Losses of iron in leachates from organic components of potting media

Losses over 18 weeks of iron (Fe) in leachates from several peats and wood wastes that had been amended with ferrous sulfate (FeSO4 . 7H2O) were generally less than 1% of the total Fe in the material. Increasing additions of Fe either had Little effect on Fe losses in leachates or lowered them, mainly through a lowering in the concentration of Fe-organic complexes in leachates. DTPA-extractable Fe in wood wastes did not decline with leaching but there were some reductions in peats. The data suggest that a single pre-plant addition of 0.75-1.0 g/L FeSO4 . 7H2O would supply enough Fe for at least six months of plant growth in media based on peat with a low native Fe content.