Soil pH in Arapahoe, CO: Lime or Sulfur?

Typical topsoil pH in Arapahoe, CO

Typical topsoil in Arapahoe, CO is pH 7.22, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Arapahoe needs, by plant

• Just outside, test first: lawn (cool-season grass) (off by 0.2), vegetable garden (off by 0.2), roses (off by 0.2).
• Sulfur: tomatoes 1.6 lb/100 sq ft; potatoes 3.9 lb/100 sq ft over 2 applications; strawberries 2.8 lb/100 sq ft over 2 applications; blueberries 5.1 lb/100 sq ft over 3 applications; azaleas and rhododendrons 4.6 lb/100 sq ft over 3 applications; blue hydrangeas 4.6 lb/100 sq ft over 3 applications; pink hydrangeas 2.3 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 7.22, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, roses.

How mixed the soil is

Of the 450,816 surveyed acres in Arapahoe, CO, 80% are near neutral (6.5-7.3), 20% are alkaline (above 7.3). Mapped soils run from pH 6.4 to 8.2, a spread of 1.8 units across 353 soil components. 80% 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 19.2% clay and 1.84% 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. 20% of mapped components carry free carbonate (lime already in the ground).

Arapahoe against the rest of Colorado

pH 7.22 is 0.05 above the Colorado median of 7.17. 35 of 63 Colorado counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Sedgwick (7.17), Huerfano (7.18), Costilla (7.19), Logan (7.2), Denver (7.24), Adams (7.25), Broomfield (7.29), Weld (7.29).

The range in Colorado runs from San Juan at 5.53 to Alamosa at 8.28; Arapahoe sits 61% of the way up.