Search

Estimating fall dormancy (FD) in alfalfa (Medicago sativa L.) is time-consuming and expensive. The objective of this study was to estimate the FD class of alfalfa using near infrared reflectance (NIR) spectroscopy. Eleven alfalfa cultivars ranging in FD from 1 to 11 were grown as spaced plants at four diverse locations. In early autumn, 55 to 65 plants were randomly selected at each location and FD determined for each plant. For each sample, NIR spectra were collected and FD values regressed against first and second derivative transformations of spectra by modified partial least squares regression. The optimum equation had a calibration [R.sup.2] of 0.90 and a mean and standard error of 7.93 ± 1.14. Blind validation samples showed that this equation could accurately predict the FD class of individual plants ([r.sup.2] = 0.85) as well as entire cultivars ([r.sup.2] = 0.94). We concluded NIR spectroscopy has the potential to estimate FD classes of alfalfa., FALL DORMANCY IN ALFALFA is related to several important traits including initiation of spring growth, growth habit, root growth, winter hardiness, freezing tolerance, herbage yield, and stand persistence (Kohel and [...]

A new population of birdsfoot trefoil (Lotus corniculatus L.) with rhizomes (RBFT) has been developed for greater persistence. No study has compared RBFT with a standard, non-rhizomatous cultivar of birdsfoot trefoil (BFT). Objectives were to: (i) compare RBFT with BFT for differences in shoot and root mass and total nonstructural carbohydrate (TNC) concentration of taproots in both clipped and non-clipped situations and (ii) describe rhizome production of clipped and non-clipped RBFT. `Norcen' BFT and RBFT were grown in field plots near Columbia, MO, in 1994 and 1995. The study had four treatments: non-clipped RBFT, clipped RBFT, non-clipped BFT, and clipped BFT. Each treatment was replicated four times in a randomized complete block. Plots were sampled biweekly for shoot and root mass and taproot TNC from early-July until the first killing frost in October. In addition, length, mass, TNC, and number of rhizomes per plant were recorded for RBFT. From mid-September until the final sampling, the shoot mass for RBFT was about half that of BFT; however, RBFT's shoot mass was less affected by clipping than was BFT's. Taproot TNC was 20 to 40 g [kg.sup.-1] greater for RBFT than BFT throughout both growing seasons. Nearly all RBFT plants exhibited rhizomes by mid, October both years. Clipping RBFT plants did not affect rhizome growth. Rhizome TNC concentration increased steadily during autumn, with a final concentration of approximately 220 g [kg.sup.-1]. The failure of clipping to decrease rhizome production, combined with higher levels of below-ground TNC, may give RBFT the ability to withstand frequent defoliation., BIRDSFOOT TREFOIL is a perennial legume used for hay and pasture throughout the world. It tolerates acid, infertile, poorly drained soils, and provides nutritious forage for livestock (Beuselinck and Grant, [...]

Methods for determining K deficiencies in alfalfa (Medicago sativa L.) are either imprecise, time-consuming, or expensive. New to the market are portable and inexpensive meters that use a K-specific electrode (KSE) to measure the K concentration of plant sap. Little research has examined the precision or accuracy of these meters for determining the K concentration in alfalfa shoots. The objective was to determine if the KSE meter could precisely and accurately estimate the K concentration in alfalfa shoots. Laboratory, greenhouse, and field experiments were conducted to test the KSE meter's ability to measure the concentration of K in aqueous solution and in alfalfa sap. Laboratory results showed that KSE meter readings are subject to interference from [Cl.sup.-], [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] ions. In greenhouse and field experiments, the KSE meter precisely estimated the K concentration in alfalfa shoots ([R.sup.2]s [is greater than] 0.74) if readings were included in a multiple regression equation that also included sample moisture content or mean stage count and air temperature. Readings taken from fresh plant sap using the KSE meter were highly biased, with the readings being four to six times lower than those obtained by flame photometry. Readings from the KSE meter, if used with other variables in a multiple regression equation, would allow users to quickly assess the K status of alfalfa shoots for a relatively small investment., WELL-NODULATED ALFALFA removes more K from the soil than any other nutrient. Alfalfa requires K to catalyze several metabolic functions. Functions such as enzyme activation, transpiration, translocation of photoassimilates, protein [...]

