Search

Context: Improving the stability of legumes in grasslands in the face of variable seasonal conditions is key to mitigating risks posed by drought. Aims: We assessed the persistence of a range of legume species and cultivars in order to inform legume choice for pasture improvement and identify priority species for further development. Methods: Twenty field experiments in four series were conducted at sites with contrasting seasonal and soil characteristics in the 'high-rainfall' (560–920 mm long-term average) Tablelands and Monaro regions of New South Wales, Australia. Legumes were grown as pure swards and assessed periodically for seedling density, plant frequency and dry matter for up to 5 years. Key results: Legume dry matter production was positively correlated with plant frequency. However, most legumes persisted poorly at most sites, particularly on soils of lower fertility. Subterranean clover (Trifolium subterraneum) cv. Goulburn was the best performing cultivar of that species across sites on the Southern Tablelands and Monaro. Yellow serradella (Ornithopus compressus) cvv. Avila and Yellotas showed promising persistence, particularly under drought conditions. White clover (T. repens) was the most broadly adapted of the perennial legumes across a range of soils, but persistence was still inadequate at many sites. Lucerne (Medicago sativa) was approximately twice as productive as the next-most productive species when soil conditions suited its growth, but it failed to persist on acidic, low-fertility soils. Conclusions: Serradella species (yellow and French, O. sativus) and white clover, in conjunction with subterranean clover, offer the best near-term prospects for diversifying legume productivity and resilience under variable seasonal conditions in tableland environments. Implications: An increased focus on phenology and seed characteristics is suggested to improve the persistence of annual and facultative perennial legume species in grasslands. Serradella and white clover are identified as the highest priorities for cultivar development for tableland environments of south-eastern Australia. This study evaluated the stability and persistence of a range of legume species and cultivars to identify viable options for grasslands of south-eastern Australia. Yellow and French serradella, white clover and subterranean clover were identified as priority species because they are already, or are close to being, viable options for use in grasslands. An increased focus on phenology and seed characteristics is suggested to improve the persistence of white clover and serradella in grasslands. [ABSTRACT FROM AUTHOR]

Legumes have underpinned transformational change on New Zealand sheep and beef farms over the last 30 years. This was through an emphasis on ewe nutrition based on lucerne or red clover dominant pastures, and increased use of subterranean and white clovers on uncultivatable hill country. Pre- and post-weaning lamb growth rates have increased, and enabled earlier slaughter of heavier lambs. The farm systems results include greater numbers of hoggets mated, higher lambing percentages and greater ewe efficiency (kg lamb weaned/kg ewe mated). Extension packages to support legume use have compared growth rates of resident and legume-based pastures, economic analyses of successful farms and management packages for the most appropriate legume in different environments. Over the same period, the dairy industry rapidly expanded in cow numbers and area onto flat irrigated land on the Canterbury Plains. The nitrogen deficiency of perennial ryegrass was overcome by a linear increase in nitrogen fertiliser use. Environmental concerns from this intensification has led to a legislated nitrogen cap of 190 kg/ha.year. This, coupled with a recent trebling in urea price, has returned attention to increasing the white clover content of these pastures. Nitrogen applications can be minimised by using diverse pastures sown with a legume, herb and <8 kg/ha of perennial ryegrass. Work on other legumes, including annuals and those with condensed tannins, has to date failed to increase their use in most pastoral settings, with the exception of the perennial lupin which is adapted to high-aluminium soils in the South Island High Country. Legumes have underpinned the New Zealand pastoral-based economy for over 100 years. White clover remains the most widely sown, but specialist red clover based pastures are providing high quality feed for fattening livestock in wetter regions of the country. In the drier east coast, lucerne management has been refined based on crop physiology principles. This has allowed earlier lambing, leading to transformational change on-farm. Subterranean clover remains the dominant annual legume used. Successful integration of legumes on-farm has required understanding of the genotype by environment by management interactions. [ABSTRACT FROM AUTHOR]

