Drought is a widespread abiotic stress that impacts plant growth, productivity and survival.A randomized complete block design pot experiment was conducted to determine the effects of drought on above-ground biomass, root biomass, root/shoot (R/S) and relative leaf chlorophyll content (SPAD) of monoculture and legume-grass mixtures at the Swift Current Research and Development Centre (SCRDC) of Agriculture and Agri-Food Canada (AAFC).The legumes were Canadian milk-vetch (Astragalus canadensis) and white prairie-clover (Dalea candida).The grasses were northern wheatgrass (Elymus lanceolatus) and side-oats grama (Bouteloua curtipendula).Three water treatments (40%, 60% and 80% field capacity) and three cuts were the abiotic factors applied.Except for monoculture side-oats grama, multiple-species forage mixtures were more adaptable than a simple grass-legume mixture or monoculture in a water-limiting environment.The forage mixtures of Canadian milk-vetch and northern wheatgrass tolerated lower moisture levels than the other mixtures.Decreased soil moisture resulted in decreased total biomass and altered biomass allocation to roots resulting in higher R/S ratios in stressed seedlings.The SPAD value of Canadian milk -vetch mixture decreased with water stress, and white prairie-clover+ northern wheatgrass and white prairie-clover+ northern wheatgrass+ Canadian milk-vetch were better adapted to low soil moisture than the monocultures.

Fall dormancy is a vital component of alfalfa (Medicago sativa L.) yield in northern climates, but selection for the trait is often done at the expense of winter survival. We performed one cycle of selection to reduce fall dormancy in two winter hardy cultivars (Yellowhead and Peace) using a new indoor screening method. We compared the reduced dormancy populations with their respective initial cultivars for fall dormancy, yield, and winter survival at four sites across Canada. During the establishment and the first production years, plants of the reduced dormancy populations were generally taller in the fall than their respective cultivar, which resulted in a one unit increase of their fall dormancy class. Under field conditions, plants of the reduced dormancy populations had a similar winter survival than those of the initial cultivars. Under simulated winter conditions, freezing tolerance was not affected by selection for reduced dormancy in Peace, whereas a decrease from - 24.0 to - 21.5 degrees C was observed in Yellowhead. However, in this cultivar, we noted a 37% yield increase under field conditions and a 40% more vigorous regrowth under simulated winter conditions in the reduced dormancy population. These results showed that the indoor selection method effectively reduced fall dormancy and that indirect responses for yield and winter survival were dependent on the genetic background used as selection material. This selection method could therefore be promising to develop alfalfa cultivars adapted to northern latitudes with high winter hardiness and improved late season yield.

Fertilizer addition can improve soil nutrients in degraded grasslands, change plant community composition, and promote community productivity. An experiment was established in 2014 near Hulunbuir Grassland Ecosystem National Field Observation Station at Hulunbuir in Inner Mongolia, China, using L14 (3(4)) orthogonal test with 14 treatments totally, to compare the change of plant community productivity and plant diversity during three years of fertilization. We monitored the dynamic responses of aboveground biomass, plant species composition, species richness, Shannon diversity, Pielou's evenness after nitrogen (N), phosphorus (P), and potassium (K) addition once a year from 2014 to 2016. Compared to the control treatment of no additional fertilizer, we found that, (1) The fertilization combination of N (274 kg ha(-1)), P (350 kg ha(-1)), and K (57 kg ha(-1)) had a greater effect on biomass after the third year of fertilizer addition; (2) Gramineae accounted for a major portion of biomass in 2016, whereas the proportion of other species declined or disappeared; and (3) the longer the fertilization treatments went on, the lower Shannon diversity and Pielou's evenness turned out to be. All these responses are strongly interrelated in a cascade of changes. The interrelationships between fertilizers and different plant communities attribute the change not only to climate shift but also to time.

