Soil pH in Ouray, CO: Lime or Sulfur?

Typical topsoil pH in Ouray, CO

Typical topsoil in Ouray, CO is pH 7.04, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Ouray needs, by plant

• Just outside, test first: lawn (cool-season grass) (off by 0), vegetable garden (off by 0), tomatoes (off by 0.2), roses (off by 0).
• Sulfur: potatoes 3.5 lb/100 sq ft over 2 applications; strawberries 2.3 lb/100 sq ft over 2 applications; blueberries 4.6 lb/100 sq ft over 3 applications; azaleas and rhododendrons 4.1 lb/100 sq ft over 3 applications; blue hydrangeas 4.1 lb/100 sq ft over 3 applications; pink hydrangeas 1.8 lb/100 sq ft.

What to do next

If your test lands near 7.04, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, roses.

How mixed the soil is

Of the 249,889 surveyed acres in Ouray, CO, 45% are alkaline (above 7.3), 33% are near neutral (6.5-7.3), 21% are moderately acidic (5.5-6.5), 1% are strongly acidic (below 5.5). Mapped soils run from pH 5 to 9, a spread of 4 units across 207 soil components. No single class covers 60% of the county, so two gardens a few miles apart here can need opposite treatments. Test your own bed.

Clay, organic matter and rates

Topsoil here averages 20.1% clay and 2.29% 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. 13% of mapped components carry free carbonate (lime already in the ground).

Ouray against the rest of Colorado

pH 7.04 is 0.13 below the Colorado median of 7.17. 22 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: Dolores (6.89), Park (6.92), Jackson (6.93), Routt (6.97), Elbert (7.07), Garfield (7.09), Yuma (7.09), Fremont (7.1).

The range in Colorado runs from San Juan at 5.53 to Alamosa at 8.28; Ouray sits 55% of the way up.