ABSTRACT
A clean environment (soil, water, and air) is a prerequisite for sustainable cropping systems, as well as human and animal health. The growth of agriculture and industry, based in large part on scienti˜c and technological advances, has improved living standards for much of the world’s population. At the same time, this growth has created environmental problems in many parts of the world. Contamination of soils with heavy metals has become a critical environmental issue because of its adverse ecological effects (An et al., 2004; Liu et al., 2007; Pinto et al., 2008). Soils contaminated with heavy metals can be found throughout the world (Cunningham et al., 1996; McGrath et al., 2002; Huang and Chen, 2003; Prista et al., 2008; Simmons et al., 2008). Industrial and mining activities have polluted soils with heavy metals in China (Wu and Zhang, 2002). Irrigation of agricultural land with sewage water containing heavy metals is a common practice in developing countries like India, because this contaminated water is also a cheap and rich source of nutrients (Singh et al., 2007). Mining and smelting operations, industrial and municipal waste, combustion of fossil fuels, and application of agricultural fertilizers can all contaminate soils with heavy metals (Chen et al., 1995; Mandal et al., 1997; Liao et al., 2005; Zhang and Duan, 2008).
