Pasture Legumes Research Articles

Clearing confusion in <i>Stylosanthes</i> taxonomy. 2. <i>S. macrocephala</i> M.B. Ferreira & Sousa Costa vs. <i>S. capitata</i> Vogel and <i>S. bracteata</i> Vogel

Stylosanthes macrocephala was described as a new species in 1977 and has become an economically important pasture legume. It has recently been claimed to be conspecific with S. capitata, also an economically important species. This paper refutes this synonymization and summarizes morphological descriptions as well as genetic studies and cytological evidence indicating that diploid S. macrocephala should be considered a separate species, even being a likely progenitor of tetraploid S. capitata. Early confusion with S. bracteata is also discussed.

Intrinsic root morphology determines the phosphorus acquisition efficiency of five annual pasture legumes irrespective of mycorrhizal colonisation.

Mycorrhizal fungi are ubiquitous in agroecosystems and form symbiotic associations that contribute to the phosphorus (P) acquisition of many plants. The impact of mycorrhizas is most pronounced in P-deficient soil and commonly involves modifications to the root morphology of colonised plants. However, the consequences of mycorrhizal colonisation on root acclimation responses to P stress are not well described. Five annual pasture legumes, with differing root morphologies, were grown to determine the effect of mycorrhizal colonisation on shoot yield, root morphology and P uptake. Micro-swards of each legume were established in pots filled with a topsoil layer that had been amended with five rates of P fertiliser. The topsoil overlaid a low-P subsoil that mimicked the stratification of P that occurs under pasture. Mycorrhizal colonisation improved P acquisition and shoot yield in the low-P soil treatments, but did not reduce the critical external P requirement of the legumes for near-maximum yield. The yield responses of the mycorrhizal plants were associated with reduced dry matter allocation to topsoil roots, which meant that the P acquisition benefit associated with mycorrhizal colonisation was not additive in the P-deficient soil. The contribution of the mycorrhizal association to P acquisition was consistent among the legumes when they were compared at an equivalent level of plant P stress, and was most pronounced below a P stress index of ~0.5. The intrinsic root morphology of the legumes determined their differences in P-acquisition efficiency irrespective of mycorrhizal colonisation.

Increase of nitrogen-use efficiency by phosphorus fertilization in grass–legume pastures

Forage legumes intercropped with grasses add nitrogen (N) to the production system and may increase forage yields. However, both phosphate fertilization and the solubility of phosphorus (P) sources may affect this contribution. This study aimed to evaluate the response of Guinea grass (Panicum maximum) intercropped with legumes and fertilized with phosphate fertilizers of different solubility. Guinea grass was grown as a single crop, fertilized or not with mineral N, and intercropped with Java (Macrotyloma axillare), or dwarf pigeon pea (Cajanus cajan); phosphorus was applied as triple superphosphate (P-TSP) or Bayovar (P-Bay), plus a control without phosphorus. The highest forage yield and N accumulation was observed in Guinea grass fertilized with N and P, with 70,364 and 60,036 kg ha−1of dry matter, resulting in 977 and 1004 kg ha−1 of N accumulated by the plants for P-TSP and P-Bay, respectively. The introduction of legumes increased the N accumulation but decreased yield of Guinea grass. The highest nitrogen use efficiency (NUE) was found with P fertilization, i.e., 56% and 54% for P-TSP and P-Bay, respectively. The use of legumes intercropped with Guinea does not improve the effectiveness of the reactive rock phosphate. Therefore, the introduction of legumes intercropping with Guinea grass may be an alternative to N fertilization only when P is not applied to low fertile soils. Broadcast and incorporated P fertilization by the time of Guinea grass sowing, not only increases forage yields but also results in higher NUE regardless of P fertilizer solubility.

