Soil pH in Red River, LA: Lime or Sulfur?

Typical topsoil pH in Red River, LA

Typical topsoil in Red River, LA is pH 6.04, already right for vegetable garden (6-7). Test before adding anything.

What Red River needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, strawberries, roses, pink hydrangeas.
• Just outside, test first: tomatoes (off by 0.2), potatoes (off by 0), azaleas and rhododendrons (off by 0).
• Sulfur: blueberries 2.3 lb/100 sq ft over 2 applications; blue hydrangeas 1.8 lb/100 sq ft.

What to do next

If your test lands near 6.04, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, potatoes, strawberries, roses, azaleas and rhododendrons, pink hydrangeas.

How mixed the soil is

Of the 214,502 surveyed acres in Red River, LA, 34% are strongly acidic (below 5.5), 34% are near neutral (6.5-7.3), 24% are moderately acidic (5.5-6.5), 8% are alkaline (above 7.3). Mapped soils run from pH 4.6 to 8, a spread of 3.4 units across 101 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 26.2% clay and 1.92% 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. 7% of mapped components carry free carbonate (lime already in the ground).

Red River against the rest of Louisiana

pH 6.04 is 0.5 above the Louisiana median of 5.54. 41 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: Tensas (5.76), Natchitoches (5.77), Madison (5.82), East Carroll (6.01), Concordia (6.11), Vermilion (6.15), Cameron (6.16), St. Landry (6.16).

The range in Louisiana runs from Allen at 4.88 to St. Bernard at 7; Red River sits 55% of the way up.