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Context: Using forage grass species with complementary growth and resource-use strategies to enhance forage plant diversity in pastures may be an alternative to traditional monocultures in tropical regions. Aims: This study aimed to determine whether a mixture of three perennial tropical forage grasses (Andropogon gayanus cv. Planaltina, Panicum maximum cv. Massai, and Brachiaria brizantha cv. BRS Piatã) could be an alternative to enhance herbage intake rates relative to their respective monocultures. Methods: The treatments corresponded to three perennial tropical forage grasses cultivated as monocultures and as a mixture composed of all three species. Defoliation management corresponded to a pre-cutting height of 35 cm and post-cutting height of 17.5 cm. Key results: The botanical composition of the mixture was dynamic throughout the experimental period, with variations in the proportion of species across seasons. The upper half of the canopy predominantly comprised leaves for all treatments. The canopy structure of the mixture allowed for greater herbage intake rates than monocultures during winter/early spring. Andropogon gambagrass showed lower herbage intake rates than the other treatments. Conclusions: The findings of this study indicate that it is possible to combine tropical forage grass species without compromising canopy structure and grazing animal responses, compared with single-species grass pastures. Implications: The selection of forage species for mixed pastures should consider their phenological cycle, growth, and resource-use strategies to achieve temporal complementarity and provide an optimal grazing environment for animals throughout the year. Increasing pasture biodiversity using forage grass species with complementary traits may be an alternative to traditional monocultures in tropical regions. This study investigated the relationship between pasture characteristics and herbage intake, indicating that combining tropical forage grass species is possible without compromising pasture dynamics and grazing animal responses. By optimizing forage diversity, we highlight the importance of species selection and seasonal complementarity for maintaining pasture structure and providing an optimal grazing environment for animals throughout the year. [ABSTRACT FROM AUTHOR]

Endophytes can have positive effects on plant health and growth, but endophytes of warm-season grasses are largely understudied, and inocula are rarely applied to cultivated grasses. To identify endophytes in warm-season grasses, 35 endophytic bacterial isolates were cultured from the roots, rhizomes, and shoots of bermudagrass (Cynodon dactylon), energy cane (Saccharum spp.), Johnsongrass (Sorghum halepense), napiergrass (Cenchrus purpureus), perennial sorghum (Sorghum bicolor × S. halepense), sorghum (Sorghum bicolor), sorghum × sudangrass (Sorghum × drummondii), and peanut (outgroup). Sequencing of the 16S rRNA fragment from the endophytes revealed that the bacterial sequences were similar to Bacillus spp. (19 isolates), Burkholderia spp. (4), Pantoea spp. (4), Pseudomonas spp. (3), Enterobacter spp. (2), Kosakonia spp. (2), and Sphingomonas sp. (1). To identify diazotrophic endophytes, DNA isolated from surface-disinfected tissue from warm-season grasses was used to amplify nifH. Bacteria containing nifH were similar to 13 genera, and sequences similar to Pseudolabrys sp. were present in the greatest number of warm-season grasses. Bacteria similar to Bradyrhizobium frederickii strain CNPSo 3447 were identified frequently from the leaves and roots of sorghum × sudangrass (and peanut roots). Using similarity to known nifH fragments, six genera were identified that had not been previously identified in grasses. Thus, a large number of endophytes were found in warm-season grasses and could enhance plant growth or grass nitrogen levels by using nitrogen fixation. [Figure: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2023.

This article examines the resilience of warm-season (C4) perennial grasses in challenging environmental and management conditions. C4 grasses are crucial for livestock nutrition in tropical and subtropical regions, and climate change may benefit their growth. The article discusses the anatomical and morphological differences that affect the resilience of C4 grasses to management practices. It also explores the distribution and physiological mechanisms of C4 grasses, as well as the impact of nitrogen management and defoliation on their growth and persistence. The article emphasizes the ability of C4 grasses to recover after grazing through the allocation of photosynthate and the storage of carbon and nitrogen. It also highlights the importance of proper soil nutrient and grazing management for maximizing forage production and reducing greenhouse gas emissions. [Extracted from the article]

Understanding leaf generation dynamics, their seasonal changes, and their responses to nitrogen fertilization (NF) is key to improving pasture utilization efficiency. The objectives of this research were to determine structural and morphogenetic variables underlying changes in herbage mass on a set of Paspalum notatum genotypes. Ten P. notatum genotypes were evaluated in experimental plots following a completely randomized block design under a split-plot arrangement for two N-rates during four periods. Increased herbage mass (HM) after N-fertilization was explained by a higher tiller density (TD) (41.8%) and tiller weight (TW) (22.1%). The increment of TW after NF was due to the increase in leaf blade length (LBL) and width (LBW). During the flowering season, NF increases the reproductive tiller density by 262.5%. Seasonal variation in HM was mainly explained by changes in LBL that modified TW. Morphogenetic traits differed between genotypes of different growth habits; therefore, different management practices are suggested. The average increase in leaf elongation rate in response to NF was about 36.7%, generating longer leaves despite reductions in leaf elongation time (LET). The depletion in LBL and consequently in TW and HM during the autumn was attributed to the reduction in LET. [ABSTRACT FROM AUTHOR]

A two‐year experiment assessed herbage production and above‐ and below‐ground characteristics of a highly productive monoculture ('BRS Zuri' guineagrass [Panicum maximum Jacq.]) and two mixtures of three grasses (Mixture 1: 'BRS Zuri' guineagrass, 'BRS Xaraés' palisadegrass [Brachiaria brizantha Stapf.], and 'Basilisk' signalgrass [Brachiaria decumbens Stapf.]; Mixture 2: 'BRS Quênia' guineagrass [Panicum maximum Jacq.], 'Marandu' palisadegrass [Brachiaria brizantha Stapf.], and 'BRS Paiaguás' palisadegrass [Brachiaria brizantha Stapf.]), cultivated in the Brazilian tropical savanna. Mixtures 1 and 2 were subjected to two grazing intensities (removal of 40 or 60% of pre‐grazing height) and 'BRS Zuri' guineagrass monoculture was defoliated to a single grazing intensity of 50%. Treatments were randomly assigned to fifteen 0.25‐ha plots and managed under intermittent stocking by cattle. Herbage accumulation rate was similar among pastures and years (p >.1). The root mass in the tussocks did not differ (p >.1), with mean values ranging between 0.62 to 1.81 kg DM m−2. Root density in the tussock interspaces was greater in the mixtures (p <.001), regardless of seasons (p =.405) and years (p =.292). The mixtures were dominated by guineagrass (70%) and palisadegrass (30%) at the end of the experiment, with the population of 'Basilisk' and 'BRS Paiaguás' being completely suppressed throughout the experimental period. Mixing guineagrass and brachiariagrasses can be an alternative to the traditional pastoral systems in the tropics, as it does not compromise herbage production and presents a capacity to produce more roots than a very productive monoculture of 'BRS Zuri' guineagrass. [ABSTRACT FROM AUTHOR]

