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Here’s a practical guide to the ideal soil pH levels for the most common crops grown in the Free State province of South Africa. The Free State has mostly sandy-loam to clay-loam soils, and pH often ranges naturally from 5.0 to 7.5, but crops perform best within narrower bands. Values are for soil pH measured in water (pH(H₂O)).

Crop

Ideal pH range

Tolerated range

Notes for Free State farmers

 

 

Ideal                                                Tolerated Ranger                                      Notes 

 

Maize (corn)

5.8 – 7.0                                              5.5 – 7.5                                                 Most important crop in FS; below 5.5 Al-toxicity common

 

Wheat

6.0 – 7.5                                              5.8 – 8.0                                                 Prefers slightly higher pH than maize

 

Sunflower

6.0 – 7.5                                              5.5 – 8.0                                                 Very tolerant, good on slightly alkaline soils

 

Soybeans

6.2 – 7.0                                              6.0 – 7.5                                                 Sensitive to acidity; lime if < 6.0

 

Dry beans

6.0 – 7.0                                              5.8 – 7.5                                                 Similar to maize

 

Grain sorghum

5.8 – 7.5                                              5.5 – 8.0                                                 More acid-tolerant than maize

 

Groundnuts (peanuts)

6.0 – 6.5                                              5.8 – 7.0                                                Very sensitive to low pH and Al

 

Potatoes

5.5 – 6.5                                              5.2 – 7.0                                                One of the few crops that like slightly acid soil

 

Lucerne (alfalfa)

6.5 – 7.5                                              6.2 – 8.0                                                 Needs liming if < 6.5; common in irrigation areas

 

Pasture (ryegrass, cocksfoot)

6.0 – 7.0                                              5.8 – 7.5                                                 Lime essential for long-term pastures

 

Canola

6.0 – 7.5                                              5.8 – 8.0                                                Growing in cooler FS areas

 

Barley

6.0 – 7.5                                              5.8 – 8.0                                                Similar to wheat

 

Oats

5.5 – 7.0                                              5.3 – 7.5                                                Fairly tolerant

 

Quick liming reference for Free State conditions

If your soil test (water pH) is:

< 5.5 → Strong likelihood of aluminium toxicity → lime urgently (maize, soybeans, groundnuts especially affected)

5.5 – 5.8 → Lime recommended for most crops except potatoes

5.8 – 6.2 → Generally fine for maize, sorghum, sunflower; lime for soybeans and lucerne

7.5 → Possible micronutrient tie-up (Fe, Mn, Zn) and some sodicity issues in clay areas

 

Most commercial farmers in the Free State aim for pH 6.0 – 6.5 in maize lands as a good compromise when rotating with soybeans or sunflower.

 

Always base final decisions on a recent soil analysis (0–15 cm for, 15–30 cm for deeper acidity checks) because dolomite lime takes 6–18 months to fully react in Free State soils.