Tripsacum Dactyloides Research Articles

Ornamental Grasses Show Minimal Response to Cultural Inputs

Full sun trial gardens were established at two sites in northern Florida. Six U.S. native and three non-native warm season grass species were evaluated in a split-plot design. Only eastern gamagrass (Tripsacum dactyloides), elliott's lovegrass (Eragrostis elliottii), gulf hairawn muhly (Muhlenbergia capillaris), little bluestem (Schizachyrium scoparium), and ‘Central Park' maiden grass (Miscanthus sinensis) showed a significant response to supplemental irrigation or fertilization. Supplemental irrigation did not influence foliage height for any of the grasses, whereas supplemental fertilization influenced foliage height only for chinese fountain grass (Pennisetum alopecuroides). The response differences between locations were attributed in part to soil types. This study observed minimal or no response of shoot growth to supplemental irrigation or fertilization for the grass species tested, thereby affirming the broad adaptability and minimal need for inputs for these ornamental landscape plants.

Stimulated Rhizodegradation of Atrazine by Selected Plant Species

The efficacy of vegetative buffer strips (VBS) in removing herbicides deposited from surface runoff is related to the ability of plant species to promote rapid herbicide degradation. A growth chamber study was conducted to compare C-atrazine (ATR) degradation profiles in soil rhizospheres from different forage grasses and correlate ATR degradation rates and profiles with microbial activity using three soil enzymes. The plant treatments included: (i) orchardgrass ( L.), (ii) smooth bromegrass ( Leyss.), (iii) tall fescue ( Schreb.), (iv) Illinois bundle flower (), (v) perennial ryegrass ( L.), (vi) switchgrass ( L.), and (vii) eastern gamagrass (). Soil without plants was used as the control. The results suggested that all plant species significantly enhanced ATR degradation by 84 to 260% compared with the control, but eastern gamagrass showed the highest capability for promoting biodegradation of ATR in the rhizosphere. More than 90% of ATR was degraded in the eastern gamagrass rhizosphere compared with 24% in the control. Dealkylation of atrazine strongly correlated with increased enzymatic activities of β-glucosidase (GLU) ( = 0.96), dehydrogenase (DHG) ( = 0.842), and fluorescein diacetate (FDA) hydrolysis ( = 0.702). The incorporation of forage species, particularly eastern gamagrass, into VBS designs will significantly promote the degradation of ATR transported into the VBS by surface runoff. Microbial parameters widely used for assessment of soil quality, e.g., DHG and GLU activities, are promising tools for evaluating the overall degradation potential of various vegetative buffer designs for ATR remediation.

The Southern Cornstalk Borer (Diatraea crambidoides (Grote), Lepidoptera: Crambidae) a New Pest of Eastern Gamagrass (Tripsacum dactyloides (L.) L., Poaceae)

Abstract The southern corn stalk borer [Diatraea crambidoides (Grote)] has become a serious pest to eastern gamagrass [Tripsacum dactyloides (L.) L.]. Managing this insect will be important to the future of this forage crop in the United States. An experiment was conducted to understand the life cycle of the southern corn stalk borer infesting eastern gamagrass. For a two year period, four plant crowns which contained numerous shoots were dug randomly each week from a field plot located in Woodward, OK. All shoots from each crown were dissected and the number of larvae and pupae present was recorded for each shoot type, i.e., reproductive or vegetative shoot. The life stages of the southern corn stalk borer in eastern gamagrass can be described by three distinct populations in northwestern Oklahoma: a) over-wintering, b) first generation, and c) second generation. Over-wintering larvae feed within a cavity near the base of the shoot or within the proaxis. Pupation occurred within the feeding cavity. Larva...