Creating xeric landscapes in lawns and prairies is a significant challenge and practical need in arid urban environments. This study examined the drought resistance of some C4 grass species for constructing urban lawns and prairies. A factorial experiment based on randomized complete block designs with four replications was conducted. Experimental treatments were two irrigation levels (100% and 50% Field Capacity (FC)) and five warm-season grass species (Andropogon gerardii Vitman, Sorghastrum nutans (L.) Nash, Panicum virgatum L., Schizachyrium scoparium (Michx.) Nash, and Bouteloua curtipendula (Michx.) Torr.). The effects of drought on physiological, morphological, and qualitative characteristics of the grass species were analyzed. Drought conditions induced a decrease in all the measured traits. However, fewer physiological, morphological, and qualitative characteristics were affected by drought stress on Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, compared to the other two species. Overall, warm-season grasses of Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, had greater adaptability to drought stress, making them promising C4 grass species for prairie or lawn landscaping in arid urban environments. Landscape professionals and decision-makers should consider using Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, as these were the most resilient grass species for drought-tolerant prairie landscaping schemes. Sorghastrum nutans and Panicum virgatum may be used as a second priority if a more diverse variety of grasses is required for drought-resilient prairie or lawn landscaping in arid cities. [ABSTRACT FROM AUTHOR]

We examined the relationship between primary productivity and diversity for grassland, meadow, and savanna (GMS) vegetation in northeastern Pennsylvania, USA, where the landscape is primarily forests, agriculture, and urban or suburban development. We surveyed primary productivity, plant species diversity, invertebrate order diversity, and avian abundance and species diversity for 14 grasslands and open areas that were actively managed and three that apparently occurred naturally. Four grasslands were dominated by warm‐season grasses with the C4 photosynthetic pathway, nine were dominated by C3 grasses, forbs, and shrubs, and four had a mixture of both types. We found hump‐shaped relationships for plant species richness and bird species richness as a function of productivity but not for invertebrate order richness. Richness of invertebrates and birds increased linearly with the number sampled at each site. The number of plant species declined with increasing proportion of warm‐season grasses, as did the number of invertebrate orders collected in sweep samples, avian abundance, and avian species richness. Multiple regression showed that both landscape and vegetative characteristics influenced the bird community. Bird species richness increased with the area of the sites, the ratio of area to edge, and the distance to the nearest open area. There was no evidence for the influence of the relative abundance of native plant species on bird or invertebrate richness. GMS restoration of farmlands and mine lands with plantings of warm‐season grasses, while possibly beneficial for some forms of wildlife, seems to be less effective in maintaining the diversity of invertebrates and birds than a mixture of warm‐season grasses, cool‐season grasses, forbs, and shrubs. [ABSTRACT FROM AUTHOR]

Abstract Background Diet is a key driver of equine hindgut microbial community structure and composition. The aim of this study was to characterize shifts in the fecal microbiota of grazing horses during transitions between forage types within integrated warm- (WSG) and cool-season grass (CSG) rotational grazing systems (IRS). Eight mares were randomly assigned to two IRS containing mixed cool-season grass and one of two warm-season grasses: bermudagrass [Cynodon dactylon (L.) Pers.] or crabgrass [Digitaria sanguinalis (L.) Scop.]. Fecal samples were collected during transitions from CSG to WSG pasture sections (C–W) and WSG to CSG (W–C) on days 0, 2, 4, and 6 following pasture rotation and compared using 16S rRNA gene sequencing. Results Regardless of IRS or transition (C–W vs. W–C), species richness was greater on day 4 and 6 in comparison to day 0 (P

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Grasses harbor diverse fungi, including some that produce mycotoxins or other secondary metabolites. Recently, Florida cattle farmers reported cattle illness, while the cattle were grazing on warm-season grass pastures, that was not attributable to common causes, such as nutritional imbalances or nitrate toxicity. To understand correlations between grass mycobiome and mycotoxin production, we investigated the mycobiomes associated with five prominent, perennial forage and weed grasses [Paspalum notatum Flügge, Cynodon dactylon (L.) Pers., Paspalum nicorae Parodi, Sporobolus indicus (L.) R. Br., and Andropogon virginicus (L.)] collected from six Florida pastures actively grazed by livestock. Black fungal stromata of Myriogenospora and Balansia were observed on P. notatum and S. indicus leaves and were investigated. High-throughput amplicon sequencing was applied to delineate leaf mycobiomes. Mycotoxins from P. notatum leaves were inspected using liquid chromatography-mass spectrometry (LC-MS/MS). Grass species, cultivars, and geographic localities interactively affected fungal community assemblies of asymptomatic leaves. Among the grass species, the greatest fungal richness was detected in the weed S. indicus. The black fungal structures of P. notatum leaves were dominated by the genus Myriogenospora, while those of S. indicus were codominated by the genus Balansia and a hypermycoparasitic fungus of the genus Clonostachys. When comparing mycotoxins detected in P. notatum leaves with and without M. atramentosa, emodin, an anthraquinone, was the only compound which was significantly different (P, 0.05). Understanding the leaf mycobiome and the mycotoxins it may produce in warm-season grasses has important implications for how these associations lead to secondary metabolite production and their subsequent impact on animal health. [ABSTRACT FROM AUTHOR]

Understanding leaf generation dynamics, their seasonal changes, and their responses to nitrogen fertilization (NF) is key to improving pasture utilization efficiency. The objectives of this research were to determine structural and morphogenetic variables underlying changes in herbage mass on a set of Paspalum notatum genotypes. Ten P. notatum genotypes were evaluated in experimental plots following a completely randomized block design under a split-plot arrangement for two N-rates during four periods. Increased herbage mass (HM) after N-fertilization was explained by a higher tiller density (TD) (41.8%) and tiller weight (TW) (22.1%). The increment of TW after NF was due to the increase in leaf blade length (LBL) and width (LBW). During the flowering season, NF increases the reproductive tiller density by 262.5%. Seasonal variation in HM was mainly explained by changes in LBL that modified TW. Morphogenetic traits differed between genotypes of different growth habits; therefore, different management practices are suggested. The average increase in leaf elongation rate in response to NF was about 36.7%, generating longer leaves despite reductions in leaf elongation time (LET). The depletion in LBL and consequently in TW and HM during the autumn was attributed to the reduction in LET.

