Bothriochloa Bladhii Research Articles

Floral development and the formation of unisexual spikelets in the Andropogoneae (Poaceae)

We investigated spikelet development in four distantly related species of the grass tribe Andropogoneae to determine whether spikelet development and the formation of unisexual florets are uniform throughout the tribe. We studied development in Bothriochloa bladhii, Coelorachis aurita, Heteropogon contortus, and Hyparrhenia hirta, and compared these with Panicum, a member of the sister tribe Paniceae. Many aspects of spikelet development in the species we have studied correlate with what is already known for Tripsacum and maize (both Andropogoneae), despite variation in how unisexual florets are distributed on the plant. The formation of unisexual spikelets is also uniform. All florets initiate both pistil and stamen primordia. In florets destined to be male, cell death occurs in the subepidermal layers of the gynoecium after the formation of a gynoecial ridge. In florets destined to be female, there is no apparent cell death in the stamens, but growth ceases after anther formation. The similarity in spikelet development and the formation of unisexual florets point to a common genetic mechanism for sex determination throughout the Andropogoneae and possibly the entire Panicoideae. Use of a cell death pathway to cause gynoecial abortion may be the basis of one morphological character that defines the subfamily.

Studies on the flora and vegetation of the Golestan National Park*, NE Iran. II. A new Poa and some new and noteworthy grass records for Iran

Poa golestanensis H. Scholz & Akhani spec. nov. is described from the Golestan National Park, NE Iran. The following species are added to the grass flora of Iran from that area: Alopecurus aequalis Sobol., Cleistogenes serotina (L.) Keng, Heteropogon contortus (L.) P. Beauv. ex Roem. et Schult., Hordelymus europaeus (L.) Harz. The occurrence in Iran of Poa compressa L., P. densa Troitsky, and Bothriochloa bladhii (Retz.) S.T. Blake which were not mentioned in Rechinger's Flora Iranica but were reported in later papers is confirmed. The maps of distribution in the Park are provided for the treated species.

Yield and Quality of WW-Iron Master and Caucasian Bluestem Regrowth

Old World bluestems (Bothriochloa spp.) have been seeded on over a million hectares of marginal farmland in Oklahoma and Texas, yet we know little about their regrowth yield and quality. The objective was to determine seasonal pattern of forage regrowth yield and quality of leaves and stems of WW-Iron Master (B. ischaemum [L.] Keng) and Caucasian (B. caucasica [Trin.] C.E. Hubb.) bluestem when 4-week regrowth was harvested at weekly intervals from early May through mid-September. Four plots of each bluestem were established in each of the 4 blocks (32 plots total). Harvesting was rotated so that 4-week regrowth of each bluestem was harvested weekly from 1 of the 4 plots in each block during 1988 and 1989 to determine regrowth yield, in vitro dry matter digestibility (IVDMD), and crude protein (CP) of leaves and stems. Forage regrowth of both species peaked in June both years. Regrowth during August averaged 10 and 35% of June regrowth in 1988 and 1989. WW-Iron Master produced 80 and 45 % greater 4-week regrowth than Caucasian in 1988 and 1989. WW-Iron Master produced 75 and 28% greater leaf regrowth than Caucasian in 1988 and 1989 and twice as many stems both years. Leaf and stem IVDMD of WW-Iron Master averaged 2 to 6 percentage units higher than Caucasian. Leaf CP of WW-Iron Master averaged 2 percentage units higher than Caucasian during May and June. However, stem CP of WW-Iron Master averaged 1 percentage unit lower than Caucasian. Grazing management plans need to consider that the majority of bluestem forage production was restricted to a 1 month period in June. This technique of sampling 4-week regrowth every week during the growing season was an effective method for determining the seasonal regrowth pattern.

