Bioremediation of chemically polluted soil cultivated with Faba bean and Maize

Abstract

A greenhouse pot experiment was undertaken to ascertain the efficiency of some organic materials on decreasing the mobility of heavy metals in soil and subsequent rates of their absorption by growing plants. An alluvial clay soil was amended with each of compost, biogas manure or humic acid, at doses of 0.5 & 1.0 %C. Faba bean (Vicia faba), as a leguminous winter crop, and maize (Zea mays), as a cereal summer crop, were planted in the amended soil. A mixture of Zn+ Pb + Cu was added at the permissible safe level of each mineral and double that permissible level. Controls of no organic or mineral addition were included. Rates of Zn, Pb & Cu uptake by plants had been measured at two plant growth periods, i.e. 45& 90 days for faba bean and 30 & 60 days for maize. Total and bioavailable amounts of those minerals were also determined in the cultivated soil at termination of the experiment. The obtained results indicated that humic acid was superior as to handicap the activity of heavy metals in soil, and thus diminished their uptake by plants, greatly at the higher rate of application, and followed descendingly by biogas manure and compost; that was the case at the first detection time. However, at the later growth period, humic acid had moved back to exchange the position with compost. Capacity of plant absorption for such metals showed the order: Zn> Cu>Pb. Faba bean took up higher amounts of the assigned minerals than maize. Contents of the heavy metals in soil oppositely reflected the position revealed in the grown plants.