Creating xeric landscapes in lawns and prairies is a significant challenge and practical need in arid urban environments. This study examined the drought resistance of some C4 grass species for constructing urban lawns and prairies. A factorial experiment based on randomized complete block designs with four replications was conducted. Experimental treatments were two irrigation levels (100% and 50% Field Capacity (FC)) and five warm-season grass species (Andropogon gerardii Vitman, Sorghastrum nutans (L.) Nash, Panicum virgatum L., Schizachyrium scoparium (Michx.) Nash, and Bouteloua curtipendula (Michx.) Torr.). The effects of drought on physiological, morphological, and qualitative characteristics of the grass species were analyzed. Drought conditions induced a decrease in all the measured traits. However, fewer physiological, morphological, and qualitative characteristics were affected by drought stress on Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, compared to the other two species. Overall, warm-season grasses of Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, had greater adaptability to drought stress, making them promising C4 grass species for prairie or lawn landscaping in arid urban environments. Landscape professionals and decision-makers should consider using Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, as these were the most resilient grass species for drought-tolerant prairie landscaping schemes. Sorghastrum nutans and Panicum virgatum may be used as a second priority if a more diverse variety of grasses is required for drought-resilient prairie or lawn landscaping in arid cities.

Background: Diet is a key driver of equine hindgut microbial community structure and composition. The aim of this study was to characterize shifts in the fecal microbiota of grazing horses during transitions between forage types within integrated warm- (WSG) and cool-season grass (CSG) rotational grazing systems (IRS). Eight mares were randomly assigned to two IRS containing mixed cool-season grass and one of two warm-season grasses: bermudagrass [Cynodon dactylon (L.) Pers.] or crabgrass [Digitaria sanguinalis (L.) Scop.]. Fecal samples were collected during transitions from CSG to WSG pasture sections (C–W) and WSG to CSG (W–C) on days 0, 2, 4, and 6 following pasture rotation and compared using 16S rRNA gene sequencing. Results: Regardless of IRS or transition (C–W vs. W–C), species richness was greater on day 4 and 6 in comparison to day 0 (P < 0.05). Evenness, however, did not differ by day. Weighted UniFrac also did not differ by day, and the most influential factor impacting β-diversity was the individual horse (R2 ≥ 0.24; P = 0.0001). Random forest modeling was unable to accurately predict days within C–W and W–C, but could predict the individual horse based on microbial composition (accuracy: 0.92 ± 0.05). Only three differentially abundant bacterial co-abundance groups (BCG) were identified across days within all C–W and W–C for both IRS (W ≥ 126). The BCG differing by day for all transitions included amplicon sequence variants (ASV) assigned to bacterial groups with known fibrolytic and butyrate-producing functions including members of Lachnospiraceae, Clostridium sensu stricto 1, Anaerovorax the NK4A214 group of Oscillospiraceae, and Sarcina maxima. In comparison, 38 BCG were identified as differentially abundant by horse (W ≥ 704). The ASV in these groups were most commonly assigned to genera associated with degradation of structural carbohydrates included Rikenellaceae RC9 gut group, Treponema, Christensenellaceae R-7 group, and the NK4A214 group of Oscillospiraceae. Fecal pH also did not differ by day. Conclusions: Overall, these results demonstrated a strong influence of individual horse on the fecal microbial community, particularly on the specific composition of fiber-degraders. The equine fecal microbiota were largely stable across transitions between forages within IRS suggesting that the equine gut microbiota adjusted at the individual level to the subtle dietary changes imposed by these transitions. This adaptive capacity indicates that horses can be managed in IRS without inducing gastrointestinal dysfunction. [ABSTRACT FROM AUTHOR]

Napier grass (Pennisetum purpureum Schumach) has been identified as a potential energy crop in Thailand. However, information regarding the biomass production characteristics of napier grass in response to K and N fertilization is required to guide management decisions for biofuel feedstock. Our objective was to determine the effects of K and N rates on biomass yield, developmental morphology, nutrient content and removal. This experiment was conducted during 2016 and 2017 at Kamphaeng Saen (KPS), Thailand. The experimental design was a split plot arranged in a randomized complete block (RCB) with four replications. Three K fertilization rates (0, 250, and 500 kg ha−1) were used for the main plots and four N fertilization rates (0, 250, 500, and 1000 kg ha−1) were arranged as subplots. With increasing N fertilization rate, most growth parameters increased, except leaf to stem ratio and dry matter concentration decreased. Total dry matter yield (TDMY) increased from 16.6 to 43.0 t ha−1 and from 15.2 to 41.6 t ha−1 in 2016 and 2017, respectively, as N rate increased from 0 to 1000 kg ha−1. However, growth and TDMY were not affected by K fertilizer. Increased TDMY resulted from an increase in the proportion of elongating tillers leading to advancing mean stage by count (MSC) from 2.35 to 2.45. Therefore, although napier grass demonstrated large biomass production under multiple harvest regimes, its higher removal rates (285.0–1615. kg K ha−1 and 86.7–422.2 kg N ha−1) were varied with fertilization rates indicating a potential for higher fertilizer requirements and production costs over time. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work was to estimate the repeatability (r) and the number of samples required to measure the nutritional value of four warm-season forage grasses growing in a semiarid region. The grasses evaluated were Urochloa mosambicensis, Cenchrus ciliaris, Digitaria pentzii, and Megathyrsus maximus. Evaluations occurred under two forage management conditions: stockpiling and grazing. Hand-plucked forage samples were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, and in vitro DM digestibility (IVDMD). Four methods were used to estimate r and the number of samples required: analysis of variance, method of principal components based on the covariance (PCCOV) and the correlation (PCCOR) matrices, and structural analysis (EVCOR). Species were compared by the probability of the difference using the t-test. The method PCCOV presents the highest coefficient of repeatability and, therefore, a lower number of samples required. Lignin is the trait that have the highest number of samples required. In terms of qualitative traits, D. pentzii and M. maximus show the best forage qualities among the species evaluated.

