Warm-season Grasses Research Articles

Early Forage Biomass and Sward Structures of Native Warm-Season Grasses Established at Different Seedling Densities

Effects of transplanted seedling density and species on sward structure of native warm-season grass (NWSG) stands were compared in a randomized complete block design. About 6-week-old NWSG (big bluestem (BB, Andropogon gerardii Vitman), eastern gamagrass (GG, Tripsacum dactyloides L.), indiangrass [IG, Sorghastrum nutans (L.) Nash] and switchgrass (SG, Panicum virgatum) seedlings were transplanted in 45-cm wide rows on clean-tilled seedbeds. Within-row spacing was 30, 25, or, 20 cm giving 10, 12, and 15 plants m-2 as low, medium, and high seedling density, respectively. During establishment, the stands were allowed uninterrupted first year growth without fertilizers or irrigation but when necessary, tall-growing broadleaf weeds were mechanically removed. In the following spring, all dead standing biomass was mowed down to allow emerging tillers access to sunlight. During the second year after planting, early-spring basal diameters, row-length intercepted by the NWSG crowns, mid-summer sward heights, and percentage bare ground were determined. From the second June after planting, and for two consecutive years, plots were harvested twice year-1 to assess forage biomass. Data showed that, unlike species, seedling density had no effect on the assessed parameters. Cumulative forage biomass, in kg DM ha-1, was the least for GG (4901) at low and the most (18,245) for SG at high seedling density during the second year. Corresponding values for the third year were 4500 and 7799 kg DM ha-1. Basal diameters ranged from 18 cm (BB) to 24 cm (IG) while percent row intercepts were from 6 (GG) to 46 (IG) with sward heights measuring 41 cm (IG) to 54 cm (GG). In each stand, percent ground cover by the NWSGs, and at every seedling density, averaged 60.5. Transplanting at ≥10 plant m-2 resulted in harvest-ready stands by the second year of establishment. And while close spacing favored the NWSGs against weeds, data showed that an initial plant density of >10 plants m-2 may not result in increased forage production worthy the additional establishment cost. Data on response to fertility management and forage quality attributes are necessary for more reliable practical recommendations.

Micronutrients Considerations for Warm-Season Grass Systems in Florida

Warm-season grasses are vital to livestock production systems and dominate ground cover in tropical and subtropical areas. Many popular warm-season grasses, such as bahiagrass and bermudagrass, have roots that penetrate deeper into the soil profile, which aids in both drought tolerance, nutrient uptake, and the minimization of soil erosion. In Florida, spodosols are the predominant soil order used for forage production and have limited fertility. Micronutrients are essential elements that are required in smaller quantities than macronutrients but are equally as important for proper plant growth and performance. An element can be considered essential for plant growth if a plant fails to complete its life cycle in the absence of the element, the elements action is specific and cannot be completely replaced by another element, it has a direct effect on the organism, or it is a constituent of a molecule that is known to be essential. The objective of this publication is to describe the role of micronutrients in warm-season grass production.

Seasonal below‐ground metabolism in switchgrass

Switchgrass (Panicum virgatum), a perennial, polyploid, C4 warm-season grass is among the foremost herbaceous species being advanced as a source of biomass for biofuel end uses. At the end of every growing season, the aerial tissues senesce, and the below-ground rhizomes become dormant. Future growth is dependent on the successful over-wintering of the rhizomes. Although the importance of rhizome health to overall year-upon-year plant productivity has been long recognized, there is limited information on seasonal changes occurring during dormancy at both the transcriptome and metabolite levels. Here, global changes in transcriptomes and metabolites were investigated over two growing seasons in rhizomes harvested from field-grown plants. The objectives were: (a) synthesize information on cellular processes that lead to dormancy; and (b) provide models that could account for major metabolic pathways present in dormant switchgrass rhizomes. Overall, metabolism during dormancy appeared to involve discrete but interrelated events. One was a response to abscisic acid that resulted in dehydration, increases in osmolytes and upregulation of autophagic processes, likely through the target of rapamycin complex and sucrose non-fermentative-related kinase-based signaling cascades. Another was a recalibration of energy transduction through apparent reductions in mitochondrial oxidative phosphorylation, increases in substrate level generation of ATP and reducing equivalents, and recycling of N and possibly CO2 through refixation. Lastly, transcript abundances indicated that cold-related signaling was also occurring. Altogether, these data provide a detailed overview of rhizome metabolism, especially during dormancy, which can be exploited in the future to improve winter survival in switchgrass.

