Adaptation of tall-grass prairie cultivars to West Louisiana

Abstract

Big bluestem (Andropogon gerardii Vitman) indiangrass Sorghastrum nutans (L.) Nash] and switchgrass (Panicum virgatum L.) are widely recognized as valuable forage and conservation species in the Great Plains and the upper South. These species occurred in natural fire-maintained longleaf pine (Pinus palustris Mill.) woodland ecosystems from southeast Texas eastward. Recent interest and even recommendations of cultivars of these species have been developed in the Louisiana longleaf pine area. Genotype origin of these species is known to affect adaptation. Adaptation of the cultivars Kaw big bluestem, Lometa indiangrass, Osage indiangrass, Blackwell switchgrass, and Alamo switchgrass to the Louisiana Coastal Plain was assessed under a natural stand of longleaf pines and in full sun at Rosepine, La. Plots were seeded in 1995, and stands were monitored through the spring of 1998. Only Alamo switchgrass and Lometa indiangrass under the pines produced sufficient stands for harvest. Production potential was greatest for Alamo switchgrass with the highest annual yield of 5,580 kg ha-1 from 2 harvests in 1996. Herbage production of 1,500 kg ha-1 did not differ between Alamo switchgrass and Lometa indiangrass in the second year of harvest when harvested in June and September for 2 consecutive years. The longleaf pine overstory apparently provided a competitive advantage during establishment, since weeds dominated plots in full sun. The 2 cultivars from southern latitudes, Alamo switchgrass and Lometa indiangrass, were superior in establishment, productivity, and stand survival. Aggressive competition from dense-growing subtropical grasses was detrimental during establishment and following defoliations.