It is well reported in the scientific literature that pastures can have similar net forage accumulation when managed with contrasting structures. However, we hypothesized that the dynamics of forage accumulation in grazed swards is linked to seasonal‐environmental conditions. Marandu palisadegrass (Brachiaria brizantha [Hochst. ex A. Rich.] was used as the forage species model. The experimental treatments were four grazing heights (10, 20, 30 and 40 cm) allocated to experimental units according to a randomized complete block design with four replicates and evaluated throughout four contrasting environmental seasons (summer, autumn, winter–early spring and late spring). Under rainy and warm periods, greater net forage accumulation was observed in pastures maintained taller; on the contrary, during the mild and dry periods, net forage accumulation rate reduced as grazing height increased. Such patterns of responses were related to compensations between tiller population density and tissues flows during summer and late spring and the reduced capacity of taller canopies to compensate lower population with greater growth rates during autumn and winter–early spring. Grazed swards changed their patterns of forage growth as they transitioned from favourable to more abiotic stressful conditions, suggesting that seasonal adjustments in grazing intensities are necessary in order to maximize forage production. [ABSTRACT FROM AUTHOR]

Questions: A paradoxical co‐existence challenges woodland and savanna restoration worldwide: How are shade‐intolerant, flammable herbaceous layers promoted while maintaining the shade‐casting, more fire‐sensitive woody regeneration that sustains overstorey structure? Where restoration success consisted of robust, diverse herbaceous layers and vigorous, well‐stocked Pinus echinata regeneration (hereafter, shortleaf‐bluestem response), we asked: are there targetable conditions of overstorey, understorey, topography, and proximity to mature Pinus echinata that simultaneously maximize desired woody and herbaceous understorey components? Do these conditions and dependent responses differ across canopy disturbance level and fire season? Location: Cumberland Plateau, Tennessee, USA (36°04′8.11″ N, 84°50′38.36″ W). Methods: We measured 12 shortleaf‐bluestem response and 17 explanatory condition variables at 345 plots spanning an experimental restoration gradient (canopy disturbance level and fire season combinations). We ordinated variation and identified response thresholds using a multivariate regression tree. Differences across tree groupings and splits associated response thresholds with specific explanatory conditions. Results: Pockets of substantial Pinus echinata regeneration (>3,000 stems/ha), C4 grass density (>40,000 ramets/ha), and herbaceous diversity (increase from 22 to 205 species) occurred 7–14 years after canopy disturbance and 3–8 fires. Such shortleaf‐bluestem response was maximized at 3 m2/ha residual tree basal area, 11% canopy closure, reduced midstorey density (5,000 small‐sapling stems/ha), and southwesterly aspects within 70 m of mature Pinus echinata. In contrast, shortleaf‐bluestem response was negligible at 11.3 m2/ha basal area and 68% canopy closure. Fire season, snag basal area, slope, and slope position effects were minimal. Conclusions: We identified specific conditions fostering the co‐existence of desired herbaceous and woody understorey components, addressing a major woodland and savanna restoration challenge and expanding on previous threshold concept applications by simultaneously considering multiple desired responses. Results can direct the restoration of imperiled shortleaf‐bluestem communities east of the Mississippi River, USA, where work has been scarce or ineffective, and similar approaches could inform fire‐dependent woodland and savanna restoration worldwide. [ABSTRACT FROM AUTHOR]

Biomass yield and adaptability to a broad range of environments are important characteristics of dedicated energy crops for sustainable bioenergy feedstock production. In addition to yield potential, the role of species diversity on ecosystem services is also growing in importance as we seek to develop sustainable feedstock production systems. The objective of this study was to compare the biomass yield potential of the commercially available germplasm of native warm-season grasses in monocultures and in blends (mixture of different cultivars of the same species) or mixtures of different species across an environmental gradient (temperature and precipitation) in the Midwest, USA. Warm-season grasses including switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), indiangrass (Sorghastrum nutans [L.] Nash), sideoats grama (Bouteloua curtipendula [Michx.] Torr.) and Miscanthus × giganteus (Greef and Deu.) were planted in 2009. Biomass was annually harvested from 2010 through 2015 for Urbana, IL and Mead, NE but only in 2010 and 2011 for Ames, IA. The effect of species in monocultures and mixtures (or blends) on biomass yields was significant for all locations. In monocultures, the annual biomass yields averaged over a 6-year period were 11.12 Mg ha−1 and 10.98 Mg ha−1 at Urbana and Mead, respectively, while the annual biomass yield averaged over a 2-year period was 7.99 Mg ha−1 at Ames, IA. Also, the annual biomass yields averaged across the different mixtures and blends at each location were 10.25 Mg ha−1, 9.88 Mg ha−1, and 7.64 Mg ha−1 at Urbana, Mead, and Ames, respectively. At all locations, M. × giganteus and 'Kanlow N1' produced the highest biomass yield in monocultures while mixtures containing switchgrass and big bluestem had the greatest mixture yield. The results from this multi-environment study suggest mixtures of different species provided no yield advantage over monocultures for bioenergy feedstocks in Illinois and Nebraska and both systems consistently produced biomass as long as April–July precipitation was near or above the average precipitation (300 mm) of the regions. [ABSTRACT FROM AUTHOR]

Preparing agricultural producers to cope with volatile weather changes, specifically drought, requires a better understanding of forage water-use efficiency (WUE) potentials. Options to improve farm resiliency to drought may include the use of C4 annual and perennial forages, which have greater production efficiency during drought than commonly used C3 forages. Our objective was to measure WUE through real-time gas exchange measurements of photosynthesis and transpiration in (1) a greenhouse study and (2) under field-grazing conditions. Growth parameters, instantaneous water use efficiency (iWUE), and mass-based WUE (mWUE) data were collected under greenhouse conditions in Study 1 for the following species: crabgrass (Digitaria sanguinalis cv. ‘Red River’), switchgrass (Panicum virgatum cv. ‘Alamo’), big bluestem (Andropogon gerardii cv. ‘OZ-70’), indiangrass (Sorghastum nutans cv. ‘Rumsey’), eastern gamagrass (Tripsacum dactyloides cv. ‘Pete’), bermudagrass (Cynodon dactylon cv. ‘Vaughn’s #1’), sorghum-sudangrass (Sorghum bicolor (L.) × Sorghum sudanese (P.) cv. ‘Greengrazer’), and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort). Study 2 occurred from 2014 to 2016, and evaluated iWUE of crabgrass, switchgrass, bermudagrass, eastern gamagrass, and a big bluestem/indiangrass mix under field conditions. Overall, in situ iWUE of crabgrass, switchgrass, eastern gamagrass, and bermudagrass did not differ, while iWUE of the big bluestem/indiangrass was less than switchgrass and crabgrass, an advantage for these species if the standardized precipitation index drops below zero. Bermudagrass, switchgrass, sorghum-sudangrass, pearl millet, and indiangrass had comparable mWUE values under greenhouse-simulated drought. These results will aid in the development of forage species recommendations for mitigating drought and improving resiliency.

