Grass-legume Mixtures Research Articles

Forage quality and energy content of perennial legume-grass mixtures at three level of n fertilization

The aim of this study was to investigate fodder quality and nutritive value of different grass-legumes mixtures influenced by various level of N fertilization. Studied factors had an impact only on the content of crude protein (CP), crude protein yield (CPY) and nitrate content in the forage. The level of N fertilizer showed a highly significant and positive impact on the CP and nitrate content. Treatment with 210 kg N ha-1 is characterized by the highest content of CP and nitrate of 189.7 g kg-1 DM and 2524 ppm, respectively, and the highest protein yield of 1.95 t ha-1. The value of nitrate in the forage does not exceed the limit that is considered hazardous to the health of animals. Energy value of forage obtained from the grasslands of ME ?7.75 and NEL?4.32 MJ kg-1 DM is lower than values obtained in other studies.

THE YIELD STABILITY AND QUALITY OF LEGUMES DURING TWO CONSECUTIVE, EXTREMELY DRY YEARS

Abstract This study highlights the effect of drought and ambient temperature on performance and herbage quality of legume monocultures and grass-legume mixtures. In a field experiment, the total dry matter yield, seasonal pattern of dry matter yield distribution, content of crude protein and crude fibre of monocultures of red clover and alfalfa and grass-legume mixtures were investigated during two consecutive dry years (2011-2012). Alfalfa cultivars Kamila and Tereza grown as monocultures or as mixtures with Festulolium braunii (cultivar Achilles) outperformed the red clover cultivars Fresko and Veles and provided a well-balanced total and seasonal dry matter yield during both years. Across all experimental years, crude protein content was significantly higher at alfalfa monocultures and mixture when compared with clover monocultures (P < 0.05). However, considerable lower content of crude fibre at clover monocultures in comparison with alfalfa ones was found. Responses of nutritive parameters of both legume species to weather variables were different. Crude protein content in red clover was independent of rainfall and temperature. In contrast, the crude fibre content correlated with temperature whereby the alfalfa monocultures showed stronger correlations (P < 0.05) than red clover monocultures.

Forage energy to protein ratio of several legume–grass complex mixtures

The energy to protein ratio of forages affects ruminant N use efficiency but little is known on its variation among legume–grass complex mixtures. Our objective was to determine the variation in the ratio of forage readily-available energy to proteins along with the associated variation in yield and digestibility by mixing three or four grass species in combination with one of two legume species. Four grass mixes [#1 – timothy (Phleum pratense L.), meadow fescue (Festuca elatior L.), and Kentucky bluegrass (Poa pratensis L.); #2 – timothy, meadow fescue, reed canarygrass (Phalaris arundinacea L.), and Kentucky bluegrass; #3 – tall fescue [Schedonorus phoenix (Scop.) Holub], meadow bromegrass (Bromus biebersteinii Roemer & J.A. Schultes), orchardgrass (Dactylis glomerata L.), and Kentucky bluegrass; #4 – tall fescue, meadow bromegrass, reed canarygrass, and Kentucky bluegrass] were grown with either alfalfa (Medicago sativa L.) or birdsfoot trefoil (Lotus corniculatus L.) at two sites with measurements taken on two simulated grazing events of the first post-establishment year. The water soluble carbohydrate (WSC) to crude protein (CP) ratio among the eight legume–grass mixtures ranged from 0.64 to 1.04, while the ratio of readily fermentable carbohydrate fractions A and B1 to readily soluble protein fractions A and B1 [(CA+CB1)/(PA+PB1)], estimated using the Cornell net carbohydrate and protein system, ranged from 4.33 to 5.64. This significant variation in the two ratios used to characterize the energy to protein balance was due to both legume species and grass mixes. Alfalfa-based complex mixtures had greater WSC/CP and (CA+CB1)/(PA+PB1) than birdsfoot trefoil-based mixtures (0.94 vs. 0.69; 5.42 vs. 4.47) but a lower in vitro true digestibility (IVTD; 902 vs. 913g/kg dry matter, DM). The grass species mix #2 (timothy, meadow fescue, reed canarygrass, and Kentucky bluegrass) provided the best combination of high readily-available energy to protein ratio (WSC/CP=0.87; (CA+CB1)/(PA+PB1)=5.08), high DM yield, and average IVTD. The complex mixtures including alfalfa and meadow fescue had the best readily-available energy to protein ratio and DM yield. Our results confirm the possibility of improving the balance between readily-available energy and proteins through the choice of species in complex mixtures made of one legume and three or four grass species.

