Pubescent Wheatgrass Research Articles

Testing cover crop species under three soil moisture conditions in a controlled greenhouse environment

Extreme climatic events, such as drought and heavy rainfall, are increasing with climate change. These events can threaten agroecosystems, including vineyards. Cover crops are often grown in vineyards for various reasons and can be an effective strategy for climate change adaptation. Understanding which cover crop species can establish well under extreme climate conditions is important. We conducted a greenhouse experiment to investigate the responses of nine cover crop species to overwatered and water-deficit conditions. Treatments included (1) overwatered soil condition, watered at 100% field capacity daily, (2) control, watered at 60%–70% every other day, and (3) water deficit, watered at 15%–20% weekly for 53 growing days. Results indicated that the total dry weight of all species decreased (most significantly) under water-deficit conditions. However, pubescent wheatgrass and red fescue did not exhibit any stress symptoms. Apart from alfalfa, all species established well under overwatered conditions despite slight yellowing of foliage for crimson clover and hairy vetch. Pearl millet and yellow sweet clover had the best establishment regardless of conditions. Our results provide important information on the selection of cover crops that can withstand climatic variability and thrive in the extreme conditions linked to the climate change scenario in Canada.

Long-Term Persistence of Cool-Season Grasses Planted to Suppress Broom Snakeweed, Downy Brome, and Weedy Forbs

Invasive plants are spreading throughout arid and semiarid rangelands of western North America. Long-lived perennial plants that can persist under harsh environmental conditions are needed to compete with invasive species. The objective of this study was to conduct a long-term evaluation of native and introduced grass species planted to suppress and prevent reinvasion of downy brome (Bromus tectorum L.), snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby), and annual forbs. Seeding treatments comprised three introduced grasses: crested wheatgrass (Agropyron cristatum [L.] Gaertner × A. desertorum [Fisch. Ex Link] Schultes), pubescent wheatgrass (Elytrigia intermedia spp. trichophorum [Host] Beauv.), and Russian wildrye (Psathyrostachys junceus [Fisch.] Nevski); a mix of these introduced grass species, three native grasses: bluebunch wheatgrass (Pseudoroegneria spicata [Pursh]), western wheatgrass (Pascopyrum smithii [Rybd.] A. Löve), and squirreltail (Elymus multisetus [J.G. Sm.] Jones); and a mix of these native grass species, or forage kochia (Bassia prostrata [L.] A.J. Scott). The treatments were seeded in October 2003. Frequency and biomass were measured in 2015 and 2017 in Howell, Utah and in 2015 and 2016 in Nephi, Utah. Crested wheatgrass persisted at both locations (> 62% frequency) along with the rhizomatous grass species, pubescent (> 65%) and western wheatgrasses (> 72%). Russian wildrye was still present at Howell (30%) with little remaining at Nephi (7%). Squirreltail frequency was 13% at Howell and 12% at Nephi. Bluebunch wheatgrass was no longer present at either location (< 1%). Forage kochia remained at Nephi (36%) with little remaining at Howell (4%). Downy brome was present at both locations and was suppressed relative to control plots, at Nephi, by crested wheatgrass and the introduced grass mix (< 9%). Downy brome was > 93% in all plots, at Howell, in 2017. In summary, crested, pubescent, and western wheatgrasses were able to persist over 12 yr at both locations.

Evaluation of Fifteen Cultivars of Cool‐Season Perennial Grasses as Biofuel Feedstocks Using Near‐Infrared

Core Ideas Harvest yield varies more across species than sugar content and accessibility. Harvest yield and sugar accessibility are both critical parameters for conversion. Near‐infrared/partial least square models are valuable for quickly evaluating biomass for bioconversion. Cool‐season (C3) perennial grasses have a long history of cultivation and use as animal forage. This study evaluated 15 cultivars of C3 grasses, when harvested in late June for increased biomass yield, as biofuel feedstocks using near‐ infrared spectroscopy (NIR) based partial least square (PLS) analysis. These grasses were grown near Iliff, CO, for three growing seasons (2009–2011). The carbohydrate composition and released carbohydrates (total glucose and xylose released from dilute acid pretreatment and enzymatic hydrolysis [EH]) were predicted for samples from the study using NIR/PLS. The results were analyzed from a biofuels perspective, where composition combined with harvest yield provided information on the carbohydrate yield available for biomass conversion processes, and released carbohydrate yield provided information on the accessibility of those carbohydrates to conversion methods. The range in harvest yields varied more among cultivars (2900 kg ha−1) than did the range in carbohydrate composition (56.0 g kg−1) or released carbohydrates (60.0 g kg−1). When comparing carbohydrate yield to released carbohydrate yield between cultivars, an efficiency as high as 87% release of available carbohydrates was obtained for pubescent wheatgrass [Thinopyrum intermedium (Host) Barkworth &amp; D.R. Dewey ‘Mansaka’], with a low of 71% for hybrid wheatgrass [Elytrigia repens (L.) nevski ´ pseudoroegneria spicata (PURSH) A. Love ‘Newhy’]. Though hybrid wheatgrass had the lowest release efficiency, its high harvest yield resulted in release of more total carbohydrates than half the other cultivars analyzed. This suggested that harvest yield, carbohydrate release, and carbohydrate composition, togetherplay significant roles in biofuel feedstock evaluation.

