Northern Wheatgrass Research Articles

Mixed‐Prairie Well Site Reclamation with Natural Recovery, Seeding, and Grazing

Reclamation of surface disturbances on grasslands is an important management issue. This research examined how cattle grazing and revegetation treatments influenced vegetation development on mixed-prairie well sites. Three seed mix treatments, dominant wheatgrass (a Triticeae tribe) (four species providing 95% wheatgrass seed in the seed mix), nondominant wheatgrass (five species with 80% nonwheatgrasses in the seed mix), and diverse (22 grass and forb species), plus a natural recovery (unseeded) treatment, with and without cattle grazing, were compared with undisturbed (control) prairie for soil seedbank, vegetation composition, ground cover, and biomass. The nondominant wheatgrass seed mix resulted in communities dominated by wheatgrass species, whereas natural recovery was dominated by early and midseral species. Seeding yielded greater aboveground biomass with < 20% bare ground; natural recovery biomass was slightly less with greater bare ground (grazed 45%, ungrazed 23%). Cattle grazing reduced cover of northern wheatgrass (Elymus lanceolatus [Scribn. & J.G.Sm.] Gould) in seeded treatments. Species richness and diversity were greater with natural recovery than with seeding and in undisturbed prairie. Multivariate tests showed that plant community composition in undisturbed prairie and natural recovery differed from seeded treatments; natural recovery was dominated by early to midsuccessional species. The short-term patterns of change in different vegetation parameters suggest that irrespective of grazing, natural recovery and seeding with a diverse native seed mix could be effective approaches for mixed-prairie reclamation.

Grass Yields Under Clipping and Watering Explain Varied Efficacy of Management Intensive Grazing on Rangelands

Management intensive grazing (MIG) may not maximize plant productivity on rangelands because of morphophysiological traits of grassland vegetation. We examined defoliation and moisture effects on the biomass yield of rhizomatous and caespitose grass pairs that were either phylogenetically similar or of similar agroclimatic adaptation, including two agronomic grasses. From relatively low to high moisture regime adaptation, species pairs included western wheatgrass (Pascopyrum smithii [Rydb.] A. Love) and needle-and-thread (Hesperostipa comata [Trin. & Rupr.] Barkw.), northern wheatgrass (Elymus lanceolatus [Scribn. & J.G. Sm.]) and western porcupine grass (H. curtiseta [Hitchc.] Barkw.), plains and foothills rough fescue (Festuca hallii [Vasey] and F. campestris Rydb.), and smooth and meadow brome (Bromus inermis Leyss. and B. riparius Rehm). Response variables were shoot yield, root-shoot ratio, and water-use efficiency. We hypothesized that caespitose grasses, regardless of their origin or adaptation to agroclimate regime, would respond more determinately in biomass accumulation. Defoliation effects on shoot biomass were more pronounced under high moisture. Low intensity−high frequency defoliation yielded similarly to deferred controls in all grasses, and the same was true for high-intensity−low-frequency (HILF) defoliation in 1 rhizomatous grass. Three of the 4 rhizomatous grasses and 1 caespitose grass yielded greater under HILF defoliation compared with high-intensity−high-frequency defoliation. Caespitose grasses allocated more biomass to roots under low moisture conditions. Water-use efficiency decreased under high moisture conditions and more intense and/or frequent defoliation and peaked in agronomic grasses. Overall, our results suggested that growth patterns corresponded more with phylogenetic similarity as opposed to growth form. A conceptual model from these results showed that across all species, only the introduced bromes generated greater biomass under HILF defoliation, and this may explain why past research consistently concludes that MIG does not enhance plant productivity on rangelands.

