Multi-species Swards Research Articles

Multispecies Swards Outperform Perennial Ryegrass Monoculture and Perennial Ryegrass-White Clover Swards – a Beef System Grazing Experiment

Multispecies Swards Outperform Perennial Ryegrass Monoculture and Perennial Ryegrass-White Clover Swards – a Beef System Grazing Experiment

Simulating grazing beef and sheep systems

CONTEXTRuminant livestock make an important contribution to global food security by converting feed that is unsuitable for human consumption into high value food protein, demand for which is currently increasing at an unprecedented rate because of increasing global population and income levels. Factors affecting production efficiency, product quality, and consumer acceptability, such as animal fertility, health and welfare, will ultimately define the sustainability of ruminant production systems. These more complex systems can be developed and analysed by using models that can predict system responses to environment and management. OBJECTIVEWe present a framework that dynamically models, using a process-based and mechanistic approach, animal and grass growth, nutrient cycling and water redistribution in a soil profile taking into account the effects of animal genotype, climate, feed quality and quantity on livestock production, greenhouse gas emissions, water use and quality, and nutrient cycling in a grazing system. METHODSA component to estimate ruminant animal growth was developed and integrated with the existing components of the SPACSYS model. Intake of herbage and/or concentrates and partitioning of the energy and protein contained in consumed herbage and/or concentrates were simulated in the component. Simulated animal growth was validated using liveweight data from over 200 finishing beef cattle and 900 lambs collected from the North Wyke Farm Platform (NWFP) in southwest England, UK, between 2011 and 2018. Annual nitrous oxide (N2O), ammonia, methane and carbon dioxide emissions from individual fields were simulated based on previous validated parameters. RESULTS AND CONCLUSIONSA series of statistical indicators demonstrated that the model could simulate liveweight gain of beef cattle and lamb. Simulated nitrogen (N) cycling estimated N input of 190 to 260 kg ha−1, of which 37–61% was removed from the fields either as silage or animal intake, 15–26% was lost through surface runoff or lateral drainage and 1.14% was emitted to the atmosphere as N2O. About 13% of the manure N applied to the NWFP and excreta N deposited at grazing was lost via ammonia volatilisation. SIGNIFICANCEThe extended model has the potential to investigate the responses of the system on and consequences of a range of agronomic management and grazing strategies. However, modelling of multi-species swards needs to be validated including the dynamics of individual species in the swards, preferential selection by grazing animals and the impact on animal growth and nutrient flows.

Interaction of multispecies sward composition and harvesting management on herbage yield and quality from establishment phase to the subsequent crop

AbstractDelayed harvest during different periods of the year may help to increase the multifunctionality in terms of simultaneous flowering resource and forage provision of ley grassland. Interaction effects of harvesting regime and the grass sward composition on herbage yield and quality were therefore investigated in two multispecies swards in the present study (a simple sward with five vs. a complex sward with 16 sown species) that lasted from the establishment phase (2017) over two main production years (2018 and 2019) until the subsequent cropping phase (2020) where legacy effects were analysed by growing annual ryegrass (Lolium multiflorum gaudini). A particular drought in the year 2018 affected the botanical composition which resulted in a lucerne‐dominated complex sward and a grass‐rich simple sward thwarting the initial aims of studying complex sward treatments. Extended regrowth in early summer increased herbage yield significantly while herbage quality, weighted over the respective periods, was hardly affected by harvesting regime. No consequence of the harvesting regime resulted during the subsequent cropping phase where the plots previously grown to the lucerne‐dominated complex sward resulted in significantly greater herbage dry‐matter yield, nitrogen yield and lower weed biomass. Overall, the interaction between harvesting management and grass sward composition was never significant. It is concluded that no negative consequence for herbage quality results at extended regrowth during part of the year. However, further studies comparing complex with simple multispecies swards should consider different soil types under more humid climate.

