Effect of Sulfur and Iron on Enzymatic Activity and Chlorophyll Content of Mungbean

ABSTRACT

A field trial was conducted at Rajasthan Agricultural University, Bikaner, India, in the summers of 2002 and 2003 to determine the effect of sulfur (S) in improving iron (Fe) nutrition of mungbean (Vigna radiata L.) grown on calcareous soils. The experiment was laid out in a split-plot design with three replications. Four levels of sulfur (0, 20, 40, and 60 kg S ha^?1) were applied in main plots. In sub-plots, eight levels of Fe were replicated. Three levels of Fe were applied as a basal application of FeSO₄ (0, 12.5, and 25.0 kg FeSO₄ ha^?1) and the remaining five were applied as a foliar application of 0.5% FeSO₄ at branching, flowering, and at both branching and flowering with or without 0.1% citric acid. The results of the experiment revealed that application of sulfur at the higher doses had a significant positive effect on activities of catalase, ascorbate peroxidase, guaiacol peroxidase, synthesis of chlorophyll, and active Fe content of green leaves compared with lower doses. Application of 0.5% FeSO₄ and 0.1% citric acid at both branching and flowering had no effect. The best results were recorded with basal application of 25.0 kg FeSO₄ in combination with 40 kg S ha^?1. The frequency of foliar application had an appreciable effect on chlorophyll synthesis, enzymatic activities, and active Fe content in green leaves. Plants that received foliar application of 0.5% FeSO₄ + 0.1% citric acid at both branching and flowering responded more than those that received treatment at either branching or flowering. For best results, it is suggested to use 25.0 kg FeSO₄ ha^?1 in a basal application along with 40 kg S ha^?1, as plants require most of their S and Fe at the early growth stages.