Soil pH in Pima, AZ: Lime or Sulfur?

Typical topsoil pH in Pima, AZ

Typical topsoil in Pima, AZ is pH 7.56 and calcareous, so sulfur won't lower it for long. For vegetable garden, choose alkaline-tolerant varieties and add compost rather than fighting the soil.

What Pima needs, by plant

• Beds or pots instead: lawn (cool-season grass), vegetable garden, tomatoes, potatoes, strawberries, roses, blueberries, azaleas and rhododendrons, blue hydrangeas, pink hydrangeas.

What to do next

If your test confirms pH near 7.56, consider raised beds for anything acid-loving; with 70% of soils here carrying free lime, sulfur will not hold.

How mixed the soil is

Of the 4,009,288 surveyed acres in Pima, AZ, 64% are alkaline (above 7.3), 34% are near neutral (6.5-7.3), 2% are moderately acidic (5.5-6.5). Mapped soils run from pH 5.8 to 8.5, a spread of 2.7 units across 413 soil components. 64% of the land falls in one class, so the county figure is a fair first guess for most yards here.

Clay, organic matter and rates

Topsoil here averages 14.4% clay and 0.78% organic matter, which this site treats as loam. Moving it one pH unit takes about 7 lb of lime or 2.3 lb of sulfur per 100 sq ft. 70% of mapped components carry free carbonate (lime already in the ground), enough that sulfur gets neutralised before it does much.

Pima against the rest of Arizona

pH 7.56 is 0.21 below the Arizona median of 7.77. 5 of 14 Arizona counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Graham (7.32), Yavapai (7.42), Greenlee (7.44), Cochise (7.46), Pinal (7.74), Apache (7.79), Coconino (7.81), Mohave (7.83).

The range in Arizona runs from Gila at 7.17 to Maricopa at 8.12; Pima sits 41% of the way up.