Indices of forage nutritional yield and water use efficiency amongst spring-sown annual forage crops in north-west China

Abstract Livestock production in China is increasing to meet demands for animal products, but is limited by feed resources. To explore additional forage options in north-west China, the biomass production and nutritive value of nine spring-sown annual crops (maize (Zea mays), sudan grass (Sorghum sudanense), small millet (Setaria italica), millet (Panicum milliaceum), soybean (Glycine max), common vetch (Vicia sativa), pea (Pisum sativum), oat (Avena sativa) and spring wheat (Triticum aestivum)) were compared under rainfed conditions over two years. Water use efficiencies for biomass (WUEDM) and nutritional yield indices, CP yield (WUECP) and relative feed value yield (WUERFV), were calculated. Maize produced the highest biomass yields of >10 t DM ha−1 and had the highest WUEDM. Biomass production was next highest in the other warm-season grasses such as sudan grass and millet species (6–9 t DM ha−1) and soybean (3–7 t DM ha−1), while spring wheat produced the most early biomass in spring (P

ABA Is Involved in Regulation of Cold Stress Response in Bermudagrass.

As a representative warm-season grass, Bermudagrass [Cynodon dactylon (L). Pers.] is widely used in turf systems. However, low temperature remarkably limits its growth and distribution. ABA is a crucial phytohormone that has been reported to regulate much important physiological and biochemical processes in plants under abiotic stress. Therefore, the objective of this study was to figure out the effects of ABA on the cold-sensitive (S) and cold-resistant (R) Bermudagrass genotypes response to cold stress. In this study, the plants were treated with 100 μM ABA solution and exposed to 4°C temperature. After 7 days of cold treatment, the electrolyte leakage (EL), malonaldehyde (MDA) and H2O2 content were significantly increased in both genotypes compared with control condition, and these values were higher in R genotype than those of S genotype, respectively. By contrast, exogenous ABA application decreased the electrolyte leakage (EL), MDA and H2O2 content in both genotypes compared with those plants without ABA treatment under cold treatment condition. In addition, exogenous ABA application increased the levels of chlorophyll a fluorescence transient curve for both genotypes, and it was higher in R genotype than that of S genotype. Analysis of photosynthetic fluorescence parameters revealed that ABA treatment improved the performance of photosystem II under cold condition, particularly for the R genotype. Moreover, cold stress significantly increased δ13C values for both genotypes, while it was alleviated by exogenous ABA. Additionally, exogenous ABA application altered the expression of ABA- or cold related genes, including ABF1, CBF1, and LEA. In summary, exogenous ABA application enhanced cold resistance of both genotypes by maintaining cell membrane stability, improving the process of photosystem II, increasing carbon isotopic fractionation under cold stress, and more prominently in R genotype compared with S genotype.

Effects of Nitrogen and Phosphorus Fertilizer and Topsoil Amendment on Native Plant Cover in Roadside Revegetation Projects.

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.