Genetic Diversity of Northern Wheatgrass (Elymus lanceolatus ssp. lanceolatus) as Revealed by Genotyping-by-Sequencing

Recent advances in next generation sequencing technologies make genotyping-by-sequencing (GBS) more feasible for the molecular characterization of plant germplasm with complex and unsequenced genomes. This study represents the first preliminary effort using GBS to discover genome-wide genetic variants of northern wheatgrass (Elymus lanceolatus ssp. lanceolatus (Scribn. and J. G. Sm.) Gould) plants and to assess the genetic diversity present in four cultivated and six wild accessions. The effort generated the first novel set of genomic resources and 5659 single nucleotide polymorphism (SNP) markers for this tetraploid grass. The diversity analysis revealed 8.8% of SNP variation residing among the 10 accessions and 1.9% SNP variation present between cultivated and wild accessions. The Bayesian analysis identified three major clusters of the assayed samples, and the principal coordinates analysis revealed the genetic distinctness of the two accessions collected from Nevada and Wyoming. The flow cytometry analysis confirmed the tetraploid nature of some of the assayed samples and estimated the average genome size to be 9.3–9.4 Gb for this species. These findings are useful for the genetic improvement of this native grass species for forage production and rangeland reclamation. The findings are also encouraging for the broad application of genotyping-by-sequencing in the characterization of genome-wide genetic variability in non-model polyploid plants.

Utilizing a multi-index decision analysis method to overall assess forage yield and quality of C3 grasses in the western Canadian prairies

Seasonal dynamic of forage quality and yield has a major impact on livestock production. A sound evaluation on quality and quantity of forage is useful for cost-effective utilization of forage. However, forage quality and yield can vary with forage species, harvest seasons and yearly climate conditions. To improve forage use efficiency, a field experiment (2008–2010) was conducted in Swift Current, Saskatchewan, Canada. Dry matter yield and quality indicators (fiber, protein, digestibility and minerals) were measured for nine cool-season grasses harvested in June, August and October. The interrelationships and attributes among quality indicators were determined by principal component analysis (PCA) and the weights of quality indicators were calculated by entropy weight (EW) method. To synthesize different attribute indicators into a comprehensive index that reflects quality ranking of different forage species, an integrated multi-index decision analysis method, i.e., PCA-based TOPSIS with EW, was used in this paper. The evaluation process and results showed that the interrelation patterns and positive or negative attributes for quality indicators were consistent with years and harvest seasons, whereas the rankings of most grasses in yield and comprehensive quality varied with years and harvest seasons. According to the yearly and seasonal rankings of forage quality and yield, flexible production tactics and adaptive management techniques should be considered within the western Canadian prairie region. For instance, Northern wheatgrass (Agropyron dasystachyum) can be recommended to be mixed with high quality forages due to its high yield in any harvest season. Meadow bromegrass (Bromus Riparius) can be recommended to be mixed with high yield forages due to its high quality in summer and fall. These findings will provide valuable information for forage breeders, and livestock and forage managers to maximize grass utilization efficiency while balancing yield and quality.

Priming seeds in aqueous smoke solutions to improve seed germination and biomass production of perennial forage species

Seeds of many forage species have dormancy, delaying germination in the field. Species from semi-arid environments may have adaptation to fire, therefore, the effects of priming seeds of common forage species in aqueous smoke solutions were studied. Seeds of eight grasses and two legumes were primed in serial dilutions of aqueous smoke solutions and then dried before germination tests. Depending on the species and concentrations of solutions, priming seeds acted independently or in interaction with light and (or) temperature to improve germination in Altai wildrye (Leymus angustus), green needlegrass (Nassella viridula), Kura clover (Trifolium ambiguum), needle-and-thread (Hesperostipa comata), northern wheatgrass (Elymus lanceolatus), orchard grass (Dactylis glomerata), plains rough fescue (Festuca hallii), Russian wildrye (Psathyrostachys juncea), and western wheatgrass (Pascopyrum smithii). Priming seeds of cicer milkvetch (Astragalus cicer) in distilled water or aqueous smoke solutions had no effect o...

