The number seven is a lucky and essential number – not only for the western alfalfa industry but also for human existence.

On the human front, the pH of human blood is seven, and that is a good thing.

“If the pH number of blood changed by just 0.2, people would die,” says Kurt Nolte, University of Arizona (UA) Cooperative Extension agent based in Yuma.

Nolte’s lucky-seven comparison kicked off his alfalfa presentation during the UA-sponsored agronomic workshop held in Parker, Ariz. in May. The workshop included multiple presentations on desert-area alfalfa production in Arizona and southern California.

Nolte says the low desert soil pH level of seven helps plants produce higher yielding quality hay for dairy cows and other uses. This is important since most desert soils in these areas are in the 8-8.5 pH range (too high). Producers should add a sulfur-water mix to the soil to lower the pH to seven.

The pH level in pure water is also seven which means what is good for water is good for alfalfa. If soil pH levels are too high (above seven), adding liquid phosphorus in alfalfa can be a solution.

“The pH level is an indicator of overall fertility and goes hand in hand with making many nutrients available to the alfalfa plant,” Nolte says. “Adjusting the soil pH to seven means the plant can take up essential nutrients in the soil.”

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Nolte advocates biannual soil tests to determine the pH level. Avoid buying pH kits at improvement stores and instead send soil samples to a professional laboratory. Costs usually vary from $25-$30 per sample.