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Abstract: Plant growth simulation models have a temperature response function driving development, with a base temperature and an optimum temperature defined. Such models function well when plant development rate shows a continuous change throughout the growing season. This approach becomes more complex as it is extended to cool‐season perennial grasses with a dormant period and bimodal growth curves. The objective of this study was to develop such a bimodal growth model for tall fescue (Schedonorus arundinaceus (Schreb.) Dumort) in the Midwest USA based on multiyear measurement trials. Functions for bimodal growth were incorporated into the ALMANAC model and applied to tall fescue using published tall fescue yields for a variety of sites and soils. Fields of cultivars “Kentucky 31” and “BarOptima Plus E34” were divided into paddocks and sampled weekly for dry‐matter accumulation. These biomass estimates were used to derive weekly growth values by differences between sequential weekly samplings. The measured values were compared to a single tall fescue simulation each year on one soil. Using these results, the ALMANAC model was modified and tested against mean reported tall fescue yields for 11 sites, with one to three soils per site. When we introduced midsummer dormancy into ALMANAC, we assumed dormancy began on the longest day of the year and lasted until the photoperiod was 0.68 hr shorter than the longest. ALMANAC simulated previously reported tall fescue yields well across the range of sites. Thus, ALMANAC shows great promise to simulate bimodal growth in this common cool‐season grass. [ABSTRACT FROM AUTHOR]

Breeding to improve biomass production of switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) for conversion to bioenergy began in 1992. The purpose of this study was (i) to develop a platform for uniform regional testing of cultivars and experimental populations for these species, and (ii) to estimate the gains made by breeding during 1992 to 2012. A total of 25 switchgrass populations and 16 big bluestem populations were planted in uniform regional trials at 13 locations in 2012 and 2014. The reference region was USDA Hardiness Zones 3 through 6 in the humid temperate United States. Significant progress toward increased biomass yield was made in big bluestem and within upland-ecotype populations, lowland-ecotype populations, and hybrid-derived populations of switchgrass. Four mechanisms of increasing biomass yield were documented: (i) increased biomass yield per se, (ii) later flowering to extend the growing season, (iii) combined later flowering from the lowland ecotype with survivorship of the upland ecotype in hybrid-derived populations, and (iv) increased survivorship of late-flowering lowland populations in hardiness zones that represent an expansion of their natural adaption zone. Switchgrass exhibited all four mechanisms in one or more improved populations, whereas improved populations of big bluestem were likely influenced by two of the four mechanisms. The uniform testing program was successful at documenting increases in biomass yield, identifying the mechanisms for increased yield, and determining adaptation characteristics and limitations of improved populations. [ABSTRACT FROM AUTHOR]

The primary objective was to determine the feasibility of harvesting switchgrass (Panicum virgatum L.) for biomass and/or forage in a single season. Plots were located at Mt. Vernon, on Viraton silt loam (fine-loamy, siliceous, active, mesic Oxyaquic Fragiudalf), and Columbia, on Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualf), both in Missouri. Forage/biomass yields and nutritive value of samples intended for forage use, were compared between four harvest management treatments: a single post-frost harvest for biomass (Treatment I), a forage harvest at boot stage followed by a post-frost biomass harvest (Treatment II), biomass harvest at postanthesis with late summer regrowth harvested as forage (Treatment III) and biomass harvest at preanthesis with late summer regrowth harvested as forage (Treatment IV). A complementary study was conducted to determine the effects of switchgrass maturity stage on efficiency of conversion to glucose through enzymatic hydrolysis. Both studies were conducted in 2010 and 2011. The single, post-frost harvest (Treatment I) yielded as much as or more biomass than any other treatment. At Mt. Vernon in both years, yields intended for forage use were greatest for Treatment II. At Columbia, forage yields were greatest for Treatment IV in 2010 while there was no difference between treatments in 2011. When forage harvests were compared, summer regrowth was generally more lignified than growth harvested at boot stage. Two-harvest systems can yield as much as single harvest systems; producers should weigh the economic value of forage vs. biomass before deciding which strategy fits best. [ABSTRACT FROM AUTHOR]