Large Mammal Use of Seminatural Grasslands and Implications for Aviation Strike Risk

Abstract Large mammals pose a significant risk to U.S. aircraft safety within airport operation areas and cost airlines millions of dollars in repairs annually. Native warm-season grass polycultures and switchgrass monocultures offer alternative land covers for airports that could benefit current risk-mitigation efforts in addition to offering economic and environmental benefits. We compared use of a native warm-season grass polyculture and switchgrass Panicum virgatum monoculture by white-tailed deer (deer; Odocoileus virginianus) and coyote Canis latrans, using remote cameras in Mississippi, during 2011–2012. Coyotes and deer were observed 27% and 51% less in switchgrass monoculture than in native warm-season grass polyculture, respectively. However, November detections and cumulative hazard score demonstrated the greatest differences between treatments, especially for deer. Considering deer and coyotes are among the most hazardous mammal species to aircraft, switchgrass monocultures could be a better alternative land cover than native warm-season grass polycultures for some airport turf areas. Increased land coverage of switchgrass monocultures could benefit airport wildlife-hazard mitigation but needs validation by comparing alternative land covers to more traditional airport land covers.

Genetic diversity and association mapping of forage quality in diverse bermudagrass accessions

Bermudagrass is a warm season grass widely cultivated for turf and fodder. Nonetheless, the grass has poor forage quality because animals that consume it fail to assimilate its organic matter efficiently. Thus, identification of the marker-trait association between simple sequence repeat (SSR) markers and forage-quality-related traits in diverse bermudagrass accessions would enable efficient selection of high forage quality bermudagrass cultivars. Association mapping of 8 forage-related-quality traits with 1474 markers was conducted in 60 diverse bermudagrass accessions from five geographical regions in China. Significant variations in eight phenotypic and physiological traits were observed among the 60 accessions. A total of 1474 alleles were amplified by 104 SSR primers. The average gene diversity and polymorphic information content for the study sample were 0.2097 and 0.1748 respectively. The clustering analysis suggested that geographic origin influenced genetic distances between accessions. A total of 76 markers significantly associated with traits at P < 0.01; 73 with a single trait and 3 with two traits each. Nevertheless, only 41 significant marker-trait associations (MTAs) were observed after Bonferroni test was separately conducted for each trait. Forty-one microsatellites had significant associations with 8 forage-quality-related traits. These markers provide a feasible means of genetically improving forage quality in bermudagrass after further authentication.

Resilience of Sandhills Grassland to Wildfire During Drought

In the Nebraska Sandhills, one of the largest contiguous grassland ecoregions remaining in North America, sandy textured soils are stabilized by fine root biomass from predominantly warm-season grasses. Concerns over destabilization have led to management that aims to avoid an undesirable state change toward mobile sand dunes. In 2012, the Sandhills experienced extreme drought conditions that coincided with the worst wildfire year on state record. According to state-and-transition models and ecosystem managers, the combination of wildfire and drought conditions should cause a state transition due to a lack of recovery of grassland vegetation and a loss of sand dune stability. To test this hypothesis, we implemented a time-since-fire study to track biomass recovery of Sandhills grassland vegetation following a wildfire on The Nature Conservancy’s Niobrara Valley Preserve in burned and unburned areas. Two yr following the wildfire, aboveground herbaceous biomass in burned areas had recovered to levels that did not differ from unburned areas, maintaining the stability of the sand dunes. This provides evidence that counters current land management frameworks that portray Sandhills grassland as highly vulnerable to destabilization when wildfires occur during severe drought conditions.

Cost-benefit analysis of native warm season grasses for transmission line right-of way revegetation