Exotic grass and shrub production evaluation and llama preference on the Bolivian Altiplano

Lack of nutritional forage during the dry season limits llama ( Lama glama) production on the Bolivian Altiplano. Minimal supplementation with stockpiled energy-rich grasses and high-protein shrubs may improve the dry season nutritional status of llamas. The purposes of this study were first, to evaluate forage production on the Altiplano of cold-hardy, drought-resistant plants successful in the Intermountain Western United States and second, the acceptability of these species to llamas. Six species of grass (pubescent wheatgrass [ Agropyron trichophorum], smooth brome [ Bromus inermis], crested wheatgrass [Hycrest] [ Agropyron cristatum × A. desertorum ], weeping lovegrass [ Eragrostis curvula], orchard grass [ Dactylis glomerata], and timothy [ Phleum pratense]) and 6 species of shrubs (black sage [ Artemisia nova], fourwing saltbush [ Atriplex canescens], saltbush [ Atriplex halimus], mountain mahogany [ Cercocarpus montanus], bitterbrush [ Purshia tridentata], and forage kochia [ Kochia prostrata]) were planted at three sites on the Altiplano and evaluated during the dormant season of the following 2 years. Data measuring row fill, biomass, and nutrient concentrations were collected for the grasses. Data measuring percent survival, biomass, and nutrient concentrations were collected for the shrubs. Preference trials including focal animal sampling and instantaneous-scan sampling evaluated the acceptance of these forages by llamas. During the first year, row fill among the grasses ranged from 30–96%. Smooth brome biomass increased from 3427 to 5420 kg dry weight/ha between years ( p ≤ 0.01) and was the most productive grass measured. Crested wheatgrass also increased from 2487 to 4687 kg dry weight/ha ( p ≤ 0.01). The most successful shrubs, forage kochia and fourwing saltbush, survived 75–90%. At one site, fourwing saltbush produced 638 kg dry weight/ha and forage kochia 616 kg dry weight/ha, more ( p ≤ 0.01) than produced at the other sites (91–316 kg dry weight/ha). Among the grasses, the highest CP concentrations were found in crested wheatgrass (9.7%) and orchard grass (9.6%). Weeping lovegrass had lower ( p < 0.01) CP concentration (3.7%). Forage kochia, contained 14.6% CP. Five grasses were similarly preferred receiving between 11 and 18% time grazed. Weeping lovegrass received less ( p ≤ 0.01) at 1–2%. The llamas refused the shrubs completely. Considering biomass and acceptability, orchard grass, pubescent wheatgrass, and smooth brome are likely selections for dry season supplementation.

Potential Hybridization of Genetically Engineered Triticale with Wild and Weedy Relatives in Canada

Triticale (xTriticosecale Wittmack) is a promising cereal platform for novel bioindustrial products being developed using genetic engineering (GE). Before GE crop varieties are approved in Canada, the potential for gene flow to wild and weedy relatives must be examined. To identify at‐risk species for hybridization and gene flow, we reviewed the phylogeny of triticale relatives, outcrossing barriers, reported crosses, and occurrence of wild relatives in Canada. Presence of genes that inhibit outcrossing, genome constitution, geographic distribution, and floral structure influence triticale hybridization potential. Hybridization experiments between triticale and parental species indicate crosses may produce viable seeds, although outcrossing with rye (Secale cereale L.) is less likely. With respect to nonparental species that occur in Canada, jointed goatgrass (Aegilops cylindrica Host) and intermediate wheatgrass (Agropyron intermedium (Host) Beauv.) should be investigated to determine if viable hybrids with triticale can occur. While there are reports of wheat (Triticum spp.) hybridization with pubescent wheatgrass [Agropyron trichophorum (Link) K. Richt.], quackgrass [Elymus repens (L.) Gould], barley (Hordeum vulgare L.), and lyme grass (Leymus arenarius Hochst), hybridization with triticale under natural conditions seem unlikely.