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]

Context. Energetic particle enhancements that are associated with corotating interaction regions (CIRs) are typically believed to arise from the sunward propagation of particles that are accelerated by CIR-driven shocks beyond 1 AU. It is expected that these sunwardtravelling particles will lose energy and scatter, resulting in a turnover of the energy spectra below ∼0.5 MeV/nuc. However, the turnover has not been observed so far, suggesting that the CIR-associated low-energy suprathermal ions are accelerated locally close to the observer. Aims. We investigate the variability of suprathermal particle spectra from CIR to CIR as well as their evolution and variation as the observer moves away from the rear shock or wave. Methods. Helium data in the suprathermal energy range from the Solar and Heliospheric Observatory/Charge, Element, and Isotope Analysis System/Suprathermal Time-of-Flight (SOHO/CELIAS/STOF) were used for the spectral analysis and were combined with data from the Advanced Composition Explorer/ SolarWind Ion Composition Spectrometer (ACE/SWICS) in the solar wind energies. Results. We investigated sixteen events: nine clean CIR events, three CIR events with possible contamination from upstream ion events or solar energetic particles (SEPs), and four events that occurred during CIR periods that were dominated by SEPs. Six of the nine clean CIR events showed possible signs of a turnover between ∼10-40 keV/nuc in the fast solar wind that trails the compression regions. Three of them even showed this behaviour inside the compressed fast wind. The turnover part of the spectra became flatter and shifted from lower to higher energies with increasing connection distance to the reverse shock. The remaining three clean events showed continuous power-law spectra in both the compressed fast wind and fast wind regions, that is, the same behaviour as reported from previous observations. The spectra of the seven remaining events are more variable, that is, they show power law, turnover, and a superposition of these two shapes. [ABSTRACT FROM AUTHOR]

Beef cattle consume more tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] than any other perennial cool-season grass in North America. Tall fescue forms a mutualistic relationship with the fungus Epichloë coenophiala (Morgan-Jones and W. Cams) C.W. Bacon & Schardl, comb. nov.; these plants are often referred to as endophyte-infected tall fescue. Agronomically, endophyte infection is good; endophyte- infected plants resist biotic and abiotic stresses better than do endophyte-free plants. However, tall fescue plants infected with a common toxic endophyte produce the ergot alkaloids that cause tall fescue toxicosis. Several agronomic practices can eliminate or reduce the effects of tall fescue toxicosis. Renovating tall fescue fields infected with a common toxic endophyte to new cultivars infected with a novel (or nontoxic) endophyte eliminates the problem for that field. Although the cost to renovate currently exceeds US$600/ha, most economic analyses show it to be a good long-term investment, especially on fields with high forage production potential. Less effective, but popular, methods of dealing with tall fescue toxicosis include adding clovers (Trifolium spp.) or other forage species to the pastures to dilute the effects of the toxins, avoiding the use of high rates of nitrogen fertilizers, feeding supplements, and rotating cattle to warm-season forages in summer. Also, the alkaloid concentration in forage can be reduced by making it (drying) into hay. Recent research shows that animal tolerance to tall fescue toxicosis is possible, although there is still much to learn about this topic. Tall fescue toxicosis is likely a reality in the beef industry for some time to come. We contend that renovation of the most productive fields to cultivars infected with a novel endophyte coupled with the prospect of using tolerant livestock in scenarios where renovation is not possible will give innovative producers a competitive edge. [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]

The daily BW gain of stocker steers grazing tall fescue [Lolium arundiriaceum (Schreb.) S.J. Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort.]-based pastures typically declines during summer. To avoid these declines, in part to mitigate the effects of tall fescue toxicosis, it is commonly advised to move cattle to warm-season forage during this period. A 3-yr (2006, 2007, and 2008) grazing study was conducted to evaluate the effect of replacing 25% of the area of a tall fescue/clover (81% endophyte-infected) pasture system with "Ozark" bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with clover (Trifolium spp.) to provide summer grazing for stocker steers (TF+BERM). The TF+BERM treatment was compared with a grazing system in which tall fescue/clover (TF) pastures were the only type of forage available for grazing. Our objective was to determine if replacement of 25% of the land area in a fescue system with bermudagrass would increase annual beef production compared with a system based solely on tall fescue. The study was conducted at the Southwest Research and Education Center of the University of Missouri near Mt. Vernon. Each treatment was rotationally stocked with 5 steers (248 ± 19.3 kg) on 1.7 ha. Fertilizer applications were applied at rates recommended for each respective forage species. Total forage production, BW gain per hectare, and season-long ADG of steers was greater (P < 0.06) for TF+BERM than for TF in 2006, but none of these measures differed (P > 0.19) in 2007 or 2008. In vitro true digestibility of pastures was greater (P = 0.01) for TF (84.4%, SEM = 0.64%) compared with TF+BERM (80.6%, SEM = 0.79%), even in summer. The decreased in vitro true digestibility of the bermudagrass pastures likely negated any benefit that animals in TF+BERM had in avoiding the ergot-like alkaloids associated with endophyte-infected tall fescue. Renovating 25% of the pasture system to bermudagrass provided some benefit to the system in years when summertime precipitation was limited (2006) but provided no value in wetter years (2007 and 2008). Although renovating endophyte-infected tall fescue pastures to a warm-season forage is a widely used practice to mitigate tall fescue toxicosis, the benefits of this practice are limited if forage quality of the warm season component is poor. [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]