Enhancing the Sustainability of Temperate Pasture Systems through More Diverse Swards

Temperate grasslands can be highly productive. However, those that are productive are generally heavily dependent on high inputs of nitrogen (N) fertilizer. Including legumes such as white clover (Trifolium repens L.) in the sward can reduce reliance on N fertilizer. Recent investigations have evaluated the potential of multispecies swards, which are defined as agronomically improved grasslands that include multiple plant functional groups, e.g., grasses, legumes, and forage forbs. Several of the benefits and challenges of multispecies swards are summarized in this review. To date, the most prominent forb species included in multispecies swards are chicory (Cichorum intybus L.) and ribgrass/ribwort plantain (Plantago lanceolata L.). Multispecies swards grown under reduced N fertilizer input conditions can produce as much biomass as monocultures receiving large quantities of N fertilizer. The nutritive value of multispecies swards may potentially be greater than grass-only swards, especially since forbs may contribute additional micro and macro minerals to livestock diet. While challenges associated with multispecies swards may include weed management and facilitating persistence of the forb species in particular, the overall evidence suggests that well-managed multispecies swards can enhance the productivity as well as environmental sustainability of grazing systems.

Source partitioning using N2O isotopomers and soil WFPS to establish dominant N2O production pathways from different pasture sward compositions.

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) emitted from agricultural soils and is influenced by nitrogen (N) fertiliser management and weather and soil conditions. Source partitioning N2O emissions related to management practices and soil conditions could suggest effective mitigation strategies. Multispecies swards can maintain herbage yields at reduced N fertiliser rates compared to grass monocultures and may reduce N losses to the wider environment. A restricted-simplex centroid experiment was used to measure daily N2O fluxes and associated isotopomers from eight experimental plots (7.8 m2) post a urea-N fertiliser application (40 kg N ha-1). Experimental pastures consisted of differing proportions of grass, legume and forage herb represented by perennial ryegrass (Lolium perenne), white clover (Trifolium repens) and ribwort plantain (Plantago lanceolata), respectively. N2O isotopomers were measured using a cavity ring down spectroscopy (CRDS) instrument adapted with a small sample isotope module (SSIM) for the analysis of gas samples ≤20 mL. Site preference (SP = δ15Nα - δ15Nβ) and δ15Nbulk ((δ15Nα + δ15Nβ) / 2) values were used to attribute N2O production to nitrification, denitrification or a mixture of both nitrification and denitrification over a range of soil WFPS (%). Daily N2O fluxes ranged from 8.26 to 86.86 g N2O-N ha-1 d-1. Overall, 34.2% of daily N2O fluxes were attributed to nitrification, 29.0% to denitrification and 36.8% to a mixture of both. A significant diversity effect of white clover and ribwort plantain on predicted SP and δ15Nbulk indicated that the inclusion of ribwort plantain may decrease N2O emission through biological nitrification inhibition under drier soil conditions (31%-75% WFPS). Likewise, a sharp decline in predicted SP indicates that increased white clover content could increase N2O emissions associated with denitrification under elevated soil moisture conditions (43%-77% WFPS). Biological nitrification inhibition from ribwort plantain inclusion in grassland swards and management of N fertiliser source and application timing to match soil moisture conditions could be useful N2O mitigation strategies.

Conservation efficiency and nutritive value of silages made from grass-red clover and multi-species swards compared with grass monocultures