Organic Carbon Effects on Soil Physical and Hydraulic Properties in a Semiarid Climate

Increasing cropping intensity in the central Great Plains of the United States has the potential to increase organic carbon (OC) stored in the soil and lead to improved soil physical properties. A cropping systems study was started in 1990 at the Central Great Plains Research Station near Akron, CO. In 2005 soil samples were taken in six 95‐mm increments to a depth of 370 mm to measure OC, water stable macroaggregates (water stable aggregates &gt; 250 μm), bulk density (ρb), total porosity (ϕtotal), water storage porosity (ϕws), and saturated hydraulic conductivity (ksat). Samples were collected from permanent grass plots {45% smooth brome [Bromus inermis (Leyss.)], 40% pubescent wheat grass [Agropyrons trichophorum (Link) Richt.], and 15% alfalfa [Medicago sativa (L.)]}, plots in a wheat {[Triticum aestivum (L.)]–corn [Zea mays (L.)]–millet [Panicum miliaceum (L.)]} rotation, and plots in a wheat–fallow rotation. Increased cropping intensity significantly increased OC, water stable macroaggregates, and ksat, but had no significant effect on ρb, ϕtotal, or ϕws Permanent grass increased OC compared with the annually cropped rotations, particularly deeper in the soil. Plots in permanent grass had greater ksat and this may indicate greater pore continuity and stability under saturated conditions. Organic carbon and water stable macroaggregates were poorly correlated. Water stable macroaggregates was negatively correlated with ρb and positively correlated with ksat Increasing soil OC may not immediately lead to changes in soil aggregation in a semiarid climate. Increased time and biological activity may be needed to convert the crop residues into organic compounds that stabilize aggregates and soil pore systems.

Revegetating Russian Knapweed (Acroptilon repens) and Green Rabbitbrush (Ericameria teretifolia) Infested Rangeland in a Single Entry

The objective of this study was to test the potential for using a single-entry procedure to revegetate Russian knapweed– and green rabbitbrush–infested rangeland. I hypothesized that simultaneously applying an herbicide and seeding in the fall would produce the highest establishment and growth of desired species. For Russian knapweed, treatments included three seeding rates (zero, low, and high) and two herbicides (with and without clopyralid plus 2,4-D) applied in either the spring (2003) or fall (2004). The seed mixture included pubescent wheatgrass, Siberian wheatgrass, and alfalfa. Grasses were seeded on October 21, 2003 (fall dormant), and April 5, 2004 (spring), using a no-till rangeland drill. The seeding rates consisted of 3.4, 6.8, and 9.3 (low) or 5.0, 9.0, and 12.3 (high) kg ha−1of alfalfa, Siberian wheatgrass, and pubescent wheatgrass, respectively. For green rabbitbrush, treatments included two seeding levels (13.5 kg ha−1of Siberian wheatgrass and not seeded) and three herbicides (clopyralid, dicamba, and 2,4-D) and a control applied in July. Clopyralid plus 2,4-D (0.21 plus 1.12 kg ha−1) and dicamba at 2.1 kg ha−1gave 61 and 66% control of Russian knapweed and green rabbitbrush, respectively. Herbicides interacted with seeding to provide the highest density of seeded species on the Russian knapweed site. These data support the hypothesis that simultaneously applying an herbicide and seeding in the fall would produce the highest establishment and growth of desired species. Conversely, only seeding affected Siberian wheatgrass establishment on the rabbitbrush sites. It may be reasonable to seed Siberian wheatgrass without controlling rabbitbrush if forage production is the primary objective.

Seeding Cool-season Grasses to Suppress White Locoweed (Oxytropis Sericea) Reestablishment and Increase Forage Production

Livestock poisoning can occur on short-grass prairies when locoweeds are actively growing in spring before warm-season grasses begin growth. White locoweed grows in early spring, completes flowering and seed production by early summer, and goes dormant. Perennial cool-season grasses may provide competition to suppress locoweed or reduce its reestablishment following control. Furthermore, these grasses may provide alternative palatable forage to livestock early in the spring. The objective of this study was to suppress white locoweed reinvasion by seeding cool-season grasses at two mixed-grass and two short-grass prairie sites. White locoweed and associated species were controlled with glyphosate (1.1 kg ai/ha) and picloram (0.38 kg ae/ha) in 3 by 15 m plots. The plots were seeded to ‘CDII’ crested wheatgrass, ‘Vavilov’ Siberian wheatgrass, ‘Luna’ pubescent wheatgrass, ‘Bozoisky’ Russian wildrye, smooth brome, ‘NewHy’ wheatgrass, sideoats grama, and ‘Immigrant’ forage kochia. In addition, a native grass pl...

