Switchgrass (Panicum virgatum L.) is a warm‐season native grass, used for livestock feed, bioenergy, soil and wildlife conservation, and prairie restoration in a large portion of the USA. The objective of this research was to quantify the relative importance of latitude and longitude for adaptation and agronomic performance of a diverse group of switchgrass populations. Six populations, chosen to represent remnant prairie populations on two north–south transects, were evaluated for agronomic traits at 12 locations ranging from 36 to 47°N latitude and 88 to 101°W longitude. Although the population × location interactions accounted for only 10 to 31% of the variance among population means, many significant changes in ranking and adaptive responses were observed. Ground cover was greater for northern‐origin populations evaluated in hardiness zones 3 and 4 and for southern‐origin populations evaluated in hardiness zones 5 and 6. There were no adaptive responses related to longitude (ecoregion). Switchgrass populations for use in biomass production, conservation, or restoration should not be moved more than one hardiness zone north or south from their origin, but some can be moved east or west of their original ecoregion, if results from field tests support broad longitudinal adaptation.

Grasslands have an underground biomass component that serves as a carbon (C) storage sink. Switchgrass (Panicum virgatum L.) has potential as a biofuel crop. Our objectives were to determine biomass and C partitioning in aboveground and belowground plant components and changes in soil organic C in switchgrass. Cultivars Sunburst and Dacotah were field grown over 3 yr at Mandan, ND. Aboveground biomass was sampled and separated into leaves, stems, senesced, and litter biomass. Root biomass to 1.1‐m depth and soil organic C to 0.9‐m depth was determined. Soil C loss from respiratory processes was determined by measuring CO2 flux from early May to late October. At seed ripe harvest, stem biomass accounted for 46% of total aboveground biomass, leaves 7%, senesced plant parts 43%, and litter 4%. Excluding crowns, root biomass averaged 27% of the total plant biomass and 84% when crown tissue was included with root biomass. Carbon partitioning among aboveground, crown, and root biomass showed that crown tissue contained approximately 50% of the total biomass C. Regression analysis indicated that soil organic C to 0.9‐m depth increased at the rate of 1.01 kg C m−2 yr−1 Carbon lost through soil respiration processes was equal to 44% of the C content of the total plant biomass. Although an amount equal to nearly half of the C captured in plant biomass during a year is lost through soil respiration, these results suggest that northern Great Plains switchgrass plantings have potential for storing a significant quantity of soil C.

Since its introduction from Eurasia, smooth bromegrass (Bromus inermis Leyss.) has become an important cool‐season forage grass in North America. The objective of this study was to document breeding progress in smooth bromegrass between 1942 and 1995 in North America. Thirty cultivars or experimental populations were tested at up to seven sites in the eastern and central USA, with a range of soil types and climates. There have been small genetic changes in forage yield, brown leafspot resistance [caused by Pyrenophora bromi (Died) Drechs.], in vitro dry matter digestibility (IVDMD), and neutral detergent fiber (NDF) concentration. Brown leafspot resistance increased gradually, averaging 0.21 units decade−1. Mean forage yield did not change for cultivars developed after 1942, but was 0.54 Mg ha−1 (7.2%) higher for the post‐1942 group than in ‘Lincoln’, a direct representative of smooth bromegrass introduced into North America. Selection for increased IVDMD led to an average increase in IVDMD of 9 g kg−1 (1.4%), an increase in forage yield of 0.33 Mg ha−1 (5.0%), and a decrease in NDF of −8 g kg−1 (−1.2%) in the post‐1942 group. The slow rate of progress for smooth bromegrass forage yield is due to its complex polyploid inheritance, emphasis on traits other than forage yield, and relatively little concentrated attention from public and private breeders.

yield of 9.0 Mg ha Ϫ1 , and sustained yields this great on dryland sites have not been documented in the study Switchgrass (Panicum virgatum L.) has been identified as a potenarea.

alfalfa mixtures are needed for DM yields over several years in response to N fertilization in the Northern Cultivars used in grass-alfalfa (Medicago sativa L.) mixtures for Great Plains. hay production in the semiarid Northern Great Plains have often lacked long-term productivity. This study was conducted to compare Alfalfa germplasm with a high proportion of its pardry matter (DM) yields of grass monocultures and grass-alfalfa binary entage from yellow flowering alfalfa [M. sativa subsp. mixtures receiving annual applications of 0 and 50 kg N ha Ϫ1 over a falcata (L.) Arcang] and with the capacity to spread 5-yr period. 'Reliant' and 'Manska' intermediate wheatgrass [Thinofrom new shoots arising from horizontal roots has dempyrum intermedium (Host) Barkw. and Dewey], 'Lincoln' smooth onstrated long-term persistence in the semiarid Northbromegrass (Bromus inermis Leyss.), 'Nordan' crested wheatgrass ern Great Plains (Heinrichs, 1975;Berdahl et al., 1989). [Agropyron desertorum (Fisch.) Schult.], 'Lodorm' green needlegrass Other legumes, including cicer milkvetch (Astragalus (Stipa viridula Trin.), and 'Dacotah' switchgrass (Panicum virgatum cicer L.) (White and Wight, 1984) and sainfoin (Ono-L.) were seeded in monoculture and in binary mixtures with 'Rangebrychis viciaefolia Scop.) (Dubbs, 1971), had inferior lander' alfalfa [Medicago sativa subsp. ϫ varia (Martyn) Arcang.] persistence to hardy alfalfa germplasm at semiarid sites. on a Parshall fine sandy loam (coarse-loamy, mixed, superactive, frigid, Pachic Haplustolls) near Mandan, ND. Plant stands of green Results from earlier studies (Kilcher and Heinrichs, needlegrass and switchgrass were inadequate, and yields were not 1966; Kilcher et al., 1966) indicated that intermediate measured. Total seasonal DM yields from two cuttings averaged 8.74 wheatgrass had poor persistence in mixtures with alfalfa and 2.71 Mg ha Ϫ1 , respectively, for grass-alfalfa mixtures and grass relative to standard and fairway crested wheatgrass monocultures at 0 kg N ha Ϫ1 . At 50 kg N ha Ϫ1 , grass-alfalfa mixtures [Agropyron cristatum (L.) Gaertner] and smooth bromeand grass monocultures averaged 8.72 and 5.04 Mg ha Ϫ1 DM yield, grass. The intermediate wheatgrass used in these tests respectively. Yields of the grass component of first cut grass-alfalfa originated from common seed that had no cultivar desigmixtures averaged 35% of total yield for intermediate wheatgrass, Abbreviation: DM, dry matter. Published in Agron. J. 93:463-467 (2001).