Indiangrass and Caucasian Bluestem Responses to Different Nitrogen Sources and Rates in the Ozarks

Alternatives to cool-season grasses are needed for summer forage production on droughty, infertile soils in the Ozarks. The objective of this research was to compare nitrogen (N) sources and application rates for improving forage production, crude protein concentration, and apparent fertilizer N recovery by 'Rumsey' indiangrass [Sorghastrum nutans (L.) Nash] and caucasian bluestem [Bothriochloa caucasia (Trin.) C.E. Hubbard]. Pure stands of each species were treated with urea, NH4NO3, or (NH4)2SO4 at 0, 56, 112, and 168 kg N ha-1 from 1985-1987. In 1988 the (NH4)2SO4 treatment was discontinued and in 1990 the N rates were increased to 0, 78, 157, and 235 kg N ha-1. Forage yields, crude protein concentrations or both were greater with NH4NO3 compared to urea in 3 out of 6 years for indiangrass and 4 out of 6 years for caucasian bluestem. Indiangrass forage yields increased with increasing N rates up to 168 kg N ha-1. Caucasian bluestem forage yields peaked at 101 kg N ha-1 in 1985, 132 kg N ha-1 in 1986, 122 kg N ha-1 in 1987, 129 kg N ha-1 in 1989, and 161 kg N ha-1 in 1990. Crude protein concentrations of both species increased linearly with N rates in most years. At the lowest N rate (56 kg N ha-1) caucasian bluestem was more efficient than indiangrass in apparent fertilizer N recovery, but at greater N rates the 2 species were similar in fertilizer N recovery. Forage yield and crude protein concentration of both species responded similarly to (NH4)2SO4 and NH4NO3.

Warm‐Season Grass Productivity and Growth Rate as Influenced by Canopy Management

AbstractWarm‐season grasses adapted to cool‐temperate environments can improve the seasonal distribution and supplement the productivity of forage systems in the northeastern USA. Management practices concerning clipping regimes for warm‐season grasses grown in the region, are not well understood. A 2‐yr field study was conducted to determine productivity and growth rates of flaccidgrass (Pennisetum flaccidum Griseb.), switchgrass (Panicum virgatum L.), bermudagrass (Cynodon dactylon L.), and Caucasian bluestem [Bothriochloa bladhii (Retz.) S.T. Blake] clipped according to sward height criteria. Treatments were replicated three times and included; first clipped at full heading; or 50% removal of short canopy and 50% and 75% removal of tall canopies at vegetative stages. Cumulative yields of warm‐season grasses were influenced by a complex clipping treatment, species, and year interaction. When first cut was made at a mature stage, 1990 and 1991 yields were similar, but were greater in 1991 than 1990 when cut early. Cumulative herbage yield of bermudagrass and Caucasian bluestem exceeded that of switchgrass and flaccidgrass when clipping was begun early in the growing season (species ✕ treatment interaction; P ≤ 0.01). Mean growth rates were greatest when canopies were managed as hay or when 75% of a tall canopy was removed, and were greater in 1991 than in 1990. Instantaneous growth rates suggest that bermudagrass and Caucasian bluestem appear to be better adapted to repeated defoliation than the tall‐growing species. Switchgrass and flaccidgrass may be best used in limited‐defoliation or conserved forage situations.

Applying an empirical model of stomatal conductance to three C-4 grasses

An empirical equation for stomatal conductance has been developed. The equation is based on a linear index, which was modified to represent nonlinear independent effects of CO 2 flux and water vapor pressure deficit. The equation was applied to data from caucasian bluestem ( Bothriochloa caucasia (Trin.) C.E. Hubb.) and two accessions of Eastern gamagrass ( Tripsacum dactyloides (L.) L.), measuring responses of leaves of the three grasses to wide ranges of environmental conditions. The equation accurately predicts stomatal conductance in these C-4 grasses, but requires measured photosynthesis as an input variable. Dependence on only environmental inputs was achieved by including the equation as the conductance submodel in a complete leaf gas exchange model, along with a photosynthesis submodel derived from a biochemically based model. This simplified submodel also describes the data well, as does the integrated model. Comparisons of model results and derived parameter values indicate important differences among gas exchange properties of the three grasses. Implementation details of the model are discussed, along with approaches for adapting it for simulating interleaf variability, water stress effects, and patchy stomatal function.

