Twenty-Year Biomass Yields of Eight Switchgrass Cultivars in Alabama

Abstract

Long-term experiments with perennial cellulosic energy crops are needed to determine stand longevity and yield trends over time, as affected by weather. Consequently, the objectives of this study were to determine the long-term biomass yields of eight switchgrass (Panicum virgatum L.) cultivars in Alabama and to evaluate effects of weather variables on annual yields. Two lowland cultivars (Alamo and Kanlow) and six upland cultivars (Blackwell, Cave-in-Rock, Kansas-Native, Pathfinder, Summer, and Trailblazer) were evaluated in a small-plot experiment in central Alabama. Plots were planted in 1989 and fertilized with 84 kg N ha−1 annually, split into two equal applications. The experiment received no P and K fertilizer, herbicides, or irrigation. Annual yields were determined by harvesting plots twice each year, from 1990 to 2009. Growing season (March 1 to October 31) precipitation ranged from 405 to 1,294 mm. All plots remained productive during the experimental period. Average yields were generally higher than those reported from other experiments and that of Alamo (23.5 Mg ha−1 year−1) was higher than yields of the other seven cultivars. Although yields of lowland cultivars varied over time, this variation was not related to age of stand or precipitation. In contrast, yields of all upland cultivars increased over the first 12 years, and yields of Blackwell, Cave-in-Rock, Kansas-Native, and Summer were positively related to precipitation. It is concluded that under similar soil, environmental, and management conditions, stands of switchgrass should be productive for 20 years or more.