Summary 1.A coordinated continental-scale field experiment across 31 sites was used to compare the biomass yield of monocultures and four species mixtures associated with intensively managed agricultural grassland systems. To increase complementarity in resource use, each of the four species in the experimental design represented a distinct functional type derived from two levels of each of two functional traits, nitrogen acquisition (N 2 -fixing legume or nonfixing grass) crossed with temporal development (fast-establishing or temporally persistent). Relative abundances of the four functional types in mixtures were systematically varied at sowing to vary the evenness of the same four species in mixture communities at each site and sown at two levels of seed density. 2. Across multiple years, the total yield (including weed biomass) of the mixtures exceeded that of the average monoculture in >97% of comparisons. It also exceeded that of the best monoculture (transgressive overyielding) in about 60% of sites, with a mean yield ratio of mixture to best-performing monoculture of 1Á07 across all sites. Analyses based on yield of sown species only (excluding weed biomass) demonstrated considerably greater transgressive overyielding (significant at about 70% of sites, ratio of mixture to best-performing monoculture = 1Á18).3. Mixtures maintained a resistance to weed invasion over at least 3 years. In mixtures, median values indicate <4% of weed biomass in total yield, whereas the median percentage of weeds in monocultures increased from 15% in year 1 to 32% in year 3. 4. Within each year, there was a highly significant relationship (P < 0Á0001) between sward evenness and the diversity effect (excess of mixture performance over that predicted from the monoculture performances of component species). At lower evenness values, increases in community evenness resulted in an increased diversity effect, but the diversity effect was not significantly different from the maximum diversity effect across a wide range of higher evenness values. The latter indicates the robustness of the diversity effect to changes in species' relative abundances. 5. Across sites with three complete years of data (24 of the 31 sites), the effect of interactions between the fast-establishing and temporal persistent trait levels of temporal development was highly significant and comparable in magnitude to effects of interactions between N 2 -fixing and nonfixing trait levels of nitrogen acquisition. 6. Synthesis and applications. The design of grassland mixtures is relevant to farm-level strategies to achieve sustainable intensification. Experimental evidence indicated significant yield benefits of four species agronomic mixtures which yielded more than the highest-yielding monoculture at most sites. The results are relevant for agricultural practice and show how grassland mixtures can be designed to improve resource complementarity, increase yields and reduce weed invasion. The yield benefits were robust to considerable changes in the relative propo...

G. 2003. Fatty acids in forages. I. Factors affecting concentrations. Can. J. Anim. Sci. 83: 501-511. When forages represent a high proportion of ruminant diets they provide a significant quantity of fatty acids (FA). Effects of growth stage, fertilization, conservation method, growth period, species, and cultivar on forage FA were determined in four experiments. Concentrations of C16:0, C18:2, C18:3, and total FA (TFA) in timothy (Phleum pratense L.) decreased (P < 0.01), respectively, by 15, 16, 31, and 23% between stem elongation and early flowering. Nitrogen fertilization (120 vs. 0 kg N ha -1 ) caused an increase (P < 0.01) of 18% of C16:0, 12% of C18:2, 40% of C18:3, and 26% of TFA concentrations. Phosphorus was not deficient and P fertilization (45 vs. 0 kg P ha -1 ) had no significant effect on timothy FA concentrations. Wilting and drying decreased (P < 0.01) timothy C18:2, C18:3, and TFA concentrations. Concentrations of C18:2, C18:3, and TFA were higher in summer regrowth than in spring growth, primarily in orchardgrass (Dactylis glomerata L.) and timothy (P < 0.01). Significant variation for all FA concentrations was observed among 12 species (P < 0.05); on average, the C18:3, C18:2, and C16:0 accounted for 88% of TFA in studied species. Timothy was the only species in which the difference among cultivars was simultaneously significant (P < 0.05) for concentrations of C18:2, C18:3, and TFA. Among the grasses, an annual ryegrass (Lolium multiflorum Lam.) cultivar had the highest C18:3 concentration (20.6 mg g -1 DM) whereas a timothy cultivar had the lowest (7.3 mg g -1 DM) (P < 0.05). Among legumes, a white clover (Trifolium repens L.) cultivar had the highest C18:3 concentration (16.5 mg g -1 DM) whereas an alfalfa (Medicago sativa L.) cultivar had the lowest (6.0 mg g -1 DM) (P < 0.05). Polyunsaturated FA concentrations in forages can be increased by harvesting timothy at an early stage of development and as fresh grass, by increasing N fertilization of timothy, and by choosing species with higher FA concentrations such as white clover and annual ryegrass. a causé une augmentation (P < 0,01) de 18% du C16:0, 12% du C18:2, 40% du C18:3 et 26% des AGT. Le P n'étant pas défici-taire, la fertilisation en P (45 vs. 0 kg P ha -1 ) n'a pas eu d'effet sur les concentrations en AG de la fléole. Les concentrations en C18:2, C18:3 et AGT de la fléole ont diminué (P < 0.01) avec le préfanage et le séchage. Les concentrations en C18:2, C18:3 et AGT étaient plus élevées en croissance d'été qu'en croissance de printemps et ce, surtout chez le dactyle (Dactylis glomerata L.) et la fléole (P < 0,01). Une variation significative entre 12 espèces a été observée pour tous les AG (P < 0,05); en moyenne, les C18:3, C18:2 et C16:0 représentaient 88% des AGT chez les espèces étudiées. La fléole était la seule espèce où la variation entre cultivars était significative à la fois pour le C18:2, le C18:3 et les AGT (P < 0,05). Chez les graminées, un cultivar de ray-grass annuel (Lolium multiflorum Lam.) avait la plus forte (...