Context: Opportunity exists to expand serradella (Ornithopus spp.) use onto heavier, duplex soil types in permanent pasture environments of south-eastern Australia. This requires cultivars with appropriate flowering times and flowering-date stability (i.e. flowering at the same date in spring regardless of timing of the autumn break). Aim: This work examined evidence of variation in flowering date and flowering-date stability in the NSW southern tablelands for a widely-used French serradella (O. sativus) cv. Margurita. Methods: Seed (sourced from a commercial supplier) was sown 21 March 2019 (Canberra, ACT) and 231 individual plants were monitored for time to first flower. A subset of plants exhibiting 'early' or 'late' flowering were identified and their seeds collected. In 2020, seed from ~15 plants from each selection was sown in Canberra in late March and early May to represent an 'early' and a 'later' break of season (n = 3). Key results: In the early-sown treatment, 'early-flowering' selections typically reached the median date of first flower (50%-flowering) from mid- to late August, while 'late-flowering' selections reached 50%-flowering early- to mid-September. When sown later, the 'early-flowering' selections began flowering from mid- to late September, while the 'late-flowering' selections flowered mid-September to early October. The 'early' selections exhibited greater flowering-date instability than 'late' selections and flowered particularly early when sown early. This indicated diversity within cv. Margurita for flowering-time control (e.g. vernalisation and/or photoperiod requirements). Implications: Evaluating cultivars of serradellas for flowering date and flowering date stability in their target environment(s) is essential to ensure cultivars are suitably adapted to these environments. Serradellas (Ornithopus spp.) are a novel legume option for the permanent pasture environments of south-eastern Australia. This paper investigated evidence of variation in flowering time characteristics within a widely used cultivar of French serradella. We recommend that new cultivars of serradellas be evaluated for flowering time characteristics in their target environment(s) to assess whether the cultivars are suitably adapted to these environments. This is essential to maximise production, feeding value and facilitate effective grazing management. [ABSTRACT FROM AUTHOR]

Context: There is interest in using serradella (Ornithopus spp.) in permanent pastures of the high rainfall zone of south-eastern Australia. However, there is little information concerning levels of hardseededness or patterns of seed softening in these environments. Aim: This study quantified seed softening of serradella species in comparison with subterranean clover (Trifolium subterraneum L.) in the Southern Tablelands and Central Slopes districts of eastern Australia. Methods: Mature seeds were placed in mesh pouches on the soil surface and were retrieved periodically to assess residual hard seed proportions throughout the growing season(s) in four experiments conducted over 2018 and 2019. Key results: Patterns of seed softening among adapted cultivars of subterranean clover were consistent: initially high proportions of hard seed, followed by rapid softening from mid-summer to the end of autumn with the remnant portion of seeds remaining hard. In contrast, diverse patterns of seed softening were observed among serradella cultivars, ranging from highly soft-seeded through to high initial hard seed portions that either softened rapidly or softened over a lengthy period. Rates of seed softening were faster in the warmer/drier environment of Cowra compared to the wetter/cooler environment of Canberra. Conclusions: The study revealed seed softening patterns among serradellas to be diverse and different to subterranean clover. This will affect management and suitability of serradella cultivars for permanent pastures. Implications: In permanent pastures, serradellas that soften slowly over several years are likely to have limited regeneration in the year after pasture establishment with a high potential for weed invasion. Serradella has many advantages as a pasture legume, however persistence and productivity in permanent pastures can be inadequate. This study quantified seed softening of serradella species in comparison with subterranean clover in the Southern Tablelands and Central Slopes districts of eastern Australia. Diverse patterns of seed softening were observed among serradella cultivars, in contrast to subterranean clover. Implications for pasture establishment of serradella in high rainfall zone permanent pastures is discussed. [ABSTRACT FROM AUTHOR]

The isoflavone formononetin (F) impacts livestock fertility and cultivars of the pasture legume Trifolium subterraneum L. (subclover) have been selected for F levels ≤0.2% of leaf dry weight. However, the impact of waterlogging (WL) on isoflavones is little studied. We investigated the response of isoflavones, biochanin A (BA), genistein (G) and F, to WL for: (1) Yarloop (high F) and eight low F cultivars each from subspecies subterraneum , brachycalycinum and yanninicum (Experiment 1); and (2) four cultivars and 12 ecotypes of ssp. yanninicum (Experiment 2). WL impacted F: estimated means increased from 0.19% (control) to 0.31% (WL) in Experiment 1 and from 0.61% to 0.97% in Experiment 2. Isoflavones under WL were highly heritable, particularly F (H 2 = 95%). The proportions of BA, G and F were little changed by WL, with strong positive correlations between free-drained and waterlogged treatments. Isoflavone contents were not related to WL tolerance, as assessed by shoot relative growth rate. In conclusion, isoflavones varied among genotypes and increased with WL, but the proportion of individual isoflavones in each genotype was stable. High F under WL was unrelated with genotype tolerance to WL. Instead, it was a consequence of inherently high F for that particular genotype. Subterranean clover (subclover; Trifolium subterraneum) is valued as a high-quality livestock feed, but its leaves contain the chemical compound, formononetin (F), that can cause reproductive difficulties in ewes in concentrations greater than 0.3% of dry matter. We found that waterlogging increases F content, irrespective of plant tolerance to waterlogging, such that some subclovers safe for grazing under the well-drained conditions are no longer safe. This new knowledge can be applied to support animal welfare and pasture management under waterlogged conditions. [ABSTRACT FROM AUTHOR]