Binary grass-clover and multi-species swards can increase herbage yields or facilitate reduced inputs of inorganic fertiliser nitrogen (N) compared with perennial ryegrass monocultures. However, the efficiency of the ensilage process and the nutritive value of silage produced from multi-species swards has not been documented. Replicate samples from grass-red clover binary mixture and multi-species mixture swards were ensiled in laboratory silos to assess the ensilability, fermentation characteristics, conservation losses and silage nutritive value compared with grass monocultures produced using inorganic N fertiliser. The results suggest that assessment of the ensilability and subsequent ensilage characteristics of binary and multi-species mixtures should be based on direct sampling from such mixtures rather than being predicted from values obtained from monocultures of constituent species. Under favourable ensiling conditions, unwilted binary mixtures and multi-species mixtures are satisfactorily preserved as silage, comparable to a perennial ryegrass monoculture receiving inorganic N fertiliser. However, when ensiled under more challenging crop conditions the mixtures exhibited a greater requirement for their preservation to be aided, compared with the perennial ryegrass monoculture. Despite the application of inorganic N reducing the legume content of multi-species mixture swards, it had relatively little effect on herbage ensilability or silage preservation. For all species treatments, silage nutritive values were primarily dependent on the pre-ensiling values, although herbage digestibility values declined during ensilage where the ensilage process was inefficient. The current study suggests that in order to be satisfactorily preserved as silage, binary grass-clover and multi-species swards have a greater requirement for an adequate rapid field wilt and/or effective preservative application compared with perennial ryegrass produced using inorganic fertiliser N.

Plant species identity drives soil microbial community structures that persist under a following crop.

Compared to monocultures, multi‐species swards have demonstrated numerous positive diversity effects on aboveground plant performance, such as yield, N concentration, and even legacy effects on a following crop. Whether such diversity effects are seen in the soil microbiome is currently unclear. In a field experiment, we analyzed the effect that three plant species (a grass, forb, and legume), and mixtures of these, had on soil fungal and bacterial community structures, as well as their associated legacy effects under a following crop, the grass Lolium multiflorum. We utilized six sward types, three monocultures (Lolium perenne, Cichorium intybus and Trifolium pratense), two bi‐species mixtures, and a mixture of the three species. Soil samples were taken from these swards in March (at the end of a three year conditioning phase) and in June, August, and September after L. multiflorum was established, that is, the legacy samplings. When present, the differing monocultures had a significant effect on various aspects of the fungal community: structure, OTU richness, the relative abundance of the phylum Glomeromycota, and indicator OTUs. The effect on bacterial community structure was not as strong. In the multi‐species swards, a blending of individual plant species monoculture effects (identity effect) was seen in (a) fungal and bacterial community structure and (b) fungal OTU richness and the relative abundance of the Glomeromycota. This would indicate that plant species identity, rather than diversity effects (i.e., the interactions among the plant species), was the stronger determinant. During the legacy samplings, structural patterns in the fungal and bacterial communities associated with the previous swards were retained, but the effect faded with time. These results highlight that plant species identity can be a strong driver of soil microbial community structures. They also suggest that their legacy effect on the soil microbiome may play a crucial role in following crop performance.

Does the Admixture of Forage Herbs Affect the Yield Performance, Yield Stability and Forage Quality of a Grass Clover Ley?

It is unclear whether the use of multi-species swards is a suitable measure for climate change adaptation by achieving high and stable dry matter (DM) production and good forage quality in grazing systems. The objective of the study is to evaluate whether a complex rather than a simple grass clover mixture enhances performance under nitrogen (N)-deficient conditions due to greater diversity in plant functional traits. During a four-year field experiment, a three-species and a seven-species grass clover mixture were compared under one cutting-for-conservation and two simulated grazing (defoliation every three or four weeks) treatments. The results revealed a similarity in the DM yields of both seed mixtures, indicating that in the given conditions the species in the simple mixture already offered crucial yield-determining functional traits. Different growth patterns, however, led to higher intra-annual yield stability in the complex mixture. In the cutting-for-conservation system, DM yields were higher, but this came at the expense of reduced metabolisable energy and crude protein contents and lower inter-annual yield stability. We conclude that higher seeding costs for multi-species mixtures are compensated by greater yield stability while offering the potential for additional eco-system services like enhanced carbon sequestration and diverse food for pollinators.

