Switchgrass, Big Bluestem, and Indiangrass

Switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and indiangrass (Sorghastrum nutans [L.] Nash) are tall warm-season (C4) grasses that predominated the North American tall-grass prairie (Weaver 1968)

Switchgrass, Big Bluestem, and Indiangrass

Switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and indiangrass (Sorghastrum nutans [L.] Nash) are tall warm-season (C4) grasses that predominated the North American tall-grass prairie (Weaver 1968)

Switchgrass Seedling Development as Affected by Seed Size

Seed size has been associated with early seedling vigor (i.e., germination rate, emergence rate, and growth) in grasses. This study was conducted to compare seedling development over a 60-d period in the field as affected by heavy seed (HS) (0.19 to 0.21 g 100 seed-1) and light seed (LS) (0.13 to 0.16 g 100 seed-1) of \u27Blackwell\u27 and \u27Trailblazer\u27 switchgrass (Panicum virgatum L.). The experiment was conducted in 1995 and 1996 at Lincoln, NE, on a Kennebec silt loam (fine-silty, mixed, superactive, mesic Cumnlic Hapludolls). The experimental design was a randomized complete block with four replicates. Seed was separated into two sizes using a South Dakota seed blower. Seed was planted into rows at a rate of 100 pure live seed per meter of row. Plants were excavated and evaluated for shoot weight, leaf area, and root weight. Shoot and root systems were morphologically staged four times during the summer. Seed size differences in switchgrass appeared to produce only slight differences in morphological development of shoot and root systems, leaf area, shoot weight, and adventitious root weight from seedling emergence to 6 wk of growth. Adventitious roots formed more quickly on seedlings from heavier than lighter seed, but the advantage to seedling establishment was minimal even when soil moisture appeared to be lacking. By 8 to 10 wk after emergence, growth and development of LS seedlings were similar to HS seedlings. Once seedlings formed two or more adventitious roots, seed size no longer affected establishment and growth. Seed size in switchgrass appears to have a minimal long-term effect on growth and development of seedlings

Morphological Development of Switchgrass as Affected by Planting Date

Late-spring and early-summer plantings of warm-season grasses often fail, due to dry soil conditions and competition from annual grass and broadleaf weeds. The objective of this study was to compare the morphological development of switchgrass (Panicum virgatum L.) planted in early, mid, and late spring in eastern Nebraska. This study was conducted in 1994 and 1995 at Lincoln, NE, on a Kennebec silt loam (fine-silty, mixed, mesic Cumulic Hapludolls). \u27Blackwell\u27 and \u27Trailblazer\u27 switchgrass were planted in mid-March, late April, and late May using a single-row, precision grass-seed cone planter to a depth of 0.6 to 1.3 cm at 98 pure live seed per linear meter of row in a split-plot design. Twenty seedlings from each plot were excavated to a depth of 20 cm with a spade. Seedling morphological parameters measured were mean stage count root (MSCR) and shoot (MSCS), leaf area, shoot weight, and primary and adventitious root weight. Plots were sampled every 10 d following the first sample date. In 1994, seedlings from the March planting date were more advanced morphologically in MSCR and MSCS, had accumulated 2.5 times more leaf area, and about 3 times more shoot and adventitious root mass than the April planting date when sampled from late May to late June. In 1995, seedlings from the March planting date generally were more advanced morphologically in root and shoot development, had accumulated 2 to 12 times more leaf area, had 2 to 10 times more shoot mass, and had 2 to 33 times more adventitious root mass than the April or May planting dates at the sample periods from early June to mid-July. We suggest that switchgrass should be planted in early spring instead of in late April and May, as suggested by previous research

Using Leaf Fluorescence for Evaluating Atrazine Tolerance of Three Perennial Warm-season Grasses

Atrazine [6-chloro-N-ethyl-N’-(1-methylethyl)-1,3,5-triazine-2,4-diamine] blocks photosymthetic electron transport in susceptible plants. The energy from the interrupted electron transport is fluoresced from the leaves of atrazine-treated plants. The purpose of this study was to evaluate leaf fluorescence as a nondestructive bioassay of the relative atrazine tolerance of 3 perennnial, warm-season grasses. Leaf section of switchgrass [Panicum virgatum L.] (high tolerance), indiangrass [Sorghastrum nutans (L.) Nash] (intermediate tolerance), and sideoats grama [Boutelouacurtipendula (Michx.) Torr.] (lower tolerance) were placed in distilled water for 20 minute and then in atrazine solutions. Fluorescence readings were taken prior to and after the atrazine treatment with a portable fluorometer. The difference between the 2 readings provided a reliable measure with low variability of the relative atrazine tolerance of the grasses studied and was effective on greenhouse- and field-grown plants. Optiumum atrazine concentrations and incubation periods were 10-3 M (atrazine in distilled H2O) and 30 min, respectively

Bromegrasses

The bromegrasses belong to the genus Bromus of which there are some 100 species (Gould & Shaw, 1983). The genus includes both annual and perennial cool season species adapted to temperate climates. Hitchcock (1971) described 42 bromegrass species found in the USA and Canada of which 22 were native (Gould & Shaw, 1983). Bromus is the Greek word for oat and refers to the panicle inflorescence characteristic of the genus. The bromegrasses are C3 species (Krenzer et aI., 1975; Waller & Lewis, 1979)

