Water limits the establishment, growth, and production of cool-season grasses on semiarid rangelands, and plant improvement programs for these areas must be capable of screening breeding lines for response to drought. Although many techniques to evaluate various morphological and physiological characteristics have been proposed, few have been used successfully in plant breeding programs. Consequently, a need exists to identify and develop rapid, reliable screening techniques that can assess integrated plant response to drought in large plant populations. Improved seedling emergence has been achieved in Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] by selecting for emergence from a deep seeding depth and long coleoptiles. Water uptake by roots is critical, and screening for enhanced seedling root growth in cool-season grasses offers considerable promise. In spite of the important role that stomatal control has in regulating plant water loss, limited success has been achieved in incorporating desirable stomatal characteristics into improved grass cultivars. Although osmotic adjustment appears beneficial in some crop species, more research is needed before cool-season grasses should be selected based on osmotic adjustment. Selection for improved water-use efficiency in cool-season grasses based on carbon isotope discrimination is a promising approach. Successful incorporation of these various traits into improved cool-season grass cultivars necessitates close cooperation between breeders and physiologists.

Plant structure should be an important determinant of species acceptability to grazing ungulates functioning under various time-energy constraints. The acceptability of 9 grasses to sheep grazing a secondary grassland community in spring, summer, and autumn in South Africa was related to the following species attributes: plant height, leaf table height, tussock diameter, stemminess, percent leaf, leaf density, percent dry matter (DM), leaf tensile strength, and leaf crude protein (CP). Species acceptability over the grazing season was positively related to tussock diameter (P less than or equal to 0.05) but negatively related (P less than or equal to 0.01) to leaf tensile strength and DM. Discriminant function analysis successfully discriminated between species in different acceptability classes in summer (P less than or equal to 0.05) and autumn (P less than or equal to 0.01) using a combination of plant structure and leaf quality attributes. Correspondence analysis indicated that preferred species were generally short and nonstemmy and had leaves of low DM, low tensile strength, and high crude protein content. Conversely, avoided species tended to be tall and stemmy with a high leaf table height, and had leaves of high DM and tensile strength but low CP levels. It is concluded that, for sheep, acceptability is determined by a combination of plant structure and leaf quality attributes.

Eight ruminally cannulated crossbred steers (average weight 336 kg) grazing native blue grama (Bouteloua gracilis [H.B.K.]) rangeland were used in a repeated measures design to evaluate effects of monensin ruminal delivery devices (MRDD) and forage phenology on ruminal digestion. Three periods were assessed: mid-August (Aug.), early October (Oct.), and mid-November (Nov.). One MRDD was placed in the reticulum of 4 steers via the ruminal cannula 21 days before each period. Intake was estimated using total fecal collections. Diet samples were collected using 3 esophageally fistulated steers. Ruminal fill was measured by ruminal evacuation; rate and extent of in situ ruminal neutral detergent fiber disappearance were estimated before ruminal evacuations. Ruminal passage rates, retention time, and apparent total tract organic matter digestibility were estimated using indigestible neutral detergent fiber. In vitro organic matter disappearance of esophageal masticate did not differ (P > .05) in Aug. and Oct. (average of 53.7%), but declined (P < .05) in Nov. (48.7%), whereas organic matter digestibility was greater (P < .10) in Aug. (62.3%) than in either Oct. (55.2%) or Nov. (53.9%). Release of monensin from the bolus (68 mg day-1) was less than expected (100 mg day-1). Intake, organic matter digestibility, ruminal passage rates, retention time, pH, and ammonia were not affected (P > .10) by MRDD. In situ neutral detergent fiber disappearance at 96 hours was decreased (P < .10) by MRDD (68 vs 65% for control and MRDD, respectively). As the grazing season progressed, intake declined (P < .10), whereas ruminal fill and retention time increased (P < .05), and passage rate of indigestible neutral detergent fiber decreased (P < .05). At 48 hours in situ neutral detergent fiber was greatest (P < .05) in Aug. and least (P < .05) in Nov.

Experiments were conducted to investigate efficiency in analysis of fecal samples by near infrared reflectance spectroscopy (NIRS) to predict cattle forage diet quality. Stability of fecal samples during shipping and methods of reducing analysis time were evaluated. In experiments with actual and simulated shipping, no difference was found between predictions from samples shipped fresh or frozen, allowing analysis time to be reduced by 1 day. Drying procedures were developed which allowed sample analysis 24 hours after arrival in the lab for an additional reduction of 1 day in analysis time. Minimal effects on NIRS predictions were observed for simulated shipping delays up to 12 days for crude protein and 14 days for digestible organic matter.

