Soil pH in Rio Arriba, NM: Lime or Sulfur?

Typical topsoil pH in Rio Arriba, NM

Typical topsoil in Rio Arriba, NM is pH 7.23, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Rio Arriba 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).
• Beds or pots instead: tomatoes, potatoes, strawberries, blueberries, azaleas and rhododendrons, blue hydrangeas, pink hydrangeas.

What to do next

If your test lands near 7.23, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, roses.

How mixed the soil is

Of the 2,962,461 surveyed acres in Rio Arriba, NM, 52% are near neutral (6.5-7.3), 40% are alkaline (above 7.3), 8% are moderately acidic (5.5-6.5). Mapped soils run from pH 4.6 to 8.8, a spread of 4.2 units across 1,706 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 19.6% clay and 1.42% 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. 51% of mapped components carry free carbonate (lime already in the ground), enough that sulfur gets neutralised before it does much.

Rio Arriba against the rest of New Mexico

pH 7.23 is 0.42 below the New Mexico median of 7.65. 3 of 33 New Mexico counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Colfax (6.99), Los Alamos (7.02), Taos (7.04), Mora (7.25), Catron (7.26), Cibola (7.39), Grant (7.44).

The range in New Mexico runs from Colfax at 6.99 to Valencia at 8.07; Rio Arriba sits 22% of the way up.