Threshold toxic limits of Cd for leafy vegetables raised on a mollisol amended with varying levels of farmyard manure.

Green house experiments were conducted during 2008809 to evaluate the threshold toxic limits of Cd in leafy vegetables grown on a Mollisol receiving varying levels of farmyard manure (FYM). The treatments involved factorial combinations of three levels of FYM (0, 2.23 and 4.46 g/kg soil), seven levels of Cd (0, 5, 10, 25, 50, 100 and 150 mg Cd/kg soil) which were imposed on three plant species (amaranthus, Fenugreek and Buckwheat). Amaranthus was most susceptible to the toxicity of Cd as compared to fenugreek and buck wheat. The threshold toxic limits of Cd in plant tissue for 10 percent reduction in the relative yields of leafy vegetables at 0, 2.23 and 4.46 g FYM/kg soil were 7.3, 29.5 and 10.3 mg Cd/kg dry matter in amaranthus, 2.5, 3.6 and 4.9 mg Cd/kg dry matter in fenugreek and 6.0, 21.0, 15.3 mg Cd/kg dry matter in buckwheat, respectively. The threshold toxic limits of 0.1 N HCl extractable Cd in soil for 10 percent reduction in the relative yields of leafy vegetables at 0, 2.23 and 4.46 g FYM/kg soil levels were 1.4, 4.0 and 2.0 for amaranthus, 3.0, 6.7 and 20.5 mg Cd/kg soil for fenugreek and 2.8, 14.5 and 14.6 mg Cd/kg soil for buck wheat, respectively. The threshold toxic limits of 0.005 M DTPA (pH 7.3) extractable Cd in soil for 10 percent reduction in the relative yields of leafy vegetables at 0, 2.23 and 4.46 g FYM/kg soil levels were 1.3, 3.3 and 1.9 for amaranthus, 1.8, 3.4 and 9.0 mg Cd/kg soil for fenugreek and 1.6, 11.5 and 7.9 mg Cd/kg soil for buck wheat, respectively.