A comparison of the effects of silver nanoparticles and silver nitrate on a suite of soil dwelling organisms in two field soils

Nanomaterials are increasingly used in a wide range of products, leading to growing concern of their environmental fate. In order to understand the fate and effects of silver nanoparticles in the soil environment, a suite of toxicity tests including: plant growth with Elymus lanceolatus (northern wheatgrass) and Trifolium pratense (red clover); collembolan survival and reproduction (Folsomia candida); and earthworm avoidance, survival and reproduction (Eisenia andrei) was conducted. The effect of silver nanoparticles (AgNP) was compared with the effect of ionic silver (as AgNO3) in two agricultural field soils (a sandy loam and a silt loam). Lethal (LC50) or sub lethal (IC50) effect levels are presented for all endpoints and demonstrate that in most cases AgNO3 (i.e. ionic silver) was found to be more toxic than the AgNP across test species. The difference in effects observed between the two forms of silver varied based on test species, endpoint and soil type. In tests that were conducted across different soil types, organisms in the sandier soil had a greater response to the Ag (ionic and nano) than those in soil with a high silt content. Earthworms (avoidance behavior and reproduction) were the most sensitive to both AgNP and AgNO3, while plant emergence was the least sensitive endpoint to both forms of Ag. The use of a test battery approach using natural field soils demonstrates the need to better quantify the dissolution and transformation products of nanomaterials in order to understand the fate and effects of these materials in the soil environment.

Late summer forage yield, nutritive value, compatibility of warm- and cool-season grasses seeded with legumes in western Canada

Biligetu, B., Jefferson, P. G., Muri, R. and Schellenberg, M. P. 2014. Late summer forage yield, nutritive value, compatibility of warm-and cool-season grasses seeded with legumes in western Canada. Can. J. Plant Sci. 94: 1139–1148. In late summer and fall, quality and quantity of forage are important for weight gain by grazing animals in western Canada. The objective of this study was to evaluate forage nutritive value, dry matter (DM) yield, and compatibility of crested wheatgrass [Agropyron cristatum (L.) Gaertn.], meadow bromegrass (Bromus riparius Rehm.), green needle grass [Nasella viridula (Trin.) Barkworth], northern wheatgrass [Elymus lanceolatus (Scribn. &amp; J. G. Sm.) Gould], western wheatgrass [Pascopyrum smithii (Rydb.) Barkworth &amp; D.R. Dewey], Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], big bluestem (Andropogon gerardii Vitman), or switchgrass (Panicum virgatum L.) in eight grass monocultures, and their binary mixtures with alfalfa (Medicago sativa L.), sainfoin (Onobrychis viciifolia Scop.), or cicer-milkvetch (Astragalus cicer L.) harvested once in August or September. A field study was conducted over a 7-yr period from 1998 to 2004 near Swift Current (lat. 50°25'N, long. 107°44'W, 824 m elev.), SK, Canada, using a randomized complete block design. Forage DM yield was similar between August and September harvests (P&gt;0.05). Binary mixtures of alfalfa–grass produced highest (P&lt;0.05) DM yield ranging from 2449 to 2758 kg ha−1. The monoculture of crested wheatgrass (2143 kg ha−1), sainfoin with crested wheatgrass (2061 kg ha−1), and cicer-milkvetch with green needle grass (1838 kg ha−1) or cicer-milkvetch with western wheatgrass (1861 kg ha−1) produced the second highest (P&lt;0.05) DM yields in the ranking. The two warm-season grasses produced the lowest (P&gt;0.05) DM yields over the 7-yr period. Monocultures of green needle grass or northern wheatgrass had the highest acid detergent fiber (ADF) and neutral detergent fiber (NDF), while warm-season grasses with legumes had the lowest. Alfalfa with western wheatgrass and alfalfa with Russian wildrye had the highest crude protein (CP) concentrations. Monocultures of meadow bromegrass, crested wheatgrass, green needle grass, or cicer-milkvetch with meadow bromegrass, and sainfoin with crested wheatgrass had the lowest CP concentrations. In vitro organic matter digestibility (IVOMD) was greater for mixtures than for the grass monocultures. Concentration of Ca and P was greater for warm-season grasses than cool-season grasses. Alfalfa with western wheatgrass was the best combination considering yield, quality, and compatibility for deferred grazing in late summer and fall in the semiarid prairies. Tested warm-season grasses are not recommended for seeding as binary mixtures with legumes for southwestern Saskatchewan.