Pasture-based dairy operators usually aim to optimize defoliation intensity to maximize forage production and nutritive value. he objective was to determine forage accumulation, nutritive value, and tiller density of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] and perennial ryegrass (L. perenne L.) when repeatedly mowed to a stubble height of 2.5, 5, 7.5, 10, 12.5, or 15 cm. In a 2-yr study conducted near Columbia, MO, plots were mown to their respective stubble height whenever they grew to a "trigger" height of 20 to 22 plate meter units (approximately 4000 kg ha-1 dry matter [DM] to soil surface). In Year 1, tall fescue mowed to 2.5 cm accumulated 14,440 kg ha-1 which was the most of any treatment. In Year 2, forage accumulation for tall fescue mowed to 2.5, 5, or 7.5 cm did not difer, but was approximately 15% more than perennial ryegrass mowed to the same heights. For both species, forage harvested at stubble heights ≥10 cm had greater nutritive value than at heights of ≤7.5 cm. Perennial ryegrass had 60% fewer tillers for stubble heights ≤7.5 cm compared to heights ≥10 cm. Tall fescue showed no diference in tiller density for any stubble height. Milk production ha-1, predicted via MILK2006, was greater for stubble heights ≤7.5 cm, primarily due to greater forage accumulation. his study showed that tall fescue is better suited than perennial ryegrass for pasture-based dairies in the Midwest because of its greater forage yield, estimated milk production, and stand (tiller) density. [ABSTRACT FROM AUTHOR]

Continental tall fescue [Festuca arundinacea Schreb. syn. Lolium arundinaceum (Schreb.) Darbysh.] is the predominant forage used by cattle producers throughout much of the Midwest. However, Mediterranean tall fescue is gaining popularity in warmer, drier climates. One major difference of Mediterranean tall fescue is that it enters a semidormant period during hot dry summers but resurges during the fall and winter months. During the autumn resurgence it has exceptional growth but does not survive prolonged freezing conditions typically found in the Midwest. To determine how both Continental and Mediterranean tall fescues respond to low temperatures that are typically encountered during the fall, the leaf extension rate (LER) was measured along with proline, simple sugars, fructan, and abscisic acid (ABA). Three Mediterranean and four Continental accessions were tested, including Kentucky-31 and Flecha as "typical" Continental and Mediterranean accessions, respectively. The greatest difference observed between these types of tall fescue occurred at 4.5°C. The Mediterranean genotypes had greater LER and fructan concentrations while the Continental genotypes possessed greater proline, ABA, and simple sugar concentrations. Kentucky-31 was typically found in the middle between the Mediterranean and the remaining Continental accessions. These data indicate that Mediterranean germplasm possesses superior cold growth, but the high proline levels produced by the Continental types may be critical for survival under cold conditions. [ABSTRACT FROM AUTHOR]

Tall fescue [Festuca arundinacea Schreb. syn. Lolium arundinaceum (Schreb.) Darbysh.] is widely used for hay and pasture in the Eastern regions of the United States, with new types of Mediterranean tall fescue possessing superior growth under cool growing conditions. However, they do not survive Midwestern winters. To date, little research has examined the role of endophyte infection on the ability of tall fescue to grow under cold conditions or survive freezing conditions. This study's objectives determined the endophyte's role in tall fescue growth and production of metabolites for nonfreezing conditions. Additionally, the role of endophyte infection on the ability of plants to survive freezing temperatures was determined. This experiment used five genotypes of tall fescue. Half of the plants from each genotype were endophyte infected (E+), with the remaining genotypes being endophyte free (E-). We report for the first time the effects of endophyte status on proline, simple sugars, and fructan accumulation when plants were grown under cold, nonfreezing temperatures and the survivability at various freezing temperatures. Endophyte removal only affected fructan concentrations at 4.5°C; however, plant genotype affected leaf extension rate, proline, sugars, and fructan concentration. The freezing test found no effect of the endophyte on tiller survival, while plant genotype was significant. These data indicate that endophyte removal has little influence on the measured traits, and plant genotype is more critical for survival under cold conditions. [ABSTRACT FROM AUTHOR]

