Redistribution of copper in alfisols under submergence. II. applied copper

Soil submergence for growing wet land rice creates typical chemical environment which is likely to affect availability of applied fertilizer copper (Cu) to the crop by transforming it into various soil fractions. An experiment was undertaken to study the effect of organic matter (as starch) application on the transformation of applied Cu in Alfisols under submergence. Copper was applied either at the beginning or after 15 days of submergence (presubmergence). Results show that more than 85% of the applied Cu was distributed in water soluble plus exchangeable (WSEX), organically complexed (OC), and amorphous iron oxides bound (AMOX) fractions at the beginning of incubation. Submergence caused decrease in WSEX, and OC [in Purulia district (S,) soil only] fractions and increase in AMOX and residual Cu fractions of applied Cu. About 15% of the applied Cu was transformed into inactive residual fraction at the end of 60 days of submergence. Copper applied in 15 days presubmerged soils transformed to a lesser extent into residual fraction than that applied in 0 day presubmerged (i.e., no presubmergence) soils. Application of organic matter in S, soil mobilized applied Cu from OC to AMOX fraction and reduced net transformation into residual fraction. Lower net transformation into residual fraction suggests that Cu may be applied in 15 days presubmerged soil for its higher use efficiency in rice crop grown in Cu deficient Alfisol.