Leaching Losses and Plant Recovery from Various Sulfur Fertilizers

Two greenhouse experiments were conducted with soils fertilized with various S fertilizers. The soils were subjected to percolation during early growth of a corn ( Zea mays , L. var. Funks G5757) crop to determine the effects of leaching rate, sulfur rate, and S source on SO 2‐ 4 leaching losses and plant growth. In the first experiment, the effects of percolation rate (0–6.1 mm d −1 ) and rate of gypsum application (0–40 µg S g −1 ) on SO 2‐ 4 leaching losses and S recovery by two successive crops were studied. Increasing the percolation rate greatly increased SO 2‐ 4 leaching losses and decreased the apparent fertilizer recovery by the first crop. Apparent S recovery was also greatly reduced with increasing amounts of applied gypsum. In the second experiment, S leaching losses from gypsum and anhydrite of various particle sizes and from powdered elemental S were evaluated at one percolation rate (3.9 mm d −1 ). The rate of SO 2‐ 4 leaching loss from powdered gypsum and anhydrite gradually decreased with time, indicating a decrease in the dissolution rate of the source as the amount of solid phase material decreased. Increasing the particle size of the materials decreased the leaching losses but had no effect on apparent S recovery by the plants. At a given particle size other than powdered materials, there were no differences in leaching losses between gypsum and anhydrite. The amount of powdered gypsum leached, however, was three times greater than the amount of powdered anhydrite leached. Leaching losses from powdered elemental S were similar to the losses from the larger‐sized particles of gypsum and anhydrite. Moderate to high percolation rates led to SO 2‐ 4 losses and decreased fertilizer efficiency. Increasing the size of gypsum particles and the use of anhydrite are promising methods of reducing such losses.