Soil profile carbon and nitrogen in prairie, perennial grass–legume mixture and wheat-fallow production in the central High Plains, USA

Conversion of native prairie land for agricultural production has resulted in significant loss and redistribution of soil organic matter (SOM) in the soil profile ultimately leading to declining soil fertility in a low-productivity semiarid agroecosystem. Improved understanding of such losses can lead to development of sustainable land management practices that maintain soil fertility and enhance soil quality. This study was conducted to determine whether conservation practices impact soil profile carbon (C) and nitrogen (N) accumulation in central High Plains. Soil samples were taken at four-depth increments to 1.2m in July of 2011 from five unfertilized fields under long-term management with varying degrees of soil disturbance: (1) historic wheat (Triticum aestivum)-fallow (HT) – managed with tillage alone, (2) conventional wheat-fallow (CT) – input of herbicides for weed control and fewer tillage operation than historic wheat-fallow, (3) no-till wheat-fallow (NT) – not plowed since 2000 and herbicides used for weed control, (4) grass–legume mixture – established in 2005 as in the Conservation Reserve Program (CRP), and (5) native mixed grass prairie (NP) – representing a relatively undisturbed reference location. Cumulative soil organic C (SOC) was not significantly different among the three wheat-fallow systems when the whole profile (0–120cm) was analyzed. However, SOC, dissolved organic C (DOC), and total soil N contents decreased in the direction NP>CRP≥NT>HT≥CT in the surface 0–30cm depth. In the surface 0–30cm depth, estimated annual SOC storage rate averaged 0.28Mg Cha−1year−1 since the cessation of tillage in 2000 and 0.58Mg Cha−1year−1 since the establishment of CRP grass–legume mixture in 2005. Cumulative soil inorganic C (SIC) accumulation ranged between 8.1 and 24.9Mgha−1and was greatest under wheat-fallow systems, particularly at deeper soil layers, relative to the perennial systems (NP and CRP). Results from this study suggest that repeated soil disturbance induced by cropping and fallow favored large accumulation of SIC which presence may result in decline in soil fertility and productivity; whereas conversion from tilled wheat-fallow to CRP grass–legume mixture offers great SOC storage potential relative to NT wheat-fallow practices.

Assessing the Effect of Securing Bales with either Polyethylene Film or Netting on the Fermentation Profiles, Fungal Load, and Plastic Consumption in Baled Silage of Grass-Legume Mixtures

Abstract. The aim of this research was to study the possibility of reducing mold growth on the surface of low-moisture baled silage, without increasing plastic costs, by replacing polyethylene net with polyethylene tying-film to secure large round bales in the baler chamber. Two trials (I and II) were performed on first and third cuts of the same grass-legume mixture located in the Po plain. In each trial, a total of 16 round bales were baled after 24 h of wilting and half of them were secured with net while the other half were secured with polyethylene film. Four bales from each secure method were randomly assigned to the wrapping layer treatments (four or six layers). All the bales were stored outdoors on their flat ends. After 250 days of storage, the bales were examined to establish their fermentative profile and microbiological quality. Total plastic consumption and costs were also evaluated. The high DM content of the silages restricted fermentation and resulted in low concentrations of acids in both trials, with pH in the inner part of the bale ranging from 5.41 to 5.70. The tying film was well distributed on the curved side and over the edges of the bales and did not show signs of damage due to mechanical operations (ejection, handling, wrapping). The use of tying film, compared to net led to a reduction in the number of holes and an improvement in the anaerobic status of the baled silage, even with just four layers of stretch-film, and resulted in a decrease in mold counts and visible mold growth over the bale surface. It was concluded that securing baled silage with tying film before wrapping could reduce the fungal load of baled silage without increasing the total plastic usage and costs.

