Evaluation of Six Extractants for their Ability to Predict Manganese Concentrations in Wheat and Soybeans

Abstract

AbstractSix extractant procedures were evaluated for their ability to relate soil Mn to Mn concentrations in wheat (Triticum aestivum) and soybeans (Glycine max L. Merr.) over three soil pH levels (pH 4.8, 5.8 and 6.8) and three rates of Mn addition. Eight Southeastern soils were treated with 0, 25, and 50 ppm Mn for wheat and 0, 2.5, and 25 ppm Mn for soybeans and the crops were grown 40 days in the greenhouse. Correlation coefficients were computed for plant Mn in relation to soil Mn extracted using six extractants: water, neutral 1N NH4OAc (with and without 0.2% hydroquinone), “double acid,” diethylenetriaminepentaacetic acid (DTPA) and ethylenediaminedi‐o‐hydroxyphenylacetic acid (EDDHA). For wheat the correlations between soil Mn extracted with both water and 1N NH4OAc and plant Mn were consistently high over the entire pH range. However, for soybeans only water had a high coefficient at pH 4.8 while DTPA and the “double acid” extractants gave food correlations at the higher two pH levels. For wheat, DTPA also gave consistently good correlations. Considering both crops studied, it was concluded that at pH 5.8 and 6.8 DTPA gives the best measure of plant available Mn in acid Southeastern soils. At pH 4.8, water would be the extractant of choice. Double acid, EDDHA, and 1N NH4OAc were intermediate in their ability to predict plant Mn concentrations and 1N NH4OAc plus hydroquinone was inferior for both crops.