THE EFFECTS OF USING COPPER FOR MITIGATING HISTOSOL SUBSIDENCE ON

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Abstract
In continuation of earlier examinations of the suitability of amending cultivated organic soils with moderate amounts of Cu for slowing down their decomposition and resultant subsidence, this greenhouse study revealed that the presence of 1060 ppm (μg·g−1) Cu in organic soil B had no adverse effect on the yield and nutrition of flooded rice grown on it, compared with the same on soil A containing 136 ppm Cu. The rice had been preceded by five crops in the same plots. The long-term study also simulated an event where the organic soil B, enriched in Cu to three times the level required for mitigating the subsidence, was mixed individually with four mineral sublayers in 1:1 vol/vol ratio for argonomic convenience. The yields and nutrition of roots, straw, and grain (with husks) of the rice crop indicated that the Cu added to these mixtures through soil B was not injurious to the crop. Similarly, data on the rice crop grown on the mineral sublayers specially amended with organic-bound Cu to possibly phytotoxic levels, and on fractionation of the soil Cu, revealed that with time the Cu in these soils was becoming less available to plants. Consequently, the rice grown on the soils did not suffer decreases in yield in spite of 600 to 1000 ppm of Cu in roots. The results confirmed earlier conclusions that the Cu needed for slowing down the subsidence by half would not be phytotoxic, even if the organic soil was mixed with certain mineral sublayers and the organic matter nearly dissipated, and extended the conclusions to include submerged culture of rice. © Williams & Wilkins 1985. All Rights Reserved.
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