Grass–Legume Proportions in Forage Seed Mixtures and Effects on Herbage Yield and Weed Abundance

Formulating grass–legume mixtures requires knowledge of how the proportion of species in a seed mixture (i.e., species evenness) affects productivity and weed abundance. We hypothesized that mixtures with more equal proportions of species in the seed mixture (i.e., greater species evenness) would have greater productivity and fewer weeds than mixtures dominated by one or two species or monocultures. Two experiments with 15 mixtures and monocultures of orchardgrass (Dactylis glomerataL.), quackgrass (Elytrigia repensL.), alfalfa (Medicago sativaL.), and white clover (Trifolium repensL.) (Exp. 1) or 15 mixtures and monocultures of meadow fescue [Schedonorus pratensis(Huds.) P. Beauv.], reed canarygrass (Phalaris arundinaceaL.), red clover (T. pratenseL.), and kura clover (T. ambiguumL.) (Exp. 2) were sown in autumn 2008 at four locations in Pennsylvania and Wisconsin. In each experiment, there were four monocultures, four mixtures dominated by one species, six mixtures dominated by pairs of species, and one equal mixture. Mixtures and monocultures were harvested four to five times each year from 2009 to 2011. Mixtures often had more biomass than the average of legume or N‐fertilized grass monocultures. Mixtures with more equal proportions of species in the seed mixture, however, did not have more biomass or fewer weeds than other mixtures. Rather, differences in yield were related to the dominant species in the mixture. Optimal legume percentages (30–40%) in the harvested biomass were achieved with a wide range of grass and legume seed proportions, which suggested that farmers have wide flexibility in formulating seed mixtures for pastures.

Strategies to Control Competition to Strip‐Planted Legume in a Warm‐Season Grass Pasture

ABSTRACTPlanting rhizoma peanut (RP) (Arachis glabrata Benth.) in tilled strips in existing bahiagrass (Paspalum notatum Flüggé) pastures may be an option for establishing legume–grass mixtures in the U.S. Gulf Coast, but management during establishment is not well defined. The objectives were to determine the effect of weed control strategies and N fertilizer on RP establishment in the strip. Treatments were the factorial combinations of six weed control strategies—(i) control (no herbicide and no mowing), (ii) mowing (every 28 d to 10‐cm stubble height), or a single application of herbicides (kg a.i. ha−1) (iii) pendimethalin (0.93), (iv) clethodim (0.10), (v) imazapic (0.07), or (vi) imazapic (0.07) plus 2,4‐D amine (0.28)—and two N rates (0 and 50 kg ha−1 yr−1). Cover (approximately 31%) and frequency (approximately 70%) of RP were not different in imazapic and imazapic plus 2,4‐D treatments, but they were greater than in the other treatments (<10 and 25%, respectively). Light reaching the level of RP in the canopy in imazapic and imazapic plus 2,4‐D treatments was ≥96% of incident light until July and was consistently greater than the other treatments. Nitrogen fertilization following herbicide treatment increased RP cover by 10 percentage points for imazapic and imazapic plus 2,4‐D. Results indicate that imazapic or imazapic plus 2,4‐D offer sufficient control of weed competition to improve establishment of strip‐planted RP, and application of 50 kg N ha−1 increases RP establishment if grass and weed competition is controlled.

Effects of growth habits of grasses on weed population and dry matter yield in grass-legume swards

Resumen en: A study was carried out over a period of two years to evaluate the ability of 12 grass-legume mixtures to compete with weeds over a 12-week period follow...

