Soil pH in Natchitoches, LA: Lime or Sulfur?

Typical topsoil pH in Natchitoches, LA

Typical topsoil in Natchitoches, LA is pH 5.77, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Natchitoches needs, by plant

• Already in range: potatoes, strawberries, azaleas and rhododendrons.
• Just outside, test first: lawn (cool-season grass) (off by 0.2), vegetable garden (off by 0.2), roses (off by 0.2), pink hydrangeas (off by 0.2).
• Lime: tomatoes 4.9 lb/100 sq ft.
• Sulfur: blueberries 1.8 lb/100 sq ft; blue hydrangeas 1.2 lb/100 sq ft.

What to do next

If your test lands near 5.77, 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 715,500 surveyed acres in Natchitoches, LA, 59% are strongly acidic (below 5.5), 29% are near neutral (6.5-7.3), 9% are moderately acidic (5.5-6.5), 3% are alkaline (above 7.3). Mapped soils run from pH 4.3 to 8, a spread of 3.7 units across 122 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 24.7% clay and 1.88% 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. 4% of mapped components carry free carbonate (lime already in the ground).

Natchitoches against the rest of Louisiana

pH 5.77 is 0.23 above the Louisiana median of 5.54. 38 of 64 Louisiana counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Bossier (5.66), Rapides (5.68), Caddo (5.75), Tensas (5.76), Madison (5.82), East Carroll (6.01), Red River (6.04), Concordia (6.11).

The range in Louisiana runs from Allen at 4.88 to St. Bernard at 7; Natchitoches sits 42% of the way up.