The Availability of Chelated Mn to Millet and Its Equilibria With Other Forms of Mn in the Soil

The use of insoluble soil‐chelated Mn, in addition to exchangeable Mn, did not increase the predictability of available Mn. In this study, 12 Indiana soils varying in organic matter, pH, texture, and parent material were collected and treated to give two levels of Mn and acidity. Available Mn was determined by cropping the soils with German Millet. Exchangeable Mn was the most important factor in determining available Mn. Since chelated and exchangeable Mn were highly correlated, the true effect of chelated Mn may not have been apparent. Inclusion of the interaction chelated Mn times percent organic matter highly significantly increased the ability to predict available Mn. Soil pH was also significant in predicting available Mn. The increase in chelated and exchangeable Mn on airdrying of the soils was related to total soil Mn.