The rapid reestablishment of vegetation in newly constructed electric transmission line rights-of-way (ROWs) is important for the control of soil erosion and compliance with associated regulations. Following establishment, routine maintenance must be performed to suppress the encroachment of woody vegetation in ROWs to provide for continuous and safe operation of electric transmission lines. Although non-native seed mixes conventionally are used for this purpose in North America, modeling ROW revegetation on locally adapted native communities could reduce longer-term management needs and provide ecological, environmental, and social benefits associated with native systems. We conducted a cost-benefit analysis to determine if ROW revegetation with a seed mix comprised primarily of native herbaceous species could be cost-effective relative to revegetation with a conventional seed mix comprised primarily of exotic herbaceous species. Our analysis synthesized data collected from a feasibility study of ROWs planted with a native seed mix and information obtained from the Tennessee Valley Authority regarding ROW revegetation and maintenance costs. Overall, the cost of revegetation with native species was ∼5% more expensive per unit area than the cost of revegetation exotic species. The degree of reduced long-term maintenance costs to make revegetation with native species a worthwhile longer-term investment would be 10–17% using a break-even analysis. Despite the initial greater expense of revegetation with native species, we suggest that associated potential maintenance cost savings and ecological, environmental, and social benefits could favor their use.

Low Biodiversity of Small Mammals in Soybean Fields in the Northern Flint Hills, Kansas

We studied small mammals in lowland soybean fields along Kings Creek on Konza Prairie during autumn 1981 and spring 1982 to assess the composition of the small mammal community in this particular cropland habitat. We also compared species composition and other community characteristics in these crop fields to those observed in native prairie, planted brome grasslands and riparian woodlands. The small mammal community in the soybean fields was dominated by seed-eating rodents as we recorded 100% deer mice (Peromyscus maniculatus) during autumn and primarily deer mice (92%) with a low proportion (8%) of white-footed mice (P. leucopus) during spring. In upland tallgrass prairie comprised primarily of warm-season grasses, the small mammal community was dominated by deer mice (32%), western harvest mice (30%; Reithrodontomys megalotis) and by white-footed mice (8%) in autumn and then by deer mice (35%), white-footed mice (22%) and harvest mice (21%) in spring. The community of small mammals in soybean fields w...

Occurrence of a subgroup 16SrIII-J phytoplasma in non-symptomatic Brachiaria decumbens cultivated in a grazing area

Brachiaria spp. are the most important and widely used warm season grasses for pasture, but are also important weeds for most economic crops in the tropics. During phytoplasma surveys in pasture fields, asymptomatic plants of Brachiaria decumbens were collected for inspection. Nested PCR detected phytoplasmas in more than 90% of sampled plants. Based on computer-simulated RFLP and a similarity coefficient calculation, a subgroup 16SrIII-J phytoplasma was molecularly characterized. Phylogenetic analysis was consistent with virtual RFLP identification. Representatives of this subgroup have been identified in diverse Brazilian regions encompassing various commercial crops. Our study revealed B. decumbens as a new host and reservoir of 16SrIII-J phytoplasma.

牧草の定着に関する研究 : IV.石灰窒素多施与による不耕起追播暖地型牧草の定着向上

牧草の定着に関する研究 : IV.石灰窒素多施与による不耕起追播暖地型牧草の定着向上

冬作牧草類と暖地型牧草との連続栽培に関する研究 : V.前作暖地型牧草立毛内に中播きしたイタリアンライグラスの播種適期と生育環境について

冬作牧草類と暖地型牧草との連続栽培に関する研究 : V.前作暖地型牧草立毛内に中播きしたイタリアンライグラスの播種適期と生育環境について

Potencial de produção de sementes de gramíneas para a implantação em gramados

The Paspalum and Axonopus genera are among the main warm season grasses used for lawns. The seed propagation contributes to the decrease of the cost of establishment, besides maintaining the exact characteristics of the mother plant genotype, because they are apomictic species. The objective of this work was to evaluate the seed production potential of seventeen grass accesses of the species Paspalum notatum, P. lepton, P. lividum and Axonopus parodii. The experiment was conducted at Capão do Leão, Rio Grande do Sul State, Brazil, in a randomized block design, with four replications. The evaluated variables were: number of inflorescences per area, number of florets per inflorescence and seed production potential (SPP). In order to measure the seed production potential of the accesses, the equation proposed is: SPP = number of florets per inflorescence x number of inflorescences per m2 . There were year, access and interaction between years and accesses effect for the traits number of inflorescences per area and seed production potential. For the number of florets per inflorescence, there was no year effect. Potential production for the 2013/2014 harvest, ranged from 19,152.00 to 135,062.70 seeds m- ², with PN 09 of the P. notatum species standing out. In the 2014/2015 harvest, the seed production potential ranged from 9,973.75 to 81,536.75 seeds m- ², highlighting the access PN 11 of the species P. notatum. The accesses PN 11, PN 09, PN 10 and AP 01 were in the top third of the seed production potential ranking in the two harvests, and “grama-batatais” was in the lower third. There is genotype-environment interaction for all characteristics evaluated. However, there are accesses that show seed production potential consistently superior to the “grama-batatais” control, and have a greater potential for exploitation in the establishment of lawns by seeds.