Application of 13CO2 measurements to the estimation of energy expenditure in goats

The use and limitations of 13C stable isotopes as tracers in animal experimentation was investigated using 13C-labeled bicarbonate to estimate CO2 production and energetic requirement of free-ranging goats. Goats were fed wheat hay (Triticum aestivum; C3) or Old World Bluestem hay (Bothriochloa caucasica; C4; OWBS) ad libitum for 21 d. Parotid salivary ducts were cannulated for saliva collection. Isotopic bicarbonate (13C) was infused at a constant rate into the peritoneal cavity. In exp. 1, saliva samples were obtained at successive 2-h periods for 20 h to establish the time to achieve equilibrium. The half-life of bicarbonate was 2.9 h for animals consuming the wheat diet and 4.1 h (P < 0.06) for animals consuming OWBS diet. The time required to reach equilibrium was 12 h for animals on the wheat diet and 16 h for animals on OWBS diet. The error in the technique arising from animals consuming C3 vs. C4 species (which have different endogenous 13C contents) was studied in exp. 2. If species composition (C3 vs. C4) of the diet remains constant within 10%, the error is negligible. In exp. 3, estimation of CO2 production from continuous saliva samples had a lower coefficient of variation (6.3 vs. 10.0%) than measurements based on spot serum samples. Energy expenditure of goats in stalls consuming hay ad libitum was similar to that of ad-libitum-fed sheep at similar body weights. The 13C methodology appears to be a promising method for measuring energy expenditure of grazing animals. Key words: Energy requirement, stable isotopes, carbon dioxide, sodium bicarbonate

Composition and susceptibility to rumen microbial degradation of nonmesophyll cell walls isolated from Caucasian bluestem [Bothriochloa caucasica (Trin)] leaf tissue

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComposition and susceptibility to rumen microbial degradation of nonmesophyll cell walls isolated from Caucasian bluestem [Bothriochloa caucasica (Trin)] leaf tissueEdward J. Piwonka, Jennifer W. MacAdam, Monty S. Kerley, and John A. PatersonCite this: J. Agric. Food Chem. 1991, 39, 3, 473–477Publication Date (Print):March 1, 1991Publication History Published online1 May 2002Published inissue 1 March 1991https://doi.org/10.1021/jf00003a009RIGHTS & PERMISSIONSArticle Views40Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (737 KB) Get e-Alerts Get e-Alerts

No‐Till Warm‐Season Grass Establishment as Affected by Atrazine and Carbofuran

AbstractTall growing, perennial, warm‐season grasses that produce 65 to 75% of their yield in mid‐summer may provide needed summer grazing; however, establishment is often slow and inconsistent when compared to cool‐season grasses. Improved establishment would make these warm‐season grasses less vulnerable to annual weed competition. No‐till plantings of switchgrass (Panicum virgatum L.) and Caucasian bluestem (Bothriochloa caucasica (Trin.) C. E. Hubbard] were made at Blacksburg, VA (37° 11' N° 80° 25' W, 610‐m elevation) on a Groseclose loam soil (clayey, mixed, mesic Typic Hapludult). Eight experiments included carbofuran (2,3‐Dihydro‐ 2,2‐dimethyl‐7‐benzofuranol methylcarbamate) at 0 and 1.1 kg a.i. ha−1 and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) at 0, 1.1, and 2.2 kg a.i. ha−1 in all possible combinations. Seedling growth, leaf appearance rates, seedling weights, density, leaf elongation rates, and heights were measured. Yields of weedfree perennial warm‐season grasses were determined in the year of planting and the year after planting. Carbofuran at 1.1 kg a.i. ha−1 placed in the row with the seed at planting enabled seedlings to develop faster, elongate more rapidly, and provided more and heavier seedlings than without carbofuran. In the year after seeding, yields of warm season grass were higher where carbofuran was applied at seeding in seven of eight experiments. Atrazine reduced herbage yields as well as population, weight, development, and leaf elongation rate of seedlings in the seeding year. Atrazine at 1.1 kg a.i. ha−1 was not detrimental to either grass in the second year of the study. Atrazine at 2.2 kg a.i. ha−1 appeared to injure switchgrass more than Caucasian bluestem. Yields in the year after planting further confirmed these observations. Atrazine at 1.1 kg a.i. ha−1 increased yields over untreated controls. However, in one of four switchgrass experiments, yields of grass treated with atrazine at 2.2 kg ai. ha−1 were lower than controls the year after planting. A yield reduction was observed in two of four caucasian bluestem experiments. All stands were nearly pure with planted species the year after planting. Carbofuran and atrazine at 1.1 kg a.i. ha1 was considered the best recommendation for establishment of switchgrass and Caucasian bluestem under the conditions of the experiment.