Silage making can be conveniently divided into field, ensiling, storage, and feed-out phases. In all of these stages, controllable and uncontrollable components can affect silage quality. For instance, silages produced in hot or cold regions are strongly influenced by uncontrollable climate-related factors. In hot regions, crops for silage are influenced by (1) high temperatures negatively affecting corn yield (whole-crop and grain) and nutritive value, (2) butyric and alcoholic fermentations in warm-season grasses (Panicum, Brachiaria, and Pennisetum genera) and sugarcane, respectively, and (3) accelerated aerobic deterioration of silages. Ensiling expertise and economic factors that limit mechanization also impair silage production and utilization in hot environments. In cold regions, a short and cool growing season often limits the use of crops sensitive to cool temperature, such as corn. The fermentation triggered by epiphytic and inoculated microorganisms can also be functionally impaired at lower temperature. Although the use of silage inoculants has increased in Northern Europe, acid-based additives are still a good option in difficult weather conditions to ensure good fermentation quality, nutritive value, and high intake potential of silages. Acid-based additives have enhanced the quality of round bale silage, which has become a common method of forage preservation in Northern Europe. Although all abiotic factors can affect silage quality, the ambient temperature is a factor that influences all stages of silage making from production in the field to utilization at the feed bunk. This review identifies challenges and obstacles to producing silages under hot and cold conditions and discusses strategies for addressing these challenges.

Treatments to reduce solids content in liquid manure have been developed, but little information is available on gaseous N emissions and plant N uptake after application of treated liquid swine manure (LSM). We measured crop yield, N uptake, and NH3 and N2O losses after the application of mineral fertilizer (NH4 NO3), raw LSM, and LSM that was decanted, filtered, anaerobically digested, or chemically flocculated. The experiment was conducted from 2001 to 2003 on a loam and a sandy loam cropped to timothy (Phleum pratense L.) with annual applications equivalent to 80 kg N ha(-1) in spring and 60 kg N ha(-1) after the first harvest. Raw LSM resulted in NH3 emissions three to six times larger (P < 0.05) than mineral fertilizer. The LSM treatments reduced NH3 emissions by an average of 25% compared with raw LSM (P < 0.05). The N2O emissions tended to be higher with raw LSM than with mineral fertilizer. The LSM treatments had little effect on N2O emissions, except for anaerobic digestion, which reduced emissions by >50% compared with raw LSM (P < 0.05). Forage yield with raw LSM was >90% of that with mineral fertilizer. The LSM treatments tended to increase forage yield and N uptake relative to raw LSM. We conclude that treated or untreated LSM offers an alternative to mineral fertilizers for forage grass production but care must be taken to minimize NH3 volatilization. Removing solids from LSM by mechanical, chemical, and biological means reduced NH3 losses from LSM applied to perennial grass.

Bolinder, M. A., Angers, D. A., Bélanger, G., Michaud, R. et Laverdière, M. R. 2002. Root biomass and shoot to root ratios of perennial forage crops in eastern Canada. Can. J. Plant Sci. 82: 731-737. Shoot to root ratios (S:R) at peak standing crop are commonly used to estimate the annual crop residue C inputs to the soil from the root biomass left in the soil at harvest. However, root biomass has often been neglected in field studies and estimates of S:R for many commonly grown forage species are not available. Our objective was to determine root biomass and S:R of seven perennial grass species and two perennial legume species under eastern Canadian soil and climatic conditions. Root biomass in three soil layers (0-15, 15-30 and 30-45 cm) was measured shortly after the second harvest in the first (1995) and second (1996) year of production. Two harvests of aboveground DM were taken each year. The total root biomass (0-45 cm) in the second year of production (average of 1437 g m -2 ) was twice that measured in the first year of production (average of 683 g m -2 ). This temporal variation was mainly explained by the increase of root biomass in the 0-to 15-cm layer. The proportion of total root biomass (0-45 cm) in the 0-to 15-cm layer increased from 54 to 71% while that in the 15-to 30-cm layer decreased from 37 to 21%; the proportion of roots in the 30-to 45-cm layer remained constant at about 10% in both years. The S:R of alfalfa for the 0-15 cm depth was significantly higher than that for most of the grasses. No significant difference in S:R was observed among grass species. Recognizing that S:R may vary with locations and climatic conditions, our results suggest that average S:R of about 1.30 (values ranged from 1.01 to 1.72) in the first production year and 0.60 (values ranged from 0.43 to 0.87) in the second production year could be used as a first approximation to estimate the amount of root biomass left in the soil to a depth of 45 cm from forage crops in eastern Canada. The S:R of forage crops, particularly grasses, were lower than those of annual crops such as small-grain cereals and corn. Le rapport biomasse aérienne : biomasse racinaire (BA:BR) mesuré lorsque les cultures sont à maturité est souvent utilisé pour estimer les apports annuels de C laissés dans le sol par la BR des plantes. Cependant, la BR a souvent été négligée dans les études au champ et il n'existe pas d'estimé du rapport BA:BR pour plusieurs espèces de plantes fourragères. Notre objectif était de déterminer la BR au champ et le rapport BA:BR pour différentes espèces de plantes fourragères pérennes sous les conditions climatiques et édaphiques de l'est du Canada. Des mesures de la BR ont été effectuées pour trois couches de sol (0-15, 15-30 et 30-45 cm) et ce, pendant deux années consécutives (la première et la deuxième année de production) quelques jours après la deuxième coupe pour sept espèces de graminées et deux de légumineuses. Une variation importante dans la BR a été observée entre la première et la deuxième année de producti...