Effect of green manuring (Sesbania aculeata) on zinc equilibria in submerged calcareous and non-calcareous soils

Abstract

A pot experiment was conducted to study the effect of green manuring (Sesbania aculeata) on pH, electrical conductivity (EC), Zn concentration and ZN equilibria in a calcareous and a non-calcareous soil under submerged conditions. The soil solutions were drawn anaerobically by gravity and analysed for pH, EC and Zn. Green manuring lowered the pH and increased the EC throughout submergence compared with the untreated control. The effect of green manuring was more pronounced in non-calcareous soil. The concentration of water-soluble Zn under submergence alone continued to decline up to the end of the experiment in both soils. But Zn concentration in green manure-amended soil was lower during the initial stages and higher in the later stages in comparison with the unamended soil. Zn potential values in the case of submergence alone were within the range of the ZnCo3-Zn2+ (aq) system up to 1 week and 4 weeks for non-calcareous and calcareous soil, respectively. Thereafter they shifted to those of the Zn-soil (unknown solid phases)-Zn2+ (aq) system. Under green manuring the values were within the range of the latter system throughout the experiment.