Bromegrasses

The bromegrasses belong to the genus Bromus of which there are some 100 species (Gould & Shaw, 1983). The genus includes both annual and perennial cool season species adapted to temperate climates. Hitchcock (1971) described 42 bromegrass species found in the USA and Canada of which 22 were native (Gould & Shaw, 1983). Bromus is the Greek word for oat and refers to the panicle inflorescence characteristic of the genus. The bromegrasses are C3 species (Krenzer et aI., 1975; Waller & Lewis, 1979)

Warm-Season Grass Establishment as Affected by Post-Planting Atrazine Application

Atrazine [6-chloro-N-ethyl-N’-methylethyl)-1,3,5-triazine-2,4-diamine] provides effective weed control during big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatrum L.) establishment. However, most other desirable warm-season grasses are susceptible to atrazine injury at establishment. The objective of this study was to determine if atrazine applications after seedling would affect susceptible warm-season grass establishment. Big bluestem, switchgrass, Indiangrass [Sorghastrum nutans (L.) Nash], sideoats grama [Bouteloua curtipendula (Michx.) Torr.], and little bluestem [Schizachyrium scoparium (Michx.) Nash] were needed into greenhouse flats or field plots and 2.2 kg a.i. atrazine/ha applied at 0 (atrazine control), 7, 14, or 21 days after planting. An untreated control was used also. In greenhouse experiments, indiangrass and sideoats grama plant survival increased when atrazine applications were delayed. Switchgrass, big bluestem, and little bluestem plant survival was not affected by atrazine application. Field studies were conducted in 1983, 1985, and 1986 using the same soil type, grass species, and application periods as the greenhouse study. Delaying atrazine application 7 or more days after planting generally favored survival of indiangrass and sideoats grama. Big bluestem, switchgrass, and little bluestem were not affected by atrazine treatment. Delaying the application of atrazine may favor the survival of atrazine sensitive species. However, further researcher needs to be conducted on various soil types and environmental conditions before this can be a recommended practice

Seedbed Effects on Grass Establishment on Abandoned Nebraska Sandhills Cropland

Perennial grass establishment on abandoned cropland in the Nebraska Sandhills difficult due to low soil fertility, organic matter, and water holding capacity and high potential erodibility. Establishment is further complicated by unpredictable precipitation and weed competition. Two warm-season grasses: sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.] and switchgrass (Panicam virgatum L.); and 2 cool-season grasses: smooth brome (Bromus inermis Leyss.) and intermediate wheat-grass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey subsp. were evaluated with spring-seeded field trials. Seedbed preparation [untilled, disced, and dead oat (Avena sativa L.) cover (DOC)] effect on seeded grass and nonseeded species densities was evaluated in 1985 and 1986 at 2 locations on Valentine sands (Aquic Ustipsamment). In 1985 1 site was irrigated. Both sites were dryland in 1986. Stand failure (\u3c 5 seedlings/m2) occurred on the dryland rite in 1985 due to low, erratic precipitation. Stands evaluated in June 1986 on plots established with irrigation in 1985 had 38, 46, and 61 plants/m2 for the untilled, disced, and DOC seedbeds, respectively. The disced or DOC seedbeds were required for successful (\u3e plants/m2) dryland seedings in 1986 at both locations. Irrigation the establishment year minimized risk of stand failure and allowed the use of my seedbed preparation or grass species studied. Sand bluestem was the only species to establish both years. However, if a dryland seedling of a cool-season species is desired, intermediate wheatgrass appeared more adapted than smooth brome

Tiller Demographics and Leaf Area Index of Four Perennial Pasture Grasses

Developing grazing systems requires basic information on the growth and development of adapted species. The objective of this field study was to determine seasonal tiller demographics and leaf area index (LAI) of intermediate wbeatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey], smooth bromegrass (Bromus inermis Leyss.), switchgrass (Panicum virgatum L.), and big bluestem (Andropogon gerardii Vitman) tiller populations. This study was conducted in 1992 and 1993 near Mead, NE, on a silty clay loam soil (Typic Argiudoll) as a randomized complete block. Monocultures were harvested six times each year for tiller demographics. Additionally, mean stage count (MSC), a quantified estimate of tiller population maturity, was determined at each harvest. The The LAI was indirectly measured using a canopy analyzer at 7- to 14-d intervals. Tiller density for all species generally declined as MSC increased. Tiller demographics were highly variable by year for intermediate wheatgrass and smooth bromegrass, which indicates that grazing management should be based on current tiller populations. Density of vegetative tillers declined most rapidly for smooth bromegrass, followed by intermediate wheatgrass, switchgrass, and big bluestem. Switchgrass and big bluestem tiller demographics were more uniform and predictable across years than intermediate wheatgrass and smooth bromegrass. The LAI for all species increased as MSC increased. Maximum The LAI for intermediate wheatgrass, smooth bromegrass, switchgrass, and big bluestem in 1992 was 4.7,5.1,4.9, and 5.8, respectively. Integrating tiller demographics and The LAI suggests that initial grazing readiness starts with smooth bromegrass in early spring, followed by intermediate wheatgrass in about 2 wk, switchgrass in late spring, and big bluestem in early summer