Diagnosis and correction of manganese deficiency in corn

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Abstract
Although manganese (Mn) deficiency in soybeans (Glycine max) has been recognized on the Atlantic Coastal Plain, it has not been well recognized in corn (Zea mays) until recent years. Hence, there is a lack of information relating to the diagnosis and correction of Mn deficiency in corn. Field experiments were conducted to determine if the Mn soil test interpretation for soybeans would work for corn. The leaf Mn critical level also was evaluated, as were soil and foliar application methods of correcting a deficiency. Corn yield response to Mn fertilization was best explained by both soil pH and Mehlich‐3 extractable Mn concentration. The influence of these two soil properties for predicting yield response was similar for corn and soybeans, but it appears that the soil Mn critical level is lower for corn than for soybeans. The critical Mn concentration in the ear leaf at early silking was found to be 11 mg kg‐1. Manganese banded with diammonium phosphate (DAP) was three times as effective as Mn broadcast with DAP in increasing the leaf Mn concentration of corn. Banding DAP also tends to increase the availability of native soil Mn. A foliar Mn rate of 0.6 kg ha‐1 applied once partially corrected a Mn deficiency, but multiple applications were required for optimum yield.