Revegetating Russian Knapweed (Acroptilon Repens) Infestations Using Morphologically Diverse Species and Seedbed Preparation

Highly degraded pastures and rangeland dominated by Russian knapweed (Acroptilon repens [L.] DC) are often devoid of desirable plants. Control efforts may be ephemeral because propagules of desirable species are not available to reoccupy niches made available by control procedures. Establishing desirable, competitive plants is essential for enduring management and restoration of Russian knapweed and other weed-infested plant communities. The objective of this study was to investigate the effectiveness of revegetating Russian knapweed–infested pastures with 3 nonnative, morphologically diverse species following 1 of 3 seedbed preparation treatments. In successive years, at 2 similar sites in southeastern Oregon, we sprayed Russian knapweed with glyphosate, then prepared the seedbed by burning, tilling, or leaving untreated. Following seedbed preparation, we seeded a perennial forb (alfalfa [Medicago sativa L.]), a bunchgrass (Siberian wheatgrass [Agropyron fragile {Roth} P. Candargy subsp. sibericum {Willd.} Melderis]), and a sod-forming grass (pubescent wheatgrass [Elytrigia intermedia {Host} Nevski subsp. trichophora {Link} Tvzel]) in monocultures and 2- and 3-species mixtures. We measured Russian knapweed and seeded-species density 1 and 2 years following seeding. The forb-seeding treatment decreased reinvasion of Russia knapweed by 50%–60% at 1 site, but otherwise, seeding treatment had little influence on total seeded-species density or Russian knapweed density. Tilling generally resulted in a 35%–40% reduction in Russian knapweed density compared with the control and resulted in the highest establishment of seeded species. Variability in annual precipitation appeared to influence seeded-species establishment between the sites. Our results suggest shallow tilling (10–15 cm) followed by drill-seeding desirable forbs and grasses may provide the best results when revegetating Russian knapweed infestations. Follow-up management should include strategies to enhance desirable species production while minimizing Russian knapweed reinvasion.

Heifer Production on Rangeland and Seeded Forages in the Northern Great Plains

Integrating use of seeded perennial cool-season grass pastures with native rangeland can increase available forage and provide a high plane of nutrition for grazing livestock. Our objective was to compare performance of yearling beef heifers grazing native rangeland with those grazing an integrated system that included seeded forages. Twice-replicated, 3-ha pastures seeded to either ‘Rosana’ western wheatgrass ( Pascopyron smithii [Rydb.] A. Love), ‘Luna’ pubescent wheatgrass ( Elytrigia intermedia [Host] Nevski), or ‘Hycrest’ crested wheatgrass ( Agropyron cristatum [L.] Gaertn. ssp. desertorum [Fisch. ex Link] A. Love) were grazed in spring, whereas twice-replicated, 3.24-ha pastures seeded to either ‘Alkar’ tall wheatgrass ( Thinopyrum ponticum [Podp.] ZW Liu & RC Wang), ‘NewHy’ hybrid wheatgrass ( Elymus hoffmannii KB Jensen & KH Asay), ‘Bozoisky’ Russian wildrye ( Psathyrostachys juncea [Fisch.] Nevski.), or ‘Prairieland’ Altai wildrye ( Leymus angustus [Trin.] Pilger) were grazed in autumn. Native rangeland was grazed during summer in the integrated system and spring, summer, and autumn in the rangeland treatment. Heifers exhibited greater weight gains on seeded pastures than on native rangeland in spring and autumn of most years. In 2 out of 3 years, heifers that grazed native rangeland during spring gained more ( P = 0.012 for gain head −1 and P = 0.021 for gain head −1 day −1 ) while grazing native rangeland during summer than heifers that grazed seeded pastures in spring. Spring + summer gains averaged (mean ± SE) 0.56 ± kg·head −1 ·d −1 and 73.1 ± kg·head −1 . Livestock managers need to consider their livestock marketing and management strategies when using seeded pastures for seasonal grazing. La integración del uso de praderas sembradas de zacates perennes de estación fría con pastizal nativo puede incrementar el forraje disponible y proveer un buen plano nutricional para el ganado en apacentamiento. Nuestro objetivo fue comparar el comportamiento productivo de vaquillas de ganado de carne de año apacentando un pastizal nativo con vaquillas apacentando un sistema integrado que incluía forrajes sembrados. Praderas de 3 ha, repetidas dos veces, sembradas con “Western wheatgrass” ( Pascopyron smithii [Rydb.] A. Love) variedad ‘Rosana’ y “Pubescent wheatgrass” ( Elytrigia intermedia [Host] Nevski) variedad ‘Luna’ o con “Crested wheatgrass” ( Agropyron cristatum [L.] Gaertn. ssp. desertorum [Fisch. ex Link] A. Love) variedad ‘Hycrest’ fueron apacentadas en primavera, mientras que praderas de 3.24 ha, repetidas dos veces, sembradas con “Tall wheatgrass” ( Thinopyrum ponticum [Podp.] ZW Liu & RC Wang) variedad ‘Alkar’, “Hybrid wheatgrass” ( Elymus hoffmannii KB Jensen & KH Asay) variedad ‘NewHy’, “Russian wildrye” ( Psathyrostachys juncea [Fisch.] Nevski.) variedad ‘Bozoisky’ o con “Altai wildrye” ( Leymus angustus [Trin.] Pilger) variedad ‘Prairieland’ fueron apacentadas en otoño; en el sistema integrado, el pastizal nativo fue apacentado en verano y en el tratamiento de solo pastizal se apacentó en primavera, verano y otoño. En la mayoría de los años, las vaquillas mostraron mayores ganancias de peso en las praderas sembradas que los obtenidos en el pastizal nativo en primavera y otoño. En 2 de 3 años, la vaquillas que apacentaron el pastizal nativo durante la primavera, ganaron más peso ( P = 0.012 para ganancia cabeza −1 y P = 0.021 para la ganancia cabeza −1 dia −1 ) cuando apacentaban el pastizal en verano que las vaquillas que apacentaron en primavera las praderas sembradas. Las ganancias de primavera + verano promediaron 0.56 ± kg·cabeza −1 ·d −1 y 73.1 ± kg·cabeza −1 . Cuando utilicen praderas sembradas para el apacentamiento estacional, los manejadores de ganado necesitan considerar su mercadeo del ganado y estrategias de manejo.

