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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]

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]

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]

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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]

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]

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]

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]

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]