Soil pH in Adams, CO: Lime or Sulfur?

Typical topsoil pH in Adams, CO

Typical topsoil in Adams, CO is pH 7.25, too alkaline for vegetable garden. Expect roughly 1.8 lb of sulfur per 100 sq ft, but only after a soil test confirms it.

What Adams needs, by plant

• Sulfur: lawn (cool-season grass) 1.8 lb/100 sq ft; vegetable garden 1.8 lb/100 sq ft; tomatoes 1.8 lb/100 sq ft; potatoes 4.1 lb/100 sq ft over 3 applications; strawberries 3 lb/100 sq ft over 2 applications; roses 1.8 lb/100 sq ft; blueberries 5.3 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 confirms pH near 7.25, work in about 18 lb of elemental sulfur per 1,000 sq ft of vegetable bed.

How mixed the soil is

Of the 699,933 surveyed acres in Adams, CO, 74% are near neutral (6.5-7.3), 24% are alkaline (above 7.3), 2% are moderately acidic (5.5-6.5). Mapped soils run from pH 6.3 to 8.2, a spread of 1.9 units across 288 soil components. 74% 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 18.1% clay and 1.48% 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. 23% of mapped components carry free carbonate (lime already in the ground).

Adams against the rest of Colorado

pH 7.25 is 0.08 above the Colorado median of 7.17. 37 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: Costilla (7.19), Logan (7.2), Arapahoe (7.22), Denver (7.24), Broomfield (7.29), Weld (7.29), Kit Carson (7.33), Cheyenne (7.35).

The range in Colorado runs from San Juan at 5.53 to Alamosa at 8.28; Adams sits 63% of the way up.