Copyright of Hladnikia is the property of Botanical Society of Slovenia / Botanicno Drustvo Slovenije and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Water scarcity is one of the most limiting environmental factors for crop productivity globally, where biochar application can play a role. To test this, a glasshouse experiment was conducted with aged biochar application with water regimes on arbuscular mycorrhizal fungi colonisation, plant growth, phosphorus nutrition and leaf gas exchange in wheat and subterranean clover. Six treatment combinations (two biochar levels of 0 and 6 t ha−1; and three water regimes of well-watered, water-stressed and watering intermittently) were arranged in factorial completely randomized block design with three replications. The wheat and subterranean clover were grown and harvested 14, 24, 34 and 44 days after sowing. In this study, aged biochar had no significant effect on plant growth for both wheat and clover, regardless of water regimes. Shoot and root dry weights increased in well-watered conditions compared to water-stressed conditions. Root length and colonised root length increased with biochar addition for wheat, mostly in well-watered treatment. Phosphorus uptake increased in biochar treatment, and the effect was higher in well-watered conditions. Leaf photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration (Ci) and transpiration rate (E) increased with biochar addition. For clover, the effect was higher in water-stressed than well-watered conditions. These results suggest that biochar may enhance water availability to clover plants in water-stressed conditions. However, the positive effect of biochar on plant growth under water-stressed conditions, varied with plant species, needs to be explored further in a range of crop species and biochar sources in addition to the material used in the current investigation. [ABSTRACT FROM AUTHOR]

The addition of self‐regenerating annual legumes into permanent pastures can benefit rapid forage growth in early spring, leading to increased pasture production and animal live weight gain (LWG). The objective of this 2‐year grazing study was to evaluate the effects of balansa clover (Trifolium michelianum) and subterranean clover (Trifolium subterraneum) on pasture and animal production in an irrigated dairy system in western Oregon, USA. Study results showed that balansa clover has a high potential to increase legume content of establishing pastures in early spring. Legume content of pastures sown with annual legumes increased by 25.3% in early spring compared to pastures sown without annual legumes. However, no significant increase in legume content was observed past the initial year of establishment. The persistence of balansa clover and subterranean clover was low in 2021, at <1% of the botanical composition. The overall benefits of balansa clover in early spring in 2020 were offset by reduced perennial forbs, white clover (Trifolium repens) and chicory (Cichorium intybus), in paddocks that were sown with annual legumes. However, this did not negatively affect the LWGs of heifers. This study found no significant difference between pastures sown with and without annual clovers pastures on dry matter production and animal production. Balansa clover was competitive in the establishment year; however, further research into improving its persistence past establishment is warranted. [ABSTRACT FROM AUTHOR]

Prospects for improving the productivity of species mixtures in transitions between phases by changing row configuration at sowing were examined in two series of field experiments in rain-fed, semi-arid environments in south-eastern Australia. The first series explored how the choice of cover crop and use of alternate drill row configurations affected establishment and yields of sward components in the transition from a cropping into a pasture phase. Cover-crop species included wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), c anola (Brassica napus L.) a nd l upins (Lupinus augustifolius L.), e ach s own i n m ixed o r a lternate d rill r ows w ith l ucerne (Medicago sativa L.) and subterranean clover (Trifolium subterraneum L.). The second series of experiments examined the productivity implications when returning from the pasture phase back into cropping following 10 contrasting pastures sown to various combinations of lucerne, subterranean clover or phalaris (Phalaris aquatica L.) sown in mixed, alternate (1:1) or double skip (1:2) row configurations in the absence of cover crops. All experiments were sown on a 0.25-m row spacing. In the transition into the pasture phase, grain yields of cover crops in the mixed drill row treatment were similar to those achieved by crops grown in the absence of pasture species but were reduced by an average of 24% in the alternate drill row configuration. Canola and lupin crop biomass were lower, compared with wheat and barley, leading to increased pasture yields in year 1, highlighting an opportunity for increased use of these species as cover/companion crops in semi-arid environments. Pasture yields beyond year 1 were reduced by ~20% in the alternate drill row treatments compared with where species were sown in mixed drill rows, with greater yield differences under more favourable growing conditions. This response largely reflected yield reductions in lucerne where it was concentrated in fewer drill rows. The alternate drill row configuration increased the abundance of subterranean clover in year 1, but this species remained a minor component of all swards beyond the establishment year. In the transition into the cropping phase, effects on grain quality could only be attributed to row configuration of the previous pasture to the extent that row configuration changed pasture composition. Grain size was smallest and protein concentration highest where previous pastures contained both lucerne and subterranean clover without phalaris. Taken together, there was little advantage in total productivity attributable to spatially separating species in drill rows at sowing. [ABSTRACT FROM AUTHOR]