Recent research shows that the meat from beef animals finished on pasture has greater concentrations of omega-3 fatty acid (FA) and conjugated linoleic acids (CLA) compared with animals finished on high-concentrate diets. However, little is known about the FA concentrations in forage that might alter these FA in the meat of pasturefinished beef. The objective was to determine the FA variation between and within forage species commonly grown in pastures in the Midwest. A secondary objective was to identify phenotypic characteristics that may be associated with individual FA. The forages analyzed included multiple cultivars of orchardgrass (Dactylis glomerata L.), tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire Schedonorus phoenix (Scop.) Holub], perennial ryegrass (Lolium perenne L.), and alfalfa [Medicago sativa L. ssp. sativa and falcata (L.) Arcang.]. Grasses had higher amounts of a-linolenic (C18:3) acid compared with alfalfa. Conversely, alfalfa had larger amounts of linoleic acid (C18:2) than did the grasses. Correlations between phenotypic traits and specific FA were found; plant total chlorophyll had the greatest correlation to total FA concentration. Overall, there is not a large amount of within-species variation that breeders could use to make large changes in FA concentrations. [ABSTRACT FROM AUTHOR]

Common tall fescue [Lolium arundinaceum (Schreb.) Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort.] is infected with a fungus that produces ergot alkaloids, a class of compounds associated with fescue toxicosis. The objective of this research was to monitor the change in concentrations of ergot alkaloids from time of clipping through storage of tall fescue hay. A 2-yr field study was conducted in Mt. Vernon, MO, in which tall fescue was baled at high moisture (204-219 g H2O kg-1 dry matter [DM]) and low moisture (102-112 g H2O kg-1 DM) then stored for 18 mo. Hay samples were collected over the 540-d period from clipping through storage and analyzed for ergovaline and total ergot alkaloid concentration. Data were analyzed using standard ANOVA procedures and break-point regression. In both years, ergovaline concentrations decreased sharply within the first month after harvest and gradually over the remaining 17 mo. In three of the four cases, most of the ergovaline disappearance occurred within 3 d after clipping. The final ergovaline concentration remained above 250 pg kg-1 DM, which is still considered toxic to livestock. In the first year, ergot alkaloid concentration followed a pattern similar to ergovaline concentration. In the second year, however, the decrease in total ergot alkaloid was gradual throughout the entire 18 mo. A general recommendation to producers would be to delay feeding toxic tall fescue hay until at least 1 mo after clipping. [ABSTRACT FROM AUTHOR]

Pasture-based dairies in the Midwest have a difficult time providing high-quality pasture during winter. Little is known about the yield and nutritive value of festulolium when stockpiled for winter grazing compared to tall fescue. In this study, the yield and nutritive value of 'Jesup' endophyte-free tall fescue [Schedonorus phoenix (Scop.) Holub.] and 'Spring Green' festulolium [Festulolium loliaceum (Hudson) P.V. Fournier] were evaluated monthly from November to March over three years. The research was conducted near Mt. Vernon, MO, on a Gerald silt loam (fine, mixed, active, mesic Aeric Fragiaqualf). In two of the three years, stockpiled tall fescue out-yielded festulolium by as much as 930 kg ha-1. Both tall fescue and festulolium yields decreased over winter by approximately the same percentage; losses from November to March ranged from 32 to >75%. The nutritive value of stockpiled festulolium was consistently greater than stockpiled tall fescue during winter. Both stockpiled festulolium and tall fescue contain sufficient crude protein and total digestible nutrients at one times maintenance to maintain most small breed dairy cows during their dry period but would be severely lacking once lactation started. Despite the greater nutritive value of stockpiled Spring Green festulolium compared to Jesup tall fescue, the low forage yield of festulolium makes its use questionable for pasture-based dairies. [ABSTRACT FROM AUTHOR]

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 x 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. [ABSTRACT FROM AUTHOR]