Growth and Nutritive Value of Three Old World Bluestems and Three Legumes in the Semiarid Texas High Plains

Benefits of legume–grass mixtures are well known but water required for legume growth limits use in semiarid, irrigation‐dependent environments. Research conducted over 4 yr (2007 to 2010) in the semiarid Texas High Plains compared alfalfa (Medicago sativa L.), yellow sweetclover [Melilotus officinalis (L.) Lam.], and sainfoin (Onobrychis viciifolia Scop.) interseeded into three old world bluestems (Bothriochloa spp.). No fertilizer N (control) and 60 kg N ha−1 treatments were applied to grasses alone. The five treatments imposed on each grass were replicated three times in a randomized complete block design with the legume and N treatments in a split‐plot arrangement. Irrigation water applied through subsurface drip was limited to 250 mm annually. Annual dry matter yield of grass monocultures exceeded grass–legume mixtures in year 1 but yield of grass–legume mixtures was similar to N fertilizer in subsequent years. Crude protein (CP) and dry matter digestibility (DMD) were higher while cell wall was lower in the mean of grass–legume mixtures than grass monocultures. Nitrogen fertilization increased CP but had little effect on cell wall or DMD (g kg−1). Nutritive value benefits from yellow sweetclover occurred in year 1 and then declined while benefits from alfalfa increased over 4 yr. Lower sainfoin stands limited nutritive value. With limited irrigation, benefits of including legumes can exceed 60 kg N ha−1 in this semiarid environment.

Changes in the forage yield and quality of legume–grass mixtures throughout a vegetation period

The aim of the present study was to determine the changes in the forage yield and quality of binary and ternary mixtures of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), smooth bromegrass (Bromus inermis Leys.), orchardgrass (Dactylis glomerata L.), and meadow fescue (Festuca pratensis Huds.) throughout a vegetation period. Plots were established in 2008 in Isparta, Turkey, in a randomized complete block design with 3 replicates. Four cuttings were done during the 2009 and 2010 vegetative periods. The levels of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and relative feed value (RFV) were determined for each monoculture and mixture. The highest total dry matter yields were obtained from the alfalfa-smooth bromegrass mixture at 16.65 t ha^{-1} in 2009 and 16.00 t ha^{-1} in 2010. Red clover exhibited the lowest NDF (368 g kg^{-1}) and ADF (256 g kg^{-1}) concentrations compared with the other forage plants, whereas alfalfa displayed the highest CP content (181 g kg^{-1}). The RFV of the mixtures ranged from 107 to 145, and the decrease in yield was larger for the grasses than the legumes throughout the vegetation period. The results indicated that alfalfa-smooth bromegrass, alfalfa-orchardgrass, and alfalfa-meadow fescue mixtures could make valuable legume-grass mixtures.

Silvipastoral approach to improve productivity of native pastures for improved livestock production in mid hills of Western Himalaya

Animal husbandry, an integrated component of hill agriculture has caused severe land degradation due to continuous grazing and massive reduction in the vegetation cover. The feeding of livestock depends primarily on natural resources, viz. grasslands, forests, cultivated fodder, field bunds, crop residues, weeds and fodder trees. The silvipasture laid out at 3 sites, viz. Ghanetta (1100 m above msl), Dagoh (1020 m above msl) in Kangra district and Jogindernagar (1175 m above msl) in Mandi district of Himachal Pradesh had a slope of 15–35%, 25–60% and 15–30%, respectively. Silipastures were laid out with active participation of native beneficiaries. Survival rate of Bauhinia variegata, Morus alba and Grewia optiva was highest (90% and above) at all the 3 sites. Growth in terms of height gained by the fodder trees was similar at all the 3 sites. At the end of third year, the 2- year-old saplings transplanted at all the 3 sites, Albizia attained a height of about 200 cm, Artocarpus (110 cm), Bauhinia (150 cm), Grewia (120 cm) and Morus (130 cm). During third year of the study fresh biomass of 31.6, 28.6 and 30.8 t/ha were harvested from Ghanetta, Jogindernagar and Dagoh with dry matter yield of 8.67, 6.98 and 7.62 t/ha, respectively. Crude protein was in the range of 12.33 to 13.46% due to grass legume mixture. The average body weight gain ranged from 358.50 to 388.53 g/day in indigenous male cattle. Runoff (% of rainfall) was higher at Jogindernagar (33.4%) followed by Dagoh (29.9%) and Ghanetta (20.4%) owing to their land slopes. Cut and carry system was most efficient at all the sites allowing only 15.8% runoff compared to 20.6% and 27.1%, respectively under controlled and traditional grazing. Among the resource conservation measures, trenching in combination with vegetative barrier allowed only 6.8% of rain as runoff compared to 38.9% under control (no measure). Trenches formed in upper, middle and lower parts along the slope retained on an average 13.9, 16.6 and 19.1 cm sediments, respectively. Among the sites, the sediment retention was highest at Dagoh (18.7 cm) followed by Joginder Nagar (16.9%) and lowest at Ghanetta (14.0 cm). Therefore, silvipasture seems to be one of the best options for regenerating and improving the Himalayan grasslands. The system can enhance the forage availability many fold, which can assure the sustainability of on-going livestock rearing and in the process the resource base gets conducive inputs for its conservation.