A 2–yr production study was conducted to evaluate 3 systems of growing stocker calves under rotational stocking. One group of steers was stocked on pasture from early April to mid August (springstocked steers = SSS), and another group of steers was stocked from early July to late October (fall–stocked steers = FSS). Steers were stratified by BW (n = 72, BW=229±llkgforSSS;n=72,BW=248±18 kg for FSS) and randomly assigned to 1 of 3 treatments. The 3 treatments were 1) rotationally stocked only (control; CON), steers rotated to a new paddock as forage availability dropped below acceptable levels in the occupied paddock; 2) rotationally stocked with distillers grains (DIST); this was the same as CON except steers were supplemented with varying amounts of distillers dried grains with solubles (DDGS) based on forage nutritive value; and 3) rotationally stocked with round–bale silage (SIL); excess forage in spring was harvested and stored as round–bale silage and fed back as needed. Total BW gain/ha over the entire grazing season did not differ between DIST and SIL (P = 0.09) steers, but both were greater thall CON (P < 0.01). Total BW gain/ha for DIST, SIL, and CON was 459 (SEM = 11.5), 402 (SEM = 31.0), and 276 (SEM = 26.2) kg, respectively. For ADG, there was a group x year (P < 0.01) and group x treatment (P = 0.02) interaction. Steer ADG for SSS did not differ between SIL and DIST (P = 0.51), but was greater than the CON (P = 0.01). The ADG for SSS was 0.79 (SEM = 0.04), 0.81 (SEM = 0.05), and 0.62 (SEM = 0.05) kg for DIST, SIL, and CON, respectively. For the FSS, ADG for all 3 treatments was different (P = 0.02). The FSS ADG was 0.72 (SEM 0.03), 0.53 (SEM = 0.04), and 0.29 (SEM = 0.04) kg for DIST, SIL, and CON, respectively. The only treatment with equivalent (P = 0.07) ADG between early and late–stocked steers (SSS vs. FSS) was DIST. Adjusting the amount of DDGS supplemented to steers based on forage nutritive value resulted in consistent BW gains throughout the grazing study, whereas steers in the SIL and CON treatments gained less BW during the latter portion of the season. Controlling forage maturity by removal in the SIL treatment resulted in total BW gains/ha that were not different than the DIST treatment. [ABSTRACT FROM AUTHOR]

A 2–yr production study was conducted to evaluate 3 systems of growing stocker calves under rotational stocking. One group of steers was stocked on pasture from early April to mid August (springstocked steers = SSS), and another group of steers was stocked from early July to late October (fall–stocked steers = FSS). Steers were stratified by BW (n = 72, BW=229±llkgforSSS;n=72,BW=248±18 kg for FSS) and randomly assigned to 1 of 3 treatments. The 3 treatments were 1) rotationally stocked only (control; CON), steers rotated to a new paddock as forage availability dropped below acceptable levels in the occupied paddock; 2) rotationally stocked with distillers grains (DIST); this was the same as CON except steers were supplemented with varying amounts of distillers dried grains with solubles (DDGS) based on forage nutritive value; and 3) rotationally stocked with round–bale silage (SIL); excess forage in spring was harvested and stored as round–bale silage and fed back as needed. Total BW gain/ha over the entire grazing season did not differ between DIST and SIL (P = 0.09) steers, but both were greater thall CON (P < 0.01). Total BW gain/ha for DIST, SIL, and CON was 459 (SEM = 11.5), 402 (SEM = 31.0), and 276 (SEM = 26.2) kg, respectively. For ADG, there was a group x year (P < 0.01) and group x treatment (P = 0.02) interaction. Steer ADG for SSS did not differ between SIL and DIST (P = 0.51), but was greater than the CON (P = 0.01). The ADG for SSS was 0.79 (SEM = 0.04), 0.81 (SEM = 0.05), and 0.62 (SEM = 0.05) kg for DIST, SIL, and CON, respectively. For the FSS, ADG for all 3 treatments was different (P = 0.02). The FSS ADG was 0.72 (SEM 0.03), 0.53 (SEM = 0.04), and 0.29 (SEM = 0.04) kg for DIST, SIL, and CON, respectively. The only treatment with equivalent (P = 0.07) ADG between early and late–stocked steers (SSS vs. FSS) was DIST. Adjusting the amount of DDGS supplemented to steers based on forage nutritive value resulted in consistent BW gains throughout the grazing study, whereas steers in the SIL and CON treatments gained less BW during the latter portion of the season. Controlling forage maturity by removal in the SIL treatment resulted in total BW gains/ha that were not different than the DIST treatment. [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]