Seed Yield Response of Three Switchgrass Cultivars for Different Management Practices¹

Abstract

Switchgrass (Panicum virgatum L.) is a valuable warm‐season native forage grass in Midwest grazing systems prompting interest in seed production to obtain adequate amounts of seed for planting purposes. Switchgrass seed production studies, however, have been primarily conducted in the Great Plains states. This study was conducted to evaluate cultivar response to row spacing and N fertilization for increasing seed yields in a more humid area of the species' natural adaptation. ‘Cave‐in‐Rock’ (C), ‘Blackwell’ (B), and ‘Pathfinder’ (P) switchgrass were established on a Webster loam (fine‐loamy, mixed, mesic Typic Haplaquoll) soil near Ames, IA, in 1978 in 20‐, 60‐, and 100‐cm rows and fertilized with N at 0, 90, and 180 kg ha−1 in 1979 and 1980. Seed yield and selected seed yield components were measured in 1979 and 1980. Seed yields averaged over 2 years, three N levels and three row spacings were 908, 319, and 388 kg ha−1 for C, B, and P, respectively. Greater lodging resistance, and greater seed yields in response to increased N level and decreased row spacing, contributed to the significantly greater seed yields of C. Seed yields of B and P were similar for all N and row‐spacing treatments. Cultivar rankings in percent fertile tillers varied between years. Inflorescences per unit area did not differ among cultivars, but total seed weight infloresence−1 averaged over years was 268 g for C, which was 54 and 40% greater than for B and P, respectively. Total seed weight inflorescence−1 seemed to be the most important seed yield component, followed by 100 seed weight for explaining seed yield differences among cultivars. Cave‐in‐Rock showed superior lodging resistance and a greater potential for increased seed production in narrow rows and at higher N levels in 2‐ and 3‐year‐old stands. Results showed that N management and row spacing of young stands of switchgrass grown for seed production in the humid Midwest varied according to the cultivar used. Cultivar susceptibility to lodging may be the most limiting factor to obtain high seed yields of some cultivars in the more humid areas of natural adaptation of switchgrass.

Biomass Production of ‘Alamo’ Switchgrass in Response to Nitrogen, Phosphorus, and Row Spacing

“…This suggests that tiller density in switchgrass may be more sensitive to intraspecific competition than tiller mass. In Iowa, tiller density decreased from 872 to 390 m −2 (average of 2 yr and three cultivars) when row spacing was reduced from 100 to 20 cm (Kassel et al, 1985). In space‐planted swards, tiller density generally influenced forage yield more than tiller mass until a dense, closed canopy formed (Montero and Jones, 1992).…”

“…Increased row spacing increased biomass yields of Alamo switchgrass in Alabama (Sladden et al, 1995), and wider rows increased seed yields of switchgrass in the Great Plains (Cornelius, 1950). On the other hand, wider rows reduced seed yields of ‘Cave‐in‐Rock’ switchgrass in Iowa (Kassel et al, 1985). It is not known if these responses of switchgrass to row spacing would be similar in lower rainfall environments.…”

Switchgrass and Big Bluestem Hay, Biomass, and Seed Yield Response to Fire and Glyphosate Treatment

“…Some commercial seed fields in the Northeast average 224 kg ha −1 of pure live seed with 112 kg N ha −1 (Andy Ernst, Ernst Conservation Seeds, Meadville, PA, personal communication, 2004). Switchgrass seed yields of up to 900 kg ha −1 have been reported in Iowa (Kassel et al, 1985); 80 to 700 kg ha −1 in Missouri (Brejda et al, 1994); and 2 to 390 kg ha −1 in Kansas (Cornelius, 1950). Big bluestem seed yields averaged 22 kg ha −1 in our study.…”

Improving Warm-Season Forage Grasses Using Selection, Breeding, and Biotechnology

“…Initially, seed production was a problem with most perennial grasses adapted to the Great Plains. Empirical (Schumacher, 1962) and formal research (Cornelius, 1950;Kassel et al, 1985) has resulted in greatly increased seed production. By using improved seed production practices, experienced seed growers in Nebraska can produce from 250 to> 1000 kg of seed ha-1 (Nebraska Crop Improvement Association, 1990, personal communications).…”