Saturday, 15 July 2006

Effects of Arsenic Contaminated Irrigation Water, Zinc and Organic Matter on the Mobilization of Arsenic in Soils in Relation to Rice (Oryza sativa L.).

Dilip Kumar Das, Dept of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, B-5/50, P.O-Kalyani, Dist- Nadia, Kalyani, 741235, India

A laboratory experiment was conducted in an Aeric Endoaquept arsenic contaminated soils (pH 7.5; 0.5 M NaHCO3 extractable arsenic, 0.22 mg/kg) taking three levels each of arsenic (0, 5 and 10 mg/kg), Zn (0, 10 and 20 mg/kg) and organic matters (well rotten FYM and vermicompost each at 0, 1 and 2 % by weight of soil) and kept for 42 days under submerged condition. Field experiment was also conducted on summer rice (cv. IET 4786 using split plot design with three replications. The main plot treatments were three levels of irrigation water namely i) continuous ponding (I0) ii) intermittent ponding (I1) and iii) intermittent ponding upto 40 days of crop growth and then continuous ponding for crop growth period (I2). The sub-plot treatment was two levels of Zn (Zn0 and Zn1, ZnSO4 @ 25 kg/ha). Fertilizers doses applied were 100:50:50 (N:P2O5:K2O) kg/ha where half of the N and full doses of P2O5 and K2O were applied as basal and 1/4th of the N was top dressed at active tillering and panicle initiation stage. The results show that the amount of arsenic content in soil decreased with the application of zinc and organic matter being greater magnitude in the treatment where combined application of arsenic and zinc @ 5 and 20 mg/kg respectively were applied. The yield of grain was also recorded highest (4.84 t/ha) in I0Zn1 closely followed by 4.83 t/ha in I1Zn1 treatment. The concentration of arsenic in grain was lowest compared to root and stem. The overall results concluded that the concentration of arsenic both in soils and in different parts of rice plants has been found to be decreased significantly with the application of zinc and organic matter under different irrigation management practices with savings of 36 cm/ha water. Key words : Arsenic, irrigation water, mobilisation, organic matter, zinc, rice.

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