Potential Use of Finely Disintegrated Iron Pyrite in Sodic and Iron‐Deficient Soils

Abstract

AbstractThe rate of chemical oxidation of iron pyrite in water was measured as a function of particle size. Reducing the particle size greatly increased the rate of oxidation. For pyrite > 250 µm, the pH of the solution leveled off at 5 after 6 hours while the clay size pyrite dropped to pH 4 within 24 hours.Application of pyrite to a slightly sodic, iron‐deficient, loamy sand soil from Colorado changed several soil properties during a 2‐mo incubation period. In these studies, pyrite was applied at 1% initially with an additional 1% after 1 mo. The soil/water ratio was 1:2. When clay size pyrite was used, the pH of the soil decreased from 8.3 to 7.8 after 1 mo and to 5.7 after 2 mo. The coarser pyrite decreased the pH only slightly. No significant change in the composition of exchangeable ions occurred during the first month, but the composition had changed sufficiently after 2 mo to flocculate the clay. The DTPA‐extractable iron increased from 1.5 to 64 ppm for the finest pyrite treatment during 1 mo, copper doubled, and manganese quadrupled during this period. Finely disintegrated pyrite may be useful for reclaiming slightly sodium‐affected soils or for providing slow release available iron.