The soils of Mediterranean semiarid environments are commonly characterized by low levels of organic matter and mineral elements, as well as severe weed infestations, which, taken together, cause an intensive use of auxiliary inputs (tillage, fertilizers, herbicides). Although cover crops are recognized to sustainably improve soil health, the impact of Trifolium subterraneum L. cover cropping needs specific attention. This research investigates for the first time the effects over 4 years of T. subterraneum and spontaneous flora cover crops, after either incorporating their dead mulches into the soil or leaving them on the soil surface, on soil organic matter (SOM), macroelements, mineral nitrogen, microelements, and weed seedbank dynamics as indicators of soil quality in an apricot orchard. Compared to a conventional management control, the T. subterraneum cover crop with the burying of dead mulch into the soil increased the amount of SOM (+ 15%), ammoniacal (+ 194%) and nitric (+ 308%) nitrogen, assimilable P2O5 (+ 5%), exchangeable K2O (+ 14%), exchangeable Na (+ 32%), exchangeable K (+ 16%), Fe (+ 15%), Mn (+ 28%), Zn (+ 36%), and Cu (+ 24%), while it decreased the weed seedbank size (‒ 54%) and enhanced weed biodiversity. These findings suggest that T. subterraneum cover cropping may be an environment-friendly tool to enhance soil quality and limit auxiliary input supply in Mediterranean orchards. [ABSTRACT FROM AUTHOR]

Copyright of Silva Lusitana is the property of Unidade de Investigacao de Silvicultura e Productos Florestais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The introduction of well-adapted species, such as Trifolium subterraneum (subclover) and Poa pratensis (Kentucky bluegrass), might enhance the forage yield and quality of dehesa pastures for feeding livestock. However, the climatic hardness and poor soils in these agrosystems may limit plant establishment and development. Since fungal endophytes have been found to alleviate the environmental stresses of their host, the aim of this study was to assess the effect of five isolates on forage yield, nutritive value, and plant mineral uptake after their inoculation in the two abovementioned plant species. Two experiments were established (under greenhouse and field conditions) using plants inoculated with two isolates in 2012/2013 (Epicoccum nigrum, Sporormiella intermedia) and three isolates in 2013/2014 (Mucor hiemalis, Fusarium equiseti, Byssochlamys spectabilis). Fusarium equiseti (E346) increased the herbage yield of T. subterraneum under greenhouse conditions, and B. spectabilis improved the forage quality of T. subterraneum by reducing fiber content and of P. pratensis by increasing crude protein. S. intermedia increased the mineral uptake of Ca, Cu, Mn, Pb, Tl, and Zn in subclover, and M. hiemalis increased the uptake of K and Sr in Kentucky bluegrass. These results evidence the potential of the studied fungal endophytes to enhance herbage yield and nutritional value of forage, although further studies should include all of the target forage species as certain host specificity in the effect was observed. [ABSTRACT FROM AUTHOR]

This paper reports on the evaluation of "summer sowing," an innovative approach to increase the adoption of recently domesticated species of hard seeded annual legumes in Mediterranean and temperate Agriculture. The research revealed that several species of annual legumes whose seed can be readily harvested on‐farm and which possess natural hard seed dormancy, may be sown into dry soil in late summer without additional processing. These studies proved that the hard seed dormancy was broken down sufficiently in the soil over 4–6 weeks to produce robust legume pastures with more than 150 seedlings per m2 following the first winter rains, in replicated field sites established across wide agro‐ecological zones in Western Australia (WA) and New South Wales (NSW). Ornithopus sativus Brot., O. compressus L. and Trifolium spumosum L. were suitable for summer sowing based on both hard seed breakdown patterns and subsequent seedling survival in WA. While in NSW, in addition to these legumes, Biserrula pelecinus L., T. vesiculosum Savi. and T. glanduliferum Boiss. were also suitable for summer sowing. A 1.5‐ to 10‐fold increase in herbage production was achieved relative to conventionally sown T. subterraneum L. This development represents a step change in forage legume development for renovated pastures in these environments. Importantly, the experiments revealed differences in G x E effects on seedling establishment, total herbage production and seed yield in different climatic zones. The summer sowing approach is presented as a revolutionary method for pasture renovation that overcomes significant barriers to adoption. [ABSTRACT FROM AUTHOR]