Drought tolerance is determined by species identity and functional group diversity rather than by species diversity within multi-species swards

Abstract Low-input grasslands depend on the presence of grasses and legumes for the provision of nitrogen and a sufficient amount and quality of herbage for livestock. Increasing variability in the amount and distribution of rainfall, associated with climate change, is a major factor affecting production from permanent grassland and particularly grass-clover swards. Previous work has shown that introduction of deep-rooting dicotyledonous forbs into grass-legume mixtures increases functional trait diversity (FTD), which facilitates the resistance and resilience of grassland to drought. It also increases species diversity and functional group diversity (FGD). However, the role of species diversity at a given level of FGD and associated FTD for the resistance and resilience of low-input grassland towards drought remains unclear. This knowledge is required to design forage mixtures adapted to drier climatic conditions. We conducted a drought-stress experiment with 16 different sown sward types, grown in cylindrical mesocosms, combining three levels of species diversity (one, three, five) and three levels of FGD (one, two, three) all being associated with FTD in terms of phenology, rooting depth and nitrogen fixation to determine whether maximum levels of species diversity or FGD promote adaptation to drought. The study was conducted over three drought-stress cycles in an open-sided greenhouse where the climate followed ambient natural conditions. Over the duration of 685 days, we found no clear species diversity effect but a distinct species identity effect on biomass production and agronomic water use efficiency. A positive species identity effect depended largely on white clover presence and on the FGD within mixtures. The best performing mixtures for resistance and resilience combined FGD and FTD in a complementary way, irrespective of whether the swards contained three or five species, as FGD and FTD were already maximized within the best-performing three-species swards. Increasing complementarity of traits by species grown in carefully designed mixtures is one measure to achieve diversity effects and facilitate future sustainable grassland production. We propose to exploit the benefits of species identity and functional group diversity in designing future mixtures to cope with drought.

Yield of binary- and multi-species swards relative to single-species swards in intensive silage systems

Binary- and multi-species sown mixtures may increase herbage yield and/or reduce inorganic nitrogen (N) requirement compared to perennial ryegrass (PRG) (Lolium perenne L.) swards. A split-plot design was used to compare yields of binary- and multi-species mixtures to single-species swards of three grasses and red clover managed for intensive silage production under varying N application rates. Perennial and Italian (Lolium multiflorum Lam.) ryegrasses had greater annual yields when grown as single species receiving 360 kg N/ha per year than in binary mixtures with red clover (Trifolium pratense L.) receiving 0 kg N/ha per year, whereas timothy (Phleum pratense L.) produced equally high yields in both situations. When no inorganic N was applied, the annual dry matter yield of Mix 1 (10,738 kg/ha; PRG, timothy, red clover and white clover (Trifolium repens L.) and Mix 2 (11,679 kg/ha; PRG, timothy, red clover, ribwort plantain (Plantago lanceolata L.) and chicory (Cichorium intybus L.)) was greater than that of a PRG sward (PRG/0N; 5,885 kg/ha) and derived more from the contribution of legumes than herbs. This yield advantage of mixtures declined as inorganic N input increased, as did the legume and herb proportions in the multi-species swards. When averaged across rates of inorganic N input, Mix 2 had a greater annual yield than Mix 1 (12,464 vs. 11,893 kg/ha). Mix 2 receiving no inorganic fertiliser N and both Mix 1 and Mix 2 receiving 120 kg N/ha per year matched the annual yield achieved by PRG receiving 360 kg N/ha per year. Our results indicate that the yield performance of binary- and multi-species grassland swards should be measured in situ rather than predicted from single-species swards of constituent species.

Sward composition and soil moisture conditions affect nitrous oxide emissions and soil nitrogen dynamics following urea-nitrogen application