Plant regeneration through somatic embryogenesis in the forage grass Caucasian bluestem (Bothriochloa caucasica)

Plantlets were regenerated from cultured seed explants of the forage grass Caucasian bluestem [Bothriochloa caucasica (Trin.) C.E. Hubbard] via somatic embryogenesis. Embryogenic callus was produced in four weeks when surface sterilized seeds were cultured on a medium containing MS-salts, B-5 vitamins, 12 mM L-proline, 2% sucrose, 0.8% agar and 5μM 2,4-D. Plantlets were regenerated in 6-8 weeks after culture initiation. Healthy root and shoot systems were produced within three weeks after the plantlets were transferred to a medium lacking 2,4-D. Approximately 95% of the plantlets survived greenhouse acclimation and produced healthy plants and viable seeds. Caucasian bluestem callus cultures exhibit natural resistance to kanamycin. High levels of kanamycin (up to 800 mg/l) did not completely inhibit callus growth. However, the regeneration of healthy-plantlets was completely inhibited by kanamycin even at low levels (50 mg/l).

Mefluidide Effect on Caucasian Bluestem Leaves, Stems, Forage Yield, and Quality

Mefluidide Effect on Caucasian Bluestem Leaves, Stems, Forage Yield, and Quality

Prediction of Botanical Composition Using NIRS Calibrations Developed from Botanically Pure Samples

Point quadrat, hand separation, and histological methods for determining botanical composition are tedious, time consuming, and expensive. Near‐infrared reflectance spectroscopy (NIRS) was used as a rapid method to predict botanical composition of grass‐legume mixtures clipped from field plots. Our objective was to determine if a group of samples, each consisting of one of three botanical components, could be used for calibration in lieu of samples containing mixtures of the components. Calibration equations were developed for NIRS prediction of a number of legumes, Caucasian bluestem [(Bothriochloa caucasica (Trin.) C.E. Hubb.], and cheatgrass (Bromus tectorum L.). Hand separations of clipped mixtures were used to validate the calibration equations. All forage samples were grown in silty soils of the Dale series. Some evidence existed for an interaction between light scatter and mixing of two pure species, but it was eliminated effectively by second derivative transformation of the spectra. Biases existed for all components (36‐61 g/kg) but were smaller than standard errors of performance (52‐104 g/kg), except for legumes. Linearity was excellent for prediction for percentage legume, and validation was more precise for legume than for Caucasian bluestem or cheatgrass. This method of calibration for a closed population is recommended. Care must be taken to validate equations using mixed samples to insure linearity of unknowns between the extremes. Further, unknowns should be scanned along with calibration samples so that the same day to day instrument variation is associated with both sample sets.

Rooting dynamics of Medicago sativa seedlings growing in association with Bothriochloa caucasica.

Medicago sativa was seeded into an established sward of Bothriochloa caucasica. Two frequencies of sward defoliation were compared to a nondefoliated control. Although 84 to 92% of the root mass at 0-20 cm belonged to B. caucasica during the spring and summer samplings, defoliation generally reduced the root mass of B. caucasica. During the summer, aboverground mass of B. caucasica ranged from 735 to 1220 g m-2 and 295 to 410 g m-2 for control and defoliation treatments, respectively. Defoliation apparently reduced the competitive effects of B. caucasica on M. sativa, as taproot and lateral root mass of M. sativa was much higher in defoliated than in control plots by the end of the growing season. Predawn xylem potential of M. sativa was 0.4 to 0.8 MPa more negative in control than in defoliated plots from mid-summer to fall. Thus, we suggest that the transpirational demand of undefoliated B. caucasica reduced soil moisture available to M. sativa, thereby reducing its growth and survival during late summer and fall, compared to defoliated treatments.

Grazing effects on shoot and root dynamics and above‐ and below‐ground non‐structural carbohydrate in Caucasian bluestem