Establishing vegetation on roadsides following construction can be challenging, especially for relatively slow growing native species. Topsoil is generally removed during construction, and the surface soil following construction ('cut-slope soils') is often compacted and low in nutrients, providing poor growing conditions for vegetation. Nebraska Department of Transportation (NDOT) protocols have historically called for nitrogen (N) and phosphorus (P) fertilization when planting roadside vegetation following construction, but these recommendations were developed for cool-season grass plantings and most current plantings use slower-establishing, native warm-season grasses that may benefit less than expected from current planting protocols. We evaluated the effects of nitrogen and phosphorus fertilization, and also topsoil amendment, on the foliar cover of seeded and non-seeded species planted into two post-construction roadside sites in eastern Nebraska. We also examined soil movement to determine how planting protocols and plant growth may affect erosion potential. Three years after planting, we found no consistent effects of N or P fertilization on foliar cover. Plots receiving topsoil amendment had 14% greater cover of warm-season grasses, 10% greater total foliar cover, and 4-13% lower bare ground (depending on site) than plots without topsoil. None of the treatments consistently affected soil movement. We recommend that NDOT change their protocols to remove N and P fertilization and focus on stockpiling and spreading topsoil following construction. [ABSTRACT FROM AUTHOR]

With most native prairie now lost, focus has turned to reconstructing grasslands with the aim of replicating ecosystem function for grassland fauna and flora. We report the results of a seven-year study (2008-2014) on the use of four floristically different prairie reconstructions by grassland birds. The study was conducted near Austin, Minnesota on a 64.75- ha (160-acre) Wildlife Management Area. Prairie reconstruction was implemented in 2005 on land previously used for row crops, and the study site consisted of eight identically sized (4.5 hectare), side-by-side of replicates of four distinct planting mixes. We used fixed-point transect surveys to document differences in the number of species and individuals of grassland birds between plot types. We found differences in the abundance of individuals and diversity of bird species between plot types, with fewer bird species and individuals present in lower plant-diversity plot types compared to higher plant-diversity plots. Eighteen species of grassland birds were recorded on the site, with none exclusively restricted to any plot type. Grassland obligate bird species, including Sturnella magna (Eastern Meadowlark), Dolichonyx oryzivorus (Bobolink), Ammodramus savannarum (Grasshopper Sparrow), Ammodramus henslowii (Henslow's Sparrow), and Passerculus sandwichensis (Savannah Sparrow), were documented using low floristic diversity, cool-season grass plots. Other species, such as Spiza americana (Dickcissel), Melospiza melodia (Song Sparrow) and Spinus tristis (American Goldfinch), showed preferences for high diversity, forb dominated plots. Our results indicate that planting a mosaic of restoration mixes may be the most successful at attracting and retaining the highest diversity of bird species. [ABSTRACT FROM AUTHOR]

The demand for dairy products from grass-fed cows is driven, in part, by their more desirable fatty acid (FA) profile, containing more n-3 FA and conjugated linoleic acids (CLA) than conventionally produced dairy products. This study investigated the effects of pearl millet (PM) vs . cool-season pasture (CSP) on animal performance and milk FA in a grazing system. Eight Holstein dairy cows were used in a repeated measures design with four-week periods. Forage type had no effect on animal performance (estimated dry matter intake, milk production, fat, or protein). The contents of CLA and n-3 FA in a serving of whole milk (3.25% fat) increased when cows grazed CSP compared to PM. A serving of whole milk from cows grazing PM had a higher content of saturated FA and branched-chain FA. In conclusion, the contents of various bioactive FA were higher in milk fat of cows grazing a CSP compared to PM. [ABSTRACT FROM AUTHOR]

Understanding of Sandhills prairie, the most expansive sand dune region stabilized by perennial grasses in the Western Hemisphere, is limited by lack of long-term vegetation data. We used a 26-year dataset to evaluate Sandhills prairie responses to year-to-year variation in precipitation, temperature, and cattle stocking rate. Basal cover, a measurement that is constant seasonally and used to detect long-term changes in bunchgrass vegetation, was measured in 38-40 permanent plots positioned along four transects spanning 769 ha from 1979 to 2007. Across this period, total basal cover averaged 2.4 % and was dominated by warm-season grasses (81.1 %). Schizachyrium scoparium (little bluestem), the dominant warm-season bunchgrass, consisted of 60.0 % relative basal cover. Warm-season grass and total basal cover responded positively to lag 3-year growing season precipitation indicating delayed responses to improved growing season conditions, but these variables also were positively associated with stocking rate. The positive responses may be due to slow spread of warm-season grasses by vegetative structures in response to favorable growing conditions in light to moderately stocked rangeland. Despite its dominance, however, warm-season grass cover had no influence on cover of other functional groups providing weak support for competition as regulator of Sandhills prairie composition. Forb cover was best related in a negative manner to 3-year running mean total precipitation, a surprising result that maybe signaling factors governing basal responses in prairie remain largely unresolved. Woody species cover, however, was positively associated with mean growing season temperatures indicating potential of these to spread under warming scenarios. [ABSTRACT FROM AUTHOR]

Biofuels and bio-based products can be produced from a wide variety of herbaceous feedstocks. To supply enough biomass to meet the needs of a new bio-based economy, a suite of dedicated biomass species must be developed to accommodate a range of growing environments throughout the USA. Researchers from the US Department of Agriculture's Agricultural Research Service (USDA-ARS) and collaborators associated with the USDA Regional Biomass Research Centers have made major progress in understanding the genetics of switchgrass, sorghum, and other grass species and have begun to use this knowledge to develop new cultivars with high yields and appropriate traits for efficient conversion to bio-based products. Plant geneticists and breeders have discovered genes that reduce recalcitrance for biochemical conversion to ethanol and drop-in fuels. Progress has also been made in finding genes that improve production under biotic and abiotic stress from diseases, pests, and climatic variations. [ABSTRACT FROM AUTHOR]

The widespread use of warm-season turfgrasses in transition zones of Europe, such as northern Italy, has been hampered by the long dormancy periods. To encourage the conversion from cool- to warm-season grasses, research is needed to identify cultivars that exhibit early spring green-up. A 2-year study was conducted at the agricultural experimental farm of Padova University from November 2006 to October 2008 to compare water-soluble carbohydrate and protein content in stolons of four bermudagrass [ Cynodon dactylon (L.) Pers.] cultivars and determine their effect on spring green-up. Samples of 'La Paloma', 'NuMex Sahara', 'Princess 77' and 'Yukon' were collected monthly, and water-soluble carbohydrates ( WSC) and crude protein ( CP) content of stolons were measured. Dry weight values of WSC and CP for each cultivar were regressed against days needed to reach 80 % green cover in spring (D80). 'Yukon' exhibited the highest rhizome dry weight and WSC content during the winter months and was the fastest to reach 80 % green cover. Conversely, 'Princess 77' was the slowest cultivar to green-up in both years. Regression analysis revealed a stronger relationship between D80 and WSC than between CP content and D80. [ABSTRACT FROM AUTHOR]