Forage legumes in grass pastures in tropical Brazil and likely impacts on greenhouse gas emissions: A review

AbstractBeef cattle producers seldom use fertilizers for their pastures in tropical regions of Brazil. Slowly, this is changing but because of the need for repeated applications, N fertilizer is rarely applied. The introduction of a forage legume is an appropriate solution for this problem, but until recently adoption has been very low as the legumes generally have not persisted in the sward. We report research on how grazing management can affect the persistence of stoloniferous legumes in pastures of Brachiaria spp. and the problems of establishing and maintaining crown‐forming legumes such as Stylosanthes spp. With suitable management, milk or bovine carcass yields can be equal or greater from mixed than from grass‐alone pastures fertilized with 120 or 150 kg Nha‐1 year−1. In addition to savings in CO2 emissions from fossil fuels for the production and distribution of N fertilizers, nitrous oxide emissions from cattle excreta and legume residues are lower than those from N‐fertilized brachiaria grass monocultures. Other studies indicate that enteric methane emissions from cattle may be mitigated when forage legumes are included in their diet. The use of forage legumes in mixed pastures for tropical regions is emerging as a feasible strategy to keep meat and milk production at acceptable levels with reduced greenhouse gas emission rates.

Milk Production, N Partitioning, and Methane Emissions in Dairy Cows Grazing Mixed or Spatially Separated Simple and Diverse Pastures.

Simple SummaryIt is possible to increase performance of grazing dairy cows while decreasing their environmental impact through incorporating high-quality pasture species that synthesize high bioactive compounds in diverse pastures. In this study, cows grazed combination of simple pastures containing perennial ryegrass and white clover or diverse pastures containing forbs known to contain bioactive compounds that can reduce methane emissions and nitrate leaching soils. The two types of pastures were grown either as mixed or spatially separated in adjacent strips. Our study indicated that spatial separation had little impact on cows’ performance, but pastures containing diverse plant species improved the production of protein and lactose in milk and reduced environmental impact, specifically by improving nitrogen utilization of cows and reducing the emission of methane per amount of feed eaten by the cows.Increasing pasture diversity and spatially separated sowing arrangements can potentially increase the dry matter intake of high-quality forages leading to improved animal production. This study investigated the effects of simple (two-species) and diverse (six-species) pastures planted either in mixed or spatially separated adjacent pasture strips on performance, N partitioning, and methane emission of dairy cows. Thirty-six mid-lactation Jersey cows grazed either (1) simple mixed, (2) simple spatially separated, (3) diverse mixed, or (4) diverse spatially separated pastures planted in a complete randomized block design with three replicates. Compared to simple pasture, diverse pasture had lower CP content but higher condensed tannins and total phenolic compounds with an overall positive effect on yield of milk solids, nitrogen utilization, including a reduction of N output from urine, and methane yields per dry matter eaten. The spatial separation increased legume and CP content in simple pasture but decreased NDF in both diverse and simple pastures. In conclusion, increasing diversity using pasture species with higher nutritive value and secondary compounds can help improving the production while decreasing the environmental effect of dairy farming, while spatial separation had a minor effect on feed intake and yield, possibly due to overall high-quality pastures in early spring.

DIVERSITY OF MICROBES IN SOIL AGGREGATE FRACTIONS UNDER DIFFERENT LAND-USE IN NORTHERN GUINEA SAVANNA, NIGERIA

Microorganisms play vital role in keeping soil healthy. Bacteria, Fungi and Actinobacteria are active in degrading soil organic matter which improves soil ecosystem functioning. There exists a dearth of information on the influence of land-use on diversity of microbes in different soil aggregate sizes in Northern Guinea Savanna of Nigeria. This study assessed the diversity of soil microbes under six different land-use practices namely forest, fallow, pasture legume, pasture cereal, date palm plantation and continuous cultivated. In each land-use soil samples were collected at two depths (0-5 cm and 5-20 cm). The soil samples were divided into two parts, one part was left as collected from the field sites (bulk soil) and the other part was separated into three aggregate fractions (>250 µm, >53 µm and <53 µm). Bacteria, Fungi and Actinobacteria were cultured, isolated and identified, and some soil chemical properties were determined. Colony forming units per gram of soil (CFU/g soil) was computed for the soil microbes. Results revealed that Bacteria is the predominant soil microbe followed by Actinobacteria and then Fungi in all the land-uses. Bacteria population ranged from 1.49x107to 8.65x107CFU/g soil, Actinobacteria population ranged from 9.32x105 to 5.85x106 CFU/g soil and Fungi population ranged between 6.75x104 and 4.21x105 CFU/g soil. Higher microbial population were observed in forest soil than soils of the other land-uses. Continuously cultivated land had the least microbial population. Silt + clay soil fraction had significantly higher bacteria while the bulk soil was significantly richer in fungal population.

