Atrazine [6-chloro-N-ethyl-N’-(l-methylethyl)-1,3,4-diamine] provides effective weed control during big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) establishment. However, most other desirable warm-season grasses are susceptible to atrazine injury at establishment. The objective of this study was to determine if atrazine application after seeding would affect susceptible warm-season grass establishment. Big bluestem, switchgrass, indiangrass [Sorghastrum nutans (L.) Nash] sideoats grama [Bouteloua curtipendula (Michx.) Torr.], and little bluestem [Schizachyrium scoparium (Michx.) Nash] were seeded into greenhouse flats or field plots and 2.2 kg a.i. atrazine/ha applied at 0 (atrazine control), 7, 14, or 21 days after planting. An untreated control was used also. In greenhouse experiments, Indiangrass and sideoats grama plant survival increased when atrazine applications were delayed. Switchgrass, big blue stem, and little bluestem plant survival was not affected by atrazine application. Field studies were conducted in 1983, 1985, and 1986 using the same soil type, grass species, and application periods as the greenhouse study. Delaying atrazine application 7 or more days after planting generally favored survival of lndlangrass and sideoats grama. Big bluestem, switchgrass, and little bluestem were not affected by atrazine treatment. Delaying the application of atrazine may favor the survival of atrazine sensitive species. However, further research needs to be conducted on various soil types and environmental conditions before this can be a recommended practice.

Liveweight (LW) changes and behavior of growing rams were measured in 1981, 1982, 1985, and 1986 at the Timahdit Experiment Station in the Middle Atlas, Morocco, at stocking rates of 2.78, 4.17, and 6.67 rams/ha during the growing season. Maximum animal production would have occurred at a stocking rate greater than any imposed in the study in all years except 1982. Increased variable costs should drive stocking rates down while increased selling price would provide an incentive to increase stocking rates. Mean grazing time of animals stocked at tight, moderate, and heavy rates was 410, 436, and 504 minutes/day, respectively. Mean resting time was 206, 174, and 106 minutes/day, respectively. Rams under light, moderate, and heavy stocking rates walked 2.1, 2.4, and 3.1 km/day, respectively. Diet IVDMD was highest early in the grazing season and lowest in the nongrowing season, and was not affected by stocking rates. Early in the spring, diet diversity was low, increased during active growth, and then deciined as the season advanced. Selectivity was lowest when forage was abundant. Dry matter intake varied with season in 1985 but not 1986. There was less opportmdty to be adaptive under heavy than under light stocking, resulting in a stocking rate by season interaction in 1986. Under heavy stocking, forage intake (G/kg LW/min) was 61 and 83% of intake under light and moderate stocking, respectively, and forage intake per km walked was 71 and 84%, respectively

Globemallows (Sphaeralcea spp.) have potential in rangeland seedings. Thirty-seven accessions of globemallow were grown at 2 sites in northern Utah and southern Idaho to quantify their agronomic attributes. Data for transplant survival, standing crop, and seed yield were collected in 1987 and 1988. Total globemallow survival (mean = 92%) and seed weights (mean = 0.8 g/plant) differed significantly (P is lesser than or equal to 0.05) among locations. Plant weight (mean = 102 g/plint) differed significantly (P is lesser than or equal to 0.05) among locations, species (S. grossulariifolia, S. coccinea, S. parvifolia, S. munroana, and interspecific hybrids), and years. In a second study, 5 globemallow accessions of 2 species and ‘Spredor 2’ alfalfa (Medicago sativa) were grown with ‘Hycrest’ crested wheatgrass (Agropyron desertorum X A. cristatum) to determine forage yields from 1985-1988. Globemallows produced significantly (P is lesser than or equal to 0.05) less forage (62 g/ml) than alfalfa (389 g/m2). Forage yield of S. munroana (76 g/m2) did not differ significantly (P>0.05) from that of S. grossulariifolia (48 g/m2). Forage yield of crested wheatgrass (mean = 101 g/m2) did not differ significantly (P>0.05) when grown with globemallow versus alfalfa. Plant breeding and selection could probably improve these agronomic attributes for globemallows seeded on rangelands.

Sixteen ruminally cannulated beef steers grazing native summer range in the Northern Great PIains were assigned to 4 treatments in a 2 X 2 factorial arrangement. Main effects were barley grain and monensin. Rolled barley (RB) containing 7.5% molasses was fed at 0 and 1.36 kg head-1 day-1. Steers received no monensin (M) or M released at 101 mg/d via a ruminal delivery device. Forage intake and digestibiIity, ruminal fermentation, and ruminal passage rate were measured during trials in: (1) June, (2) July, and (3) August. Diet samples were collected from esophogeally fistuIated steers during each trial. Dietary crude protein was greater (P<0.05) during trials 1 (15.2%)and 3 (14.3%) than in trial 2 (10.2%). In vivo organic matter (OM) digestibiiity, ruminal fluid passage rate, and fermentation variables varied by trial (P<0.01). Forage OM intake was reduced (P<0.10) by RB, but was not influenced (P>0.10) by M or the M and RB combination. In vivo OM digestibility was increased (P<0.05) by M, while RB had no effect. Particulate passage was not affected by M or RB but gastrointestinal tract fill was reduced by monensin (P<0.05). Ruminal fluid passage rate was affected by the RB X M X Trial interaction (P<0.05). Within June and July, fluid passage rate was similar among treatments and ranged from 14.0 to 11.3 %/h, respectively. During trial 3, a RB X M interaction (P<0.05) increased fluid passage rate. Ruminal ammonia-N concentration was similar among treatments. Barleey lowered (P<0.05) ruminal pH and increased (P<0.10) total volatile fatty acids. A RB X M X Trial interaction (P<0.05) was noted for molar proportions of acetate, propionate, and butyrate. Within trials, RB, M, and their combination affected (P<0.01 to P<0.10) acetate, propionate, and butyrate. We conclude that barley, monensin, and forage quality infiuence ruminal fermentation, passage rate, and intake traits of steers grazing summer range.