Agronomic performance of eastern gamagrass cultivars and experimental germplasm grown on the southern plains

Eastern gamagrass ( Tripsacum dactyloides (L.) L. [Poaceae]), evaluated for forage yield, quality, and seed production in the southern plains region of the US, produced between 13,417 and 18,015 kg/ha (11,979 and 16,084 lb/ac) dry matter when harvested 3 times per year without supplemental irrigation in 2008 and 2009. In this study, 4 cultivars and 3 experimental populations were evaluated. Seed yield collected in 2010 ranged from 181 to 436 kg/ha (162 to 389 lb/ac) with significant differences among entries. Crude protein did not differ significantly between entries and ranged from 1720 to 2002 kg/ha (1536 to 1788 lb/ac). Digestibility ranged from 7543 to 9670 kg/ha (6735 to 8634 lb/ac) with only one entry significantly less digestible. The knowledge provided herein about improved cultivars along with local knowledge from other growers in your region who have established and maintained eastern gamagrass stands will be useful when selecting a cultivar.

Composition of Native Warm‐Season Grasses for Bioenergy Production in Response to Nitrogen Fertilization Rate and Harvest Date

Information about the interaction of harvesting and N fertilization on composition of warm‐season grasses grown as biofuel feedstocks is limited. Our objective was to determine composition of warm‐season grasses as influenced by N fertilization rates and harvest dates. A field study was conducted near Ames, IA, during 2006 and 2007. The experimental design was a split‐split plot arranged in a randomized complete block with four replications. Big bluestem (Andropogon gerardii Vitman), eastern gamagrass (Tripsacum dactyloides L.), indiangrass (Sorghastrum nutrans L. Nash), and switchgrass (Panicum virgatum L.) were main plots. Three N application rates (0, 65, and 140 kg ha−1) were subplots, and 10 harvest dates were sub‐subplots. In both years, delaying harvest increased cellulose, lignin, and C concentrations, but decreased ash and N concentrations, however, the magnitude of these effects varied among species. On average, big bluestem had the highest cellulose (430.5 g kg−1) and C concentration (450.5 g kg−1) while switchgrass had the highest lignin concentration (58.5 g kg−1) among four species. Big bluestem had the lowest ash concentration (47.5 g kg−1) whereas indiangrass had the lowest N concentration (5.5 g kg−1). With increasing rates of N, average N, C, cellulose, and lignin concentrations increased 19 to 29%, 0.6 to 2.2%, 0.7 to 5.7%, and 5.6 to 23.9%, respectively, whereas ash concentration declined 1.8 to 18.4%, varied among species. Our results indicated that in general, warm‐season grasses supplied with N fertilizer at 140 kg ha−1 and harvest delayed until fall have the optimal composition for biomass feedstock production.

Reducing Herbicides and Veterinary Antibiotics Losses from Agroecosystems Using Vegetative Buffers

Multiple species vegetative buffer strips (VBSs) have been recommended as a cost-effective approach to mitigate agrochemical transport in surface runoff derived from agronomic operations, while at the same time offering a broader range of long-term ecological and environmental benefits. However, the effect of VBS designs and species composition on reducing herbicide and veterinary antibiotic transport has not been well documented. An experiment consisting of three VBS designs and one continuous cultivated fallow control replicated in triplicate was conducted to assess effectiveness in reducing herbicide and antibiotic transport for claypan soils. The three VBS designs include (i) tall fescue, (ii) tall fescue with a switchgrass hedge barrier, and (iii) native vegetation (largely eastern gamagrass). Rainfall simulation was used to create uniform antecedent soil moisture content in the plots and to generate runoff. Our results suggested that all VBS significantly reduced the transport of dissolved and sediment-bound atrazine, metolachlor, and glyphosate in surface runoff by 58 to 72%. Four to 8 m of any tested VBS reduced dissolved sulfamethazine transport in the surface runoff by more than 70%. The tall fescue VBS was overall most effective at reducing dissolved tylosin and enrofloxacin transport in the runoff (>75%). The developed exponential regression models can be used to predict expected field-scale results and provide design criteria for effective field implementation of grass buffers. Our study has demonstrated that an optimized VBS design may achieve desired agrochemical reductions and minimize acreage removed from crop production.