Tiller Persistence of Eight Intermediate Wheatgrass Entries Grazed at Three Morphological Stages

Intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. &amp; D.R. Dewey subsp. intermedium] provides high quality forage for hay and pasture in the Great Plains of North America but lacks persistence under grazing. We investigated the effect of grazing at early vegetative, mid‐culm elongation, and boot stages on tiller persistence of three cultivars and five experimental lines of intermediate and pubescent wheatgrass [T. intermedium subsp. barbulatum (Schur) Barkw. &amp; D.R. Dewey]. The study, located near Mandan, ND was seeded in 1997, hayed in 1998 and 1999, and grazed from 2000 to 2002. Four tillers were marked on one plant per plot in May 2000. Number of newly emerged tillers (tiller recruitment) and tiller mortality were recorded on the four original tillers and subsequently recruited tillers in mi‐May, July, and September. Tiller replacement ratios, which incorporated cumulative recruitment and mortality, were greatest on plots grazed during early vegetative and mid‐culm elongation. Tiller recruitment, tiller mortality, and tiller replacement ratio had a year × treatment interaction. In 2000, grazing during the early vegetative stage resulted in significantly higher tiller replacement ratios than grazing during late boot or no grazing, and grazing during mid‐culm elongation and late boot had greater tiller recruitment but also greater tiller mortality than the other two treatments. Tiller replacement ratio had a grazing treatment × entry interaction in 2001. ‘Mandan 1871’ had the greatest tiller replacement ratio and tiller recruitment among entries. The results indicate time of grazing and cultivar selection influence the persistence of tillers of intermediate wheatgrass primarily through their effect on tiller recruitment.

Heifer Production on Rangeland and Seeded Forages in the Northern Great Plains

Integrating use of seeded perennial cool-season grass pastures with native rangeland can increase available forage and provide a high plane of nutrition for grazing livestock. Our objective was to compare performance of yearling beef heifers grazing native rangeland with those grazing an integrated system that included seeded forages. Twice-replicated, 3-ha pastures seeded to either ‘Rosana’ western wheatgrass (Pascopyron smithii [Rydb.] A. Love), ‘Luna’ pubescent wheatgrass (Elytrigia intermedia [Host] Nevski), or ‘Hycrest’ crested wheatgrass (Agropyron cristatum [L.] Gaertn. ssp. desertorum [Fisch. ex Link] A. Love) were grazed in spring, whereas twice-replicated, 3.24-ha pastures seeded to either ‘Alkar’ tall wheatgrass (Thinopyrum ponticum [Podp.] ZW Liu RC Wang), ‘NewHy’ hybrid wheatgrass (Elymus hoffmannii KB Jensen KH Asay), ‘Bozoisky’ Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski.), or ‘Prairieland’ Altai wildrye (Leymus angustus [Trin.] Pilger) were grazed in autumn. Native rangeland was grazed during summer in the integrated system and spring, summer, and autumn in the rangeland treatment. Heifers exhibited greater weight gains on seeded pastures than on native rangeland in spring and autumn of most years. In 2 out of 3 years, heifers that grazed native rangeland during spring gained more (P = 0.012 for gain head-1 and P = 0.021 for gain head-1 day-1) while grazing native rangeland during summer than heifers that grazed seeded pastures in spring. Spring + summer gains averaged (mean +/- SE) 0.56 +/- 0.01 kg head-1 d-1 and 73.1 +/- 1.6 kg head-1. Livestock managers need to consider their livestock marketing and management strategies when using seeded pastures for seasonal grazing.