Milk production, nitrogen utilization, and methane emissions of dairy cows grazing grass, forb, and legume-based pastures.

Achieving high animal productivity without degrading the environment is the primary target in pasture-based dairy farming. This study investigated the effects of changing the forage base in spring from grass-clover pastures to forb or legume-based pastures on milk yield, N utilization, and methane emissions of Jersey cows in Western Oregon. Twenty-seven mid-lactation dairy cows were randomly assigned to one of three pasture treatments: grass-clover-based pasture composed of festulolium, tall fescue, orchardgrass, and white clover (Grass); forb-based pasture composed of chicory, plantain, and white clover (Forb); and legume-based pasture composed of red clover, bird's-foot trefoil, berseem clover, and balansa clover (Legume). Pastures were arranged in a randomized complete block design with three replicates (i.e., blocks) with each replicate grazed by a group of three cows. Production and nutritive quality of the forages, animal performance, milk components, nitrogen partitioning, and methane emissions were measured. Feed quality and dry matter intake (DMI) of cows were greater (P ≤ 0.05) for Legume and Forb vs. Grass, with consequent greater milk and milk solids yields (P < 0.01). Cows grazing Forb also had more (P < 0.01) lactose and linoleic acid in milk compared with cows grazing the other pastures, and less (P = 0.04) somatic cell counts compared with Grass. Cows grazing Forb had substantially less (P < 0.01) N in urine, milk, and blood compared with cows grazing the other pastures, with not only a greater (P < 0.01) efficiency of N utilization for milk synthesis calculated using milk urea nitrogen but also a larger (P < 0.01) fecal N content, indicating a shift of N from urine to feces. Both Forb and Legume had a diuretic effect on cows, as indicated by the lower (P < 0.01) creatinine concentration in urine compared with Grass. Methane emissions tended to be less (P = 0.07) in cows grazed on Forb vs. the other pastures. The results indicate that Forb pasture can support animal performance, milk quality, and health comparable to Legume pasture; however, Forb pasture provides the additional benefit of reduced environmental impact of pasture-based dairy production.

Metabolic Profiling Provides Unique Insights to Accumulation and Biosynthesis of Key Secondary Metabolites in Annual Pasture Legumes of Mediterranean Origin.

Annual legumes from the Mediterranean region are receiving attention in Australia as alternatives to traditional pasture species. The current study employed novel metabolic profiling approaches to quantify key secondary metabolites including phytoestrogens to better understand their biosynthetic regulation in a range of field-grown annual pasture legumes. In addition, total polyphenol and proanthocyanidins were quantified using Folin–Ciocalteu and vanillin assays, respectively. Metabolic profiling coupled with biochemical assay results demonstrated marked differences in the abundance of coumestans, flavonoids, polyphenols, and proanthocyanidins in annual pasture legume species. Genetically related pasture legumes segregated similarly from a chemotaxonomic perspective. A strong and positive association was observed between the concentration of phytoestrogens and upregulation of the flavonoid biosynthetic pathway in annual pasture legumes. Our findings suggest that evolutionary differences in metabolic dynamics and biosynthetic regulation of secondary metabolites have logically occurred over time in various species of annual pasture legumes resulting in enhanced plant defense.