RAPD and Internal Transcribed Spacer Sequence Analyses Reveal Zea nicaraguensis as a Section Luxuriantes Species Close to Zea luxurians

Genetic relationship of a newly discovered teosinte from Nicaragua, Zea nicaraguensis with waterlogging tolerance, was determined based on randomly amplified polymorphic DNA (RAPD) markers and the internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA using 14 accessions from Zea species. RAPD analysis showed that a total of 5,303 fragments were produced by 136 random decamer primers, of which 84.86% bands were polymorphic. RAPD-based UPGMA analysis demonstrated that the genus Zea can be divided into section Luxuriantes including Zea diploperennis, Zea luxurians, Zea perennis and Zea nicaraguensis, and section Zea including Zea mays ssp. mexicana, Zea mays ssp. parviglumis, Zea mays ssp. huehuetenangensis and Zea mays ssp. mays. ITS sequence analysis showed the lengths of the entire ITS region of the 14 taxa in Zea varied from 597 to 605 bp. The average GC content was 67.8%. In addition to the insertion/deletions, 78 variable sites were recorded in the total ITS region with 47 in ITS1, 5 in 5.8S, and 26 in ITS2. Sequences of these taxa were analyzed with neighbor-joining (NJ) and maximum parsimony (MP) methods to construct the phylogenetic trees, selecting Tripsacum dactyloides L. as the outgroup. The phylogenetic relationships of Zea species inferred from the ITS sequences are highly concordant with the RAPD evidence that resolved two major subgenus clades. Both RAPD and ITS sequence analyses indicate that Zea nicaraguensis is more closely related to Zea luxurians than the other teosintes and cultivated maize, which should be regarded as a section Luxuriantes species.

Unique Dairy Applications of Eastern Gamagrass Forages in Central Wisconsin: I. Yield Potential

Replacement dairy heifers (Bos taurus) offered diets comprised largely of corn (Zea mays L.) silage or other high‐energy forages often become overconditioned, which may damage their future performance as lactating cows. Our objective was to assess the yield potential of a perennial C4 grass, eastern gamagrass [Tripsacum dactyloides (L.) L.], for incorporation into fiber‐demanding, dairy‐heifer or dry‐cow diets. Replicated field plots of ‘Pete’ eastern gamagrass were evaluated within nine harvest systems and four N fertilization regimes. For single‐harvest systems, dry matter (DM) yields increased across harvest dates, reaching numerical maximums of 7192, 9764, and 7554 kg ha−1 by mid‐August of 2007, 2008, and 2009, respectively. During each year, there was a strong linear (P < 0.001) effect of harvest date; however, higher‐ordered effects varied within year. Relatively large yield increases (≥1812 kg ha−1) between early and mid‐August during 2008 and 2009 suggest that better yields could be achieved by delaying single harvests of eastern gamagrass beyond mid‐August. Yields of DM from double‐harvest systems were not competitive with single‐harvest systems timed in mid‐August. Nitrogen fertilization increased (P < 0.001) DM yields, exhibiting both linear (P < 0.001) and quadratic (P = 0.027) effects of application rate. However, efficiency of N usage was reduced as fertilization rates increased.

Unique Dairy Applications of Eastern Gamagrass Forages in Central Wisconsin: II. Nutritive Value and Energy Density

Recently, perennial warm‐season grasses have received considerable interest, largely through bioenergy initiatives, but their suitability for limiting caloric intake by fiber‐demanding livestock classes, such as dairy replacement heifers (Bos taurus) and/or dry cows has not been explored. Our objectives were to evaluate eastern gamagrass [Tripsacum dactyloides (L.) L.] forages harvested from nine single‐ or double‐harvest systems with four N fertilization regimes for macromineral, protein, and fiber composition, and then to estimate the energy densities for these forages by the summative approach. Across the 3‐yr trial, concentrations of neutral‐detergent fiber (NDF) from single‐harvest systems increased with mostly linear (P < 0.001) and quadratic (P = 0.010) effects of harvest date, reaching maximum concentrations ranging from 746 to 801 g kg−1 by early or mid‐August. Similarly, concentrations of lignin increased with delayed harvest dates across single‐harvest systems in predominantly linear (P < 0.001) patterns. Generally, concentrations of lignin were lower than reported for eastern gamagrass forages grown at more southerly latitudes, and ranged from 37.5 to 46.0 g kg−1 in mid‐August. As a result, estimates of total digestible nutrients (TDN) determined by the acid‐detergent lignin option for calculating truly digestible fiber remained relatively high through mid‐August (582 g kg−1). Adjusting truly digestible fiber on the basis of the alternate in vitro 48‐h neutral‐detergent fiber digestibility (NDFD) approach resulted in reduced TDN estimates for eastern gamagrass. In northern climates, eastern gamagrass forages have large concentrations of NDF, and could be used to dilute dietary energy for livestock species with low or moderate energy requirements.