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. Mycorrhizal fungi are ubiquitous in agroecosystems and contribute to the phosphorus acquisition of many plants. Five annual pasture legumes were grown to determine the effect of mycorrhizal fungi on plant adaptations to low phosphorus supply. Mycorrhizal colonisation improved the shoot yield and phosphorus acquisition of the legumes in phosphorus-deficient soil, but markedly reduced root acclimation responses to phosphorus deficiency. The relative efficiency of phosphorus acquisition was dependent on the intrinsic root morphology of the legumes, irrespective of mycorrhizal colonisation. [ABSTRACT FROM AUTHOR]

Low phosphorus (P) constrains productivity of many of the permanent pastures of south-eastern Australia where wool and meat production are important. Whereas the need for fertilisation with P is indisputable for many soils, the benefits of liming to ameliorate soil acidification are not always clear in terms of forage production or quality. This experiment, by measuring botanical composition and groundcover over 10 years, aimed to address the issue of forage composition and groundcover. Merino wethers were continuously grazed on a permanent pasture under two stocking rates (low and high) following treatments with three rates of surface-applied lime and two rates of P. The lime rates were: nil, and sufficient to raise the pHCaCl2 of the 0–10 cm soil layer to 5.0 and to 5.5. Phosphorus was added as two rates of single superphosphate: 125 kg ha–1 every 2–3 years, and 250 kg ha–1 every year. Two hypotheses were proposed: (i) as lime application rate increased, it would lead to the pasture swards having a higher percentage of species favourable for grazing animal production, and a higher level of sward groundcover would be maintained; and (ii) legume presence would be favoured by a higher level of applied P over the long term. The Millennium Drought (1997–2008), which coincided with this experiment (1998–2008), tended to mask or reduce lime effects; nevertheless, the higher legume content in the sward, as well as the superior groundcover found in the high lime–high P treatments at various times throughout the experiment and at its completion compared with the nil-lime control, indicated positive forage effects of lime application. Moreover, by the termination of the experiment in 2008, groundcover generally tended to be lower under nil lime than in treatments that had received lime. The higher proportion of legume in the sward was closely linked to greater applied P, although this did not occur at the low stocking rate in the absence of lime. By contrast, similar high P–low stocking rate treatments but with applied lime had the highest clover contents. It is proposed that the poor persistence of the treatment without lime may be due to a combination of poor legume seedset, because of excessive competition from accompanying grasses, and aluminium toxicity adversely affecting legume growth. Soil acidity is a serious problem reducing the production of crops and grazing animals, and although lime can reduce acidity, it is expensive because high rates are required. This research follows the effect of lime on the pasture composition of desirable legumes and perennial grasses. The higher legume content in the sward found in high lime–high phosphorus treatments at times throughout the experiment and at its completion compared with the nil-lime control indicated the value of lime application. [ABSTRACT FROM AUTHOR]

Aims: Phosphorus (P) is usually stratified in the topsoil layer under pasture, due to the broadcast application of fertiliser, excreta and leaf-litter deposition on the soil surface, and minimal soil disturbance. The objective of this study was to investigate root proliferation and P acquisition in response to P stratification by comparing two Trifolium subterraneum cultivars with contrasting root morphologies. Methods: Clover micro-swards were grown with deficient, constrained and sufficient P supplied in a topsoil layer overlying a P-deficient subsoil that mimicked the stratification of P that occurs under pasture. Phosphorus labelled with 33P- and 32P-radioisotope tracer was mixed throughout the topsoil and subsoil layers, respectively. Results: The shoot yield and total plant P uptake of the cultivars increased in response to increased topsoil P supply. The length of roots produced by the cultivars was equivalent in each of the P treatments, although the specific root length achieved by the cultivars was substantially different. In the P-constrained and P-sufficient treatments, ~91% and ~ 99% of total plant P was acquired by topsoil roots, respectively. In contrast, subsoil roots acquired 60–74% of total plant P in the P-deficient treatment. Conclusions: Topsoil roots were most important for P acquisition when P was highly stratified, whereas subsoil roots contributed to P acquisition when P was uniformly distributed throughout the P-deficient soil profile. Selection for prolific nutrient-foraging roots, in conjunction with plasticity for subsoil exploration, may improve the P-acquisition efficiency of T. subterraneum genotypes and confer adaptability across a range of soil-P environments. [ABSTRACT FROM AUTHOR]