Ecotoxicity of Aged Uranium in Soil Using Plant, Earthworm and Microarthropod Toxicity Tests

Discrepancies about probable no effect concentrations (PNEC) for uranium in soils may be because toxicity tests used freshly contaminated soils. This study used 3 soils amended with a range of uranium concentrations 10years previously. The toxicity tests with northern wheatgrass (Elymus lanceolatus); earthworm (Eisenia andrei) were not affected below ~1,000mgUkg(-1), and the soil arthropod Folsomia candida was not affected below ~350mgUkg(-1). Survival of Orthonychiurus folsomi was diminished 20% (EC(20)) by ~85-130mgUkg(-1), supporting a PNEC in the range of 100-250mgUkg(-1) as derived previously.

Above-Ground Net Primary Production for Elymus lanceolatus and Hesperostipa curtiseta After a Single Defoliation Event

Abstract Above-ground net primary production (ANPP) of northern wheatgrass ( Elymus lanceolatus [Scribn. & J. G. Sm.] Gould) and western porcupine grass ( Hesperostipa curtiseta [Hitchc.] Barkworth) was determined after defoliation to a 7.5 cm stubble height on five landform elements in the Northern Mixed Prairie that had been ungrazed for > 25 yr. Landform elements included north aspect–concave slopes, north aspect–convex slopes, south aspect–concave slopes, south aspect–convex slopes, and level uplands. ANPP was determined for 2 yr after defoliating plots once in May, June, July, August, September, October, November, or April. Northern wheatgrass and western porcupine grass ANPP varied among landform elements ( P P ≥ 0.22). Month of defoliation did not influence ANPP of northern wheatgrass ( P ≥ 0.69), but that of western porcupine grass was reduced by August and September defoliations ( P

Toxicity of petroleum hydrocarbon distillates to soil organisms

Canadian standards for petroleum hydrocarbons in soil are based on four distillate ranges (F1, C6-C10; F2, >C10-C16; F3, >C16-C34; and F4, >C34). Concerns have arisen that the ecological soil contact standards for F3 may be overly conservative. Oil distillates were prepared and characterized, and the toxicity of F3 and two subfractions, F3a (>C16-C23) and F3b (>C23-C34), to earthworms (Eisenia andrei), springtails (Orthonychiurus folsomi), and northern wheatgrass (Elymus lanceolatus), as well as the toxicity of F2 to earthworms, was determined. Clean soil was spiked with individual distillates and measured concentrations were determined for select tests. Results agree with previous studies with these distillates. Reported toxicities of crude and petroleum products to invertebrates were generally comparable to that of F3 and F3a. The decreasing order of toxicity was F3a > F3 > F3b with invertebrates, and F3a > F3b > F3 with plants. The toxicities of F3a and F3b were not sufficiently different to recommend regulating hydrocarbons based on these distillate ranges. The results also suggest that test durations may be insufficient for determining toxicity of higher distillate ranges, and that the selection of species and endpoints may significantly affect interpretation of toxicity test results.

Comparison of biological and chemical measures of metal bioavailability in field soils: Test of a novel simulated earthworm gut extraction