Efectos de los hábitos de crecimiento de pastos sobre las adventicias y los rendimientos en praderas de gramíneas y leguminosas

Durante un período de dos años, se evaluó la capacidad de 12 mezclas de gramíneas y leguminosas pratenses tropicales para competir con las adventicias durante 12 semanas después de la plantación en 2004 y después de un corte en 2005. Se registraron la altura de planta, número de hojas, la población de adventicias y la producción de materia seca (MS) de las adveenticias y mezclas de pastos en las semanas 6 y 12 después de la siembra. El número de hojas de las gramíneas pratenses aumentó lentamente durante las primeras 8 semanas después de la siembra, luego aumentó exponencialmente entre las 9 y 12 semanas, llegando a 145 hojas/planta. Las gramíneas de crecimiento erecto forman más hojas (p

Set-aside fields in agri-environment schemes can replace the market-driven abolishment of fallows

Economic pressures from increased commodity prices and the growing demand for land for biomass plantations led to the abolition of compulsory set-aside fields in the European Union in 2008, affecting ca. 10% of total agricultural area. This area is now managed more intensively, and this is expected to adversely affect farmland biodiversity. Unfortunately, no mitigation of set-aside loss was introduced. Here we examined, whether or not set-aside fields managed in voluntary agri-environment schemes have the potential to improve farmland bird populations, as indicators of farmland biodiversity. We chose one, two and three year-old set-aside fields sown by a grass–legume mixture when established and selected winter cereal fields and semi-natural grasslands in Hungary as control sites. Relative abundance of birds was assessed; species were assigned to feeding guilds and classified according to their European conservation status. Species richness of herbaceous plants, cover of bare ground and vegetation height were used as covariates. Set-aside fields had higher species richness and abundance of birds compared to the adjacent winter cereal fields, similar to semi-natural grasslands. We found a positive correlation between set-aside age and farmland bird species richness and abundance. This can be explained mainly by the altered vegetation, especially the shorter vegetation height from the second year in the set-aside fields. We found no difference in the distribution pattern of species richness and abundance between feeding guilds according to set-aside age and habitat types. The wide scale application of voluntary set-aside management in agri-environment programs therefore has a high potential to mitigate the negative effects from the loss of compulsory set-aside schemes, and thus need the allocation of considerable resources in the forthcoming reformed CAP.

Effect of legume-cereal mixtures on the diversity of bacterial communities in the rhizosphere

Aboveground plant diversity is known to influence belowground diversity and ecosystem processes. However, there is little knowledge of soil microbial succession in legume-grass mixtures. Therefore, this study was designed to determine the effect of oat and common vetch binary mixtures at three seeding rates on soil bacterial communities. Denaturing gradient gel electrophoresis (DGGE) of 16S rDNA fragments was used to profile the structure of the bacterial community in the rhizosphere. Compared with a monoculture of common vetch and oat, the Shannon-Weaver index and species richness of the mixtures were increased. Thirteen cloned monocultures and mixtures of oat and common vetch soil 16S rDNA sequences were deposited to NCBI. Based on the sequencing results, the bands could be identified as related to Proteobacteria, Bacteroidetes and Cyanobacteria. Common vetch did not have some bacteria relatives to Sphingomonas spp. Some bacterial taxa could be detected in the ratio of 1:1 and 1:2, but not in the ratio of 1:3, e.g. Myxococcales. The results suggested that the belowground diversity could be promoted by mixed cropping systems.  

