Grazing studies were carried out over a 5-year period using pregnant cows, yearling calves and 2-year-old heifers to investigate the influence of diet on intake, methane (CH4) emissions and retention of nitrogen (N). Monoculture legume (birdsfoot trefoil, BFT and cicer milkvetch, CMV) or grass (meadow bromegrass, MBG) pastures were rotationally stocked, and during year 4 and year 5, treatments were contrasted with total mixed rations (TMR) fed in confinement. The sulfur hexafluoride (SF6) method was used to continuously measure enteric CH4 emissions. Intake was greater on legume pastures and on TMR than on grass pastures, and enteric CH4 emissions per unit of intake were lower on legumes compared with grass pastures. Legume pastures had elevated non-fiber carbohydrate (NFC) concentrations (400 g kg−1 dry matter; DM) typical of perennial legumes cultivated in the Mountain West. A N balance calculated in 2017–2018 demonstrated that N retention was greater for TMR and legume than grass pastures. Enteric CH4 emissions of grazing cow herds account for the majority of greenhouse gas (GHG) emissions from beef production and can be significantly reduced by using highly digestible forage legumes. The N retention of legumes can potentially enhance the efficiency of N use, thereby increasing the sustainability of grasslands.

In this field study, we determined the effects of water stress, rainfed or irrigated conditions on the arbuscular mycorrhizal fungal (AMF) root colonization in the late-seral Stipa clarazii, the earlier-seral S. tenuis and the early-seral S. gynerioides at different developmental stages and sampling dates. We had two goals: (1) to document the levels of AMF root colonization, and (2) to examine the plant stress responses during imposed water stress in the three Stipa species. We tested the hypothesis that the effects of water stress on Stipa grasslands depend upon the interactions between plant AMF status and plant species. No consistent patterns in AMF root colonization frequency were observed relative to soil water levels. This suggests that AMF root colonization is highly plastic and responds to environmental factors that we do not yet understand. Mycorrhiza colonization was greater in the late-seral than in the earlier-seral species. Higher AMF root colonization levels in S. clarazii may partly explain its higher competitive ability in comparison with the earlier-seral species.

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Considerable research has been directed towards the study for obtaining Medicago sativa varieties to be used for the production of proteic concentrates. For this purpose the behaviour of two lucerne populations was studied under different cutting regimes. During the period 1977-79 for each of the two populations, 1200 genotypes divided into groups of 400 plants were cut when their mean height reached 30, 45 cm and at flowering time. Green matter yield per plant at each cut, percentage of dry matter yield, protein content and number of surviving plants were considered.

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