Warm‐Season Grass Diversity in Yield, Plant Morphology, and Nitrogen Concentration and Removal in Northeastern USA

Abstract

Abstract Six genera of warm‐season grasses were grown in Pennsylvania for 9 yr on a fine‐loamy, mixed mesic, Aquic Fragiudult, to determine their potential as forage grasses on droughty sites. Effects of applied N on yield, plant morphology, and N composition of forages were studied during Years 4 through 7, when N was applied to half of each plot area. Big bluestem, Andropogon gerardii Vitman, and switchgrass, Panicum virgatum L., showed much cultivar variation in stand development, whereas asiatic bluestem, Bothriochloa spp., and indiangrass, Sorghastrum nutans (L.) Nash, developed productive stands in one season. Mean yield of ‘NJ 50’ switchgrass was higher than that of all other grasses, yield of ‘Niagara’ big bluestem was higher than that of other big bluestems, and yield of ‘Ky 591’ indiangrass was higher than that of other indiangrasses. The percentage of grasses showing a yield response to applied N increased each year, from 32% in 1981 to 67% in 1984. Mean yield response to N varied greatly among cultivars, P < 0.001. Nitrogen concentration in forage varied among bluestems and indiangrasses, but not among switchgrasses. Mean N removed in first‐harvest forage ranged from 16 kg ha −1 yr −1 for untreated ‘Plains’ asiatic bluestem to 97 kg ha −1 yr −1 for N‐treated NJ 50 switchgrass. Flowerstem density and height were affected differently by N, depending upon plant species and cultivar. The sheath‐stem component of dry matter yield was 60 g kg −1 higher when N was applied than when no N was applied. In the ninth year, approximately one‐half of the cultivars had stand ratings exceeding 80% ground cover.