Observations on a Globally Rare Leafhopper (Limotettix minuendusHamilton, Hemiptera: Cicadellidae) in Maryland, U.S.A.

Limotettix minuendus Hamilton (Homoptera: Cicadellidae) (Fig. 1) is a globally rare species with only two known localities. It is a member of the apparently plesiomorphic subgenus Dryola, which includes only one other species, L. elegans, found from northern Michigan to southern Texas (Hamilton 1994). Though at the time it was undescribed and lacked a scientific name, L. minuendus was discovered by the late Robert Whitcomb and Michael Coan in 1970 in Prince George’s County, MD, at Beltsville Agricultural Research Center (BARC). Over a decade later, two subsequent collections were made by Whitcomb to the north in Baltimore County, MD, both from Soldiers Delight Natural Environment Area (NEA). The BARC population of L. minuendus was extirpated around 1980, and the species is now believed to be extant only at Soldiers Delight NEA. As is typical for most Cicadellidae (Whitcomb, et al., 1986), the narrow distribution of L. minuendus is in stark contrast to its host plant, Eleocharis tenuis Willd., which is widely distributed throughout the state and is considered to be globally secure (NatureServe 2009). Habitat conditions differ considerably between the historic BARC location and Soldiers Delight NEA. The BARC population occurred in a ditch adjacent to an old field characterized by grasses including Awnless brome (Bromus inermis Leyss.), Bermuda grass (Cynodon dactylon (L.) Pers.), Weeping lovegrass (Eragrostis curvula (Schrad.) Ness), Tall fescue (Festuca arundinacea Schreb.), Northern gamagrass (Tripsacum dactyloides (L.) L.) and Zoysia grass (Zoysia sp.) (Whitcomb, pers. comm.). All plant nomenclature follows Gleason and Cronquist (1991). The soil type was probably sand or clay (Kirby, et al., 1967) although the precise location of the site remains uncertain. In contrast, Soldiers Delight NEA (700 ha) encompasses a serpentine barrens ecosystem with indigenous oak savanna and grassland communities. Restoration of these communities has been ongoing since 1988 by manual clearing of non-indigenous Virginia pine (Pinus virginiana Mill.) and prescribed burning. Historically, there were two records for L. minuendus from the NEA, both of which were discovered by Robert Whitcomb in the early-mid 1980s. The first was from a streamside clearing, the second from an upland roadside clearing. From 2006 to 2009, we attempted to determine the habitat requirements of L. minuendus so that we could direct future survey efforts to other potential sites in Maryland. With only three reported sites, one of which was destroyed and 352 ENTOMOLOGICAL NEWS

Chromosome control of apomixis in maize-gamagrass hybrids

The results of long-term studies on the transmission of the mode of asexual reproduction through seeds to maize from gamagrass, a closely related wild plant, performed in the Laboratory of Plant Cytology and Apomixis are summarized. The first apomictic hybrids between Zea mays and Tripsacum dactyloides were obtained in this laboratory more than 40 years ago and have been maintained until the present time. Cytogenetic studies on the hybrids have shown that at least nine chromosomes of the wild parent are necessary for the expression of asexual reproduction through seeds. In addition, the genes controlling two elements of apomixis (apomeiosis and parthenogenesis) have been found to be inherited independently from each other.