Perennial Grass Establishment Integrated with Clopyralid Treatment for Yellow Starthistle Management on Annual Range1

Yellow starthistle is an aggressive annual forb that has invaded millions of hectares of California's annual range. Control efforts such as burning and herbicides have been effective for short-term management. However, recruitment from the seedbank or reinvasion of the annual grassland system results in a rapid return to yellow starthistle dominance. Establishing perennial grasses would be ideal for suppression of yellow starthistle. However, a lack of effective weed control options in California during a seeding program has limited perennial grass establishment. Clopyralid was used to control yellow starthistle annually for 1, 2, or 3 yr to provide a window of reduced competition for pubescent wheatgrass establishment. Total plant cover, yellow starthistle density, biomass, and seedhead number were quantified for 6 yr. Clopyralid treatment significantly reduced yellow starthistle and allowed pubescent wheatgrass establishment with a single treatment. Both clopyralid treatment and pubescent wheatgrass est...

Prairie Grasses as Hosts of the Western Corn Rootworm (Coleoptera: Chrysomelidae)

We evaluated 21 prairie grass species thought to be among those dominant 200 yr ago in the western Great Plains as larval hosts of the western corn rootworm, Diabrotica virgifera virgifera LeConte. Maize, Zea mays L., and sorghum, Sorghum bicolor L., were included as positive and negative controls. Twenty pots of each test species were planted, and each pot was infested 5 wk later with 20 neonate western corn rootworm larvae. Four pots within each of four replications were randomly assigned a sample date for larval extraction. The remaining pot from each replication was used to monitor adult emergence. At 5, 10, 15, and 20 d after infestation, pot contents from assigned pots were placed in Tullgren funnels equipped with 60 W-lights for extraction of larvae. The percentage of larvae recovered, larval head capsule width, and adult emergence varied significantly among the grass species. The percentage of larvae recovered from western wheatgrass, Pascopyrum smithii (Rydb.); pubescent wheatgrass, Elytrigia intermedia (Host); and side-oats grama, Bouteloua curtipendula Michx., was not significantly different than that from maize when sample dates were combined. The number of adults produced from pubescent wheatgrass was not significantly different than the number produced from maize. The average dry weight and head capsule width of adults produced from grass species were not significantly different than the head capsule widths and dry weights of those adults from maize. Overall, adults were produced from 14 of the 23 species evaluated. The results from this study are discussed in relation to the potential ancestral hosts of western corn rootworm larvae and in relation to resistance management of transgenic maize.

Spring Grazing Reduces Seed Yield of Cool‐Season Perennial Grasses Grown in the Southern Great Plains

Information is lacking regarding management of cool‐season perennial grasses for seed production in the southern Great Plains. Our objective was to determine the effect of spring grazing on seed yield of cool‐season perennial grasses grown in the southern Great Plains. Treatments consisting of no spring grazing by beef cattle (Bos spp.), limited spring grazing, and extended spring grazing were applied to ‘Paiute’ orchardgrass (Dactylis glomerata L.), ‘Lincoln’ smooth bromegrass (Bromus inermis Leyss), and ‘Manska’ pubescent wheatgrass (Thinopyrum intermedium subsp. barbulatum (Shur) Barkw. &amp; D.R. Dewey) in 1998 to 2000, and to pubescent wheatgrass alone in 2001. Date of first hollow stem, when elevation of apical meristems became evident, was also determined. Limited vs. no spring grazing led to decreased seed yield in 7 of 10 Species × Year combinations, whereas extended vs. limited spring grazing led to declines in seed yield in six of nine Species × Year combinations. Date of first hollow stem occurred from late March to early April for orchardgrass and smooth bromegrass, and early to mid‐April for pubescent wheatgrass. Seed yield of orchardgrass and pubescent wheatgrass decreased as grazing time after first hollow stem increased. Commercial seed production of smooth bromegrass, which averaged 336 kg ha−1 with no spring grazing, may be feasible in the Southern Plains. However, spring grazing does not appear to be a viable component of seed production systems for cool‐season perennial grasses in the Southern Plains based on the likelihood of decreased seed yield associated with spring grazing.

