INFLUENCE OF SOIL-MOISTURE REGIMES AND ORGANIC-MATTER APPLICATION ON THE EXTRACTABLE ZN AND CU CONTENT IN RICE SOILS

A laboratory incubation experiment was conducted to study the influence of three moisture regimes, viz (i) waterlogged (W1), (ii) alternate waterlogged and saturated (W2) and (iii) continuous saturated (W3) and two levels of organic matter application, viz (i) 0 (T1) and (ii) 0.5% of the soil (T2) in their all possible combinations on the extractable (N NH4OAC, pH 7.0) zinc and copper in three lowland alluvial rice-growing soils of West Bengal (India). The results showed that the extractable zinc and copper content in soils recorded marked decrease on incubation under all the moisture regimes, but the same was most prominent under the continuous saturated moisture regime (W3), followed by waterlogged (W1) and alternate waterlogged and saturated (W2) moisture regimes. Application of organic matter brought about further decrease in the content of these elements. Organic matter application combined with saturated moisture regime brought about the greatest decrease both in zinc and copper content. The microbiological immobilisation and the antagonistic effect of increased concentration of extractable iron, manganese and phosphorus have been suggested as the possible reasons for the observed decrease of the content of extractable zinc and copper. © 1979 Martinus Nijhoff Publishers.