Soil pH in Petroleum, MT: Lime or Sulfur?

Typical topsoil pH in Petroleum, MT

Typical topsoil in Petroleum, MT is pH 7.34 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 Petroleum 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 7.34, consider raised beds for anything acid-loving; with 33% of soils here carrying free lime, sulfur will not hold.

How mixed the soil is

Of the 980,999 surveyed acres in Petroleum, MT, 54% are near neutral (6.5-7.3), 43% are alkaline (above 7.3), 2% are moderately acidic (5.5-6.5), 1% are strongly acidic (below 5.5). Mapped soils run from pH 4.6 to 8.8, a spread of 4.2 units across 350 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 33.8% clay and 1.72% organic matter, which this site treats as clay. Moving it one pH unit takes about 11.5 lb of lime or 3.4 lb of sulfur per 100 sq ft. 33% of mapped components carry free carbonate (lime already in the ground), enough that sulfur gets neutralised before it does much.

Petroleum against the rest of Montana

pH 7.34 is right at the Montana median of 7.3. 32 of 56 Montana counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Stillwater (7.33), Toole (7.33), Carter (7.34), Judith Basin (7.34), Broadwater (7.41), Sheridan (7.41), Roosevelt (7.43), Powder River (7.44).

The range in Montana runs from Flathead at 6.02 to Wheatland at 7.77; Petroleum sits 75% of the way up.