Increased emissions of N2O, a potent greenhouse gas (GHG), from agricultural soils is a major concern for the sustainability of grassland agriculture. Emissions of N2O are closely associated with the rates and forms of N fertilisers applied as well as prevailing weather and soil conditions. Evidence suggests that multispecies swards require less fertiliser N input, and may cycle N differently, thus reducing N loss to the environment. This study used a restricted simplex-centroid experimental design to investigate N2O emissions and soil N cycling following application of urea-N (40 kg N ha−1) to eight experimental swards (7.8 m2) with differing proportions of three plant functional groups (grass, legume, herb) represented by perennial ryegrass (PRG, Lolium perenne), white clover (WC, Trifolium repens) and ribwort plantain (PLAN, Plantago lanceolata), respectively. Swards were maintained under two contrasting soil moisture conditions to examine the balance between nitrification and denitrification. Two N2O peaks coincided with fertiliser application and heavy rainfall events; 13.4 and 17.7 g N2O-N ha−1 day−1 (ambient soil moisture) and 39.8 and 86.9 g N2O-N ha−1 day−1 (wet soil moisture). Overall, cumulative N2O emissions post-fertiliser application were higher under wet soil conditions. Increasing legume (WC) proportions from 0% to 60% in multispecies swards resulted in model predicted N2O emissions increasing from 22.3 to 96.2 g N2O-N ha−1 (ambient soil conditions) and from 59.0 to 219.3 g N2O-N ha−1 (wet soil conditions), after a uniform N application rate. Soil N dynamics support denitrification as the dominant source of N2O especially under wet soil conditions. Significant interactions of PRG or WC with PLAN on soil mineral N concentrations indicated that multispecies swards containing PLAN potentially inhibit nitrification and could be a useful mitigation strategy for N loss to the environment from grassland agriculture.

Herbage nutritive value of binary- and multi-species swards relative to single-species swards in intensive silage systems

The nutritive value of sown binary- and multi-species grassland mixtures may differ from the values expected based on single-species swards of their constituent species. Field plots were established in a split-plot design to assess the nutritive value of binary- and multi-species mixtures compared to single-species swards of three grass species and red clover (RC) (Trifolium pratense L.) managed for intensive silage production. The nutritive value of grass–legume binary mixtures reflected the values of the constituent species grown on their own, and thus may be predicted from monoculture values. The relatively low digestibility (dry matter digestibility [DMD]) and crude protein (CP) content of the Italian ryegrass (Lolium multiflorum L.) sward compared to perennial ryegrass (Lolium perenne L.) and timothy (Phleum pratense L.) suggests that it may have a limited role in binary- or multi-species swards. Herbage nutritive value in the multi-species swards (Mix 1: perennial ryegrass, timothy, RC and white clover [Trifolium repens L.]; Mix 2: perennial ryegrass, timothy, RC, ribwort plantain [Plantago lanceolata L.] and chicory [Cichorium intybus L.]) appeared to be influenced more by the presence of legumes than herbs. Compared to perennial ryegrass, the multi-species swards had a slower rate of DMD decline prior to Cut 1, but subsequently had lower DMD values at the mid-season harvests. Both multi-species mixtures exhibited DMD, water-soluble carbohydrate (WSC) and CP values that would not have been predicted from their constituent species and thus need to be measured on herbage from field plots growing these mixtures.

Herb species inclusion in grazing swards for dairy cows—A systematic review and meta-analysis

A systematic review and meta-analysis were conducted to estimate the effect of herb species on milk production and urinary nitrogen (UN) excretion from grazing dairy cows. Grazing swards consisting of herb species grown with either a grass species or a grass and legume (multispecies swards) were compared with non-herb-containing swards consisting of a grass species grown as a monoculture or grass-legume swards (simple swards). A literature search was completed using the online databases CAB Direct, Web of Science, and Google Scholar, using the search strategy "dairy cow", "herb OR forb OR phorb", and "grazing". Milk production data, variance, and sample size were required for eligibility. In all, 116 studies were identified. Following eligibility screening, 11 papers from 6 journals, published between 2006 and 2018, were available for analysis. Studies were from New Zealand (N = 7), Australia (N = 3), and the United States (N = 1). The population was either Holstein Friesian or Holstein Friesian × Jersey dairy cows, with a range in mean daily milk yield (MY) from 12.1 kg to 34.7 kg (mean = 18.6 kg). A total of 25 comparisons were used for milk production analysis, with 324 and 284 cows included in multispecies and simple sward groups respectively. Data analysis was conducted in R using a random effects, robust variance estimation model (R Foundation for Statistical Computing, Vienna, Austria). Heterogeneity was reported using the I2 statistic. Milk production was significantly increased. Analysis of MY resulted in a weighted mean difference (WMD) of +1.20 kg/d (95% CI = 0.90, 1.49; I2 = 4%). Fat and protein kg were also significantly increased (WMD +0.06 kg/d; CI = 0.01, 0.11). Urinary nitrogen excretion was estimated from milk urea nitrogen when reported (n = 6). A WMD of -28.1 g of N/d (95% CI = -81.1, 24.9) was generated, with heterogeneity high among studies (I2 = 75%). This meta-analysis shows the potential benefits of multispecies swards. Although we saw no significant difference in UN excretion, an increase in milk production was found.