Integrating Annual and Perennial Warm‐season Grasses in a Temperate Grazing System

ABSTRACTWarm‐season grasses (WSG) can supply badly needed forage in summer when cool‐season grasses (CSG) are often unproductive. This study was conducted from 2005–2007 in central Illinois to compare annual and perennial WSG pasture types integrated into a CSG grazing system. The objective was to compare summer herbage mass, forage nutritive value, cattle (Bos taurus) performance, and variable costs between CSG systems integrated with either annual (AWSG) or native, perennial warm‐season grass (NWSG) pastures. The AWSG pastures were established with sorghum‐sudangrass cultivars [Sorghum bicolor (L.) Moench], and eastern gamagrass [Tripsacum dactyloides (L.) L.] dominated NWSG pastures. Beef cow–calf groups were moved between CSG and WSG pastures during summer based on forage availability. Both WSG pasture types averaged 61% more herbage mass (493 g m−2) in mid‐summer compared with CSG pastures (204 g m−2). Except for one sampling date, herbage mass on NWSG pastures either exceeded (P < 0.05) or was equal to AWSG pastures. The nutritive value of AWSG forage was consistently higher than NWSG (P < 0.05), but cow and calf performance was similar on both pasture types. A simple cost analysis showed that AWSG pastures were more expensive to maintain even though establishment costs of NWSG pasture were much higher. Our results suggest NWSG pastures may be the better option for livestock producers seeking a longer‐term solution to summer forage deficits associated with CSG.

Plant Diversity in an Imperiled Gamagrass Community in Northeastern Texas

Cowleech Prairie Preserve, located on the Cowleech Fork of the Sabine River, Hunt County, northeastern Texas, is a wet-to-mesic blackland prairie-wetland complex that represents a plant community currently undescribed by the National Vegetation Classification. However, it bears similarities with those globally imperiled communities having eastern gamagrass (Tripsacum dactyloides) as a first-order dominant. Objectives of this study were to document floristic composition and examine changes in composition and dominance of species from late spring to early autumn and to better define classification of this community as a recognized association. We collected data on species richness, composition, ground cover, and abundance of forbs during early autumn 2003 and late spring 2004. Total number of species (species richness) recorded was 56 in autumn and 61 in spring. However, these seasonal differences in species richness were not significant. Poaceae (grasses) was the most dominant family in autumn, with gamagrass forming the most predominant ground cover. In contrast, sedges and forbs were dominant in spring. Many species of forbs (47.0% in spring and 62.0% in autumn) had a limited distribution among transects, occurring in only one of five transects during the two seasons. In addition, 21.4 and 29.5% of species of forbs were unique to autumn and spring, respectively. Beautiful false dragon-head (Physostegia pulchella), a species endemic to the blackland prairies of Texas, was recorded in spring. This study represents the first comprehensive floristic documentation of the Cowleech Prairie Preserve.

Suther Prairie: Vascular Flora, Species Richness, and Edaphic Factors

Piedmont prairie communities of the southeastern United States were common prior to European settlement. Suther Prairie in Cabarrus County, North Carolina is among the best-known examples of such an ecosystem. This study provides a complete floristic list of species observed at the site from 1997–2007. Sampling over the 10 yr period included fixed transects and general floristic inventories. During the 2006–07 growing seasons, additional transects and 90 randomly placed 1 m2 quadrats were established for sampling species frequency. Soil in six of these random quadrats was sampled at three depths (0–10 cm, 11–20 cm, 21–30 cm) for pH, organic C, total N, and extractable P, K, Ca, Mg, Zn, Mn, Cu, B, and Na.There were 208 species documented during the 10 yr sampling period. In 2006–07 142 new species were identified, but 49 previously documented species were not re-located. Of the 208 species, 66 were graminoids (36 grasses and 30 sedges/rushes). Ninety of these had previously been reported from prairie habitats. Obligate or facultative wetland species comprised 32% of the list. Thirteen species were rare, watch-listed, or uncommon for North Carolina. Big Bluestem (Andropogon gerardii) and Eastern Gamagrass (Tripsacum dactyloides var. dactyloides) had the highest frequency of occurrence during the 2006–07 sampling. Species richness was 6.8 species per m2. Levels of Ca and Mg were much higher than normal for Piedmont soils, and there was significant variation in soil C, N, P and Zn levels among the sampled depths.

