Manganese‐iron relationship in soybean grown in calcareous soils¹

Paper No. K‐600–74 College of Agriculture, Shiraz University, Shiraz, Iran.

Abstract

Although a positive response to iron (Fe) is, usually, expected in calcareous soils; this has not been always the case; and in some instances a depressing effect has been observed. An induced micronutrient imbalance is suspected. This experiment was designed to study the effect of Fe fertilizer on the plant micronutrients. Twenty three highly calcareous soils (18–46% calcium carbonate equivalent; pH 7.7–8.4; and a wide range of extractable Fe) from southern Iran were used in an eight‐week greenhouse experiment to study the effect of Fe fertilizers on soybean [Glycine max (L.) Merr.] growth and chemical composition. The statistical design was a 23 × 3 factorial arranged in a completely randomized block with three replications. Treatments consisted of 23 soils and three levels of applied Fe (0, 10, and 20 mg Fe/kg as FeEDDHA). Uniform doses of nitrogen (N), phosphorus (P), copper (Cu), manganese (Mn), and zinc (Zn) were applied to all pots. Dry matter (DM) and micronutrients concentrations and uptakes of plant tops were determined and used as the plant responses. Application of Fe either had no significant effect on DM or even decreased it. The plant concentration and uptake of Fe increased significantly in all soils. The concentrations and uptakes of Cu and Zn did not change but those of Mn decreased significantly. The negative effect of Fe application was, therefore, attributed to the interference of Fe with Mn nutrition. The mechanism involved appears to be the restriction in Mn translocation from soil to root and/or from root to the plant tops.

Notes

Paper No. K‐600–74 College of Agriculture, Shiraz University, Shiraz, Iran.

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