatible pumps and plumbing work with an irrigation specialist before scaling up.

The farther your current water chemistry sits from the ideal, the larger the payoff you’ll see in healthier plants, cleaner fruit, and a leaner fertilizer bill often in a single season.

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