Abstract
Many different kinds of soil additives have been studied with the aim of preventing and/or correcting iron deficiencies of plants. Application rates have varied from as little as “parts per million”; of several Fe chelates, to as much as many tons per hectare of acidifying soil amendments, or organic materials such as manures, sewage sludges and plant residues. The chelate Fe EDDHA has generally been considered to be the most effective soil applied material in alleviating chlorosis: its use is somewhat limited, however, by its relatively high cost. Broadcast applications of acidifying materials such as elemental sulfur and sulfuric acid must generally be excessively high to be effective. Recent studies involving band placements of these acidifying materials have shown some promise. Several industrial by‐products have also proven effective, especially when concentrated in bands close to germinating seeds.