The effect of grazing versus cutting on dry matter production of multispecies and perennial ryegrass‐only swards

AbstractDry matter (DM) production of multispecies swards compared to perennial ryegrass (Lolium perenne; PRG) swards under intensive grazing warrants investigation as it is relatively unknown. A 5 × 2 factorial experiment, with five sward types and two defoliation methods, was used to investigate the effect of grazing versus cutting on dry matter (DM) production of multispecies and PRG‐only swards. Five sward types were established namely: a PRG‐only sward, receiving 250 kg N ha−1 year−1 (PRG250), and a PRG‐only sward (PRG90), a two‐species sward with PRG and white clover (Trifolium repens; PRGWC), a six‐species sward (6S) and a nine‐species sward (9S), each receiving 90 kg N ha−1 year−1. Cutting plots measured 1.95 × 10 m and grazing plots measured 10 × 10 m. All plots were harvested concurrently every 21–30 days from April‐November for two years (2015 and 2016). A strip from the grazing plots was cut for DM yield determination prior to turning in cattle for grazing. There was an interaction between sward type and defoliation method (p < .01), whereby there was no effect of defoliation method on the PRG‐only swards, however, the annual DM production of PRGWC, 6S and 9S swards reduced under grazing compared to cutting (p < .001; on average 1,929 kg DM/ha lower). Multispecies swards had lower DM production under grazing compared to cutting, while the DM yield of PRG‐only swards was unaffected by defoliation method.

Milk yield and nitrogen excretion of dairy cows grazing binary and multispecies pastures

AbstractThree grazing experiments were carried out in late spring (early lactation), summer (mid‐lactation) and autumn (late lactation) to compare the effects of perennial ryegrass cultivar or grass species, sown in binary or multispecies mixtures, on milk yield and nitrogen excretion of dairy cows. Replicated groups of multiparous Holstein Friesian × Jersey cows were offered either a control or high‐sugar perennial ryegrass (Lolium perenne) or tall fescue (Festuca arundinacea) base grass in a binary mixture with white clover (Trifolium repens) or in a multispecies mixture with additional legumes, bromegrass (Bromus willdenowii) and forbs. During each 9‐day experiment, botanical composition, milk production and faecal and urine composition were measured. Milk solid (MS) yield for the control ryegrass, high‐sugar ryegrass and tall fescue grass types averaged, respectively, 1.53, 1.64 and 1.70 kg MS cow−1 day−1 for a binary mixture sward, compared with 1.65, 1.54 and 1.53 kg MS cow−1 day−1 for a multispecies sward. Legume content influenced milk production more than the number of species present in a mixture. There was lower urine N concentration from a multispecies sward compared with a binary mixture. Urine N concentration of cows grazing the control ryegrass, high‐sugar ryegrass and tall fescue grass types averaged, respectively, 4.6, 5.3 and 6.8 g N L−1 for a binary mixture, compared with 4.1, 3.9 and 3.9 g N L−1 for a multispecies mixture. Feeding dairy cows on multispecies swards containing forbs presents an opportunity to reduce N losses without compromising milk yield.