Management of native warm-season grasses for beef cattle and biomass production in the Mid-South USA.

Native grasses, such as switchgrass (SG; L.), big bluestem (BB; Vitman), indiangrass (IG; Nash), and eastern gamagrass (EG; [L.] L.) may be capable of providing desirable summer forage for cattle as well as a source of biomass for renewable energy. To evaluate that potential, experiments were conducted at 2 locations in Tennessee comparing weaned beef () steers (268 ± 25 kg initial BW) during early-season grazing (Early; 30 d, typically corresponding to May, followed by postdormancy biomass harvest) and full-season grazing (Full, mean duration = 98 d). For Exp. 1, which compared SG, a blend of BB and IG (BBIG), and EG, ADG was greater ( < 0.05) for BBIG (1.02 kg/d) than SG (0.85 kg/d), and both were greater ( < 0.05) than EG (0.66 kg/d). Grazing days for SG and EG were similar (389 and 423 animal unit days [AUD]/ha, respectively) and exceeded ( < 0.05) that of BBIG (233 AUD/ha) during Full. In Exp. 2 (SG and BBIG only), rates of gain were comparable to that of Exp. 1, but AUD were 425 (SG) and 299 (BBIG) AUD/ha. Such rates of gain and grazing days indicate that these grasses can provide desirable summer forage for growing cattle. Early produced 211 to 324 kg BW gain/ha, depending on experiment and forage, followed by dormant-season harvests of 7.5 to 10.5 Mg/ha of biomass, indicating a potential for beef cattle forage and biomass production on the same land resource. Native grasses provided productive summer pasture and good rates of gain on growing cattle and could contribute to forage programs, especially where cool-season grasses currently predominate.

Month of Seeding Effect on Low-Input Establishment of Cool- and Warm-Season Turfgrasses in Continental Transition Zone

This research was conducted to determine the degree of success, by month, in seeding establishment of tall fescue (Festuca arundinacea Schreb., Kentucky bluegrass (Poa pratensis L.), Bermudagrass (Cynodon dactylon [L.] Pers. var. dactylon), and zoysiagrass (Zoysia japonica Steud.) at two locations in the moist, Midwest, continental transition zone on a prepared seed bed without irrigation or cover. The four species were planted every month of the year starting in September 2005. Starter fertilizer and siduron were applied the same day as seeding with no subsequent management except mowing. Percent cover of living turfgrass was recorded in each of 24 months after seeding. Tall fescue (80%) and Bermudagrass (73%) provided the best percent cover over all planting dates. Kentucky bluegrass provided 65% and zoysiagrass 24% cover. The cool-season grasses performed best in the July-to-March plantings; tall fescue 88% and Kentucky bluegrass 72%. Bermudagrass (94%) established best in the January-to-April plantings, while Zoysiagrass (32%) established best in the November-to-March plantings. Germination and seedling survival after germination of all species were inhibited by limited moisture during summer. The warm-season grasses were further limited by winter kill in the August, September, and October seedings. These results emphasize the risk in spring-seeding as well as the value in dormant-seeding of both warm- and cool-season turfgrasses for low-input, nonirrigated establishment.