Background Incorporation of legume species into native North American pastures is considered an effective method to increase native pasture productivity and improve the nutritive value of forage. This study evaluated the effects of inclusion of purple prairie clover (PPC, Dalea purpurea Vent.), a native legume forage, with native cool-season grasses on the in vitro fermentation and in situ digestibility of mixed forages. Methods Whole plant PPC and mixtures of cool-season grasses were harvested when the PPC reached the vegetative (VEG), full flower (FL) and seedpod (SP) stages, and were combined in ratios (DM basis) of 0:100, 25:75, 50:50, 75:25 and 100:0 at each maturity. In vitro ruminal incubations using these mixtures were conducted for 48 h to determine gas production (GP), in vitro DM disappearance (IVDMD), total volatile fatty acids (VFA) and ammonia-N production. Mixtures of forages harvested when the PPC reached the FL stage and 50:50 mixture of forages harvested at VEG, FL and SP stages were incubated in the rumen of three heifers for 0, 2, 6, 12, 24, 48, 72 and 96 h to determine in situ degradabilities of DM, neutral detergent fibre (aNDF) and crude protein (CP). Results Contents of aNDF and ADF increased ( P < 0.01), while CP decreased ( P < 0.001) as PPC matured. Concentrations of extractable condensed tannins in PPC ranked as FL > VEG > SP ( P < 0.05). Regardless of PPC proportions in the mixture, GP decreased ( P < 0.05) with increasing PPC maturity. Increasing PPC proportions linearly increased ( P < 0.001) GP, IVDMD and total VFA at VEG, but linearly decreased ( P < 0.001) them at SP. Irrespective of PPC maturity, ammonia-N production linearly increased ( P < 0.01) with increasing proportions of PPC and the concentration was higher ( P < 0.05) at VEG than at FL and SP stages. Increasing proportion of PPC at either maturity linearly increased ( P < 0.001) molar percentage of acetate (A) and branched-chain VFA, but linearly decreased ( P < 0.001) molar percentage of propionate (P), resulting in a linearly increase ( P < 0.001) in the A:P ratio. Increasing FL PPC in the mixture linearly and quadratically ( P < 0.01) increased a (soluble fraction), but linearly and quadratically decreased ( P < 0.01) b (potentially degradable fraction) for DM and aNDF, resulting in linear ( P < 0.05) and quadratic ( P < 0.01) increases in DM and aNDF maximum potential degradabilities ( a + b ). Effective degradabilities of DM and aNDF were also linearly and quadratically increased ( P < 0.05), and CP was quadratically increased ( P < 0.05) with increasing FL PPC, with the greatest effective degradability being observed with ratios between 50:50 and 75:25. Ruminal maximum potential degradabilities of DM and aNDF decreased ( P < 0.001) as the forage matured. Effective degradability of DM ranked as VEG > FL > SP ( P < 0.001), whereas the effective degradability of aNDF was similar between VEG and FL and both were greater ( P < 0.01) than SP. Conclusions Inclusion of vegetative PPC in a mixed forage diet resulted in the greatest digestibility and incorporation of PPC before seedpod stage with native grasses had a positive effect on ruminal fermentation. Effects of PPC on ruminal digestion depend on both the stage of maturity and its proportion in mixed legume-grass pastures. Pastures containing 50% of PPC in full flower stage would likely provide the greatest quality diet to grazing ruminants subject to potential animal selectivity.

In the grassland ecosystem, soils are subjected to a range of stresses which may affect their physical and biological properties, as well as the plant community biomass. As biomass is affected by long-term soil properties, we sought to establish a direct link between biomass and resilience to fertilization and soil aeration. We evaluated biomass yield in grasslands managed across a gradient of nitrogen (N), phosphorus (P), and potassium (K) fertilizers at Hulunbuir in Inner Mongolia, China, from 2014 to 2017. Based on the estimates from the simulated optimization and optimal theoretical regression model, we recommend applying N (231.50-238.82kg ha(-1)), and P (187.25-218.75 kg ha(-1)), and K (28.28- 33.32 kg ha(-1)) annually to maximize biomass in the non-aerated grassland. The positive effect of nitrogen and phosphorus on biomass was significantly higher than unfertilized treatment. The effects of aeration on biomass were less explicit. Simultaneously, we compared the Shannon-Wiener Index and Species richness for the suitable fertilizer levels. Shannon-Wiener diversity and Species richness became lower the longer the fertilization treatments lasted. Thus, nutrient resorption is resulting in a decrease in species diversity and richness, while it is an important strategy for increasing plant biomass.