The Hempstead Plains, located in Nassau County, New York, contains remnants of the only naturally occurring prairie east of the Appalachian Mountains. It originally encompassed approximately 12,500 ha. Although the area receives higher amounts of rainfall for a typical tall-grass prairie ecosystem, approximately 114 cm of precipitation per year, its well-drained, dark-colored soil sited above glacial outwash, available natural seed bank, and history of fires enabled development of a tall-grass prairie. This study identified prairie remnants within the historical extent of the Hempstead Plains delineated by the 1928 soil survey from the United States Department of Agriculture. Image analysis of infrared color 8-bit orthophotographs was used for an unsupervised classification on a 156-ha primary study area containing a known prairie remnant, centered on the Red Golf Course at Eisenhower Park in East Meadow. The resulting 16 classes were combined into six more general classes before undergoing an error assessment based on field and orthoimagery ground-truthing of 1,000 random points. As confirmed by site visits, analysis was generally able to distinguish prairie grass from non-native grasses using remote sensing, as native warm-season prairie grasses are dormant from late fall to early spring. Overall accuracy for the six classes was 89 %. Accuracy of the warm-season grass class was 81 % for producer's accuracy and 83 % for user's accuracy. This study identified additional sites containing warm-season grasses and potential prairie remnants in Nassau County. [ABSTRACT FROM AUTHOR]

High yielding, native warm-season grasses could be used as renewable bioenergy feedstocks. The objectives of this study were to determine the effect of warm season grass monocultures and mixtures on yield and chemical characteristics of harvested biomass and to evaluate the effect of initial seeding mixture on botanical composition over time. Switchgrass ( Panicum virgatum L.), indiangrass [ Sorghastrum nutans (L.) Nash], and big bluestem ( Andropogon gerardii Vitman) were planted as monocultures and in all possible two- and three-way mixtures at three USA locations (Brookings and Pierre, SD and Morris, MN) during May 2002. Biomass at each location was harvested after a killing frost once annually from 2003 to 2005. Total biomass yield significantly increased with year at all locations. Switchgrass monocultures or mixtures containing switchgrass generally out-yielded big bluestem or indiangrass in monocultures or the binary mixture. Cellulose and hemicellulose concentrations were higher in 2004 and 2005 compared with 2003. Switchgrass or mixtures containing switchgrass tended to have less cellulose than either big bluestem or indiangrass. Results were more variable for total N, lignin, and ash. Switchgrass was the dominant component of all mixtures in which it was present while big bluestem was dominant when mixed with indiangrass. Indiangrass was maintained only in monocultures and declined over years when grown in mixtures at all locations. Our results indicated if biomass yield in the northern Great Plains is a primary objective, switchgrass should be a component of binary or tertiary mixtures that also contain big bluestem and/or indiangrass. [ABSTRACT FROM AUTHOR]

St. augustinegrass\Stenotaphrum secundatum (Walt.) Kuntze] is a popular turfgrass in the southern United States as a result of its superior shade tolerance and relatively low input requirements. However, it is the least cold-tolerant of commonly used warm-season turfgrass species. 'Raleigh', released in 1980, has superior cold tolerance and is adapted and widely used in U.S. Department of Agriculture hardiness zones 8 to 9. More than 25 years after its release, 'Raleigh' is still the industry's standard in terms of cold tolerance. However, the original foundation and breeder stock fields of the cuitivar have been lost, placing the integrity of the cultivar at risk. The objectives of this study were to investigate whether current 'Raleigh' production fields across the southern United States are true to the original source. In this study, 15 amplified fragment length polymorphism (AFLP) primer combinations were used to assess levels of genetic variability among three original stocks of 'Raleigh' and 46 samples obtained from sod farms and universities in six states. Genetic similarities among the original stocks were Sij = 1, whereas similarities between this group and all other samples ranged from 0.24 to 1.0. Results based on cluster analysis, principal coordinate analysis, and analysis of molecular variance (AMOVA) revealed separation between original stocks of 'Raleigh' and some commercial samples. Results from this study offer further evidence that molecular markers provide a useful and powerful technique for identity preservation of clonally propagated cultivars and the detection of genetic variants in sod production fields and turfgrass breeding programs. [ABSTRACT FROM AUTHOR]

Soil organisms play important roles in regulating ecosystem-level processes and the association of arbuscular mycorrhizal (AM) fungi with a plant species can be a central force shaping plant species' ecology. Understanding how mycorrhizal associations are affected by plant invasions may be a critical aspect of the conservation and restoration of native ecosystems. We examined the competitive ability of old world bluestem, a non-native grass (Caucasian bluestem [ Bothriochloa bladhii]), and the influence of B. bladhii competition on AM root colonization of native warm-season prairie grasses ( Andropogon gerardii or Schizachyrium scoparium), using a substitutive design greenhouse competition experiment. Competition by the non-native resulted in significantly reduced biomass production and AM colonization of the native grasses. To assess plant-soil feedbacks of B. bladhii and Bothriochloa ischaemum, we conducted a second greenhouse study which examined soil alterations indirectly by assessing biomass production and AM colonization of native warm-season grasses planted into soil collected beneath Bothriochloa spp. This study was conducted using soil from four replicate prairie sites throughout Kansas and Oklahoma, USA. Our results indicate that a major mechanism in plant growth suppression following invasion by Bothriochloa spp. is the alteration in soil microbial communities. Plant growth was tightly correlated with AM root colonization demonstrating that mycorrhizae play an important role in the invasion of these systems by Bothriochloa spp. and indicating that the restoration of native AM fungal communities may be a fundamental consideration for the successful establishment of native grasses into invaded sites. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of this research were to determine the effect of N levels and plant maturity on the nutritive quality of four warm-season grasses, and to evaluate relationships between forage quality and morphological development. Indiangrass (Sorghastrum mutans L. Nash), big bluestem (Andropogon gerardii Vitman), Eastern gamagrass (Tripsacum dactyloides L.), and switchgrass (Panicum virgatum L.) were grown in four replications, applied with 3N levels (0, 65, and 140kg/ha), and harvested on ten dates at approximately 2-week intervals for first seven harvest dates and 3-week intervals for last three harvest dates. For all species, harvesting at early maturity increased (P<0.05) forage quality including increased in vitro dry matter digestibility (IVDMD) and crude protein (CP), and decreases in neutral detergent fiber (aNDF) concentrations, whereas allowing forage to reach later maturity reduced forage quality with declines in IVDMD and CP and increases in aNDF concentration. The aNDF concentration in warm-season grasses with the exception of big bluestem increased with N fertilization at 65kg/ha, while N fertilization at 140kg/ha had no consistent effect on aNDF concentration of the four grass species across both years. Nitrogen fertilization increased (P<0.05) the IVDMD value across four grass species in 2006, whereas it decreased (P<0.05) the IVDMD value for switchgrass and did not affect (P>0.05) the IVDMD value for the other three species in 2007. The concentration of CP for all four warm-season grass species increased (P<0.05) at higher rates of N fertilization. Therefore, although there were variations in the effect of N fertilization on aNDF and IVDMD making drawing conclusions difficult, N fertilization could improve forage quality for warm-season grasses through increasing the concentration of CP. For big bluestem, switchgrass, and indiangrass, forage quality parameters showed a quadratic relationship to mean stage by count (MSC), with coefficients of determination ≥0.96 for IVDMD, 0.88 for aNDF, and 0.88 for CP, respectively. However, predicting forage quality changes based on MSC did not provide reasonable estimates (P>0.05) for eastern gamagrass. [Copyright &y& Elsevier]