Influence of climate variation on phenolic composition and antioxidant capacity of Medicago minima populations

Medicago minima is a pasture legume that grows almost all over the world. In Tunisia, it occupies various climatic environments and is considered the most abundant annual Medicago plant. However, this species is unconsumed and unused by humans. This study aimed to explore the phytochemical characteristics of Medicago minima selected from different provenances in Tunisia and subsequently investigate the influence of environmental factors on their phenolic composition and antioxidant activity. Therefore, a calorimetric method and DPPH tests provided the total phenolic and total flavonoid contents and antioxidant potential in roots, stems, leaves and seeds. High performance liquid chromatography (HPLC) identified and quantified four phenolic acids and three flavonoids in the studied organs. Roots and leaves showed the greatest phenolic compound content and had high antioxidant activity. Rutin and syringic acid (leaves) represent a characteristic for this species. For each organ, principal component analysis of phenolic profiles showed that the root’s phenolic composition could be an indication of the plant adaptation to even small changes in its environments. Plants originating from a cold climate, higher altitude or semi-arid environment had the highest phenolic compound contents in their organs. Our findings provide useful information for the exploitation of the phenolic compounds in these weeds for the development of environmental sustainability.

The Impact of Herbicide Application and Defoliation on Barley Grass (Hordeum murinum subsp. glaucum) Management in Mixed Pasture Legumes

Barley grass (Hordeum murinum subsp. glaucum.) is an annual weed associated with grain revenue loss and sheep carcass damage in southern Australia. Increasing herbicide resistance led to a recent investigation into effective integrated weed management strategies for barley grass in southern Australia. Field studies in Wagga Wagga, New South Wales (NSW) during 2016 and 2017 examined the effect of post-emergent herbicide applications and strategic defoliation by mowing on barley grass survival and seed production in a mixed legume pasture. Statistically significant differences between herbicide-only treatments in both years showed propaquizafop to be more than 98% effective in reducing barley grass survival and seed production. Paraquat was not effective in controlling barley grass (58% efficacy), but led to a 36% and 63.5% decrease in clover and other weed biomass, respectively, after 12 months and increased lucerne biomass by over three-fold after 24 months. A single repeated mowing treatment resulted in a 46% decline in barley grass seedling emergence after 12 months and, when integrated with herbicide applications, reduced other weed biomass after 24 months by 95%. Resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides observed in local barley grass populations led to additional and more focused investigation comparing the efficacy of other pre- and post-emergent herbicides for barley grass management in legume pastures. Haloxyfop-R + simazine or paraquat, applied at early tillering stage, were most efficacious in reducing barley grass survival and fecundity. Impact of defoliation timing and frequency on barley grass seedlings was also evaluated at various population densities, highlighting the efficacy of repeated post-inflorescence defoliations in reducing plant survival and seed production. Results highlight the importance of optimal environmental conditions and application timing in achieving efficacious control of barley grass and improving pasture growth and biomass accumulation.

Productivity and persistence of Kura clover and white clover mixtures with grasses

AbstractThere is a lack of persistent forage legumes for permanent pastures in eastern Canada. Kura clover (Trifolium ambiguum M. Bieb.; KC) is a long‐lived species, with demonstrated potential in various regions, however, there is a lack of information on its performance in mixtures with grasses and no comparisons with white clover (Trifolium repens L.; WC), the main legume species recommended for pastures in eastern Canada. Objectives were to evaluate the potential of KC when grown in mixtures with grasses and compare its performance with WC based‐mixtures and N‐fertilized grass monocultures. Twenty treatments that included KC, WC, and six perennial grasses species (Kentucky bluegrass [Poa pratensis L.; KB], meadow bromegrass [Bromus biebersteinii Roem. &amp; Schult., MB], orchardgrass [Dactylis glomerata L., OR], smooth bromegrass [Bromus inermis L.; SB], tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.; TF], and timothy [Phleum pratense L.; TI]) seeded alone and in binary mixtures were seeded in 2 yr at two sites and monitored for up to four production years. During the first production year, WC‐based mixtures yields were overall greater than those of KC‐based mixtures, while in the second production year and onwards, KC treatments had similar or greater yields than WC, illustrating the greater persistence of KC. Adding KC to grasses also increased total forage yields by 13% on average compared to N‐fertilized solo‐seeded grasses. The performance of specific KC–grass mixtures was variable across sites‐years with no specific mixture being consistently more productive. Kura clover is adapted to contrasting environments of Québec and appears to be a suitable alternative to WC.