AbstractThe objective of this study was to characterize changes in morphology and shoot/root total nonstructural carbohydrate (TNC) relationships in Caucasian bluestem (Bothriochloa caucasica) under grazing. Pastures were continuously grazed by steers weighing about 225 kg from mid‐May to late September of 1983 and 1984. Heavily grazed (H) swards produced more tillers m−1 than lightly grazed (L) swards. Number of tillers declined in both treatments during the midsummer drought period; however, the reduction was much less in H than in L swards. Above normal precipitation in August 1983 allowed number of tillers to rapidly recover (by approximately 4000 and 8000 m−1 for L and H treatments, respectively) reaching 10 700 and 17 800 tillers m−1 respectively, in late September. After 2 years of grazing, H swards initiated twice as many roots on an area basis; however, ability to penetrate soil to lower depths may have been reduced. Heavily grazed Caucasian bluestem had lower concentrations of total non‐structural carbohydrate (TNC) in shoots (P < 0.04) in both years, but had higher (28% at the end of 1984) TNC concentration in roots compared to lightly grazed (P= 001) plants. Greater root mass was found in lightly grazed swards; therefore, we suggest that root growth and TNC concentration tend to be inversely related. Total amount of TNC was higher in L swards, but during the course of the study total above and below‐ground TNC in H swards remained stable. Total above‐ground TNC pools are subject to short‐term variation and dilution from senescent herbage, thus TNC pools in individual plant parts may be a better indication of plant response.

Evaluation of mixed lucerne and caucasian bluestem hay diets fed to sheep

Several in vitro experiments, a digestion trial and a growth trial were performed to determine dry matter (DM) and fiber digestibilities, rate and extent of in vitro DM disappearance, ammonia-nitrogen (NH3-N) release, N metabolism variables, intake and average daily gain in sheep fed various combinations of lucerne and caucasian bluestem hay. Dietary treatments were prepared with lucerne replacing bluestem at 0, 25, 50, 75 and 100% of dietary DM. Associative effects between forages were evaluated. In vitro NH3-N accumulation exhibited a cubic response (P < 0.01) to percentage of lucerne at 6 h of incubation. A positive associative effect on NH3-N accumulation was evident at 6 h, with the 25% lucerne substrate having greater NH3-N accumulation compared with the 0 and 100% lucerne substrates. The extent of DM, acid detergent fiber (ADF) and cellulose disappearance, and the rate of DM and neutral detergent fiber (NDF) disappearance, decreased (P < 0.05) linearly as the percentage of lucerne increased. However, the addition of lucerne resulted in a linear increase (P < 0.01) in the rate of in vitro DM digestion early in fermentation (0–24 h).In the digestion trial, DM, NDF, ADF and cellulose digestibilities decreased linearly (P < 0.001) as dietary lucerne level was increased. Nitrogen intake, apparent N digestibility and N balance were found to increase linearly (P < 0.001) with increasing lucerne percentage. Quadratic responses (P < 0.05), indicating that positive associative effects occurred between lucerne and caucasian bluestem, were found for hemicellulose digestibility, apparent N digestibility and percent N retained. Metabolic fecal N was determined to be 5.78 g N kg−1 DM intake and no effect (P > 0.90) was observed on true N digestibility due to increasing lucerne in the diet. Diets varying in lucerne were fed ad libitum to 2 pens of lambs (6 lambs per pen; average initial weight, 20 kg) in a 56-day growth trial. Dry-matter intake increased linearly (P < 0.05) as the percentage of lucerne in the diet increased. Quadratic (P < 0.05) responses to an increasing percentage of lucerne were observed for average daily gain (ADG) and feed to gain ratio.Addition of lucerne to caucasian bluestem hay increased the amount of N and cell solubles available for microbial growth and fiber digestion, resulting in increased intake and animal performance despite decreased digestibility.

Nitrogen utilization, ruminal fermentation and abomasal nitrogen flow in sheep fed caucasian bluestem hay supplemented with lucerne or urea