Bioavailability of metals in soil is a major factor influencing estimates of risk associated with exposure of ecological receptors. Metal concentrations in soil are often compared to ecological screening benchmarks, which are based on total concentrations in soil. Often, the total concentration is not correlated with toxicity. No standardised method exists for determining the bioavailability of metals in soil to ecological receptors. Several surrogate measures of bioavailability were compared to the results of a battery of toxicity tests using copper (Cu), lead (Pb), and zinc (Zn)-contaminated soils collected from a former industrial area. A calcium chloride (CaCl 2) extraction, cyclodextrin (HPCD) extraction, simulated earthworm gut (SEG) test, and earthworm bioaccumulation test were performed using the soils. Extractable metals using the CaCl 2 solution were not correlated with any biological responses of earthworms ( Eisenia andrei), collembola ( Folsomia candida), northern wheatgrass ( Elymus lanceolatus), or alfalfa ( Medicago sativa L.). Concentrations of metals in the HPCD extracts were highly variable and were not adequate for revealing adverse effects. E. andrei tissue concentrations were variable but were predictive of adverse effects to invertebrates. The results of the SEG test correlated with most of the biological endpoints. Bioavailable Cu was correlated with adverse effects to invertebrates and plants using the SEG test. Overall, coefficients of determination associated with the relationships between the biological responses and each measure of bioavailability indicated that those for the SEG test were greater than those for the other surrogate measures of bioavailability. Further validation is required before this test is routinely used to estimate metal bioavailability and toxicity.

INCREASED SENSITIVITY AND VARIABILITY OF PHYTOTOXICITY RESPONSES IN ARCTIC SOILS TO A REFERENCE TOXICANT, BORIC ACID

Industrial and human activities in the Arctic regions may pose a risk to terrestrial Arctic ecosystem functions. One of the most common terrestrial toxicological end points, primary productivity, typically is assessed using a plant phytotoxicity test. Because of cryoturbation, a soil mixing process common in polar regions, we hypothesized that phytotoxicity test results in Arctic soils would be highly variable compared to other terrestrial ecosystems. The variability associated with phytotoxicity tests was evaluated using Environment Canada's standardized plant toxicity test in three cryoturbated soils from Canada's Arctic exposed to a reference toxicant, boric acid. Northern wheatgrass (Elymus lanceolatus) not only was more sensitive to toxicants in Arctic soils, its response to toxicants was more variable compared to that in temperate soils. The phytotoxicity of boric acid in cryosols was much greater than commonly reported in other soils, with a boric acid concentration of less than 150 microg/g soil needed to inhibit root and shoot growth by 20%. Large variability also was found in the phytotoxicity test results, with coefficients of variation for 10 samples ranging from 160 to 79%. The increased toxicity of boric acid in cryosols and variability in test response was not explained by soil properties. Based on our admittedly limited data set of three different Arctic soils, we recommend that more than 30 samples be taken from each control and potentially impacted area to accurately assess contaminant effects at sites in northern Canada. Such intensive sampling will insure that false-negative results for toxicant impacts in Arctic soils are minimized.

BIOGEOCHEMICAL TOXICITY AND PHYTOTOXICITY OF NITROGENOUS COMPOUNDS IN A VARIETY OF ARCTIC SOILS

Ammonium nitrate (NH(4)NO(3)) is a common water pollutant associated with many industrial and municipal activities. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the Arctic tundra, which will reduce nitrogen loading to surface water. The toxicity of ammonium nitrate to Arctic soils, however, is poorly understood. In the present study, we characterized the biogeochemical toxicity and phytotoxicity of ammonium nitrate solutions in four different Arctic soils and in a temperate soil. Soil was exposed to a range of ammonium nitrate concentrations over a 90-d period. Dose responses of carbon mineralization, nitrification, and phytotoxicity endpoints were estimated. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resilience was investigated by dosing nitrogen-impacted soils with boric acid. Ammonium nitrate had no effect on carbon mineralization activity and only affected nitrification in one soil, a polar desert soil from Cornwallis Island, Northwest Territories, Canada. In contrast, ammonium nitrate applications (43 mmol N/L soil water) significantly impaired seedling emergence, root length, and shoot length of northern wheatgrass (Elymus lanceolatus). Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 and 280 mmol N/L soil water, which corresponds to 2,100 to 15,801 mg/L of ammonium nitrate in the application water. Arctic soils were more resistant to ammonium nitrate toxicity compared with the temperate soil under these study conditions. It is not clear, however, if this represents a general trend for all polar soils, and because nitrogen is an essential macronutrient, nitrogenous toxicity likely should be considered as a special case for soil toxicity.