High‐throughput phenotyping reveals growth of Medicago truncatula is positively affected by arbuscular mycorrhizal fungi even at high soil phosphorus availability

Societal Impact StatementArbuscular mycorrhizal fungi (AMF) may contribute to enhanced yield and nutrition of host plants for the purpose of sustainable agriculture. However, the growth response of the host plant to mycorrhizal colonization is generally only measured at harvest, and thus management decisions regarding AMF are made using only a single time point. This study highlights that AMF can provide growth benefits to the host plant over its life. Greater knowledge of how plants respond to AMF over time will improve understanding of how the association functions and ultimately lead to improved management decisions regarding AMF in an agricultural context.Summary Colonization by arbuscular mycorrhizal fungi (AMF) can result in variable responses in the growth and mineral nutrition of host plants, and is highly dependent on soil nutrient condition; limited studies have addressed the effects of AMF on plant growth over time. The aim of this study was to investigate the AMF effects on plant growth over the life of the plant, and interactions with soil phosphorus (P) and zinc (Zn) availability. We used a high‐throughput shoot phenotyping system to examine the temporal growth responses to AMF and soil P and Zn availabilities in the pasture legume Medicago truncatula. Plants were either inoculated with Rhizophagus irregularis or mock‐inoculated, and were examined under two soil P and five soil Zn availability treatments. Plants were then destructively harvested to obtain final biomass and shoot nutrition data. The growth of M. truncatula plants over time responded very differently to AMF depending on the soil P availability. At low P, projected shoot area and absolute growth rate (AGR) became increasingly greater in the mycorrhizal plants over the course of the experiment. At high P, there was a positive growth response to AMF until approximately 40 days after planting, after which the AGR of the non‐mycorrhizal plants increased and the response to AMF became neutral. Zinc availability was highly interactive with P availability, but not with AMF inoculation. This research demonstrates that growth responses to mycorrhizal fungi change over the plant's life, and are highly dependent on soil P availability.

Isoflavone supplementation, via red clover hay, alters the rumen microbial community and promotes weight gain of steers grazing mixed grass pastures.

Biochanin A, an isoflavone present in the pasture legume red clover (Trifloium pratense L.), alters fermentation in the rumen of cattle and other ruminants. Biochanin A inhibits hyper-ammonia-producing bacteria and promotes cellulolytic bacteria and fiber catalysis in vitro and ex vivo. Consequently, biochanin A supplementation improves weight gain in grazing steers. Red clover contains biologically active isoflavones that may act synergistically. Therefore, the objective was to evaluate the effect of two levels of red clover hay on growth performance and the microbial community in growing steers grazing mixed grass pastures. A grazing experiment was conducted over 2 early growing seasons (2016 and 2017) with 36 cross-bred steers and twelve rumen-fistulated, growing Holstein steers for evaluation of average daily gain and rumen microbiota, respectively. Steers were blocked by body weight and assigned to pastures with one of four treatments: 1) pasture only, 2) pasture + dry distillers’ grains (DDG), 3) pasture + DDG + low level of red clover hay (~15% red clover diet), or 4) pasture + DDG + high level of red clover hay (~30% red clover diet). DDG were added to treatments to meet protein requirements and to balance total protein supplementation between treatments. All supplementation strategies (DDG ± red clover hay) increased average daily gains in comparison to pasture-only controls (P < 0.05), with a low level of red clover supplementation being the most effective (+0.17 kg d-1 > DDG only controls; P < 0.05). Similarly, hyper-ammonia-producing bacteria inhibition (10–100-fold; P < 0.05), fiber catalysis (+10–25%; P < 0.05) and short chain fatty acid concentrations were greatest with the low red clover supplement (+~25%; P < 0.05). These results provide evidence that lower levels or red clover supplementation may be optimal for maximizing overall microbial community function and animal performance in grazing steers.