Shoot growth and phosphorus–nitrogen relationship of grassland swards in response to mineral phosphorus fertilization

The sustainable P management of grassland ecosystems require a better understanding of the effect of P fertilization on the growth of grassland swards and the relationship between shoot P and N concentrations with the overall goal of developing improved methods of predicting P requirements of grassland swards. Our objectives were to determine the importance of P supply during the primary growth in spring, to analyze the optimal relationship between shoot P and N concentrations for timothy (Phleum pratense L.) and multi-species swards under a wide range of P nutrition, and conditions of soil and climate, and to confirm for grassland swards the decrease in the N:P ratio during crop growth previously reported for annual crops. Experiments with varying rates of P fertilization were conducted for two to five consecutive years at sites with timothy swards in Canada (Lévis, Normandin, Charlottetown, and Quebec) and Finland (Maaninka), and at sites with multi-species swards from long-term P fertilization experiments in Switzerland (Les Verrières) and France (Ercé). Dry matter (DM) yield, and N and P concentrations were measured on four dates with one-week intervals from the vegetative to late heading stages of development during primary growth. Our results (i) indicate that a P deficiency mostly affects the early season growth of grassland swards corresponding to shoot biomass less than approximatively 1MgDMha−1, (ii) confirm the optimal relationship between shoot P and N concentrations for timothy and multi-species swards but with variations of the relationship with the level of N nutrition and between timothy and multi-species swards, and (iii) confirm for grassland swards the decrease in the N:P ratio during the primary growth and the close relationship of the N:P ratio to shoot biomass.

Species Diversity Effects on Productivity, Persistence and Quality of Multispecies Swards in a Four-Year Experiment.

Plant species diversity may benefit natural grassland productivity, but its effect in managed grassland systems is not well understood. A four-year multispecies grassland experiment was conducted to investigate the effect of species diversity–legumes and non-leguminous forbs–on productivity, persistence and sward quality under cutting or grazing regimes and with or without slurry application. Three mixtures were established– 3-mix: grass, red and white clover, 10-mix: 3-mix plus birdsfoot trefoil and six non-leguminous forbs, and 12-mix: 10-mix plus lucerne and festulolium. Species diversity increased sward production and yield persistence under cutting regime. The 12-mix had the highest yield from the second year onwards and no statistically significant yield reduction over four years, while annual yields in the 3-mix and 10-mix decreased significantly with increasing grassland age. The higher yield in the 12-mix was mainly due to the inclusion of high-yielding lucerne. The 10-mix and 12-mix had lower proportions of unsown species than the 3-mix, the difference being dependent on grassland age. Generally, the 3-mix had higher concentrations of in-vitro organic matter digestibility (IVOMD), neutral detergent fiber (NDF) and crude protein (CP), and a lower concentration of ash than the 10-mix and 12-mix. Slurry application increased annual yield production by 10% and changed the botanical composition, increasing the proportion of grass and decreasing the proportion of legumes. Compared to cutting, grazing increased forage production by 9% per cut on average and lowered legume and forb proportions in the mixtures, but yields did not differ among the three mixtures. Overall, our results suggest that species diversity increases sward productivity and persistence only under an ungrazed cutting regime. We conclude that increasing species diversity by selecting appropriate species with compatible management is key to achieving both high yields and high persistence in managed grasslands.

Effects of defoliation frequency and nitrogen fertilization on the production and potential for persistence of Dactylis glomerata sown in multispecies swards

