Soil pH in Rio Grande, CO: Lime or Sulfur?

Typical topsoil pH in Rio Grande, CO

Typical topsoil in Rio Grande, CO is pH 7.92 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 Rio Grande 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 7.92, consider raised beds for anything acid-loving; with 73% of soils here carrying free lime, sulfur will not hold.

How mixed the soil is

Of the 266,912 surveyed acres in Rio Grande, CO, 82% are alkaline (above 7.3), 18% are near neutral (6.5-7.3). Mapped soils run from pH 6.7 to 9.4, a spread of 2.7 units across 71 soil components. 82% 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 17.9% clay and 1.26% 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. 73% of mapped components carry free carbonate (lime already in the ground), enough that sulfur gets neutralised before it does much.

Rio Grande against the rest of Colorado

pH 7.92 is 0.75 above the Colorado median of 7.17. 61 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: Pueblo (7.76), Delta (7.8), Otero (7.82), Conejos (7.84), Alamosa (8.28).

The range in Colorado runs from San Juan at 5.53 to Alamosa at 8.28; Rio Grande sits 87% of the way up.