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Soil Science Society of America Journal Abstract -

Reaction of MnEDTA Applied Alone or with Ammonium Polyphosphate Fertilizer to Soils1


This article in SSSAJ

  1. Vol. 44 No. 3, p. 621-626
    Received: Sept 17, 1979
    Accepted: Feb 11, 1980

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  1. J. J. Mortvedt2



Manganese ethylenediamine tetraacetate (MnEDTA) applied alone to some low-Mn, high-Fe soils generally is not an effective Mn source for plants; apparent substitution of other soil cations for Mn in MnEDTA decreases plant availability of applied Mn. A laboratory study was conducted to estimate cation substitution for Mn in MnEDTA by determining changes with time in H2O-soluble cations in treated soil. Four moist soils (pH 5.4 to 7.7) were treated with MnEDTA at rates of 0, 25, and 100 ppm Mn; soils were aerobically incubated up to 148 days. In addition, MnEDTA was applied to these soils with 10-15-0 (10-34-0 oxide basis) fluid polyphosphate fertilizer at rates of 1,500 ppm P and 100 ppm Mn. The application rate simulated that in soil around a fertilizer band of 10-15-0 containing 1% Mn at a rate of 50 kg of P/ha (100 lb of P2O5/acre).

Water-soluble Mn increased with MnEDTA rate in all soils just after application but decreased with time to the level of untreated soils. In soils treated with MnEDTA alone, H2O-soluble Fe increased with time in acid soils, and H2O-soluble Ca increased in limed or calcareous soils, suggesting substitution of these cations for Mn in the EDTA molecule. Levels of H2O-soluble Mg, Zn, and Cu in all soils were not affected by application of MnEDTA.

Application of MnEDTA with 10-15-0 reduced the apparent rate of cation substitution for Mn in MnEDTA by precipitation of competing cations in soil. Thus, Mn in MnEDTA should remain available to plants for a longer time with band application in fluid polyphosphate fertilizers than with mixed application alone or with other fertilizers to soil.

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