The contribution of nitrogen fixed by annual legume pastures to the productivity of wheat in two contrasting Mediterranean environments in central Chile

Annual legume pastures exhibit high resilience and productivity in Mediterranean climate regions and can be an important source of nitrogen (N) for temperate cereals in integrated livestock production systems. This work seeks to evaluate the inputs of N fixed by annual legume mixtures (composed of 3–4 species and cultivars) grown for one, two or three years in a cropping sequence, and their contribution to soil N availability, N uptake and the grain yield of wheat, and compares this with the cereal rotation of oats and wheat with and without N fertilizer. Two field experiments comprising annual legume-wheat rotations were carried out in two contrasting Mediterranean environments in central Chile, the interior dryland in the eastern part of the coastal mountain rage, and the Andean foothills, over four growing seasons (2008–2011). At both experimental sites two mixtures of annual legumes were used in rotation with wheat. The duration of the pasture phase was between one and three years. In the interior dryland, the shoot DM of mixture M1 (T. subterraneum + M. polymorpha + T. michelianum) was higher than M2 (T. subterraneum + B. penicilius + O. compressus), and in the Andean foothills M4 (T. subterraneum + T. vesiculosum + O. compressus) was more productive than M3 (two cv. of T. subterraneum + T. incarnatum). The amount of N2 fixed by the legume mixtures, estimated by the 15N natural abundance technique, ranged between 28 and 87 kg N ha−1 in the interior dryland, and between 176 and 385 kg N ha−1 in the Andean foothills, representing respectively around 25 and 23 kg N ha−1 fixed for every Mg of shoot DM accumulated by the annual legumes. Wheat grain yields following legume mixtures represented 53–104 % of the 3.39 Mg ha−1 produced after oats with N fertilizer in the interior dryland, and between 68 and 101 % of 6 Mg ha−1 attained after oats in the Andean foothills, in 2011. N use efficiency (NUE) of wheat was significantly (P ≤ 0.05) higher in legume-based crop rotation than after oats with or without N fertilizer, at both sites. Legume mixtures also improved the N uptake (NUPE) and N utilization (NUtE) efficiencies of wheat compared to those observed after oats with N fertilizer, at both sites. Important differences among legume mixtures and the duration of the pasture phase were observed at both sites.

Legume-based silvopastoral systems drive C and N soil stocks in a subhumid tropical environment

Silvopastoral systems include trees or shrubs and grasses and are considered a sustainable method of restoring degraded pastures and increasing carbon and nitrogen stocks in tropical soils. We hypothesize that establishing shrub-tree legumes in a signalgrass pasture has the potential to increase soil C and N stocks. Thus, we investigated a silvopastoral system over four years in a subhumid tropical zone in northeastern Brazil to determine the soil C and N stocks and the organic matter chemical fractions. The experimental design consisted of i-pure signalgrass (Brachiaria decumbens), ii-signalgrass intercropped with gliricidia (Gliricidia sepium) and iii-signalgrass intercropped with sabiá (Mimosa caesalpiniaefolia). Measurements were taken at 0, 4 and 8 m away from the legume rows and at random in the pure signalgrass pasture. Soil samples were obtained in the second and fourth years after silvopastoral system implementation at 0–10, 10–20, 20–40, 40–60 and 60–100 cm soil depths at each distance in triplicate to produce compound samples. These were used to determine the C and N contents and stocks, as well as the soil organic matter chemical fractions. Within two years, the gliricidia and sabiá soil C stocks directly below the legume row at 100 cm depth increased by 45% and 35%, respectively, while the soil N stock tripled at all distances. The soil organic matter increased over the two years, and the humin proportion in the soil organic matter (SOM) increased in the silvopastoral system soils. Overall, after four years of silvopastoral system establishment, this system showed the potential to store N and achieve soil C stock levels that are within the global average range for these systems.

