The USDA-Water Erosion Prediction Project (WEPP) is a new technology based on the fundamentals of hydrology, soil physics, plant science, hydraulics, and erosion mechanics. WEPP hydrology includes simulation of excess rainfall using the Green and Ampt infiltration equation, surface runoff routing, evapotranspiration, percolation, and surface drainage. Hydrometeorological, soil, topography, and vegetation data from a range in Texas were used to test the WEPP rangeland hydrology model. Measured surface runoff and root zone soil water content from the site were compared with the simulated results of the WEPP model. The results indicate that the WEPP model (version 93.0) is capable of simulating soil water content and storm runoff. The Nash and Sutcliffe coefficient, NSR, between measured and simulated root zone soil water content and storm runoff was .88 and .84, respectively, for the bare ground plots. However, for the plots with herbaceous vegetation the discrepancy between model simulated storm runoff and soil water content was more than expected (NSR = .46 and NSR = .53, respectively).

One identified potential source of error in nutritional evaluations using the in vitro technique is the drying method used on test substrates. This study was conducted to determine what effect, if any, different drying methods have on the dry matter disappearance of 4 browse species in moose (Alces alces L.) inoculum. Browse species were Scots pine (Pinus sylvestris L.), birch (Betula pendula Roth, Betula pubescens Ehrh.), willow (Salix spp.), and sweetgale (Myrica gale L.). In addition, we determined the effects of drying method on neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) concentration of the browse species. Each species was either freeze-dried (-40 degrees C) or oven-dried at 35 degrees, 60 degrees and 105 degrees C, respectively. High drying temperatures significantly depressed (P<0.0001) in vitro dry matter disappearance (WDMD) in all browse species tested except of Scats pine. High temperatures also reduced NDF (P<0.05) in all the species, while ADF and ADL were elevated (P<0.05) in all specks except Scats pine. We conclude that freeze-drying is the most preferable method to be used on forage and browse samples being evaluated for nutritional quality.

This study determined forage production and cover of several plant species resulting from the use of water harvesting catchments with catchment: cultivated area ratios of 1:1 and 1.25:1 and contributing aprons with 7, 10, and 15% slope gradients. Plots with 1.25:1 ratios produced more forage and had more cover than plots with 1:1 and 0:1 ratios. Plots with 7, 10, and 15% slope gradients had similar forage production and cover. Tuft planted plots produced more forage and cover than seeded plots. Ghorka (Elionurus hirsutus (Vahl) Munro), blue panicum (Panicum antidotale Retz.), and buffer (Cenchrus ciliaris L.) grasses produced similar forage and cover, which was higher than khev grass (Sporobolus helvolus (Trin.) Th. Dur. & Schinz) production and cover.

Studies were initiated in 1980 and 1984 to compare animal performance, dietary P levels, and serum mineral levels of P supplemented and unsupplemented replacement beef heifers (Bos taurus). Phosphorus supplementation levels averaged 4 g day-1 from 14 November 1980 and 24 January 1984, respectively, until 1 September 1980 and 15 October 1984, respectively, when supplemental P was raised to 6 g day-1. Heifers in both studies received mixed hay, primarily smooth bromegrass (Bromus inermis Leyss.), and rolled oats during their first winter and hay only the second winter. During the summer they grazed on native pastures which contained primarily western wheatgrass (Pascopyrum smithii (Rydb.) A. Love), needleandthread (Stipa comata Trin. and Rupr.), green needlegrass (S. viridula Trin.), blue grama (Bouteloua gracilis (H.B.K.) Griffiths), and upland sedges (Carex spp.). Hereford and Hereford-Angus cross heifers in the first study showed no weight gain or serum P response to supplemental P, but conception rate over the 2 studies was lower (P<0.05) for the unsupplemented heifers and 75% of the open heifers occurred in the first study. Hereford-Simmental heifers used in the second study demonstrated an immediate weight gain response (P<0.06) to supplemental P which persisted to the end of the study in 1985, but there was only 1 open heifer in the unsupplemented group in this study, compared to 3 in the first study. Serum P was higher (P<0.06) for P supplemented than control heifers only when they were removed from summer pasture in the second study. Diet P (2.10 g kg-1) for unsupplemented Hereford-Simmental heifers during the winter of 1984 was mar- ginal, but diet P (2.53 g kg-1) for unsupplemented Hereford and Hereford-Angus heifers during the winter of 1980-1981 was clearly above recommended levels. Modest weight gain differences in the second study, serum P data and differences in conception rate suggest that Northern Great Plains forages are marginal to deficient in P for replacement beef heifers, but P supplementation would be expected to produce small and variable benefits

