Organic amendments: effects on cereals growth and cadmium remediation

Cadmium (Cd) is one of the toxic metals that adversely affect plant growth. Organic amendments may not only enhance nutrient status of soil, but they may also form complexes with Cd and reduce its availability to plants. This experiment was conducted to determine whether organic amendments (compost and biogas slurry) could stabilize/extract Cd and alleviate the adverse effects of Cd on the growth of two cereals, wheat and maize. Organic amendments along with four varying levels of Cd (0, 5, 20, 50 mg kg^-1 soil) were prepared with soil. Effect of these amendments on tolerance indices, root/shoot dry biomass, tissue Cd concentration, Cd uptake and translocation were studied. Biogas slurry caused maximum increase in tolerance indices of wheat and maize (100–112 and 117–133 %, respectively, as compared to control), whereas compost caused significant increase in their dry biomass. Negative correlation between root dry biomass of wheat (r = -0.37) and maize (r = -0.53) to Cd revealed its suppressive effects. Dry biomass of plant correlated with organic amendments in wheat (r = 0.83–0.98), whereas weak correlation was observed in maize (r = 0.30–0.40). Compost significantly reduced Cd uptake in wheat and maize; however, it increased Cd translocation in plants. Based on the results of this study, root was the major sink of Cd when soil was amended with or without organic amendments. Biogas slurry removed 97 % Cd from artificially polluted water after 13 h at pH 6. The additions of compost in soil and biogas slurry in wastewater are recommended to stabilize/extract Cd.

Keywords
Bioremediation; Cadmium stress; Biosorption; Compost; Biogas slurry; Wheat; Maize