Greenhouse Gas Emissions From Cropping and Grazed Pastures Are Similar: A Simulation Analysis in Australia

The agricultural sector has potential to provide greenhouse gas (GHG) mitigation by sequestering soil organic carbon (SOC). Replacing cropland with permanent pasture is one practice promoted for its potential to sequester soil carbon. However, pastures frequently support livestock, which produce other GHG emissions that could negate the abatement from increased SOC, especially given the declining rate of SOC sequestration through time. Our purpose was to determine whether the abatement provided by SOC storage in permanent pastures was offset by livestock emissions, and to thus compare emissions from grazed pasture systems with those from cropping systems. We investigated this question for three case study farms in locations with contrasting climate, soils and management representative of Australian cropping and livestock systems. Three cropping scenarios were defined that had increasing amounts of SOC inputs: Cropburn, crop residues burned before sowing (lowest SOC input); Cropstubble, crop residues retained; and Cropintensity, uncropped fallow phases replaced with short-term green manure legume crops. The on-farm GHG emissions profiles of these cropping scenarios were compared with those from two livestock scenarios utilizing continuous stocking: Livestockgrass, stocked permanent grass pasture; and Livestocklegume, stocked permanent legume pasture; the latter having higher SOC input than the former. Crop yields, pasture growth rates and emissions of carbon dioxide (CO2) and nitrous oxide (N2O) from the soil were simulated with the APSIM farming systems model. Livestock emissions were predicted using Australian GHG accounting emission factors. For the farms in this study, the SOC sequestered in the stocked permanent pastures was offset by emissions from livestock, and emissions from cropping scenarios were similar to or significantly less than those from the livestock scenarios. These findings: (1) demonstrate the importance of using net GHG abatement potentials from combined emissions rather than a single GHG abatement process when evaluating potential abatement practices, and (2) question the potential for GHG mitigation through the agricultural sector because climate and soil characteristics in different locations can alter the abatement potential of management practices, and because change in management practice can have feedbacks on other management practices and hence on GHG abatement potential.

Morphological diversity within a core collection of subterranean clover (Trifolium subterraneum L.): Lessons in pasture adaptation from the wild.

Subterranean clover (Trifolium subterraneum L.) is a diploid self-pollinated annual pasture legume native to the Mediterranean region and widely sown in southern Australia and other countries with Mediterranean-type climates. This study utilised a core collection of 97 lines, representing around 80% of the genetic diversity of the species, to examine morphological diversity within subterranean clover. A total of 23 quantitative agro-morphological and 13 semi-quantitative morphological marker traits were assayed on the core collection and 28 diverse Australian cultivars as spaced plants in a replicated common garden experiment. Relationships between these traits and 24 climatic and edaphic parameters at their sites of origin were also examined within the core collection. Significant diversity was present for all traits. The Australian cultivars had similar levels of diversity to the core collection for several traits. Among the agro-morphological traits, time to flowering, leaf size and petiole diameter in mid-winter, plant area in late winter, maximum stem length, content of the oestogenic isoflavone biochanin A and total isoflavone content, were correlated with seven or more environmental variables. These can be considered highly adaptive, being the result of strong environmental selection pressure over time. For the first time in a clover species, morphological markers, including leaf mark, anthocyanin pigmentation and pubescence traits, have been associated with rainfall and soil parameters. This suggests they either have an adaptive role or the genes controlling them may be linked to other genes controlling adaptive traits. This study demonstrated the value of core collections to examine diversity within much larger global collections. It also identified adaptive traits from wild plants that can be utilised to develop more productive and persistent subterranean clover cultivars. The high heritability of these traits indicates that selection gains can be readily made.

Introduction of forage legumes into Aruana Guineagrass pasture

The experiment was developed at the Instituto de Zootecnia in Nova Odessa-SP. It was designed to evaluate forage mass, forage legumes ratio in the available forage mass and the transfer potential of the nitrogen fixed by the forage legumes to Aruana Guineagrass pasture grazed by lambs under intermittent grazing. The treatments consisted of the introduction of four accessions of forage legumes in the pasture of Megathyrsus maximum cv. Aruana and a treatment of Aruana Guineagrass pasture (without legumes), totalling five treatments. The Aruana Guineagrass pasture was established five years ago. The forage legumes treatments were: Neonotonia wightii NO 253 (Perennial soy NO 253), Neonotonia wightii NO 2348 (Perennial soy NO 2348), Macrotyloma axillare NO 279 (Macrotyloma legume) and Calopogonium mucunoides NO 1194 (Calapo legume). The experimental design was made up of random blocks with three replicates. The Calapo legume showed the lowest mean forage mass in the three seasons (400 kg/ha). The mean forage mass of the Perennial soy NO 253, Perennial soy NO 2348 and Macrotyloma legume did not show significant differences in the three seasons. Furthermore, the Calapo legume ratio in the pasture was the lowest in the total forage mass (13%) among the intercropped forage legumes (31.9% at 43.2%). Perennial soy NO 253, Perennial soy NO 2348 and Macrotyloma legume showed suitable ratio in the forage mass when intercropped with Aruana Guineagrass. These forage legumes also promoted the highest crude protein content in the Aruana Guineagrass. Thus, it is possible to advise the introduction of Perennial soy NO253, Perennial soy NO2548 or Macrotyloma legume in established Aruana grass pasture.