The inclusion of legumes in semi-arid native grasslands may promote the productivity and nutritive value of forage. This study was designed to assess the effect of legumes (the introduced legume Medicago sativa or the native legume Dalea purpurea) and soil P fertility (addition of 0, 50, or 200 P(2)O(5)kg/ha at seeding) on the dry matter and nutrient content of native grasses mixtures, compared with the commonly used introduced forage grass Bromus biebersteinii grown with M.sativa. Plant harvests were performed in September 2008, July 2009 and September 2009. Plants nutrient content, N-15 value and dry matter were analysed. Results show that the M.sativa enhanced the N and P concentrations of native grass mixtures early in the summer, as well as the N concentration in Bouteloua gracilis in late summer of the driest year, 2009. The higher AM fungal diversity promoted by M.sativa was positively correlated with the dry matter and nitrogen uptake of M.sativa and with the P concentration of native grasses, in early summer. Overall, this study shows that M.sativa promoted beneficial AM fungal taxa and improved forage production in the semi-arid prairies.

It has been reported that condensed tannins (CT) from some forages decreases methane production. Purple prairie clover (PPC; Dalea purpurea Vent.) and white prairie clove (WPC; D. candida Michx. ex Willd) are native legumes adapted to the North American prairie and contain high concentration of CT. The objective of this study was to assess the effects of CT in PPC and WPC on ruminal fermentation and methane production. Whole-crop PPC and WPC were harvested at full flower stage and divided into two equal portions. One portion was freeze-dried and the other was sun-cured. Batch culture incubations were conducted using conserved forages as a substrate with and without inclusion of polyethylene glycol (PEG), which inactivates CT. Each incubation was repeated twice with two fermentation vials for each treatment in each run of the incubation. Concentration of CT (g/kg DM) in freeze-dried and sun-cured PPC and WPC were 90.5 ± 16.91, 88.1 ± 2.53, 62.8 ± 2.41 and 58.1 ± 2.82 respectively. Inclusion of PEG increased (Pin vitro DM disappearance (IVDMD), total gas production (GP) and ammonia concentration with PPC, regardless of conservation method. Freeze-dried PPC had greater (P<0.01) IVDMD and GP, but lower (P<0.01) ammonia concentration than sun-cured PPC. However, with WPC, no difference was observed in IVDMD or GP between the freeze-dried and sun-cured samples with or without PEG. Similar to PPC, addition of PEG also increased (P<0.05) ammonia concentration when WPC was incubated. Methane production was similar between the two forages and addition of PEG did not affect methane production from either forage. The greater effects of PEG on IVDMD, GP and ammonia production for PPC than for WPC is likely due to the higher concentration of CT in PPC than WPC. The results indicated that CT in PPC and WPC had no effect on ruminal methane production despite their high concentrations in these forages. Key Words:

Purple prairie clover (PPC; Dalea purpurea Vent.),a native legume adapted to the North American prairie, is considered an excellent forage for ruminants and therefore is valuable for the remediation of native grass pastures. The objective of this study was to assess the impact of different levels of inclusion of PPC harvested at varying stages of maturity on the ruminal digestion of mixed native forage. Whole-crop PPC and native mixed grasses were harvested at vegetative (VEG), full-flower (FL) and seedpod (SP) stages of PPC. To assess maturity, PPC at each maturity was combined with mixed grasses at a ratio (DM basis) of 50:50. PPC harvested at FL was then combined with mixed grasses in ratios of 0:100, 25:75, 50:50, 75:25 and 100:0 to evaluate the effect of proportions of PPC on digestibility. Nylon bags containing respective substrates were incubated for 0, 2, 6, 12, 24, 48, 72 and 96 h in the rumen of three heifers to determine in situ degradabilities of DM, NDF and CP. Forages harvested at the VEG and FL stages had similar soluble (a) and potential degradable (b) fractions of DM and NDF, and both were greater (PFL>SP (P< 0.01). In contrast, effective degradability of NDF was similar between VEG and FL and both were greater (P< 0.05) than SP. Increasing PPC in the mixture linearly (Pa and b fractions of DM and NDF and the a fraction of CP. Effective degradabilities of DM, NDF and CP were linearly (P<0.001) and quadratically (P<0.001) increased with PPC, with the greatest effective degradability observed with ratios between 50:50 and 75:25. Efects of PPC on ruminal digestion depend on both the growth stage and its proportion in mixed legume-grass pastures.These results suggest that pastures that contain from 50–75% of PPC in full flower would have the highest nutritive value.