A metabolism study evaluated the influence of increasing quantities (0-30% dry matter basis) of mountain big sagebrush (Artemisia tridentata ssp. vaseyana Rydb. Beetle) on dry matter intake and in vivo digestibility of wether diets. Diets consisted of hand-harvested, coarse-ground and frozen current year's growth of mountain big sagebrush leaves and twig tips mixed with chopped native grass hay. Dry matter intake decreased from 93 to 23 g dry matter day-1 kg metabolic weight-1 and in vivo dry matter digestibility from 59 to 0% with increasing levels of sagebrush in the diet. With increasing levels of sagebrush in the diet, water, lignin, and nitrogen contents increased in the diet, but decreased in the dung, while fiber components decreased in both the diet and dung. Total nitrogen intake decreased from 1.58+/-0.041 to 0.406+/-0.070 g day-1 kg metabolic weight-1, and nitrogen retention decreased from 0.80 g day-1 kg metabolic weight-1 with no sagebrush to a slight loss of nitrogen with 30% sagebrush in the diet. Mountain big sagebrush was not readily consumed by wethers when fed together with grass; as low as 10% sagebrush in the diet seems to adversely influence intake and digestibility. Therefore, when other more favorable forages are not available, sheep and other ruminants with similar physiological responses to mountain big sagebrush may not meet their nutrient requirements through increased sagebrush consumption.

Grazing can have a profound impact on soil water through its influence on infiltration via treading and on evapotranspiration through defoliation. Hydrologic changes in rangelands are most often associated with heavy grazing intensities although these changes do not increase linearly with grazing intensity. The objectives of this study were to quantify the impacts of grazing on the soil water regimes of sloped areas of the foothills fescue grasslands of Alberta. The study site was located at the Agriculture Canada Research Station at Stavely, Alberta. The effects of 2 grazing intensities (heavy = 2.4 AUM ha-1 and very heavy =4.8 AUM ha-1) for 2 grazing treatments (short duration = 1 week in mid-June and continuous grazing = May through October) were compared to an ungrazed control. The study was initiated in June 1988 and ended in April 1991. Surface soil water and soil water with depth were measured throughout each growing season using a neutron probe. Surface soil water (0 to 7.5 cm) across slope positions was lowest in the control and highest in the continuous very heavy treatments, but the trend in profile soil water (to 50 cm) was the opposite. Total profile soil water in the short duration very heavy treatment was greater than that in the continuous very heavy treatment, while soil water in the short duration heavy treatment was similar to that in the continuous heavy treatment. Vegetation at the study site was regularly water-stressed, as evidenced by soil water that was often below permanent wilting point, generally by mid-summer each year. Soil was near or below permanent wilting point in the autumn, regardless of its status throughout the growing season. Profile soil water was similar across treatments in autumn, indicating vegetation is using all available soil water. In contrast, soil water was generally near or above field capacity every spring, indicating the importance of snowmelt infiltration in these ecosystems. Only major (greater than 75 mm) summer rainstorms recharged soil water to field capacity. Thus it is concluded that maintenance of a vegetative cover that will trap snow for potential snowmelt infiltration is critical to soil water recharge of these ecosystems. Any grazing management regime that enhances litter accumulation and carryover should facilitate such snowmelt soil water recharge.

Thirty-six weanling steer calves (avg wt = 174 +/- 14 kg) were grazed on either wheat, irrigated improved, or native rangeland pastures from December 1989 to December 1990. Irrigated improved pastures consisted of 2 cool-season [tall wheatgrass [Agropyron elongatum (Host.) Beauv.], tall fescue (Festuca arundinacea Schreb.) 2 warm-season [bermudagrass (Cynodon dactylon (L.) Pers.], bluestem (Bothriochloa ischaemum Keng.), and annual wheat. Wheat pastures were grazed from 13 December to 11 April. Warm-season pastures were grazed from 30 May (bermudagrass) or 27 June (bluestem) until 3 October. Cool-season pastures were grazed at other days during spring and fall seasons. Rumen evacuation procedures were used to evaluate forage quality and estimate forage intake during each grazing season. Winter rangeland pastures were lower in nutritional quality (based on protein and fiber contents) and in vitro organic matter digestibility (53 vs 85%, P < 0.05) compared to wheat pasture. During spring, rangeland pastures were still lower in protein and higher in fiber but in vitro organic matter digestibility (72, 73, 72%; respectively, for wheatgrass, fescue and rangeland) was similar (P = 0.70) for all forages. Rangeland and warm-season pastures were similar in quality during summer but rangeland pastures were higher (P< 0.10) in in vitro organic matter digestibility (65, 69, and 73%; respectively, for bermudagrass, bluestem, and rangeland). Rangeland pastures were again lower in quality and digestibility than cool-season grasses during the fall. There were no difference (P>0.10) in organic matter intake (% of body weight) during winter, summer, and fall season but during spring organic matter intake was greater (P < 0.10) for steers on rangeland pasture than for those on cool-season grasses.

To understand how different techniques might affect diet estimates for cattle, the esophageal-fistula and bite-count techniques were compared using trained cattle. For the Texas Coastal Bend, bite-count was not as reliable a technique as the esophageal fistula. These techniques differed in estimation of forage classes and plant species in cattle diets. The esophageal-fistula technique was more accurate however, the bite-count technique may be acceptable if analyses are limited to only those plant species making up >2% of the diet.