Soil pH in Northwest Arctic Borough, AK: Lime or Sulfur?

Typical topsoil pH in Northwest Arctic Borough, AK

Typical topsoil in Northwest Arctic Borough, AK is pH 5.23, too acidic for vegetable garden. Expect roughly 9.1 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Northwest Arctic Borough needs, by plant

• Already in range: potatoes, blueberries, azaleas and rhododendrons, blue hydrangeas.
• Lime: lawn (cool-season grass) 9.1 lb/100 sq ft over 2 applications; vegetable garden 9.1 lb/100 sq ft over 2 applications; tomatoes 9.1 lb/100 sq ft over 2 applications; strawberries 5.6 lb/100 sq ft over 2 applications; roses 9.1 lb/100 sq ft over 2 applications; pink hydrangeas 7 lb/100 sq ft over 2 applications.

What to do next

If your test confirms pH near 5.23, spread about 91 lb of ground limestone per 1,000 sq ft of vegetable bed in 2 doses, ideally in fall.

How mixed the soil is

Of the 6,751,923 surveyed acres in Northwest Arctic Borough, AK, 77% are strongly acidic (below 5.5), 13% are moderately acidic (5.5-6.5), 6% are alkaline (above 7.3), 4% are near neutral (6.5-7.3). Mapped soils run from pH 4 to 7.9, a spread of 3.9 units across 218 soil components. 77% 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 6.8% clay and 9.46% organic matter, which this site treats as loam. At 9.46% organic matter the soil buffers like a heavier one, which pushes it into the loam bracket. 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).

Northwest Arctic Borough against the rest of Alaska

pH 5.23 is right at the Alaska median of 5.26. 12 of 27 Alaska counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Kusilvak Census Area (old Wade Hampton) (5.04), Haines Borough (5.1), Valdez-Cordova Census Area (5.15), Matanuska-Susitna Borough (5.2), Kusilvak Census Area (5.26), Juneau Borough (5.3), Petersburg Borough (5.3), Sitka Borough (5.3).

The range in Alaska runs from Ketchikan Gateway Borough at 4.52 to Yakutat City and Borough at 6.08; Northwest Arctic Borough sits 46% of the way up.