Incorporation of legume species into re-established North American native prairie pastures is considered an effective method to increase pasture productivity and improve the nutritive value of the stand. The objective of this study was to determine the effects of proportions of purple prairie clover (PPC; Dalea purpurea Vent.) and white prairie clover (WPC; D. Candida Michx. ex Willd) in native pasture on the nutritive value of the forage. Samples were collected at vegetative (VEG), full-flower (FL) and seedpod (SP) stages for PPC and at FL and SP for WPC. Mixed cool-season native grasses were collected from re-established native pasture at time of harvest of PPC and WPC. The PPC and WPC at each maturity were combined with the grasses harvested at the same time in the ratios (DM basis) of 0:100, 25:75, 50:50, 75:25 and 100:0. In vitro ruminal incubations were conducted for 48 h to determine gas production (GP), in vitro DM disappearance (IVDMD), VFA, and ammonia production. Data were analyzed using the MIXED model of SAS. WPC-grass mixtures had greater (P<0.01) GP, IVDMD, NDF disappearance (NDFD) and VFA and ammonia production than PPC-grass mixtures. Increasing PPC proportions linearly increased (P<0.001) GP and IVDMD at the VEG stage, but linearly decreased (P<0.001) them at the SP stage. In contrast, increasing WPC linearly increased (P<0.001) GP and IVDMD, but linearly decreased (P<0.01) NDFD at FL stage. Irrespective of type of clovers, ammonia production and molar proportion of acetate linearly increased (P<0.01) and molar proportion of propionate linearly decreased (P<0.001) with increasing legume proportions. The results indicated that at the same growth stage WPC-grass mixtures had greater nutritive value than PPC-grass mixtures. Inclusion of vegetative D. purpurea or flowering D. candida in prairie pastures, if consumed, will improve forage digestibility if grazed at the vegetative or flowering stages.

We conducted a series of three greenhouse studies to study the allelopathic effects of seven native perennial North American forage species alone and mixed on three problematic weeds including dandelion [Taraxacum officinale (Weber) ex Wigg.], scentless chamomile (Matricaria perforata Merat), and foxtail barley (Hordeum jubatum L.). Shoot dry weight and root to shoot ratio of weeds were affected by leachate from forage species in all three experiments. In the first experiment, leachate from little blue stem [Schizachyrium scoparium (Michx.) Nash] reduced the shoot dry weight of weeds up to 58%. In the second experiment, leachate of little blue stem, western wheatgrass [Pascopyrum smithii (Rydb.) Love], and sideoats grama [Bouteloua curtipendula (Michx.) Torr.] reduced shoot dry weight of weeds up to 72% and this number increased up to 90% in the third experiment. In the last experiment, no synergistic effects of mixed leachate from different forage species on shoot dry weight of weeds were observed. In this study, dandelion and foxtail barley allocated less to roots and shoots, respectively. In conclusion, our results showed that root leachate from western wheatgrass, little blue stem, and sideoats grama can reduce the aboveground and belowground growth of weeds. These findings suggest that the use of allelopathic species may provide weed control and management benefits in seeded pastures and native prairie restorations.

Canadian milkvetch (Astragalus canadensis) is a North American plant species in the legume family and some of this plant is fatally poisonous to livestock. The poisoning is attributed to the natural occurrence of notrotoxins, i.e., 3-nitropropanoic acid and 3-nitropropanol, present as aglycones and conjugated forms in the plant. Those compounds cause nitrite oxidization of hemoglobin and inhibition of cellular metabolism. To determine the toxicity of the plant, it is very important to develop an analytical method for the contents of the compounds in the plant. In this study, we have successfully developed an extraction procedure followed by HPLC-UV analysis to simultaneously analyze notrotoxins. The aglycones could be released from its conjugated forms in the freeze dried plant and extracted by water at room temperature. An HPLC-UV method using a Phenomenex Kinetex 2.6 μ F5 100 Å 100 × 4.6 mm column with pH 3.5 phosphonate buffer as mobile phase have been developed and validated for the detection of the two compounds at 210 nm. This developed procedure for the analysis of 3-nitropropanoic acid and 3-nitropropanol has proven simple and efficient and it has been successfully applied for batch sample analysis.

