Soil pH in Ottawa, MI: Lime or Sulfur?

Typical topsoil pH in Ottawa, MI

Typical topsoil in Ottawa, MI is pH 5.88, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Ottawa needs, by plant

• Already in range: potatoes, strawberries, azaleas and rhododendrons.
• Just outside, test first: lawn (cool-season grass) (off by 0.1), vegetable garden (off by 0.1), roses (off by 0.1), pink hydrangeas (off by 0.1).
• Lime: tomatoes 4.2 lb/100 sq ft.
• Sulfur: blueberries 2.1 lb/100 sq ft over 2 applications; blue hydrangeas 1.4 lb/100 sq ft.

What to do next

If your test lands near 5.88, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, potatoes, strawberries, roses, azaleas and rhododendrons, pink hydrangeas.

How mixed the soil is

Of the 343,971 surveyed acres in Ottawa, MI, 47% are moderately acidic (5.5-6.5), 27% are near neutral (6.5-7.3), 25% are strongly acidic (below 5.5), 1% are alkaline (above 7.3). Mapped soils run from pH 3.7 to 7.6, a spread of 3.9 units across 398 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 10% clay and 3.23% 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. 3% of mapped components carry free carbonate (lime already in the ground).

Ottawa against the rest of Michigan

pH 5.88 is 0.16 below the Michigan median of 6.04. 35 of 83 Michigan counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Newaygo (5.82), Cheboygan (5.83), Mackinac (5.84), Emmet (5.88), Dickinson (5.89), Allegan (5.92), Delta (5.92), Montcalm (5.98).

The range in Michigan runs from Baraga at 4.72 to Huron at 7.03; Ottawa sits 50% of the way up.