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass ( Panicum virgatum L.), giant miscanthus ( Miscanthus x giganteus), giant reed ( Arundo donax L.), weeping lovegrass [ Eragrostis curvula (Shrad.) Nees], kleingrass ( Panicum coloratum L.), and Johnsongrass ( Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168 kg N ha) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate ( p = 0.08), but was affected by year and species interactions ( p < 0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0 Mg ha in 2009, but only 13.0 Mg ha and 9.8 Mg ha in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0 Mg ha, respectively. Giant miscanthus established poorly, producing only 4.7 Mg ha. Across years, giant reed had the highest biomass yield, 33.2 Mg ha at 168 kg N ha, and the highest nutrient concentrations and removal rates (162 to 228 kg N ha, 23 to 25 kg P ha, and 121 to 149 kg K ha) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75 kg N ha, 5 to 12 kg P ha, and 44 to 110 kg K ha) across years, demonstrating its merits as a low-input bioenergy crop. [ABSTRACT FROM AUTHOR]

Abstract: Tallgrass prairie restoration has been practiced for more than 75years, yet few studies have systematically tested restoration methods over large geographic regions with the intent of refining methodology. In this study, we used three planting methods (dormant-season broadcast, growing-season broadcast and growing-season drill) fully crossed with three levels of seed species richness (10, 20, and 34 spp). We replicated the study on nine former agricultural fields located from east-central Iowa (Neal Smith National Wildlife Refuge) to northwestern Minnesota (Litchfield, Fergus Falls and Morris Wetland Management Districts), USA, within the northern tallgrass prairie biome. Objectives were to evaluate the relative influences of planting method, seed mix richness, and their interactions, on (1) planted cover (both total and by guild) and richness, (2) exotic species cover, and (3) non-planted native species cover. Optimal techniques varied between the two study areas: the dormant broadcast method produced greater cover of planted species at the Minnesota sites and the growing-season drill method produced greater cover of planted species at Iowa sites. The dormant broadcast method strongly favored establishment of perennial forbs while the growing-season drill favored warm-season grasses. Although increasing richness of the seed mix produced greater planted species richness, this did not result in greater resistance to exotic invasion. We conclude that, if planting during the growing season, drilling seed is preferable to broadcasting, but if the choice is between broadcasting seed in the dormant or growing season, the dormant season is preferred. [Copyright &y& Elsevier]

Aerenchynia are air-filled spaces in the root cortex that help maintain oxygen supply to roots in saturated soils. We examined aerenchyma formation in roots and its effect on the suitability of 26 native warm-season grass cultivars from six species for use in riparian areas. In a greenhouse study, all cultivars exhibited extensive aerenchyma formation in well-drained soil, and percent aerenchyma was greater in the well-drained control than in the saturated treatment (89% versus 71%, respectively). However, the presence of extensive aerenchyma development did not guarantee good root growth under anaerobic conditions. Suitable plant materials for inclusion in riparian areas were found among four of the six warm-season species examined, although a wide range in suitability was observed within species where multiple cultivars were tested. Nine cultivars representing a range of responses were further evaluated at four field locations subjected to flooding and soil saturation. Red River prairie cordgrass (Spartina pectinata L.) provided superior performance at all locations. The worst performing cultivars in the greenhouse study also performed poorly in the field. However, not all cultivars that performed well in the greenhouse also performed well in the field. Osage Indiangrass (Sorghastrum mutans L.) was the third ranked cultivar for flooding tolerance in the greenhouse but had acceptable performance at only one of the four field sites. Conversely, Meadowcrest eastern gamagrass (Tripsacum dactyloides L.) exhibited oniy moderate flooding tolerance in the pot study but had among the lowest mortality, highest vigor, and highest biomass at three of the four locations. Controlled environment studies were useful for eliminating unacceptable cultivars, but field studies were necessary to identify suitable material for riparian areas. [ABSTRACT FROM AUTHOR]

Abstract: Switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and indiangrass (Sorghastrum nutans (L.) Nash) are native warm-season grasses commonly used for pasture, hay, and conservation. More recently switchgrass has also been identified as a potential biomass energy crop, but management of mixtures of these species for biomass is not well documented. Therefore, the objectives of our study were to: (1) determine the effects of harvest timing and N rate on yield and biomass characteristics of established warm-season grass stands containing a mixture of switchgrass, big bluestem, and indiangrass, and (2) evaluate the impact of harvest management on species composition. Five N rates (0, 56, 112, and 224kgha−1 applied annually in spring and 224kgha−1 evenly split between spring and fall) and two harvest timings (anthesis and killing frost) were applied to plots at two South Dakota USA locations from 2001 to 2003. Harvesting once a year shortly after a killing frost produced the greatest yields with high concentrations of neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) along with lower concentrations of total nitrogen (TN) and ash. This harvest timing also allowed for the greatest percentage of desirable species while maintaining low grass weed percentages. While N rates of 56 and 112kgha−1 tended to increase total biomass without promoting severe invasion of grass and broadleaf weed species, N application did not always result in significant increases in biomass production. Based on these results, mixtures of switchgrass and big bluestem were well suited for sustainable biomass energy production. Furthermore, N requirements of these mixtures were relatively low thus reducing production input costs. [Copyright &y& Elsevier]

Infestations of the exotic perennial Spotted knapweed ( Centaurea maculosa Lam.) hinder the restoration and management of native ecosystems on droughty, infertile sites throughout the Midwestern United States. We studied the effects of annual burning on knapweed persistence on degraded, knapweed-infested gravel mine spoils in western Michigan. Our experiment included 48, 4-m2 plots seeded to native warm-season grasses in 1999 using a factorial arrangement of initial herbicide and fertility treatments. Beginning in 2003, we incorporated fire as an additional factor and burned half of the plots in late April or May for 3 years (2003–2005). Burning increased the dominance of warm-season grasses and decreased both biomass and dominance of knapweed in most years. Burning reduced adult knapweed densities in all 3 years of the study, reduced seedling densities in the first 2 years, and reduced juvenile densities in the last 2 years. Knapweed density and biomass also declined on the unburned plots through time, suggesting that warm-season grasses may effectively compete with knapweed even in the absence of fire. By the end of the study, mean adult knapweed densities on both burned (0.4-m2) and unburned (1.3-m2) plots were reduced to levels where the seeded grasses should persist with normal management, including the use of prescribed fire. These results support the use of carefully timed burning to help establish and maintain fire-adapted native plant communities on knapweed-infested sites in the Midwest by substantially reducing knapweed density, biomass, and seedling recruitment and by further shifting the competitive balance toward native warm-season grasses. [ABSTRACT FROM AUTHOR]