Aims: The experiment was conducted to understand how root morphological traits contributed to the contrasting P-acquisition efficiencies of two Trifolium subterraneum cultivars. Methods: Phosphorus acquisition, root length proliferation and root acclimation to P deficiency were investigated by varying the P supply (20–300 mg P kg−1) and planting density (1–12 plants pot−1) of clover micro-swards. Results: The shoot yield of both cultivars increased in response to increased P supply and increased planting density. Higher planting densities increased shoot yield by reducing the time to leaf canopy closure. In P-deficient soil, the 'less P-efficient' cultivar acquired less P and yielded relatively poorly compared with the 'more P-efficient' cultivar when planting density was low (<6 plants pot−1). However, the P acquisition and yields of the cultivars were equivalent when planting density was high (~6–12 plants pot−1). Both cultivars proliferated nutrient-foraging roots in response to P limitation and space (i.e. lower planting densities). However, the proliferation responses of the cultivars differed, particularly in response to space. Conclusions: Differential proliferation responses, combined with differences in specific root length, explained how the cultivars differed in P-acquisition efficiency. The results indicate that inappropriate cultural conditions (e.g. planting densities) may confound attempts to define P-efficient root traits and to identify genotypes with improved P-acquisition efficiency. [ABSTRACT FROM AUTHOR]

Self-reseeding annual cover crops can regenerate in subsequent years without tilling the seedbed and can be part of a strategy to protect vineyard soil from erosion. We compared 22 such cultivars in a 1-year-old ‘Syrah’ wine-grape vineyard located at 1,400 feet in Lake County. We found significant differences between species in the amount of biomass produced in 2004 and 2005. All of the species studied were relatively low statured and fit well in vineyard middles. Pressure bomb readings taken after the cover crops stopped growing showed that with a dry spring (2004), vines with cover crops were modestly more stressed than those under tillage prior to July irrigations, but after irrigation the cover-cropped vines were slightly less stressed. In 2005, which had rainfall in late spring, there were no differences in vine water status throughout the season. We conclude that water use by the cover crop must have been relatively low and did not result in excessive vine water stress.

The incorporation of chicory (Cichorium intybus) into phased crop-pasture farming systems requires an understanding of the dynamics of nitrogen (N) mineralisation of residues and the potential supply of N to subsequent crops. A 3-year field experiment was conducted to compare relative N mineralisation rates from the pure chicory pasture, compared to the chicory-subterranean clover (Trifolium subterraneum) or lucerne (Medicago sativa)-subterranean clover pastures. Existing pastures were chemically fallowed in either spring or the following autumn. Soil mineral N and soil gravimetric water content were measured at 0, 6 and 12 months after pasture removal. Six months after pasture removal, chicory-subterranean clover pasture exhibited the highest N mineralisation rate for the spring and autumn removals (0.36 and 0.37 kg mineral N ha−1 day−1, respectively), whereas lucerne-subterranean clover pasture had the lowest for the spring and autumn removals (0.04 and 0.05 kg mineral N ha−1 day−1, respectively). However, the daily N mineralisation rate for the lucerne-subterranean clover pasture increased dramatically to 0.51 and 0.98 kg mineral N ha−1 day−1 12 months after pastures were removed in spring and autumn, respectively. In contrast, the chicory pasture produced 0.15 vs 0.63 kg mineral N ha−1 day−1 for the spring and autumn removals, respectively. Including subterranean clover in mixtures with chicory significantly increased the availability of mineral N by 28% with the spring removal and 45% with the autumn removal compared to the pure chicory pasture. Due to the quicker rate of N mineralisation with chicory-based pastures, an opportunity exists to remove chicory-based pastures later than lucerne-based pastures without having a detrimental effect on N supply to the following crop while still providing additional feed for livestock. • Nitrogen mineralisation of chicory residues occurs more rapidly than lucerne residues. • Including subterranean clover in a mixture with chicory significantly increases soil mineral nitrogen. • Chicory-based pastures can be removed later than lucerne-based pastures prior to cropping phase in a semi-arid environment. [ABSTRACT FROM AUTHOR]

Nine natural populations of subterranean clover (Trifolium subterraneum L.) coming from different eco-geographical sites of the North-East Algeria, have been studied for their chromosome number and karyotype features. The study is part of the evaluation and valorization of plant genetic resources of fodder and pastoral interest in Algeria. The results of mitosis detect two groups of populations, and reveal diversity in the number among and within populations. The Algerian populations of T. subterraneum are characterized by two chromosomic formulas. The first formula (2n=2x=16m) (median), more common in most of the studied populations, is in conformity with previous reports in this species. The karyotype of these populations is symmetrical for size and form. The second (2n=2x= 18m), is detected for the first time and described as a new chromosomal formula in T. subterraneum. The latter is relatively more frequent than the first one and characterizes the populations coming from high altitude areas. The karyotype (2n=2x=18m) is relatively symmetrical. At the level of the two established Karyotypes, satellites are highlighted at the first pair. A variation in the size and frequency of these satellites is observed. The species exhibits regular meiotic behaviour, confirming the presence of two basic chromosome numbers (x=8 and 9). The study also highlights the role of ecological factors (Altitude and Rainfall) of the originating environment of Algerian populations in the variation and evolution of chromosome numbers in T. subterraneum. The new cytogenetic data can be exploited in the taxonomy of the species in Algeria in order to select and develop this plant genetic resource in the agricultural field.