BIOGEOCHEMICAL TOXICITY AND PHYTOTOXICITY OF NITROGENOUS COMPOUNDS IN A VARIETY OF ARCTIC SOILS

Ammonium nitrate (NH(4)NO(3)) is a common water pollutant associated with many industrial and municipal activities. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the Arctic tundra, which will reduce nitrogen loading to surface water. The toxicity of ammonium nitrate to Arctic soils, however, is poorly understood. In the present study, we characterized the biogeochemical toxicity and phytotoxicity of ammonium nitrate solutions in four different Arctic soils and in a temperate soil. Soil was exposed to a range of ammonium nitrate concentrations over a 90-d period. Dose responses of carbon mineralization, nitrification, and phytotoxicity endpoints were estimated. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resilience was investigated by dosing nitrogen-impacted soils with boric acid. Ammonium nitrate had no effect on carbon mineralization activity and only affected nitrification in one soil, a polar desert soil from Cornwallis Island, Northwest Territories, Canada. In contrast, ammonium nitrate applications (43 mmol N/L soil water) significantly impaired seedling emergence, root length, and shoot length of northern wheatgrass (Elymus lanceolatus). Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 and 280 mmol N/L soil water, which corresponds to 2,100 to 15,801 mg/L of ammonium nitrate in the application water. Arctic soils were more resistant to ammonium nitrate toxicity compared with the temperate soil under these study conditions. It is not clear, however, if this represents a general trend for all polar soils, and because nitrogen is an essential macronutrient, nitrogenous toxicity likely should be considered as a special case for soil toxicity.

Potential utilization of native prairie grasses from western Canada as ethanol feedstock

The utilization of native grass species for potential biomass feedstocks of the emerging ethanol industry requires more information about their cellulose and hemicellulose concentration. Ten native species were grown at seven sites across the prairie region of western Canada for two to four growing seasons. Northern wheatgrass, Elymus lanceolatus, produced high concentrations of cellulose (363 g kg-1) but low concentrations of hemicellulose (266 g kg-1). Green needlegrass, Nasella viridula, produced high concentrations of both constituents (351 and 307 g kg-1). Four warm-season grasses, big bluestem, Andropogon gerardii, little bluestem, Schizachyrium scoparium, prairie sandreed, Calamovilfa longifolia, and switchgrass, Panicum virgatum, had 346, 342, 340 and 338 g kg-1, respectively, concentrations of cellulose and also exhibited a positive response to temperature that resulted in increased hemicellulose concentration. Accumulated thermal time (degree day base 10°C) was correlated to hemicellulose concentrations in the warm-season grasses but not for cool-season grasses. Holocellulose (cellulose + hemicellulose) concentration differences varied among site-years but warm-season grasses were more stable in hollocellulose concentration than cool-season grasses. Key words: Biomass, native grasses, cellulose, hemicellulose, biofuel

Forage quality of seeded native grasses in the fall season on the Canadian Prairie Provinces

There is renewed interest in re-seeding native grasses in the prairie region of western Canada but there is limited information on their forage quality for fall grazing. We evaluated forage quality in early fall of nine native and one introduced grass species for 2 to 4 yr at five locations. The neutral detergent fiber (NDF) was high due to the advanced growth stage of the plants but varied among grass species at all sites . Western wheatgrass, Pascopyrum smithii, exhibited the lowest NDF and highest in vitro organic matter digestibility (IVOMD). Northern wheatgrass, Elymus lanceolatus, exhibited the highest crude protein while western wheatgrass ranked second highest for crude protein. Indiangrass, Sorghastrum nutans, exhibited the highest P and Ca concentrations, while green needle grass, Nasella viridula, and mammoth wildrye, Leymus racemosus, exhibited the lowest concentrations. Acid detergent fiber (ADF) was not highly correlated to IVOMD, presumably due to the mature phenological stage at sampling. Western wheatgrass forage was nutritionally adequate to maintain a dry beef cow during the second trimester of pregnancy. Other species did not “cure on the stem” as had been previously reported and would require supplementary energy and protein to be utilized for fall pastures. Key words: Forage quality, fiber, protein, P, C4 grasses, C3 grasses

