Influences of starch and Zn-EDTA on Zn-desorption and rice ( Oryza sativa L.) nutrition under different moisture regimes.

Desorption of Zn from sorbed Zn in soils is controlled by different moisture regimes in rice fields and thus control the Zn availability to rice. A laboratory experiment was conducted at different moisture regimes viz. flooded-dried, alternate wetting and drying and preflooding condition in two Inceptisols and two Alfisols of West Bengal, India, with (50 g kg-1) and without starch as control to investigate the desorption of adsorbed Zn from Zn-EDTA (0.0, 0.1, and 0.2 Mg Zn g-1 soil). Percent desorption of Zn was found significantly higher on alternate wetting and drying condition in Alfisols. Starch applications enhanced desorption under flooded-dried and alternate wetting and drying, but decreased it under preflooding conditions. The variations in Zn desorption among soils and moisture treatments are the result of changes in soil pH, Fe-oxides, bonding energy constants, and free energies for Zn adsorption. After desorption experiment a pot trial was conducted with rice (cv. IET-4094) under alternate wetting and drying moisture conditions. The results show that the dry matter yield and 1000 grain weight of rice are appreciably higher when alternate flooding and drying moisture condition was maintained. This finding was in close agreement with the Zn desorption studies under the alternate flooding and drying moisture regimes. [ABSTRACT FROM AUTHOR]