In recent decades several pasture legumes have been available in southern Australia as potential alternatives to the most widely used annual pasture legume Trifolium subterraneum. Little is known about their soil phosphorus (P) requirements, but controlled environment experiments indicate that at least some may differ in their P fertiliser requirements. In this study, pasture legume varieties, including T. subterraneum as the reference species, were grown at up to four sites in any one year over a 3-year period (in total, seven site × year experiments) to measure herbage growth responses in spring to increased soil P availability. A critical soil test P concentration (corresponding to 95% maximum yield) was estimated for 15 legumes and two pasture grasses. The critical soil P requirements of most of the legumes did not differ consistently from that of T. subterraneum , indicating their soil fertility management should follow the current soil test P guidelines for temperate Australian pastures. However, the critical P requirement of Medicago sativa was higher than that of T. subterraneum , but remains ill-defined because extractable soil P concentrations in these experiments were often not high enough to permit a critical P estimate. Three forage crop legumes (Trifolium incarnatum , Trifolium purpureum , Trifolium vesiculosum) and two pasture legumes (Ornithopus compressus , Ornithopus sativus) had lower critical soil test P concentrations. It may be feasible to manage pastures based on these species to a lower soil test P benchmark without compromising yield. Extractable phosphorus concentrations of soil corresponding to near-maximum pasture legume growth can be used as benchmarks for soil phosphorus management in temperate grass–legume pastures. In this study, the soil phosphorus requirements of alternative pasture legumes used in southern Australia were assessed and compared with that of the widely used legume Trifolium subterraneum. The results indicate that published soil test phosphorus benchmarks for T. subterraneum are appropriate for many alternative legumes, but also demonstrate that some can be fertilised to lower benchmark concentrations without compromising yield. [ABSTRACT FROM AUTHOR]

In alkaline soils in arid and semi-arid areas toxic concentrations of the micronutrient boron (B) are problematic for many cereal and legume crops. Molecular markers have been developed for B toxicity in cereals and Medicago. There is a need for such tools in clovers— Trifolium. To this end, we undertook a genome-wide association study (GWAS) with a diversity panel of subterranean clover (Trifolium subterraneum L.), an established model pasture legume for genetic and genomic analyses for the genus. The panel comprised 124 T. subterraneum genotypes (97 core collection accessions and 27 Australian cultivars). Substantial and useful diversity in B toxicity tolerance was found in T. subterraneum. Such variation was continuously distributed and exhibited a high broad sense heritability H 2 = 0.92. Among the subspecies of T. subterraneum , ssp. brachycalycinum was most susceptible to B toxicity (P < 0.05). From the GWAS, the most important discoveries were single-nucleotide polymorphisms (SNPs) located on Chr 1, 2, and 3, which mapped to haplotype blocks providing potential genes for a B toxicity tolerance assay and meriting further investigation. A SNP identified on Chr 1 aligned with Medicago truncatula respiratory burst oxidase-like protein (TSub_ g2235). This protein is known to respond to abiotic and biotic stimuli. The identification of these novel potential genes and their use to design markers for marker-assisted selection offer a pathway in pasture legumes to manage B toxicity by exploiting B tolerance. [ABSTRACT FROM AUTHOR]

In the summer-dominant rainfall zone of inland northern New South Wales and southern Queensland, tropical grass-temperate legume mixed pastures can provide forage for grazing livestock for most of the year; however, the effect of canopy cover and its interaction with ground cover for regeneration of Trifolium subterraneum (subterranean clover) are not known. An experiment was conducted using established Digitaria eriantha with two levels of canopy cover (defoliated to 0.1 m and undefoliated) and four levels of ground cover (ranging from bare to 75%). Plots were oversown with subterranean clover seed in May-June, and legume establishment and spring herbage production were assessed. Low rainfall throughout the experiment resulted in poor clover establishment and production but seedling densities were significantly higher in the defoliated treatments (14 cf. 6 seedlings/m2). Herbage production was also significantly higher in the defoliated plots (530 cf. 302 kg DM/ha). There was no effect of ground cover. These findings indicate that management strategies that remove excess forage and reduce canopy cover of tropical grass pastures in late summer will maximise regeneration of subterranean clover in autumn. [ABSTRACT FROM AUTHOR]