Differences in growth rate among 3 subspecies of big sagebrush (basin big sagebrush, mountain big sagebrush, and Wyoming big sagebrush) for mature plants have been reported by a number of workers. Little has been reported on comparisons of seedling growth rate among these 3 subspecies. Results of this study indicated that (1) over an extended period and in a non-water-limiting environment, the rate of seedling growth In Wyoming big sagebrush approached zero and was less than that of seedlings of basin and mountain big sagebrush; (2) basin and mountain big sagebrush continued to have nonnegligible growth rates even at the end of the study; and (3) Wyoming big sagebrush reached its point of maximum growth rate approximately 2 weeks earlier than did the other 2 subspecies. It appears that Wyoming big sagebrush has evolved, placing 2 important growth characteristics under genetic control: (1) the maximum growth rate is attained earlier (when more water is available to sustain such growth) than in the other 2 subspecies, possibly enhancing its ability to survive on xeric sites during the early stages of growth; and (2) top growth produces smaller aboveground parts, enhancing survival after the early stages.

This study determined responses of vegetation and soils to different rates and seasonal schedules of first-year irrigation in combination with varied N-P fertilization on cold desert mined lands. Certain irrigation treatments increased soil water content initially, but had no appreciable effects on soil salinity or fertility. Specific rates and schedules of irrigation temporarily benefited total stand and dominant perennial grass establishment and productivity, but treatment effects diminished or reversed over time. Subdominant shrubs and perennial forbs were more persistently enhanced by specific irrigation treatments. Fertilization did not modify plant response to irrigation regimes. Although annual species were positively influenced by fertilization with heavier rates of irrigation, such stimulation proved ephemeral and perennial species never responded to fertilization under any irrigation regime.

Herbage biomass for blue grama (Bouteloua gracilis [H.B.K. Lag]), pinyon ricegrass (Piptochaetium fimbriatum [H.B.K.] Hitche.), New Mexico muhly (Muhlenbergia pauciflora Buckl.), other grasses and forbs was estimated on 25 pinyon-juniper stands of varying overstory cover on the Fort Stanton Experimental Ranch in south-central New Mexico. Negative 2nd degree polynomial curves best expressed the relationships between total understory and blue grama biomass and overstory canopy cover. Positive polynomial relationships were shown for cool-season graazs, New Mexico muhly, and pinyon ricegrass. Reducing pinyon-juniper canopy cover would likely increase blue grama production and reduce production of New Mexico muhly and pinyon ricegrass.

A management strategy using short-duration grazing and fertilization was simulated in a study with individual ‘Ermelo’ weeping lovegrass [Eragrostis curvula (Shrad.) Nees] plants. Influence of 2 levels of clipping [unclipped during the growing season and clipped (C) to 10-cm stubble height each time regrowth reached 40 cm]; fertilizer [unfertilized and 70-34-44 kg N-P-K/ha (F)]; and watering frequency [irrigated to field capacity at 7- (WET) and 14 (DRY) day intervals] on cumulative herbage dry matter yield, crude protein yield, and water-use efficiency, and root mass of individual weeping lovegrass plants grown in soil contained in polyethylene tubes was determined. Clipping combined with fertilization improved herbage dry matter yield and water-use efficiency. Fertilized plants yielded at least 5.4 g crude protein/tube as compared to less than 2.0 g crude protein/tube produced by unfertilized plants. Between 1 June and 15 September 1983 WET-F- treated plants provided sufficient regrowth for 5 harvest events with an average of 24-day intervals between harvests. In contrast, regrowth of WET-, DRY-F, and DRY-treated plants was harvested 3 times with intervals between harvests averaging between 32 and 35 days. Clipping had no effect on root mass of WET-, DRY- F-, and DRY-treated plants, but reduced root mass of WET-F- treated plants by 44%. Based on this simulation of a fomge management strategy, periodii harvest of weeping lovegrass combined with fertilization improved herbage dry matter yield and water-use efficiency without adversely affecting root mass when interval between harvest events avenged 32 to 35 days.

Components of the organic matter were studied in soil under 3 Mixed Prarie types: grassland dominated by needle-and-thread/blue grama (Stipa comata Trin. and Rupr./Bouteloua gracilis (HBK.) Lag. ex Steud.) in good range condition; grassland significantly modified by grazing, dominated by blue grama and in poor range condition; and grassland, dominated by needle-and-thread/blue grama in good range condition, but converted to cropland and under continuous wheat for 4 years. The soils were sampled on 13 April 1988. Concentrations of total organic carbon in the upper 2 cm were 1.39, 2.70, and 1.87%, respectively. The higher organic carbon under blue grama was caused by an active, ramified, fine rootmass which gave rise to most of the monosaccharides being of microbial origin. The monosaccharides in the lower Ap horizon in the cropland were generally of plant origin from incorporated straw. The Ah horizons of the needle-and-thread/blue grama and blue grama sites and the Ap horizon of the cultivated site yielded 244, 696, and 370 migrograms g-1 organic acids in the alkaline-soluble fraction of the soil, respectively. Although most of the organic compounds identified were present in all 3 soils, the quantitative patterns were quite different. Differences exist due to inputs by different species, and 4 years of cropping also made significant soil chemical changes. This study demonstrated the importance of recognizing the history of the soils studied when describing soil quality.