Detection of maize centromeric repeats in the relatives of maize using fluorescence <I>in situ</I> hybridization

In order to analyze the conservation of maize centromeric satellite DNA (CentC) and centromeric retrotransposon (CRM) in the subspecies and relatives of Zea mays, dual fluorescence in situ hybridization (FISH) was used to detect the existence and distribution of the above two repetitive sequences in Zea mays ssp. mexicana, Z. diploperennis, Z. perennis, Tripsacum dactyloides, Coix lacryma-jobi, and Sorghum bicolor. In Z. mays ssp. mexicana, Z. diploperennis, and Z. perennis, both CentC and CRM probes produced strong or relatively strong signals in the centromeric regions of all chromosomes. There was an obvious variation in the intensity of hybridization signals on different chromosomes, indicating that different centromeres have different amounts of CentC and CRM sequences. In some centromeres, the intensity of CentC signals differed from that of CRM signals and was free from overlapping. In T. dactyloides, only weak CentC and CRM signals were detected in the centromeric regions of most chromosomes, while in C. lacryma-jobi and S. bicolor only relatively strong or strong CRM signals primarily located in the centromeric regions were detected. This result indicates that CentC is highly conserved among the subspecies of Z. mays and the species of Zea, and has high conservation in Tripsacum, a genus that is most closely related to Zea, and CRM is conserved among the species of grass family either closely or distantly related to Zea.

Eastern Gamagrass Management for Pasture in the Mid‐Atlantic Region: I. Animal Performance and Pasture Productivity

Eastern gamagrass [Tripsacum dactyloides (L.) L.] (EG) is a native, warm‐season perennial grass with potential as pasture for the eastern United States, but its value has not been well studied. The objective of this 4‐yr experiment was to estimate forage mass (FM) for EG that maximizes steer (Bos taurus) performance and pasture productivity. Five treatments (three continuously and two rotationally stocked) were compared with a continuously stocked ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] control. The three continuously stocked treatments had mean FM (10‐cm stubble) levels of 559 kg ha−1 (Short), 1103 kg ha−1 (Medium), and 1932 kg ha−1 (Tall). Rotational treatments consisted of two subdivisions with steers moved on a 10 to 14 d interval (FM = 1348 kg ha−1) and10 subdivisions with steers moved every 3 to 4 d with a 27 to 36 d regrowth interval (FM = 2061 kg ha−1). The average daily gain (ADG) from the Medium continuously stocked treatment was greatest at 0.90 kg (P = 0.02) and produced similar annual gain per hectare (735 vs. 749 kg ha−1; P = 0.08) as Short. Rotational pastures had greater FM than continuously stocked (1705 vs. 1198 kg ha−1; P = 0.03), but the least ADG (0.67 vs. 0.79 kg; P = < 0.01). Bermudagrass produced less ADG than EG (0.57 vs. 0.79 kg; P < 0.01), but gain per hectare was similar (662 kg ha−1) and stocking rate was greater (10.0 vs. 6.7 head ha−1; P < 0.01). Eastern gamagrass has potential as a special purpose pasture for the region when greater ADG is the goal.

Eastern Gamagrass Management for Pasture in the Mid‐Atlantic Region: II. Diet and Canopy Characteristics, and Stand Persistence

Eastern gamagrass [Tripsacum dactyloides (L.) L.] (EG), a native warm‐season perennial grass, lacks evaluation for use in grazing systems. Our objective was to test EG in a 4‐yr experiment to estimate forage mass (FM) that maximizes steer (Bos taurus) performance and pasture productivity. Pasture canopy characteristics, diet selection by grazing steers, and stand persistence from EG continuously grazed at Short, Medium, and Tall heights and two rotationally stocked treatments were compared with continuously stocked ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] (BG). The EG had proportionally more green leaf (78.2 vs. 24.5%), less stem (4.4 vs. 45.2%), less heads (0.4 vs. 5.6%), and similar dead tissue (17.0 vs. 24.8%). Plant fractions were similar in proportion among EG treatments. Digestible leaf mass was greater in EG than in BG (P < 0.01; 713 vs. 292 kg ha−1) and dominated the EG canopies with a linear (P < 0.01) increase in leaf mass with increasing FM (194–922 kg ha−1). Diets were similar in IVTOD (738 g kg−1), CP (151 g kg−1), and NDF (654 g kg−1) when continuously stocked but greater (P < 0.01) in IVTOD (791 g kg−1), and least in NDF (624 g kg−1) from the rotation. Stand declined linearly (P = 0.09) with decreasing FM (Tall = 34.5 and Short = 11.7% basal cover) but was similar between the two rotational systems (35.5%). Continuously stocking EG at about 38 cm gave greatest steer daily gain but rotations may prevent declines in stands with some sacrifice in gains.

