Soil Test Interpretation for Vegetable Farms

Every Southeast state soil lab (NCDA, Clemson, UGA, ALFA, UT, VA Tech) reports similar numbers with different names. Here's how to read them and what to do at each threshold for vegetable ground.

pH

Target 6.2–6.8 for most vegetables. Below 6.0: lime at 1–2 tons/acre (ag lime). Above 7.2 (rare in Southeast): elemental sulfur to lower. Blueberries are the exception — target 4.8–5.2.

Phosphorus (P)

Reported as P₂O₅ index or lb/acre. Vegetable target: index 60+ (NC scale) or 40–80 lb/acre elsewhere. Below index 25: apply 60–120 lb/acre P₂O₅ (broadcast at bed prep). Above 100: skip P entirely — over-application is common on manure-fed farms and blocks micronutrient uptake.

Potassium (K)

Vegetable target index 60+. Below 25: apply 100–200 lb/acre K₂O. Tomatoes and peppers especially benefit from K side-dress at first fruit set.

Ca / Mg / base saturation

Target Ca base saturation 65–75%, Mg 10–20%. Low Mg (below 10%): dolomitic lime. Low Ca on adequate pH: gypsum at 500 lb/acre.

CEC

Cation Exchange Capacity — the soil's holding capacity. Sandy Coastal Plain: 2–5. Piedmont clay: 8–15. Low CEC means split fertilizer applications (leaching risk).

Micronutrients

Zn, Mn, B tests matter most for brassicas and cucurbits. Deficiency shows as tissue-level symptoms first — foliar sprays are usually the fix.

Pair with the tomato/pepper nitrogen budget — soil tests don't cover N, and N is where fertilizer money is won or wasted.