Four crossbred wether lambs with ruminal and abomasal cannulae were used in a Latin square design to measure nitrogen (N) utilization, ruminal fermentation parameters and abomasal N flows for diets of caucasian bluestem hay alone (BLUESTEM) and supplemented with 50% lucerne (BLUE + LCRN), 9.6 g urea once daily (DOSED UREA) or 9.6 g day−1 urea continuously infused (INFUSED UREA). Lambs consuming BLUE + LCRN had lower (P < 0.05) intakes of neutral detergent fiber (NDF), hemicellulose and cellulose, and lower (P < 0.05) digestibility of acid detergent fiber (ADF) compared with those fed BLUESTEM, DOSED UREA or INFUSED UREA. Supplementation increased (P < 0.05) N intake and apparent digestibility regardless of the source. At 4 h post-feeding, ruminal ammonia (NH3-N) was increased (P < 0.05) by N supplementation over the BLUESTEM diet. The BLUE + LCRN diet resulted in lower (P < 0.05) ruminal pH from 2 to 8 h post-feeding compared with BLUESTEM, DOSED UREA or INFUSED UREA. Total concentration of ruminal volatile fatty acids (VFA) at 2 h post-feeding was greater (P < 0.05) for BLUE + LCRN compared with BLUESTEM, DOSED UREA or INFUSED UREA. Proportions of acetate, butyrate, iso-butyrate and iso-valerate were unaffected (P > 0.10) by supplementation. Propionate was increased (P < 0.05) on the BLUE + LCRN diet. No differences (P > 0.10) in abomasal flow of particulate dry matter (DM), non-NH3-N (NAN) and microbial N were evident. More (P < 0.05) NH3-N reached the abomasum in lambs receiving supplemental N. Ruminal escape of feed N was greater (P < 0.05) for the BLUESTEM diet compared with BLUE + LCRN and INFUSED UREA. Microbial N, as a percentage of total abomasal N, did not differ (P > 0.05) between diets. Results of this study indicate that low levels of ruminal NH3-N found on the BLUESTEM diet were not limiting microbial protein synthesis. Supplementation with lucerne appeared to stimulate the rate of early ruminal fermentation as evidenced by lower ruminal pH and greater concentration of total ruminal VFA 2 h post-feeding. This may help to explain the improved performance observed with the addition of a legume to a warm-season grass diet.

Forage Yield, Nonstructural Carbohydrate Levels, and Quality Trends of Caucasian Bluestem

AbstractInformation is limited on growth pattern and the effects of management on regrowth yield, quality, and total nonstructural carbohydrate (TNC) levels of Caucasian bluestem [Bothriochloa caucasica (Trin.) C.E. Hubb.] grown in the southern Corn Belt. Field studies on a Creldon silt loam soil (fine, mixed, mesic Mollic Fraguidalf) were conducted to determine trends of the above parameters under various primary growth harvests (one‐time harvests at 0, 14, 28, 42, and 56 d after 4 June) and summer and late‐season regrowth harvests (initial harvest on 18 June and 16 July, respectively, with regrowth harvests 14, 28, 42, 56, 70, and 84 d later). Yield increased linearly (104 and 55 kg ha−1 d−1, respectively) for primary growth and summer regrowth, while late‐season regrowth yield had a cubic trend (y = 201 − 11x + 2.3x2 − 0.02x3; x = days after initial harvest). In vitro dry matter digestibility declined linearly with time (2.9 g kg−1 d−1) in primary growth, but the rate of decline varied depending on length of delay for summer and late‐season regrowth (y = 548 − 4.0x + 0.26x2; y = 436 + 0.9x − 0.19x2, respectively). Crude protein declined quadratically under all treatments (y = 125 − 1.0x − 0.005x2; y = 137 − 3x + 0.001x2;y = 71.2 + 1x − 0.001x2, respectively, for primary growth and summer and late‐season regrowth). Neutral detergent fiber levels increased linearly for primary growth and late‐season regrowth (y = 668 + 1.9x;y = 662 + 1.1x, respectively), while summer regrowth response was quadratic (y = 637 + 2.7x − 0.002x2). Digestible dry matter yield increased throughout the season until it declined in late September. Total nonstructural carbohydrate levels were lower than previously found in native C4 grasses and may not be as important for survival in Caucasian bluestem. Our data indicate that a mid‐June defoliation, with further defoliation up to late summer, may optimize Caucasian bluestem's potential in livestock grazing systems.

Soil Nitrogen Accumulation in Fertilized Pastures of the Southern Plains

Marginal farmlands seeded to grasses in the Southern Great Plains usually have been depleted in N by cropping, cultivation, and erosion. This study measured soil N accumulation over 20 to 22 years in N fertilized weeping lovegrass (Eragrostis curvula) or Old World bluestem (Bothriochloa caucasica) pastures seeded into old flelds as compared to adjacent unfertilized old field pastures dominated by sand dropseed (Sporobolus cryptandrus). Significantly more (P<O.05) total N was found in the surface 5 cm of soil from the fertilized pastures. Total N was not signiflcantly different between the old fleld and N fertilized pastures at greater depths. Two different samplings resulted in an estimated 8 and 5 kg N ha-lyrl (standard error of the mean difference 2.4, n=4 and 2.0, n=10, respectively) greater N accumulation in the N fertilized pastures as compared to the old fleld pastures. Nitrogen input into the N fertilized pastures as fertilizer and protein supplement was 45 kg N ha-lyrl greater than into the old fleld pastures. Thus, a relatively small proportion of the N input into the N fertilized pasture was accounted for as increased soil N. The N accumulation rate in the N fertilized pastures appears to be considerably slower than the N depletion rate under past farming practices.

