A greenhouse study was carried out to study the effect of Hexavalent chromium, under flooding conditions on growth and biological yield of rice. Plastic pots were uniformly packed with 10 kg portions of the tested soils (clay soil from Moshtohor and sandy one from Inshas). Rice grains were sown in all pots and thinned to 3 plants per pot after 20 days from sowing. Hexavalent chromium (Cr6+) was applied at doses of 0, 10, 20, 40, 80 and 160 mg Cr kg soil and samples of soil solution were collected after 5, 20, 35, 50 and 65 days from Cr addition for determination of both Cr3+ and Cr6+. Rice was also sampled at the aforementioned dated for analyses of total uptake.
The obtained results showed the following:
The reducing of Cr6+ to Cr3+ was very actually on day 5 after Cr addition then is sharply decreased by prolonging the time of soil solution sampled after Cr addition. In the clay soil, a time period of 5 days was considered the optimum contact time to achieve the highest rate of Cr6+ reduction, while in the sand one increased time of soil solution sampling sharply decreased the amount of Cr3+ leached from the soil.
The dry matter (DM) yield of rice shoots and roots significantly decreased with increasing applied Cr6+ rate to the soil. The retarding effect of Cr6+ addition to plant growth occurred in both tested soils, but the reducing in Dm yield of shoots and roots was more drastic in the sand soil as compared with the clay one. Chromium content in plant organs (shoots and roots of rice) were progressively increased to increasing the tare of applied Cr6+. However, the amount of Cr obtained by plants grown on the sand soil was higher than that recorded with the clay one. Chromium content in rice seeds of plants grown on the sand soil increased upon raising the rate of Cr applied from 20 to 160 mgkg-1 as compared with the control treatment, while in the clay one the rate of applied Cr showed no significant influence.
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