Soil pH in Caddo, LA: Lime or Sulfur?

Typical topsoil pH in Caddo, LA

Typical topsoil in Caddo, LA is pH 5.75, too acidic for vegetable garden. Expect roughly 5.6 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Caddo needs, by plant

• Already in range: potatoes, strawberries, azaleas and rhododendrons.
• Lime: lawn (cool-season grass) 5.6 lb/100 sq ft over 2 applications; vegetable garden 5.6 lb/100 sq ft over 2 applications; tomatoes 5.6 lb/100 sq ft over 2 applications; roses 5.6 lb/100 sq ft over 2 applications; pink hydrangeas 3.5 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 confirms pH near 5.75, spread about 56 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 502,585 surveyed acres in Caddo, LA, 48% are strongly acidic (below 5.5), 24% are near neutral (6.5-7.3), 24% are moderately acidic (5.5-6.5), 4% are alkaline (above 7.3). Mapped soils run from pH 4.3 to 8, a spread of 3.7 units across 156 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 20.3% clay and 1.58% 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. 6% of mapped components carry free carbonate (lime already in the ground).

Caddo against the rest of Louisiana

pH 5.75 is 0.21 above the Louisiana median of 5.54. 36 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: Lafayette (5.55), West Feliciana (5.6), Bossier (5.66), Rapides (5.68), Tensas (5.76), Natchitoches (5.77), Madison (5.82), East Carroll (6.01).

The range in Louisiana runs from Allen at 4.88 to St. Bernard at 7; Caddo sits 41% of the way up.