Trace Elements Laboratory, Physics Department, North Eastern Hill University, Shillang, Meghalaya, 793022.
1Present Address: Institute of Agriculture, Visva Bharati, Sriniketan, Birbhum, West Bengal.
Transformation of native and applied zinc in six wetland rice soils under submergence was studied. Distribution of zinc fraction in soils showed that 65.6 to 76.6 per cent of total zinc remains in residual forms, while 1.12 to 2.73, 2.17 to 3.93, 3.08 to 5.31, 4.07 to 6.64 and 12.30 to 19.50 per cent remain in water soluble plus exchangeable, organically complexed, manganese oxides, amorphous sesquioxides and crystalline sesquioxides bound form, respectively. The applied zinc was transformed to the latter five forms following their relative order of preponderance in native soils and constituted, on an average, 4.18, 23.08, 19.64, 18.83 and 19.56 per cent, respectively of the applied amount. Submergence caused gradual decrease in all the forms of zinc. Significant positive correlation of Mn-oxides forms of zinc with drymatter yield and zinc uptake by rice plants indicated that plants withdrew Zn from the Mn-oxides fraction. Correlation data also indicate that these fractions of zinc are in a state of dynamic equilibrium and show a significant dependence on pH, organic carbon, CEC and clay content.
Acid soils, submergence, transformation, zinc fractions, rice
