Organic Manures for Cadmium Tolerance and Remediation

Abstract Cadmium (Cd) has become the most-concerning contaminant among heavy metals for soil and food-chain contamination. It has emerged as a major risk to human health and environment sustainability due to its greater mobility and accelerated loading in environmental components worldwide, due to enhanced industrialization and intensified agricultural production, particularly in the developing countries. Cd stabilization in contaminated soil via organic manures is an environmentally amiable, pragmatic, and low-cost methodology for remediation of contaminated soil. Incorporation of organic matter in polluted soils is acknowledged as the most-promising remediation technique at present. Due to highly humified carbon content in manures, these can potentially influence the sorption and immobilization capacity of soil components for Cd. Formation of insoluble complexes and adsorption with solid organic matter results in reduced mobility of Cd. Dissolved organic C in pore water can bind Cd. However, the use of organic manures as remediation agents in soil systems is also being questioned by many researchers that these manures could be the potential source of contamination rather than remediation. This chapter would help readers to understand the sources and dynamics of Cd in cultivated agricultural fields. Moreover, it highlights the biochemistry of various types of manures available. It also explains the mechanism about how Cd in soil solution is transformed from soluble or exchangeable fractions into organically bound fraction by manures. How plants are fortified against Cd toxicity by manure application to soil has also been discussed in detail.