Cadmium application and pH effects on growth and cadmium accumulation in switchgrass

Recent efforts have been initiated to develop switchgrass (Panicum virgatum L.), which requires nitrogen (N) for productivity, as a bioenergy crop. Alternatives to inorganic fertilizers are needed to reduce input costs and maintain a positive energy balance. Municipal sludge may be an economical source of N and other nutrients for biomass production but switchgrass's response to heavy metals in the sludge is unknown. A study was conducted to determine the interaction of soil pH and Cd application on biomass accumulation and Cd allocation of switchgrass. 'Alamo' switchgrass was grown in pots at five soil pH levels (4.0, 5.1, 5.8, 6.6, and 7.3) and four soil Cd levels (0, 50 100, and 200 mg Cd kg(-1)). Two hundred milligrams Cd kg(-1) decreased biomass accumulation of all plant components by 95%. Cadmium concentrations of 900 mg kg(-1) were found in root tissue of plants grown in soil with 200 mg Cd kg(-1) and a pH of 4.0. Soil pH should be maintained near neutral to minimize Cd accumulation by switchgrass.