Productivity and Survival of Defoliated Wheatgrasses in the Rolling Plains of Texas

In the Texas Rolling Plains, cool‐season perennial grasses may complement limited forage availability in March–May and October–December. In two experiments conducted at Vernon, TX, on a sandy loam soil (fine‐loamy, mixed, thermic Udic Paleustalfs), we evaluated productivity and persistence of crested [Agropyron cristatum (L.) Gaertn. × A. desertorum (Fisch. ex Link) J.A. Schultes], hybrid [Elytrigia repens (L.) Nevski × Pseudoroegneria spicata (Pursh) L‘ve], intermediate [Thinopyrum intermedium (Host) Barkworth &amp; D.R. Dewey], pubescent [T. intermedium ssp. barbulatum (Schur) Barkw. &amp; D.R. Dewey], and tall wheatgrass [T. ponticum (Podp.) Barkworth &amp; D.R. Dewey] under combinations of 3‐ or 6‐wk defoliation frequency at 7.5‐ or 15‐cm. About 64% more herbage yield was harvested from all species at the 7.5‐ vs. 15‐cm defoliation height in the first, but only from crested, hybrid, and pubescent wheatgrass in the second growing season. Frequent defoliation increased herbage by 22% in Experiment A or 37% in Experiment B only in the first growing season. Tiller survival increased with frequent defoliation in intermediate wheatgrass by 33% in Experiment A and up to 70% in Experiment B, but decreased by 52% in hybrid and by 33% in pubescent wheatgrass in Experiment A, and up to 50% in Experiment B. Lower nighttime soil temperatures increased tiller survival during summer in swards defoliated at the 7.5‐ vs. 15‐cm height. Wheatgrass productivity increased under intensive or frequent defoliation in the first, but declined in several species in the subsequent growing season, making their potential to complement forage base limited.

Establishment of a plant regeneration system for wheatgrasses (Thinopyrum, Agropyron and Pascopyrum)

Wheatgrasses (Thinopyrum, Agropyron and Pascopyrum spp.) are a ubiquitous group of cool-season grasses used throughout much of the semiarid temperate world. In order to explore the potential of biotechnology to accelerate conventional breeding efforts, we developed an efficient plant regeneration system for different wheatgrass species: tall wheatgrass [Thinopyrum ponticum (Podp.) Liu and Wang], intermediate and pubescent wheatgrass [Thinopyrum intermedium (Host) Barkw. and D.R. Dewey], crested wheatgrass [Agropyron cristatum (L.) Gaertner], and western wheatgrass [Pascopyrum smithii (Rydb.) Love]. Embryogenic callus was induced from mature and immature embryos and immature inflorescence with an induction frequency in the range of 0.5–8.3% for the different wheatgrass species tested. Individual embryogenic calluses were then used to establish single genotype-derived suspension cultures. Efficient plant regeneration was achieved from the established em-bryogenic suspensions with regeneration frequencies in the range of 20–65% for tall wheatgrass, 21–40% for intermediate and pubescent wheatgrasses, 32–51% for crested wheatgrass, and 25–48% for western wheatgrass. The cell suspension-derived wheatgrass plants were fertile and phenotypically normal in the field. The efficient plant regeneration system provides a solid basis for genetic transformation of wheatgrasses.

Productivity and Survival of Defoliated Wheatgrasses in the Rolling Plains of Texas

In the Texas Rolling Plains, cool-season perennial grasses may complement limited forage availability in March–May and October–December. In two experiments conducted at Vernon, TX, on a sandy loam soil (fine-loamy, mixed, thermic Udic Paleustalfs), we evaluated productivity and persistence of crested [Agropyron cristatum (L.) Gaertn. × A. desertorum (Fisch. ex Link) J.A. Schultes], hybrid [Elytrigia repens (L.) Nevski × Pseudoroegneria spicata (Pursh) L‘ve], intermediate [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey], pubescent [T. intermedium ssp. barbulatum (Schur) Barkw. & D.R. Dewey], and tall wheatgrass [T. ponticum (Podp.) Barkworth & D.R. Dewey] under combinations of 3- or 6-wk defoliation frequency at 7.5- or 15-cm. About 64% more herbage yield was harvested from all species at the 7.5- vs. 15-cm defoliation height in the first, but only from crested, hybrid, and pubescent wheatgrass in the second growing season. Frequent defoliation increased herbage by 22% in Experiment A or 37% in Experiment B only in the first growing season. Tiller survival increased with frequent defoliation in intermediate wheatgrass by 33% in Experiment A and up to 70% in Experiment B, but decreased by 52% in hybrid and by 33% in pubescent wheatgrass in Experiment A, and up to 50% in Experiment B. Lower nighttime soil temperatures increased tiller survival during summer in swards defoliated at the 7.5- vs. 15-cm height. Wheatgrass productivity increased under intensive or frequent defoliation in the first, but declined in several species in the subsequent growing season, making their potential to complement forage base limited.