Effect of sewage sludge and furnace waste on the content of selected elements in the sward of legume-grass mixture

Industrial landfills resulting from operations of various industries, particularly power generation, create specific habitat conditions for flora. Among the waste which may be used for recultivation of dumping heaps there is sewage sludge, which contains a considerable amount of nutrients crucial for plants. This investigation aimed at identification of the effect of sewage sludge and furnace ashes on the content of selected elements in a mixture of grass and white clover recommended for furnace ash heap recultivation. The experimental design comprised 6 treatments (each in four replications), which differed in a dose of the supplied sewage sludge and furnace ashes: 1) control (without waste admixture), 2) 200 t d.m. of sewage sludge, 3) 200 t d.m. of ash, 4) 150 t d.m. of sludge + 50 t d.m. of ash, 5) 50 t d.m. of ash + 150 t d.m. of ash, 6) 100 t d.m. of ash + 100 t d.m. of ash. The content of macroelements in plants depended on the treatment and ranged from 2.58-31.2 g Mg, 3.16-5.85 g Ca, 16.95-18.46 g K, 0.26-1.25 g Na and 2.27-3.37 g P kg –1 d.m. Plants grown exclusively on furnace ashes had the highest content of Mg, Ca and K, whereas the highest P and Na concentrations were noted in plants cultivated exclusively on sewage sludge. While assessing the content of macroelements in the plant mixture in view of its fodder value, it was found that the content of Mg and K met the standards set for good quality feeds, the amounts of Ca and Na were below the optimum, whereas the P concentration was close to the optimum value.

The Benefit of Color Information in Digital Image Analysis for the Estimation of Legume Contribution in Legume–Grass Mixtures

ABSTRACTEfficient detection of spatial legume dry matter (DM) contribution in legume–grass mixtures is of great importance for targeted management of legume‐based swards. Legume coverage may be an appropriate indicator for the contribution of legumes, because it can be assessed by on‐the‐go systems with digital image analysis (DIA). To examine the perspectives of DIA a pot experiment, under controlled conditions, was conducted across a wide range of legume species (white clover [Trifolium repens L.], red clover [Trifolium pratense L.], and alfalfa [Medicago sativa L.]), legume proportion (0–800 g kg−1), and growth stage (start of tillering to start of heading). In this study, an advanced procedure for the determination of legume DM contribution by DIA is suggested. The DIA procedure comprises the analysis of color images and applies an advanced function to predict legume DM contribution from legume coverage by considering total sward biomass. This resulted in an accurate prediction of legume contribution (grams per kilogram) with R2 of 0.90, 0.94, and 0.93 for red clover, white clover, and alfalfa, respectively. For validation, swards of a field experiment were used. It showed that legume detection is possible, but for practical field application some further adjustments are necessary.

Slit seeded grass-legume mixture improves coal mine reclamation

Slit seeding (sowing into shallow cuts to the soil surface) was evaluated on coal mine reclamation in the North Bohemian Brown Coal Basin (Czech Republic) between 2001 and 2008, on plots both with and without biodegradable waste enrichment. Prior to experimentation (in 2000, once) were applied dehydrated, anaerobically digested wastewater sludge, 200 (41) t/ha fresh mass (dry mass), together with paper mill waste, 400 (131) t/ha, and bark substrate Envima, 400 (145) t/ha. Spontaneous herbaceous cover was enhanced each end of April from 2001 to 2003 by slit seeded grass-legume mixture containing Festuca pratensis L. (46%); Lotus corniculatus L. (22%); Coronilla varia L. (18%); Festuca rubra L. (9%); and Medicago lupulina L. (5%). All slit seeded species proliferated better on surface strip mine deposits without biodegradable waste enrichment and brought beneficial changes in a number of parameters over the ensuing five years due to lower competition with native expanding eutrophic species including Calamagrostis epigejos L.; Cardaria draba L.; Urtica dioica L.; and Galium aparine L. Available organic carbon (extracted from field-moist soil by 0.5 mol/L K<sub>2</sub>SO<sub>4</sub>) showed a notable tendency toward values 10–66 mg C/kg DM (dry mass), microbial biomass 302–1131 mg C/kg DM, basal respiration 3.9–5.8 mg C/kg DM/h, and metabolic quotient (basal respiration/microbial biomass carbon) × 1000 = 5.2–7.9.    

