Submitted to: American Forage and Grassland Council Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/13/1997
Publication Date: N/A
Citation: Interpretive Summary: Switchgrass is a warm-season perennial bunchgrass that is widely adapted and has a high potential as a renewable energy source. Switchgrass, however, requires substantial inputs of nitrogen fertilizer to maximize yields. Municipal sludge can be an economical source of nitrogen as well as other nutrients. Sludge may also contain significant amounts of heavy metals, such as cadmium, which may accumulate in soils to toxic levels. These studies were conducted to evaluate the effect of switchgrass variety and soil pH on the response of switchgrass to cadmium. Growth of switchgrass was reduced by 25% at cadmium solution concentrations of 8 ppm. Biomass production of switchgrass was severely reduced at high cadmium levels in the soil. Highest plant tissue concentrations of cadmium were found in roots at the high cadmium treatment level and a low soil pH. Application of cadmium-enriched sludge increased cadmium concentrations in leaf blades and roots by 10- to 200-fold, respectively. Switchgrass appears to be tolerant of cadmium at low to moderate levels.
Technical Abstract: Recent efforts have been initiated to develop switchgrass (Panicum virgatum L.) as a bioenergy crop. Switchgrass requires input of nitrogen (N) fertilizer in order 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, response to heavy metals in th sludge is not known. Two studies were conducted to determine the role of 1) cultivar and cadmium (Cd) rate and 2) soil pH and Cd rate on biomass accumulation and allocation of switchgrass. Cadmium concentrations in tissue were also determined for the latter study. Cultivars differed only slightly for biomass accumulation and allocation, and there were no interactions with Cd rate (P > 0.05). Solution Cd levels of 16 ppm decreased biomass yields by 31% for roots and 47% for shoots. Two-hundred ppm Cd decreased biomass accumulation of all plant components by 95%. Cadmium concentrations in plant tissue varied with soil pH and Cd rate. Cadmium concentrations of 900 ppm were found in root tissue at 200 ppm Cd and pH 5.1. Switchgrass translocates little Cd to the aboveground portion of the plant and appears to tolerate moderate levels of applied Cd.