Soil pH in La Plata, CO: Lime or Sulfur?

Typical topsoil pH in La Plata, CO

Typical topsoil in La Plata, CO is pH 6.88, already right for vegetable garden (6-7). Test before adding anything.

What La Plata needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, roses.
• Just outside, test first: tomatoes (off by 0.1).
• Sulfur: potatoes 3.2 lb/100 sq ft over 2 applications; strawberries 2.1 lb/100 sq ft over 2 applications; blueberries 4.4 lb/100 sq ft over 3 applications; azaleas and rhododendrons 3.7 lb/100 sq ft over 2 applications; blue hydrangeas 3.7 lb/100 sq ft over 2 applications; pink hydrangeas 1.4 lb/100 sq ft.

What to do next

If your test lands near 6.88, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, roses.

How mixed the soil is

Of the 764,772 surveyed acres in La Plata, CO, 47% are near neutral (6.5-7.3), 33% are alkaline (above 7.3), 10% are moderately acidic (5.5-6.5), 10% are strongly acidic (below 5.5). Mapped soils run from pH 5 to 8.5, a spread of 3.5 units across 287 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 21.6% clay and 1.53% 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. 24% of mapped components carry free carbonate (lime already in the ground).

La Plata against the rest of Colorado

pH 6.88 is 0.29 below the Colorado median of 7.17. 17 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: Custer (6.75), Douglas (6.81), El Paso (6.81), Archuleta (6.83), Dolores (6.89), Park (6.92), Jackson (6.93), Routt (6.97).

The range in Colorado runs from San Juan at 5.53 to Alamosa at 8.28; La Plata sits 49% of the way up.