Ergot alkaloids are a class of toxic compounds, some of which are produced by a fungal endophyte in tall fescue (Festuca arundinacea Schrch.). The objective of this research was to measure total ergot alkaloid content in tall fescue by near-infrared (NIR) spectroscopy with a calibration developed from immunochemical reference data. Eighty-four tall fescue samples were collected from experiments at the University of Missouri. Samples were from plants that varied in maturity, endophyte status, genotype, growing environment, and storage and preservation treatment. Samples were scanned by NIR radiation and analyzed chemically for ergot alkaloid content using a commercial immunoassay. An empirical prediction equation was developed by regressing NIR reflectance data against absorbance data from the immunoassay. The initial calibrations achieved a 1 — variance ratio (VR) of 0.86 with a mean and standard error of cross validation (SECV) of 0.606 ± 0.12; however, this was possible only when stockplied tall fescue samples were omitted from the population. Stockpiled samples were checked for chemical accuracy and spectral similarity to the population, and another set of calibrations was developed. The final calibration, which omitted only those stockpiled samples that were infected with a toxic endophyte, had a 1 — VR of 0.89, with a mean and SECV of 0.682 ± 0.11. We concluded that total ergot alkaloid content in tall rescue can be quantified by NIR spectroscopy with a calibration developed from immunochemcial data, though it may not be possible to include samples of stockpiled tall fescue if they are infected with a toxic endophyte. Such a calibration can be robust and precise, reliably predicting an entire class of compounds in a diverse population of tall rescue samples. [ABSTRACT FROM AUTHOR]

The trade-off between summer water conservation from alfalfa production and the effects on plant growth, agricultural crop value, and grower returns in the low desert area (Imperial, Palo Verde, Parker and Yuma Valleys of California and Arizona) was analysed using an experimental plot in the Palo Verde Valley. The purpose was to provide a basis for evaluating water conservation decisions and policies. Four summer dry-down periods (withdrawing water for a predetermined period) of 0 days (control), 35 days, 70 days, and 105 days were analysed. Our results show that whereas the various dry-down periods would provide water conservation ranging from 254 to 944 million m3, the region would experience agricultural income decline by US $16 to US $73 million. For growers, benefits of dry-down would be effective only if the water price exceeds US $0.045 m-3 in California and US $0.036 m-3 in Arizona. Also dry-down would have possible adverse effects in the following areas including declines in plant stand density, long-term productivity, service industry sales, employment and biological benefits of soil fertility and organic matter that is attributed by the alfalfa plant in which case agriculture’s and growers monetary losses could increase. [ABSTRACT FROM AUTHOR]

Laboratory bioassay and field experiments were conducted to characterize the dose response of weeds to methyl iodide and methyl bromide as soil fumigants. The patterns in potency of both fumigants and in sensitivity of different weed species to the fumigants were distinguished with the use of logistic dose-response models. Similar to its response to methyl bromide fumigation, Amaranthus retroflexus L. was the most sensitive to methyl iodide fumigation. Cyperus rotundus L. was the least sensitive to methyl iodide fumigation, whereas Portulaca oleracea L. was the least sensitive to methyl bromide. Lolium multiflorum Lam., Abutilon theophrasti Medik., Chenopodium album L., P. oleracea. Brassica kaber (D.C.) L.C. Wheeler and Cyperus esculentus L. were similar in sensitivity to methyl iodide. Methyl iodide was as potent as methyl bromide for A. retroflexus but more potent than methyl bromide for L. multiflorum, A. theophrasti, C. album, P. oleracea, B. kaber, C. esculentus and C. rotundus. The dose response for weeds in the field was similar to (hat obtained in laboratory bioassays. Under field conditions, 280 kg ha-1 methyl iodide killed all species tested except Solanum nigrum L Methyl iodide appears to be a suitable replacement for methyl bromide because it can be used in situations similar to methyl bromide fumigation, has superior efficacy against a broad spectrum of pests and has ii low potential for degrading the earth's ozone lavers. [ABSTRACT FROM AUTHOR]