Arbuscular mycorrhizal (AM) fungi play an important role in the functioning and sustainability of agroecosystems, but they are also susceptible to changes in land use. The objective of this study was to determine the impact of agricultural land use practices on AM fungal communities and identify the factors that drive their assembly in the Mixed Prairie ecoregion of the North American Great Plains. Soil samples were collected from the four dominant agricultural land use types in this region (annual cropping, native grassland, tame grassland, and roadside ditches) at five locations and at three soil depths (0-15, 15-30, and 30-60 cm). The diversity and composition of the AM fungal communities were assessed using high throughput sequencing (454 pyrosequencing). We found that land use type significantly influenced the diversity and composition of the AM fungal communities. Annual cropland had the lowest diversity and a distinct community composition compared to the other land use types. This effect was most pronounced in the upper soil depth (0-15 cm), but was still evident in the lower depths (15-30 and 30-60 cm). Further analysis found a trend for AM fungal communities at lower soil depths to be a nested subset of communities in the top soil depth. Structural equation modeling revealed that land use affected AM fungal communities indirectly through the modification of plant communities and soil properties.

In situ and in vitro experiments were conducted to evaluate the effect of forage conservation method on the chemical composition, ruminal degradation, and intestinal digestion of purple prairie clover (PPC), which was conserved as freeze-dried forage (FD), silage (SIL), or hay (Hay). In situ dry matter (DM), neutral detergent fiber (NDF), and crude protein (CP) degradabilities were determined by incubating the forages in three rumen-cannulated heifers for 0, 1, 2, 4, 8, 24, 48, and 72 h. Intestinal DM and CP digestions were estimated by incubating 12 h ruminal in situ residues in a modified three-step in vitro procedure. Ensiling decreased (P < 0.001) extractable condensed tannins (CT) but increased (P < 0.001) protein-and fiber-bound CT compared with FD and Hay. The ruminal disappearance of CP at 8 and 24 h was affected by conservation method (P < 0.001), ranked as SIL > FD > Hay. The effective degradability of DM was lower (P < 0.001) for Hay than for FD and SIL. Ensiling lowered (P < 0.001) whereas haymaking increased (P < 0.001) intestinal digestion of CP compared with the fresh PPC. There were no differences in intestinal DM digestion among the three conserved forages. The results suggest that PPC conserved as Hay may conserve the biological activity of CT via preserving extractable CT more than as SIL, thus having the potential to improve protein utilization in ruminants.

Question: Native species have the potential to provide productive, drought-resistant communities for seeded rangelands and ecological restoration. Little is known, however, about how to identify multispecies mixtures with optimal levels of productivity and stress resistance from the thousands of possible community configurations. Here we examine if empirical models can be used to predict highly productive community configurations of seven native grasses and legumes in controlled conditions from the very large pool of possible communities, and which basic measure of community structure best predicts function.Location: Greenhouses in Saskatchewan, Canada.Methods: We used a greenhouse experiment, where established communities varied in species and functional group richness, evenness, species and functional group identity, following a response surface design. We measured community productivity and evaluated the predictive power of a range of empirical models linking diversity and productivity.Results: Productivity increased with increased functional dispersion, relative growth rate and decreased competitive effect. Selection effects were evident, with the abundance and occurrence of particular species or functional groups and plant traits also linked to increased productivity. Among the strongest predictors of productivity were the presence and abundance of perennial C-3 grasses (particularly Pascopyrum smithii), likely because of the high early relative growth rate and strong competitive effect of those species.Conclusions: We compiled and compared the ability of a range of empirical models to predict high-productivity community configurations, and tested the accuracy of the best models in a confirmatory experiment. The relationship between predicted and observed productivity was significantly correlated in the confirmatory experiment, and demonstrates that under controlled conditions, basic measures of community structure can predict community function. This approach has potential, but variability within treatments may limit the accuracy of results. The models developed can be used as a screening tool, narrowing the search window for high functioning seed mixtures for use in ecological restoration.