The influence of harvest management and fertilizers on herbage yields of cool-season grasses grown in the Aspen Parkland of northeastern Saskatchewan

This study was conducted to evaluate the impact of harvest and fertilizer management on the herbage yield of various grass cultivars grown in the Aspen Parkland region of northeastern Saskatchewan. A series of three experiments were set out: site 1 at Pathlow, Gray Luvisolic soil, 1980; site 2 at Melfort, Deep Black Chernozemic soil, 1979; and site 3 at Pathlow, 1986. At site 1, the design was a split-split plot with fertilizer treatments as mainplots (unfertilized and fertilized, initially with 11N-22P kg ha−1 incorporated 5 cm into soil and thereafter, 50N-13P kg ha−1 broadcast each year). Ten grass cultivars were seeded as subplots and harvest systems as subsubplots (two-cut and four-cut). At site 2 Melfort, the experimental design was similar to site 1, but without the fertilizer treatments. Fertilizer was applied to all plots at the same rates as site 1. At site 3, Pathlow, 14 grass cultivars were seeded with the same experimental design as site 2, but 10 kg S ha−1 was applied each year with the N and P fertilizer. At site 1 Pathlow, the only experiment with the unfertilized control, fertilizer increased the average herbage yield to 2.47 t ha−1 from 1.42 t ha−1 for unfertilized control plots. Frequent cutting (four-cut system) showed reduced annual yields of 1.70, 5.28 and 1.93 t ha−1 compared with 2.19, 7.08, and 2.87 t ha−1 (two-cut system), respectively, for sites 1, 2 (5-yr period) and 3 (7-yr period). A greater response to fertilizer was observed with the 2-cut system, 1.19 t ha−1, than with the four-cut system, 0.91 t ha−1, which resulted in a fertilizer × cutting management interaction at site 1. With some exceptions, most of the species were not significantly different in ranking based on herbage yield over the three test sites, but meadow bromegrass [Bromus biebersteinii (Roem &amp; Schult.)] ranked higher in yield on the less fertile Pathlow Gray Wooded soil sites than on the more fertile Melfort Deep Black soil site. Crested wheatgrass (Agropyron cristatum L.) ranked high in herbage yield at all three sites. Crested wheatgrass, smooth bromegrass (Bromus inermis Leyss.) and meadow bromegrass, the most commonly grown species in Saskatchewan, yielded well under the simulated hay and pasture conditions. Other cultivars such as Clarke intermediate wheatgrass [(Elytrigia intermedia (Host) Nevski], Elbee northern wheatgrass [Elymus lanceolatur (Scribn. and Smith)] and Lodorm green needlegrass (Stripa viridula Trin.) should be considered for pasture and hay by farmers and ranchers in northern Saskatchewan. Key words: Grass, harvest management, pasture, hay, fertilizer

Effects of grazing dates on forage and beef production of mixed prairie rangeland

Conventional belief is that mixed prairie range is harmed by early spring use but not by moderate grazing after the grasses have flowered. Our hypothesis was that mixed prairie range may be grazed for a limited period in the growing season providing rest is allowed for the remainder of the year. This 6-yr test was established on a rolling site of range pasture, which contained, by area, 65% upland mixed prairie, 5% lowland bluegrass (Poa spp.) and 30% crested wheatgrass (Agropyron cristatum). The species mix is commonly found in southern Canadian prairies. The mixed prairie grasses were needle and thread (Stipa comata), northern wheatgrass (Elymus lanceolatus), western wheatgrass (Pascopyrum smithii) and blue grama (Bouteloua gracilis). Each pasture was 1.6 ha and was grazed with yearling beef cattle once a year beginning mid-May; the end of June; mid-August or late September. Forage yields in grazing-exclusion cages averaged 580, 2960, and 1370 kg ha−1 for the mixed prairie, lowland grasses, and crested wheatgrass, respectively. The date of grazing in the previous year did not affect current-year maximum forage yield. The main determinant of maximum forage yield was a combination of spring soil moisture plus April to June precipitation. Available forage for grazing, on average, doubled from mid-May until the end of June for the three forage types. There were year-by-grazing date interactions, which were related to distribution of precipitation. Mixed prairie was the preferred forage at the last two grazing dates. Forage digestibility, N and P content were highest during the May and June grazing period and declined thereafter. Average daily gain of the steers decreased from 0.9 kg d−1 in May and late June to 0.2 kg d−1 by late September. Annual carrying capacity (in standard animal units) was 40 d ha−1 in May and averaged 55 d ha−1 for the other dates, which were not different. Grazing mixed prairie did not have a negative effect on the yield of native grasses when used for only one short period per year. Delayed use from mid May to end of June increased available forage and carrying capacity. Key words: Mixed grass prairie, crested wheatgrass, grazing, weather effects