Short-term impact of fallow frequency and perennial grass on soil organic carbon in a Brown Chernozem in southern Alberta

Maximum sequestration of atmospheric C in agricultural soils of the Canadian prairies can be achieved by the replacement of crop rotations that include summer fallow with continuous cropping or perennial forages. However, few studies have documented potential gains of soil organic C (SOC) in the region with the greatest use of fallow, the Brown soil zone. A dryland crop rotation study was initiated in 1992 on a Chin clay loam (Orthic Brown Chernozem) in southeastern Alberta on a site that had previously been under conventional irrigated cereal production. The study included fertilized and unfertilized treatments of the following crop rotations: fallow-wheat (FW), fallow-wheat-wheat (FWW), continuous wheat (W) and grass (G). The grass rotation consisted of pubescent wheatgrass (Agropyron trichophorum) harvested for hay. Total organic-, light fraction- and 10-wk mineralized-C and -N were determined in fall 1997, 6 yr after study initiation. Growing season precipitation (April through August) was 43% above long-term normals in the first 2 yr of this study, supporting excellent grass establishment and high crop yields, but was below normal thereafter. Fertilization with N and P increased average rotation yields by 21 to 56%, with the greatest yield increases in the G and W rotations. Total SOC to 15 cm (equivalent mass basis) was 1.5 Mg ha-1 higher (P = 0.03) in the W rotation and 3.0 Mg ha-1 higher (P = 0.0001) in the G rotation than in the FW rotation, but was not affected by fertilizer treatment or the interaction of fertilizer and crop rotation treatments. Low variability in measured SOC allowed us to detect differences as low as 1.3 Mg ha-1 among crop rotations, demonstrating that small effects of crop management on SOC can be detected using appropriate methods at uniform sites. Much of the gain in SOC in the G treatment was in mineralizable and light fraction material, indicating that this gain in SOC would be readily lost upon reversion to annual cropping. A simple calculation of residue C inputs and conversion to SOC showed that most of the gain in SOC in the W treatment was due to increased crop residue inputs, but that both increased inputs and reduced decomposition rates likely affected SOC gains in the G treatment. The average gain in SOC during the 6-yr period of this study was 0.25 Mg ha-1 yr-1 due to the elimination of fallow and 0.5 Mg ha-1 yr-1 due to establishment of a perennial forage. Key words: Soil organic matter, carbon sequestration, summer fallow, light fraction

Quality and Persistence of Forages in the Northern Great Plains

Integrating use of seedings of perennial cool-season grasses with native range is used to increase available forage and for maintaining a high plane of nutrition for grazing livestock. Our goal was to evaluate performance of yearling cattle and stand persistence of 3 released wheatgrass cultivars. Twice replicated 3-ha pastures were seeded to ‘Rosana’ western wheatgrass [Pascopyron smithii (Rydb.) A. Love], ‘Luna’ pubescent wheatgrass [Elytrigia intermedia (Host) Nevski], and ‘Hycrest’ crested wheatgrass {[Agropyron cristatum (L.) Gaertn.] ssp. desertorum (Fisch. ex Link) A. Love} in autumn 1994. Yearling steers (n = 8) grazed from 9 May to 12 June 1997 and 24 April to 15 June 1998. Yearling heifers grazed from 27 April to 18 June 1999. Hycrest produced the largest herbage standing crop in spring 1997 (912 kg ha -1 ) and 1998 (1,223 kg ha -1 ) (P < 0.05), but by spring 1999 standing crops averaged 656 kg ha -1 , and cultivars were not significantly different. Digestible organic matter standing crop did not differ among pastures of seeded species, but declined (P < 0.05) from May to June each year. Crude protein standing crop varied among cultivars (P < 0.05) in April and May 1998 and May 1999; however, no clear trends emerged. Crude protein standing crops consistently declined from April-May to June. Average daily gains were similar among cultivars in 1997, but greater (P < 0.05) on Hycrest (1.28 kg day -1 ) than Rosana (1.03 kg day -1 ) in 1998. Gains on Hycrest (0.74 kg day -1 ) and Rosana (0.78 kg day -1 ) were greater (P < 0.05) than on Luna (0.52 kg day -1 ) in 1999. These findings show in some years, Hycrest provided more forage in spring than Rosana, and will allow an increase in livestock numbers. Based on the encroachment of invading species, persistence of Luna is marginal of the 335-mm precipitation zone in the Northern Great Plains.