AbstractManagement decisions should facilitate the dominance of C3 perennial grasses over annuals. This study examined the effects of defoliation frequencies and nitrogen fertilization on the productivity and potential for persistence of Dactylis glomerata L. (DG cocksfoot, perennial) in multispecies swards. Treatments were randomly applied to 24 mini‐swards of DG + Bromus willdenowii Kunth (BW prairie grass, annual/biennial) in a factorial design of four defoliation frequencies, based on number of leaves per tiller, by two nitrogen winter fertilization levels (N− or N+). Regardless of fertilization, very frequent and repeated defoliations were related to decreases of about 43% of aboveground biomass and frequent defoliations with decreases of about 44% of vegetative tillers associated with horizontal space occupation and potential for persistence. Nevertheless, differences in DG aerial productivity or reserves were not detected between frequent and optimal defoliation frequencies. Combined effects of N+ and optimal frequency were related to root biomass increment of about 200%, compared with frequent defoliation, associated with competitiveness and survival of DG. Optimal defoliation frequency would have ecological but not production advantages, compared with frequent defoliations. The results are discussed in terms of more objective decision‐making in the management of multispecies swards.

Pasture intake and milk production of dairy cows rotationally grazing on multi-species swards

Increasing plant species diversity has been proposed as a means for enhancing annual pasture productivity and decreasing seasonal variability of pasture production facing more frequent drought scenarios due to climate change. Few studies have examined how botanical complexity of sown swards affects cow performance. A 2-year experiment was conducted to determine how sward botanical complexity, from a monoculture of ryegrass to multi-species swards (MSS) (grasses-legumes-forb), affect pasture chemical composition and nutritive value, pasture dry matter (DM) intake, milk production and milk solids production of grazing dairy cows. Five sward species: perennial ryegrass (L as Lolium), white clover and red clover (both referred to as T as Trifolium because they were always sown together), chicory (C as Cichorium) and tall fescue (F as Festuca) were assigned to four grazing treatments by combining one (L), three (LT), four (LTC) or five (LTCF) species. Hereafter, the LT swards are called mixed swards as a single combination of ryegrass and clovers, whereas LTC and LTCF swards are called MSS as a combination of at least four species from three botanical families. The experimental area (8.7 ha) was divided into four block replicates with a mineral nitrogen fertilisation of 75 kg N/ha per year for each treatment. In total, 13 grazing rotations were carried out by applying the same grazing calendar and the same pasture allowance of 19 kg DM/cow per day above 4 cm for all treatments. Clover represented 20% of DM for mixed and MSS swards; chicory represented 30% of DM for MSS and tall fescue represented 10% of DM for LTCF swards. Higher milk production (+1.1 kg/day) and milk solids production (+0.08 kg/day) were observed for mixed swards than for ryegrass swards. Pasture nutritive value and pasture DM intake were unaffected by the inclusion of clover. Pasture DM, organic matter and NDF concentrations were lower for MSS than for mixed swards. Higher milk production (+0.8 kg/day), milk solids production (+0.04 kg/day) and pasture DM intake (+1.5 kg DM/day) were observed for MSS than for mixed swards. These positive effects of MSS were observed for all seasons, but particularly during summer where chicory proportion was the highest. In conclusion, advantages of grazing MSS on cow performance were due to the cumulative effect of improved pasture nutritive value and increased pasture DM intake that raised milk production and milk solids production.

Evaluation of a Rising Plate Meter for Use in Multispecies Swards

Core Ideas The accuracy of rising plate meter in multispecies swards has not been tested thoroughly. Forcing X intercept to zero increases the precision of the calibration equations. Higher‐order polynomial regressions do not result in more accurate forage estimates. The rising plate meter (RPM) provides rapid estimates of herbage mass (HM). Accurate calibration of the RPM is difficult due to variability in forage management, growth, and species composition. The RPM is typically calibrated by linear regression of HM and RPM height; however, the r2 is usually low. Curvilinear regression, with the X intercept set to zero, could provide a more robust calibration equation and decrease variability in RPM estimates. Three Pennsylvania organic dairy farms grazing lactating dairy cattle on multispecies pastures were used to determine measured HM and estimated HM using a RPM. Removal of the X intercept increased the adjusted r2 of all equations between 42.8 and 89.0%. Use of quadratic and cubic regression only resulted in 0.01 to 0.02 increase in adjusted r2. Linear regression remains the simplest and preferred method of calibration; however, error can be reduced by setting calibration equations so that zero RPM height is associated with zero HM.