The response of selected plant species to a single application of factorial combinations of nitrogen (N), phosphorus (P), and sulfur (S) on 2 lodgepole pine (Pinus contorta Dougl.) clearcut-logged sites in British Columbia was evaluated over 3 years. Increasing N rates typically resulted in higher forage standing crop on both sites, in all years. but standing crop at Fly Creek was nearly double that at Beaverdam Lake. On both sites, forage yields peaked at 400 kg N/ha in 1982 and carry-over of the fertilizer effect lasted for 3 years although yields declined annually. Addition of P to N applications enhanced (P < 0.05) total standing crop, other grass standing crop, and pinegrass (Calamagrostis rubescens Buckl.) standing crop at Beaverdam Lake and grass standing crop at Fly Creek, but had no effect (P > 0.05) on other species and groups. Sulfur, added to N applications, enhanced total yields compared to control on both clearcuts although at Fly Creek this response nearly doubled that produced at Beaverdam Lake. Nitrogen fertilization increased (P < 0.05) pinegrass crude protein (CP) content, particularly in the first year after fertilization. Acid detergent fiber (ADF) generally increased in response to increasing N levels in 1982, but declined compared to control in 1983 and 1984. Elevated forage CP levels, litter N concentrations, and soil N levels in 1984 indicated that the carry-over response on these forest sites resulted directly from N remaining in the soil or again becoming available for plant growth.

The effects of droplet size and spray volume (spray-mixture application rate) on honey mesquite (Prosopis glandulosa Torr.) mortality were evaluated using 0.55 to 0.58 kg ae (acid equivalent) ha-1 clopyralid (3,6 dichloro-2-pyridinecarboxylic acid). A factorial combination of 3 spray volumes (19, 37, and 75 liters ha-1) and droplet sizes of 325 +/- 25, 475 +/- 25, and 625 +/- 25 micrometers nominal volume median diameter were replicated 3 times at both Andrews and Big Lake, Tex., during June 1989. The experiment was repeated in 1990 at Big Lake and Campbellton, Tex., without the 75 liters ha-1 spray volume. Honey mesquite mortality and canopy reduction 16 months after application were significantly less on the 625 micrometer droplet treatments in 2 of 4 experiments, when compared to plots treated with smaller droplet sizes. Mortality increased with larger spray volumes, particularly with 625 micrometer droplets. Relative mortality data from the 4 experiments clearly demonstrated that larger droplet sizes require larger spray volumes for greatest efficacy.

The mass of grass roots of blue grama (Bouteloua gracilis (HBK.) Lag. ex Steud) and rough fescue (Festuca campestris Rydb.) to a depth of 13 cm is similar but the carbon contents of their respective soils are quite different. The objective of the present study was to determine some of the physical and chemical changes of blue grama and rough fescue root masses during decomposition under both Brown (Mixed Prairie) and Black Chernozemic (Fescue Prairie) soil-forming conditions. Roots of each species in fine-mesh nylon bags were buried in the Ah horizon of both a Brown and a Black Chernozemic soil. Sixteen collections were made between November 1987 and June 1989 to determine diminution, loss of dry matter and gross energy, and changes in the concentration of carbon, nitrogen, methoxyl groups, alkaline-soluble organic acids and phenols, structural and nonstructural carbohydrates, lignin, and monosaccharides. Differences in substrate quality were only partially responsible for the increased decomposition of root mass in the Brown Chernozemic soil-forming environment. Comminution of root mass was significantly greater under the Mixed Prairie than under the Fescue Prairie conditions for both species. The nitrogen content of blue grama roots increased (from 1.17 to 1.56%) while that of rough fescue decreased (from 1.53 to 1.26%) significantly over the duration of the experiments at both sites. Methoxyl group content and energy levels were not useful parameters. Organic acid, phenols, and nonstructural carbohydrate contents decreased with time. Lignin concentration displayed a significant upward trend for both species (from 232 to 280 for blue grama and for 205 to 247 mg/g for rough fescue) in the Black Chernozemic soil only.

In a 4-year field study, 25 perennial triticeae grasses, representing a wide range of genomes and genome combinations, were evaluated as potential hosts for the bluegrass billbug (Sphenophorus parvulus Gyllenhal [Coleoptera: Curculionidae]). Root-sample data suggested that Russian wildrye (Psathyrostachys juncea [Fischer] Nevski) was unsuitable for billbug reproduction. Numbers of immatures varied significantly among remaining entries. Rhizomatous entries were more tolerant of billbug injury than caespitose entries. Plant mortality rates were frequently 50% or higher for self-pollinated caespitose entries with the SH genome complement (Elymus spp.). Losses to billbugs among the remaining species, particularly those with the J, N, and P genomes, were insignificant. Billbugs did not discriminate between native and introduced grasses, as resistant and susceptible entries were identified in both groups. The results obtained here may aid in selecting triticeae grasses for reseeding in areas where billbugs have damaged stands in the past.