Defoliation and Cold-Hardiness of Northern Wheatgrass

Freezing temperatures in winter were hypothesized to be a major cause of mortality of tillers following defoliation of northern wheatgrass (Agropyron dasystachyum [Hook.] Scribn., syn. Elymus lanceolatus [Scribn. S 2) exposing them to -15 degrees C for 0 to 15 days. The LT50 (temperature at which 50% of tillers died) of northern wheatgrass tillers in early winter ranged from -29.5 to < -36.0 degrees C in 1992-93, and averaged -24.0 degrees C in 1993-94. In late winter LT50 ranged from -18.1 to -22.6 degrees C in 1992-1993, and it averaged -22.0 degrees C in 1993-1994. The LDur50 (duration at which 50% of tillers died) of tillers exposed to -15 degrees C for 0 to 15 days ranged from 8.0 to 13.1 days in early winter, and 2.7 to 4.7 days in late winter. Unexpectedly mowed tillers were generally more cold-hardy than those from control. In early winter LT50 was 1.5 to 10 degrees C lower for mowed than control tillers. The hypothesis that defoliation reduces cold-hardiness of northern wheatgrass was rejected. The degree or duration of cold stress in the field is generally insufficient to reduce tiller survival in northern wheatgrass. Late winter through early spring is a critical period for tiller survival of northern wheatgrass because cold-hardiness declines this time of the year. Maintaining insulating cover can moderate soil temperatures and reduce damage to plants from freezing temperatures.

Regrowth and Rest Requirements of Northern Wheatgrass following Defoliation

Degree-days required for standing crop and above-ground net primary production of northern wheatgrass (Agropyron dasystachyum [Hook.] Scribn., syn. Elymus lanceolatus [Scrib. &Smith] Gould) mowed to a 5-cm stubble to recover to levels similar to an unmowed control were determined in southwestern Saskatchewan. Nine, single mowing treatments and an unmowed control were established from early May through late August in 1991 and 1992 on a clayey range site at 2 locations. Green and dead phytomass and above-ground net primary production were determined for 2 to 3 years following mowing. Degree-days required for recovery of green and dead standing phytomass on mowed plots decreased linearly and were highly correlated (r2 = 0.64 to 0.99) with the number of days plots were mowed after 1 May. Regardless of mowing date, green phytomass did not recover to control levels the year of mowing. Each day mowing was delayed past 1 May reduced the number of degree-days required for total recovery of green phytomass on mowed plots by 15.7 in 1991 and 17.7 in 1992. Degree-days required for recovery of standing dead on mowed plots were reduced 17.6 in 1991 and 15.8 in 1992. Degree-days required for recovery of above-ground net primary production declined linearly (r2 = 0.67 and 0.99) as mowing was delayed after 1 May. More degree-days were required for the 1991 than 1992 plots. At least 2 and sometimes 3 growing seasons were required to accumulate enough degree-days to allow full recovery of green and standing dead phytomass and above-ground net primary production on mowed plots. For optimum sustained production, a grazing system should be used on northern wheatgrass-dominated rangeland with a 2 year rest period applied to paddocks after grazing.