Mobility of organic and inorganic zinc fertilizers in soils

Zinc sulfate (ZnSO4 center dot H2O) has traditionally been the reliable source of zinc (Zn) fertilizer, but other sources of Zn are also available. Some are derived from industrial by-products, varying from flue dust reacted with sulfuric acid to organic compounds derived from the paper industry. The degree of Zn mobility in Zn sources derived from these various by-products is related to the manufacturing process, the source of complexing or chelating agents (organic sources), and the original product used as the Zn source. Many claims are made regarding the relative efficiency of traditional inorganic Zn fertilizers and complexed Zn sources. The objective of this column study was to compare the mobility of several commercial Zn fertilizer materials (organic and inorganic) that are commonly used to correct Zn deficiencies in soils. The sources included three granular inorganic Zn sources, two granular organically complexed Zn sources, and liquid ZnEDTA. Soil columns were leached five times with deionized water. Leaching events were separated by approximately 48 h. At the conclusion of the leaching phase, columns were analyzed for plant-available Zn. Water solubility was the primary factor affecting Zn movement, not total Zn content or organic complexation of the fertilizers. The Zn sources evaluated can be separated into three groups: ZnEDTA, ZnLigno, and ZnSO4 were the most mobile Zn sources; the ZnOx55 was less mobile, but seemed mobile enough to meet crop needs; ZnOx26 and ZnSuc were relatively immobile Zn sources.