Warm-season grasses and legumes have the potential to provide forage throughout the Mediterranean summer when there are high temperatures and low rainfall and when cool-season grasses become less productive. Twenty-nine non-native, warm-season pasture species (twenty-three grasses and six legumes) were assessed for their adaptability to the coastal plain of southern Italy in terms of their productivity and nutritional quality. The investigated species were compared with two reference species widely used in a Mediterranean environment: a grass ( Festuca arundinacea) and a legume ( Medicago sativa). The species differed in their phenological and biological characteristics, i.e. start of vegetative resumption, first flowering and cold resistance, from each other and from the control species. From the second year after establishment, warm-season perennial grasses had high dry-matter (DM) yields and, in many cases, a more than adequate nutritional quality. As for legumes, the control, M. sativa gave the best results in all the investigated characters. Among the grasses, seven species ( Chloris gayana, Eragrostis curvula, Panicum coloratum, Paspalum dilatatum, Pennisetum clandestinum, Sorghum almum, Sorghum spp. hybrid) had DM yields greater than the control species and had their maximum growth during the hottest period of the year, when F. arundinacea, the control grass species, was dormant. Eragrostis curvula had the highest annual DM yield (21·1 t ha−1) and P. clandestinum provided the best combination of agronomic and yield characteristics which were similar to those of M. sativa. The seven above-mentioned species have the potential to supply hay or grazing and contribute to broadening and stabilizing the forage production calendar in Mediterranean-type environments. [ABSTRACT FROM AUTHOR]

Unprecedented opportunities for biofuel development are occurring as a result of rising fossil fuel prices, the need to reduce greenhouse gases, and growing energy security concerns. An estimated 250 million hectares (ha) of farmland could be utilized globally to develop a bioenergy industry if efficient and economical perennial biomass crops and bioenergy conversion systems are employed. In temperate zones, C 4 or warm-season grass research and development efforts have found switchgrass (Panicum virgatum) and Miscanthus capable of producing biomass yields of 10 to 20 oven dried tonnes (ODT)/ha/yr, while in tropical areas Erianthus and napier grass (Pennisetum purpureum) are producing 25 to 35 ODT/ha/yr. The potential to annually produce 100 barrels of oil energy equivalent/ha with a 25:1 energy output to input ratio appears achievable with high-yielding, N-fixing warm-season grasses grown on marginal lands in the tropics. Commercialization of densified herbaceous plant species has been slow because of the relatively high alkali and chlorine contents of the feedstocks, which leads to clinker formation and the fouling of boilers. This challenge can be overcome by improving biomass quality through advances in plant breeding and cultural management to reduce the chlorine, alkali, and silica content and through the use of new combustion technologies. Warm-season grasses can be readily densified provided suitable grinding and densification equipment and pressure are utilized. The major advantages of producing densified warm-season grasses for BIOHEAT include: it is the most efficient strategy to use marginal farmlands in most temperate and tropical climates to collect solar radiation; it has an excellent energy balance; the feedstocks can be used conveniently in a variety of energy applications; and it is relatively environmentally friendly. Densified warm-season grass biofuels are poised to become a major global fuel source because they can meet some heating requirements at less cost than all other alternatives available today. [ABSTRACT FROM AUTHOR]

Preparing agricultural producers to cope with volatile weather changes, specifically drought, requires a better understanding of forage water-use efficiency (WUE) potentials. Options to improve farm resiliency to drought may include the use of C4 annual and perennial forages, which have greater production efficiency during drought than commonly used C3 forages. Our objective was to measure WUE through real-time gas exchange measurements of photosynthesis and transpiration in (1) a greenhouse study and (2) under field-grazing conditions. Growth parameters, instantaneous water use efficiency (iWUE), and mass-based WUE (mWUE) data were collected under greenhouse conditions in Study 1 for the following species: crabgrass (Digitaria sanguinalis cv. 'Red River'), switchgrass (Panicum virgatum cv. 'Alamo'), big bluestem (Andropogon gerardii cv. 'OZ-70'), indiangrass (Sorghastum nutans cv. 'Rumsey'), eastern gamagrass (Tripsacum dactyloides cv. 'Pete'), bermudagrass (Cynodon dactylon cv. 'Vaughn's #1'), sorghum-sudangrass (Sorghum bicolor (L.) × Sorghum sudanese (P.) cv. 'Greengrazer'), and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort). Study 2 occurred from 2014 to 2016, and evaluated iWUE of crabgrass, switchgrass, bermudagrass, eastern gamagrass, and a big bluestem/indiangrass mix under field conditions. Overall, in situ iWUE of crabgrass, switchgrass, eastern gamagrass, and bermudagrass did not differ, while iWUE of the big bluestem/indiangrass was less than switchgrass and crabgrass, an advantage for these species if the standardized precipitation index drops below zero. Bermudagrass, switchgrass, sorghum-sudangrass, pearl millet, and indiangrass had comparable mWUE values under greenhouse-simulated drought. These results will aid in the development of forage species recommendations for mitigating drought and improving resiliency. [ABSTRACT FROM AUTHOR]

We studied the establishment of native warm-season grasses on gravel mine spoils infested by spotted knapweed (Centaurea maculosa), an exotic perennial that is difficult to control on droughty, infertile sites. We applied factorial combinations of sewage sludge (0 and 11.9 Mg ha-1 [5.3 tons ac-1]) and herbicide (none; 2,4-D; and glyphosate) to evaluate their effects on native grass establishment and on competition between native grasses and spotted knapweed. While native grasses were successfully established with all treatment combinations, sludge application reduced their densities. Warm-season grass biomass subsequently increased rapidly on both sludge and control plots. Both herbicide treatments reduced density and biomass of knapweed during the first two years of the study, but glyphosate and sludge interacted to produce increased knapweed biomass during the third year. For this reason, it may be desirable to delay application of sludge amendments until warm-season grasses are well established in herbicide-treated areas. The response of knapweed to improved soil fertility was dependent on the degree of grass competition, and where this remained high, knapweed dominance was suppressed. While warm-season grasses appeared to compete successfully with spotted knapweed, additional control measures may be required to maintain grass dominance on this and similar knapweed-infested sites. [ABSTRACT FROM AUTHOR]