Economic and conservation implications of converting exotic forages to native warm-season grass

Intensive agriculture can have negative environmental consequences such as nonpoint source pollution and the simplification of biotic communities, and land sharing posits that conservation can be enhanced by integrating agricultural productivity and biodiversity on the same land. In the Southeastern United States, native warm-season grasses (NWSG) may be a land sharing alternative to exotic forages currently in production because of greater livestock gains with lower fertilizer inputs, and habitat for grassland birds. However, uncertainty regarding costs and risk poses an important barrier to incorporating NWSG in livestock operations. We evaluated the economic and conservation implications of NWSG conversion among small, operational-scale pastures (6.8–10.5 ha) during 2011–2012 at the Prairie Research Unit in Monroe Co., Mississippi (USA). We used partial budgets to compare the marginal rate of return (MRRe) from converting exotic grass pastures to either a NWSG monoculture of Indiangrass (Sorghastrum nutans) or a NWSG mix of Indiangrass, little bluestem (Schizachyrium scoparium), and big bluestem (Andropogon gerardii). We similarly compared changes in productivity of dickcissels (Spiza americana), a grassland bird specializing in tall structure. Average daily gain (ADG) of steers and revenue were consistently higher for NWSG treatments than exotic grass pasture, but ADG declined between years. Indiangrass pastures yielded consistently positive MRRe, indicating producers would receive 16–24% return on investment. Marginal rate of return was lower for mixed NWSG (−12 to 3%), driven by slightly lower livestock ADG and higher establishment costs than for Indiangrass. Sensitivity analyses indicated that MRRe also was influenced by cattle selling price. Conversely, mixed NWSG increased dickcissel productivity by a greater degree than Indiangrass per amount invested in NWSG conversion, suggesting a tradeoff between livestock and dickcissel production between the two NWSG treatments. Given continued increases in livestock prices, NWSG could be a sustainable land sharing alternative to exotic pastures currently in production, but subsidies and changes in management may be required for NWSG conversion to be viable for producers and to maintain conservation benefits.

Accelerated development in Johnsongrass seedlings (Sorghum halepense) suppresses the growth of native grasses through size-asymmetric competition.

Invasive plant species often dominate native species in competition, augmenting other potential advantages such as release from natural enemies. Resource pre-emption may be a particularly important mechanism for establishing dominance over competitors of the same functional type. We hypothesized that competitive success of an exotic grass against native grasses is mediated by establishing an early size advantage. We tested this prediction among four perennial C4 warm-season grasses: the exotic weed Johnsongrass (Sorghum halepense), big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparius) and switchgrass (Panicum virgatum). We predicted that a) the competitive effect of Johnsongrass on target species would be proportional to their initial biomass difference, b) competitive effect and response would be negatively correlated and c) soil fertility would have little effect on competitive relationships. In a greenhouse, plants of the four species were grown from seed either alone or with one Johnsongrass neighbor at two fertilizer levels and periodically harvested. The first two hypotheses were supported: The seedling biomass of single plants at first harvest (50 days after seeding) ranked the same way as the competitive effect of Johnsongrass on target species: Johnsongrass < big bluestem < little bluestem/switchgrass, while Johnsongrass responded more strongly to competition from Johnsongrass than from native species. At final harvest, native plants growing with Johnsongrass attained between 2–5% of their single-plant non-root biomass, while Johnsongrass growing with native species attained 89% of single-plant non-root biomass. Fertilization enhanced Johnsongrass’ competitive effects on native species, but added little to the already severe competitive suppression. Accelerated early growth of Johnsongrass seedlings relative to native seedlings appeared to enable subsequent resource pre-emption. Size-asymmetric competition and resource-pre-emption may be a critical mechanism by which exotic invasive species displace functionally similar native species and alter the functional dynamics of native communities.

Manure nitrogen characteristics from horses fed warm season grass hays

Manure nitrogen characteristics from horses fed warm season grass hays