Herbage mass, botanical composition, forage nutritive value, and preference of grass–legume pastures under horse grazing

AbstractCool‐season perennial grasses are the foundation of productive horse pastures in the north‐central United States. The addition of legumes in pastures can increase forage mass and digestible energy content, yet little research has investigated grass–legume pastures under horse grazing. The objectives of this research were to evaluate herbage mass, botanical composition, forage nutritive value, and preference of grass–legume pastures under horse grazing. Plots consisting of orchardgrass (Dactylis glomerata L.), Kentucky bluegrass (Poa pratensis L.), and meadow fescue (Festuca pratensis Huds.) were planted in monoculture and in binary mixtures with alfalfa (Medicago sativa L.) or white clover (Trifolium repens L.) and grazed by horses in Minnesota during the 2013, 2014, and 2015 grazing seasons. Herbage mass, weed mass, and forage nutritive values were determined prior to grazing, and horse preference was evaluated following grazing. When evaluating herbage mass, the inclusion of alfalfa resulted in a consistently higher mass than grass monoculture. Kentucky bluegrass mixtures resulted in a decreased mass of non‐sown (weed) species and an increase in horse preference. Improved forage nutritive values were also observed with the inclusion of legumes regardless of grass species, including higher crude protein and neutral detergent fiber digestibility at 48 h and lower neutral detergent fiber. As a result, using grass–legume mixtures in pastures can provide benefits for grazing horses and pasture productivity.

Defining the waterlogging tolerance of Ornithopus spp. for the temperate pasture zone of southern Australia

Increasing the area sown to Ornithopus spp. (serradella) can reduce overall fertiliser requirements in Australian permanent pastures owing to their greater nutrient-acquisition efficiency than that of more widely used pasture legumes such as Trifolium spp. However, uncertainty regarding waterlogging tolerance of Ornithopus spp. may restrict their adoption in the high-rainfall zone of southern Australia. The waterlogging tolerance of cultivars and accessions of three species of Ornithopus (O. compressus, O. sativus and O. pinnatus) was determined by comparing root and shoot growth of plants in deoxygenated, stagnant agar nutrient solution (simulated waterlogging) with growth in aerated nutrient solution. The responses were benchmarked against the known waterlogging-tolerant pasture legume Trifolium michelianum. All Ornithopus cultivars were highly impacted by the deoxygenated stagnant treatment, including those of the anecdotally waterlogging-tolerant O. pinnatus. The 14-day stagnant treatment reduced root dry mass by 32–62% and relative growth rate (RGR) of roots by 36–73%. At the same time, root porosity increased from 1.4% to 8.8%. Following a 14-day recovery period, during which plants were returned to aerated nutrient solution, Ornithopus spp. failed to increase their shoot RGR (particularly for O. sativus cultivars); however, root RGR returned to that of the aerated controls. The stagnant conditions inhibited transport of potassium (K+) to the shoots in all species, as evidenced by lower shoot tissue K+ concentrations, with O. compressus and O. sativus most adversely affected (45% and 48% of the tissue concentration of aerated control plants). We conclude that the suggested area for Ornithopus spp. adaptation should not preclude areas of high rainfall because they have root adaptations that would assist them in coping with transient water excess; however, soil types and surface profiles conducive to long-term waterlogging should be avoided to negate significant productivity losses.