Seedling Root Development and Morphology of Cool‐Season and Warm‐Season Forage Grasses

A detailed description of grass seedli ng root morphology is essential to understand the differences in the establishment process among grasses. A repeated greenhouse study using a 1:1 mixture of Sharpsburg silty clay loam (fine, montmorillonit|c, mesic Typic Argiudolls) and coarse sand was conducted to determine root morphology differences at the third‐leaf stage among nine cool‐season forage grasses, creeping foxtail (A1opecurus arundinaceous Poir., reed canarygrass, (Phalaris arundinacea L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), russian wildrye (Elymus junceus Fish.), crested wheatgrass [Agropyron cristatum (L.) Gaertn.], intermediate wheatgrass [A. intermedium (Host) Beauv.], and western wheatgrass (A. smithii Rydb.); and nine warm‐season forage grasses, sideoats grama [Bouteloua curtipendula (Michx.) Tort.], blue grama [B. gracillis (H.B.K.) Lag. ex. Steud.], sand lovegrass [Eragrostis trlchodes (Nutt.) Wood], big bluestem (Andropogon gerardii var. gerardii) Vitman), sand bluestem [A. gerardii var. paucipilus (Nash) Fern.], little bluestem [Schizachyrium scoparium (Michx.) Nash], caucasian bluestem [Bothriochloa caucasica (Trin.) C.E. Hobb.], indiangrass [Sorghastrum nutans (L.) Nash], and switchgrass (Panicum virgatum L.). These grasses were selected as representative forage grasses of the northern USA. Andropogoneae species reached third leaf emergence 3 to 5 days earlier than other warm‐season grasses and 3 to 15 days earlier than cool‐season grasses. Most cool‐season grasses had no or little subcoleoptile internode elongation except Aveneae species. Aveneae species and warm‐season grasses, except Chlorideae species, had root development from the subcoleoptile internode. Sand bluestem had less subcoleoptile internode root development than big bluestem. Seminal root development was greater in species of the Triticeae tribe. Adventitious root development occurred by the three‐leaf stage on species of all tribes except for Andropogoneae members. Most grasses were in a juvenile period of root growth at third leaf emergence. Stage of root development did not coincide with stage of shoot development among species.

Grazing Effects on the Total Nonstructural Carbohydrate Pools in Caucasian Bluestem1

AbstractTotal nonstructural carbohydrates (TNC) may be overemphasized relative to other factors governing plant survival in pastures. A grazing study was conducted on established 1‐ha pastures of Caucasian bluestem [Bothriochloa caucasica (Trin.) C.E. Hubb.] during 1983–1984 at the Forage and Livestock Research Laboratory, 2 km west of El Reno, OK. The objective was to compare allocation of TNC to leaf, stem (plus sheath), stem base, and dead components of heavily or lightly grazed Caucasian bluestem. Soils were fine‐silty Pachic Haplustolls of the Dale Series. Put‐and‐take stocking was used to maintain high and low grazing pressures from mid‐May to late September both years. Pastures were sampled four times in 1983 and three times in 1984 by excavating representative plants, separating them into plant parts, and analyzing for TNC. Heavy grazing pressure initially decreased (P&lt;0.1) concentrations of TNC in all living tissues. However, no differences in TNC concentration due to grazing pressure were found the second year. On six of seven sampling dates over 2 yr, grazing pressure did not affect (P&gt;0.1) the amount of TNC located in stem bases. Stem bases contained more than half the total shoot TNC in heavily grazed plants; however, lightly grazed plants contained much more total shoot TNC (as much as seven times greater) compared to heavily grazed plants, due to light utilization by animals. A densely appressed physical arrangement of stem bases provided sites for tiller initiation and protection from grazing. Crown architecture in Caucasian bluestem, together with physiological and morphological adjustments, ensured a nongrazeable mass of stem bases containing sufficient quantities of TNC to sustain plants under heavy grazing.