Intake, Digestibility, and Nitrogen Balance of Steers Fed Gamagrass Baleage Topdressed at Two Rates of Nitrogen and Harvested at Sunset and Sunrise

ABSTRACTMaximum diurnal accumulation of soluble carbohydrates in warm‐season grasses is an economic way of increasing hay quality; however, in the humid East, haymaking is difficult. This study evaluated gamagrass (Tripsacum dactyloides L.), topdressed with either 56 (LO) or 168 (HI) kg N ha−1, direct baled after mowing in the afternoon (PM/LO and PM/HI) or morning (AM/LO and AM/HI), wrapped with plastic film, and conserved as baleage. The four baleage treatments were evaluated by steers for dry matter intake (DMI), digestibility, and N retention. Neither harvest time nor N rate altered DMI (mean = 1.87 kg 100−1 kg body weight). Digestion was similar between PM and AM baleage but greater (P = 0.05) for HI vs. LO N rate (536 vs. 506 g kg−1) as was cellulose digestion (P = 0.02; 656 vs. 617 g kg−1). The digestion of crude protein was greater (P = 0.01) in the AM vs. PM baleage (519 vs. 443 g kg−1) and greater (P = 0.02) in HI vs. LO N rate (520 vs. 441 g kg−1). Fermentations differed (P < 0.01) between PM and AM baleage, as pH averaged 5.4 and 4.5, respectively. Greatest (P < 0.01) amounts of alcohols and least fatty acids occurred in PM baleage and N rate reduced (P < 0.01) alcohols but increased fatty acids. Total nonstructural carbohydrates (TNC) prebaling was 120 g kg−1 in the PM and 97 g kg−1 in the AM, but baleage averaged <38 g kg−1 and explains the lack of steer response to the PM harvest. Gamagrass preserved well as baleage and was readily consumed, but the TNC fraction was not preserved.

Nitrogen Influences Biomass and Nutrient Partitioning by Perennial, Warm‐Season Grasses

Recent attention has focused on the use of perennial, warm‐season grasses as renewable energy crops. The objective of this study was to assess the effects of N fertilization on partitioning of biomass and nutrients between above‐ and belowground plant components by four warm‐season grass species in Iowa. In 2006–2007, established stands of big bluestem (Andropogon geradii Vitman), switchgrass (Panicum virgatum L.), indiangrass [Sorghastrum nutans (L.) Nash], and eastern gamagrass [Tripsacum dactyloides (L.) L.] were fertilized with 0, 65, 140, or 220 kg N ha−1 in the spring and harvested following frost in the fall. Dependent on grass species and year, yield response to N was linear or quadratic. Optimum yield after 2 yr was 13.5 Mg ha−1 at 140 kg N ha−1 for all grasses except eastern gamagrass, which demonstrated lower yield and a consistent linear N response. Nitrogen inputs had pronounced but grass‐specific effects on root biomass and nutrient partitioning. For big bluestem and switchgrass, 140 kg N ha−1 maximized root biomass and favored allocation of nutrients to roots over shoots. In contrast, for indiangrass and eastern gamagrass, root biomass and root nutrient allocation were adversely affected by N inputs. For all grasses, 220 kg N ha−1 shifted allocation of nutrients to shoots over roots. Selection of crops and management practices that optimize yield, and maintain a high level of resource partitioning to roots at low to intermediate N input rates will promote the development of productive and efficient bioenergy systems.

Evaluation of native warm-season grass cultivars for riparian zones

Aerenchyma 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 (<i>Spartina pectinata</i> 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 (<i>Sorghastrum nutans</i> 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 (<i>Tripsacum dactyloides</i> L.) exhibited only 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.