Switchgrass tolerance to cadmium: Uptake and translocation

Recent efforts have been initiated to develop switchgrass (Panicum virgatum L.) as a bioenergy crop. Switchgrass requires input of nitrogen (N) to be productive. 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; however, the response of switchgrass to heavy metals in the sludge is not known. Two greenhouse studies and a 2-yr field study were conducted to determine the interaction of (1) cultivar and cadmium (Cd) application, (2) soil pH and Cd application, and (3) soil moisture and Cd application on biomass accumulation and Cd allocation of switchgrass. In the first experiment, 'Alamo', 'Blackwell', 'Cave-in-Rock', and 'Trailblazer' switchgrass were grown in sand culture and were watered twice weekly with nutrient solution containing 0, 1, 2, 4, 8, or 16 mg Cd L{dollar}sp{lcub}-1{rcub}.{dollar} Cultivars differed (P {dollar}{dollar} 0.05) affected by either irrigation or Cd level in 1995 or 1996. Concentrations of Cd in aboveground tissue ranged from 0.36 to 0.87 mg kg{dollar}sp{lcub}-1{rcub}.{dollar} Alamo switchgrass translocated little Cd to the aboveground portion of the plant at all Cd application levels and tolerated 100 kg ha{dollar}sp{lcub}-1{rcub}{dollar} of applied Cd. However, in different environments and management systems, Cd concentrations in aboveground tissue may increase to levels above suggested maximum tolerance levels. Producers should maintain soil pH near neutral to minimize Cd accumulation by switchgrass.