Abstract
Wettable sulfur (S) mixed with a Pineda fine sand (an Arenic Glossaqualf with 7.8 pH and 1.5% calcium carbonate equivalent) quickly acidified the soil, but the effect was lost within 8 weeks at low application rates and within 21 weeks at the highest rate (1 g S/kg soil or 1 lb S/1000 lb soil). Granular S mixed with the soil took one year to produce maximum pH reduction of 0.3, 0.4, and 0.9 pH units at 250, 500, and 1000 mg S/kg soil (1/4, 1/2, and 1 lb S/1000 lb soil), respectively . Wettable sulfur (S), surface-applied at 100 g/m2 (0.036 oz/10 ft2), lowered the pH of the upper 5 cm (2 in) of soil to the 5.6 to 5.8 range for one to two months before the pH returned to > 7.0; granular S took about five months to lower the pH to 6.7 but the soil pH was 6.2 two years after application. Wettable S at 20 g/kg soil (0.32 oz S/lb soil) in a small cylindrical zone resulted in a temporary depression of pH within the treated zone but had no effect on pH in other areas of the container. Mixing up to 1.0 g iron sulfate/kg soil (0.016 oz/lb soil) failed to reduce soil pH. Live-oak trunk diameter and plant height were not affected by any of the soil treatments in the two-year experiment.
Lowering of Calcareous Soil pH in Field-Grow Containers