BIOMASS AND NITROGEN ACCUMULATION IN SWITCHGRASS - EFFECTS OF SOIL AND ENVIRONMENT

Grasslands are the basis of animal agriculture in the northeastern USA . Adapted warm-season grasses make a valuable contribution to grasslan d production in this region, but knowledge of the interactive effects between soils and environment on their production is limited. Our obje ctive was to examine and evaluate the interactive effects of soils and environment on biomass and N accumulation by switchgrass (Panicum vir gatum L. cv. Cave-n-Rock), an adapted warm-season grass. The study was conducted for 3 yr on four sites in central Pennsylvania selected to provide differences in soil water holding capacity and temperature reg ime. Switchgrass was treated with 0 and 84 kg N ha(-1) as NH4NO3. Biwe ekly biomass samples were taken starting 15 June and continued until t he grass reached heading stage, approximately 31 July. Biomass accumul ation rates for this 31-d period ranged from 157 to 211 kg ha(-1) d(-1 ). Soil N, N fertilization, and temperature controlled biomass accumul ation rates. Total N uptake rates ranged from 1.49 to 2.63 kg ha(-1) d (-1) and were controlled by soil N levels and N fertilization. Fertili zer N recovery averaged about 40%, and was lowest where native soil N exceeded 2.0 g kg(-1).