Schellenberg, M. P. and Biligetu, B. 2015. The effects of temperature and scarification on seed germination of three Dalea species. Can. J. Plant Sci. 95: 1117–1120. Ecological varieties of North American native plants are used for reclamation or rangeland seeding in Canada. The objectives of the study were to determine the optimum temperature for seed germination and to evaluate the effect of seed scarification on germination of ecological varieties of purple prairie clover [Dalea purpureum (Vent) Rydb.], white prairie clover [Dalea candida (Michx.) Willd.], and a wild collection of hairy prairie clover [Dalea villosa (Nutt.) Spreng var. villosa]. Germination was studied in growth chambers with constant temperatures of 5, 10, 20, and 30°C for 28 d using a randomized complete block design (RCBD). An additional germination experiment was conducted at 20°C after seed scarification. Based on days to initiate first germination and final germination, the optimum temperature for germination was 20°C for the three species. Final germination was the highest for purple prairie clover (51%), intermediate for white prairie clover (27%), and lowest for hairy prairie clover (5%). Seed scarification increased final germination by around 20% for all three species.

A 3-year (2009 to 2011) grazing study was conducted to assess the effects of purple prairie clover (PPC; Dalea purpurea Vent) on fecal shedding of total Escherichia coli in cattle. Three pasture types were used in the experiment: bromegrass (Check), mixed cool season grasses with PPC (Simple), and mixed cool and warm grasses with PPC (Complex). Pastures were rotationally grazed during a summer and fall grazing period. PPC was grazed in summer at the vegetative or early flower stage and at the flower or early seed stage during the fall. Fecal samples were collected for enumeration of E. coli and chemical analyses. Forage samples were collected throughout grazing for analysis. Condensed tannins (CT) were only detected in Simple and Complex pastures that contained PPC, with higher concentrations found in the fall than in the summer. Fecal counts of E. coli in cattle grazing Simple and Complex pastures linearly decreased (P < 0.05) over summer to fall in all 3 years, an outcome not observed in cattle grazing the Check pasture. Across the three grazing seasons, fecal E. coli was lower (P < 0.05) in cattle grazing Simple and Complex pastures than in those grazing the Check pasture during the fall. During the fall, feces collected from cattle grazing the Check pasture had higher (P < 0.05) values for pH, N, NH3-N, total volatile fatty acids, and branched-chain volatile fatty acids, but a lower (P < 0.05) acetate:propionate ratio than feces collected from cattle grazing Simple or Complex pastures. In a second experiment, two strains of E. coli were cultured in M9 medium containing 25 to 200 μg/ml of PPC CT. Growth of E. coli was linearly (P < 0.01) reduced by increasing levels of PPC CT. Scanning electron micrographs showed electron-dense filamentous material associated with the outer membrane of E. coli cells exposed to CT. Incorporation of PPC into forage reduced the fecal shedding of E. coli from grazing cattle, likely due to the anti-E. coli properties of PPC CT.

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. & J. G. Sm.) Gould], western wheatgrass [Pascopyrum smithii (Rydb.) Barkworth & 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>0.05). Binary mixtures of alfalfa–grass produced highest (P<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<0.05) DM yields in the ranking. The two warm-season grasses produced the lowest (P>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.

Adding inorganic P- and N-fixing legumes to semi-arid grasslands can increase forage yield, but soil nutrient concentrations and plant cover may also interact to modify soil fungal populations, impacting short- and long-term forage production. We tested the effect of plant assemblage (seven native grasses, seven native grasses + the domesticated N-fixing legume Medicago sativa, seven native grasses + the native N-fixing legume Dalea purpurea or the introduced grass Bromus biebersteinii + M. sativa) and soil P concentration (addition of 0 or 200 P2O5 kg ha(-1) at sowing) on the diversity and community structure of arbuscular mycorrhizal (AM) fungi and total fungi over two consecutive years, using 454-pyrosequencing of 18S rDNA and ITS amplicons. Treatment effects were stronger in the wet year (2008) than the dry year (2009). The presence of an N-fixing legume with native grasses generally increased AM fungal diversity, while the interaction between soil P concentration and plant assemblage modified total fungal community structure in 2008. Excluding interannual variations, which are likely driven by moisture and plant productivity, AM fungal communities in semi-arid grasslands appear to be primarily affected by plant assemblage composition, while the composition of other fungi is more closely linked to soil P.