Impact of Humic Acid Amendments on Alleviating the Harmful Effects of Cadmium in Radish and Bean Plants

The present study is focused on the role of humic acid on alleviating the harmful effect of cadmium on growth, yield and some physiological processes in radish and bean  plants. Two Pot experiments were carried on  summer seasons of 2010 and 2011 at the Experimental Farm, ElBostan, Faculty of agriculture, Damanhour University, Egypt. Four different levels of cadmium (0, 25, 50 and 75 ppm) and two levels  of humic acid (control and 150 mg/kg soil) were used in minimizing the harmful effects of cadmium on radish 'Balady' and common bean 'Giza 4' plants. The obtained results revealed that all  the assigned concentrations of cadmium induced significant decrease in all the studied vegetative growth characters (plant fresh and dry weight, number of leaves and total leaf area /plant) , yield characters (number of green pods, yield of green and dry  pods, seed yield/plant of bean and root characters of radish plants) and leaves chemical constituents  (Chlorophyll, nitrogen, phosphorous and potassium) compared to control in both seasons. On contrary increasing cadmium concentration  in the  soil increased cadmium content in root, leave and seeds of common bean and radish plants as compared to control in both seasons. Common bean plants was more sensitive than radish plants to elevated levels of Cd in growing media. Humic acid treatments was able to minimize the harmful effect of cadmium in all the studied characters and improve the concentrations of photosynthetic pigments, nitrogen, phosphorous and potassium in leaves of common bean and radish plants grown in cadmium polluted soils as well as  decreased cadmium content in root, stem, leave and seeds of common bean and radish plants as compared to control .