Nitrogen fixation in annual and perennial legume-grass mixtures across a fertility gradient

Background and aims The selection of legume species and species mixtures influences agroecosystem nitrogen (N) and carbon cycling. We utilized a fertility gradient to investigate the effects of plant species interactions on biological N fixation of an annual and perennial legume in response to shifting soil resource availability.

Forage legume species determine the nutritional quality of binary mixtures with perennial ryegrass in the first production year

There is increasing interest in forage legumes as ruminant feeds in Europe as alternatives to using mineral N fertilizer on temporary grassland. Successful management of grass–legume mixtures depends on the suitability of the forage legume species to the cutting frequency, and its nutritional quality for animals. An experiment was completed in 2004 and 2005 on two sites at the University of Kiel (Germany) to examine the response of legume-perennial ryegrass (Lolium perenne L.) mixtures to cutting frequency in terms of dry matter (DM) yield, N2 fixation, net energy for lactation (NEl), plant cell wall content, and crude protein (CP) content and CP fractions in the first production year. Different legumes in binary mixtures with perennial ryegrass (L. perenne L.), red clover (Trifolium pratense L.), white clover (Trifolium repens L.), hay-type and grazing-type alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), Caucasian clover (Trifolium ambiguum M. Bieb.) and two monocultures of perennial ryegrass (with and without cattle slurry supplying 20gN/m2) were examined under two cutting frequencies. All legume–grass mixtures outperformed perennial ryegrass with and without slurry in terms of DM yield, irrespective of cutting frequency. Production from both birdsfoot trefoil and Caucasian clover in grass–legume mixtures were very low, similar to unfertilized pure stands of grass, and the low production was consistent with slow and deficient establishment of birdsfoot trefoil and Caucasian clover, as observed by others. Nutritional quality of Caucasian clover was comparable to white clover. The companion grass benefited from the N transferred by forage legumes and their growth habit. This was especially evident for white clover, resulting in the highest companion grass yield and, in consequence, high mixture DM yield in both the 3 and 5 cut systems. Differences in agronomic performance of the legume–grass mixtures, and the grass monocultures, were related to the legume species in the mixture rather than cutting system. Forage legume species determined the nutritional quality and yield of binary mixtures with perennial ryegrass in the first production year.

Grass–Legume Mixtures Suppress Weeds during Establishment Better than Monocultures

Maintaining a diversity of plant species in pastures may reduce weed invasion. Knowledge of how the proportion of species in a mixture (i.e., species evenness) affects weed invasion would be useful in formulating seed mixtures. We hypothesized that forage mixtures with greater species evenness would reduce weed invasion at establishment better than mixtures dominated by a few species (low species evenness) or monocultures. Fifteen mixtures and monocultures of orchardgrass (Dactylis glomerata L.), quackgrass (Elytrigia repens L.), alfalfa (Medicago sativa L.), and white clover (Trifolium repens L.) were sown in autumn 2008 at four locations in Pennsylvania and Wisconsin. There were four monocultures, four mixtures dominated by one species (evenness = 0.64), six mixtures dominated by pairs of species (evenness = 0.88), and one equal mixture (evenness = 1). We measured the amount of naturally occurring weeds in harvested herbage at each location in 2009. At two locations, we added seed of plumeless thistle (Carduus acanthoides L.) and canola (Brassica napus L.; a surrogate weed) to each treatment during autumn of 2008 and measured their establishment and dry mass during 2009. Grass–legume mixtures resisted weed invasion better than monocultures. Within mixtures, however, species evenness did not influence weed invasion. Species evenness did not affect resource use (light interception or soil inorganic N levels). Individual forage species had a strong effect because weed proportions decreased curvilinearly as orchardgrass proportion of the seed mixture increased. Selecting appropriate species to use in mixtures is more important than the evenness of the species in the mixture.