Long-term studies on switchgrass grown on a marginal area in Greece under different varieties and nitrogen fertilization rates

Switchgrass (Panicum virgatum L.) is a perennial grass that has been selected as a candidate bioenergy crop for USA in the early 80s, while the research in Europe started a decade later. A long-term study on switchgrass had been carried out (1998â2015) on a marginal area in Greece comparing five varieties (having lowland or upland ecotype) at increasing nitrogen fertilization rates (0, 75 and 150 kg N haâ1). Due to the successful establishment of the plantation quite satisfactory yields were recorded even at the establishment year (8.9 Mg DM haâ1) and the ceiling yields were recorded in the 2nd year and came up to 20 Mg DM haâ1. The under study lowland varieties (Alamo, Kanlow and Pangburn) were more productive compared to the upland varieties (Blackwell and CIR) with mean dry yields 12.37 and 11.39 Mg haâ1, respectively and showed higher resistance to lodging. Among the five under study varieties, Alamo was the best performing giving an average yield of 12.7 Mg DM haâ1, averaged over all treatments and years, while CIR was the least performing producing a corresponding average yield of 10.8 Mg DM haâ1. From the fourth growing season and onwards significantly higher yields were recorded under increasing N fertilization up to 150 kg N haâ1 with an average yield of 13.9 Mg DM haâ1 (150 kg N/ha) over all varieties and years. The corresponding yields for the other two tested nitrogen rates (0 and 75 kg N/ha) were 10.31 and 11.69 Mg DM haâ1, respectively