Tedera, (Bituminaria bituminosa C.H. Stirt var. albomarginata) a herbaceous deep rooted perennial legume is being evaluated as a summer-autumn feed for sheep production in South Western Australia (SWA). As soils of SWA are generally infertile it was necessary to determine the requirement of phosphorous (P), potassium (K) and sulfur (S) for growth of tedera compared with subterranean clover. This was carried out using four glasshouse experiments. Results showed that tedera has the same requirement for P application, about 40% lower for K and none for S compared to subterranean clover. Critical tissue concentrations for 90% maximum yield of herbage were also determined. Results showed tedera required about one and half times more P, about half the K in the tissue compared to subterranean clover. Tedera showed no herbage response to additions of S. This study warrants further investigation under both glasshouse and field conditions. [ABSTRACT FROM AUTHOR]

Studies were undertaken to examine the potential for manipulating the ecosystem by altering forage species composition, intensity of grazing or by adding Rhizobium, to enhance productivity of subterranean clover (Trifolium subterraneum) forages affected by the soilborne pathogens Pythium irregulare and Rhizoctonia solani. Levels of tap and lateral root disease on clover and its productivity were differentially and significantly affected by the relative proportions of clover to annual ryegrass (Lolium rigidum). In the presence of P. irregulare, both tap and lateral root disease decreased as percentage clover composition increased (R2 = 0.58, 0.59, respectively); there was no such significant effect in the presence of R. solani (R2 = 0.08, 0.18, respectively). Increasing and maintaining high clover content in forage offers a means to both reduce root disease and increase productivity and forage legume stand persistence. With simulated grazing studies, continuous (i.e. intensive) grazing in the presence of P. irregulare resulted in the most severe tap and lateral root disease, poorest nodulation and smallest roots and shoots compared with intermittent grazing. Hence, reducing grazing intensity also offers potential for significantly increasing productivity of root‐rot‐affected clover forage. For Rhizobium studies, nodulation was reduced in the presence of P. irregulare or R. solani; the extent of this was dependent upon which pathogen and the clover variety. Overall, these different studies highlight significant potential for manipulating the ecosystem to better manage soilborne pathogen complexes and improve productivity and persistence in annual legume forage systems adversely affected by soilborne oomycete and fungal pathogens. [ABSTRACT FROM AUTHOR]

ABSTRACT: A pot experiment was conducted to study the nodulating capacity of some forage legumes. Birdsfoot trefoil (Lotus corniculatus L), sainfoin (Onobrychis viciifolia Scop.) and subterranean clover (Trifolium subterraneum L.) were grown in pure culture (100%) and in mixtures with tall fescue (Festuca arundinacea Schreb.) in the ratios: birdsfoot trefoil + tall fescue (50:50%); sainfoin + tall fescue (50:50%); subterranean clover + tall fescue (50:50%); birdsfoot trefoil + subterranean clover + tall fescue (33:33:33%); sainfoin + subterranean clover + tall fescue (33:33:33%). Birdsfoot trefoil from the crops cultivated in pure stands showed the highest nodulation rating (31), followed by sainfoin (26) and subterranean clover (26). Nodulation rating in binary mixtures with grass component increased to 16.1% for birdsfoot trefoil and to 23.1% for subclover. Birdsfoot trefoil, both in pure stands and in mixtures, showed the highest phosphorus use efficiency for nodule formation.

Intercropping field experiments with maize and Phaseolus beans are conducted at the Thünen-Institute of Organic Farming (Schleswig-Holstein, SL, 740 mm, 8.7 °C) from 2014-2016. As known from previous experiments, maize and beans have a very low competitiveness against weeds, due to their relative slow youth development. Therefore, the beans were sown subsequently to the mechanical weed control with harrow and hoe, at the 4-leaf development stage (BBCH 14) of maize. Hence a mechanical weed control after bean emergence is critical, a field experiment is conducted to find out whether the establishment of an additional catch crop can reduce weed pressure substantially. For this purpose two catch crop mixtures are evaluated in pure maize plots as well as in intercropping plots with scarlet runner beans (Phaseolus coccineus, cv. Preisgewinner) or common runner beans (Phaseolus vulgaris, cv. Tarbais) respectively. As control variants, plots without undersown crops were used. The undersown crop mixtures are composed of Italian ryegrass (cv. Gersimi, sowing density: 15 kg ha-1), which is combined with subterranean clover (cv. Seaton Park, sowing density: 30 kg ha-1) in US1 and with Chicory (cv. Puna II, sowing density 7.5 kg ha-1) in US2. The highest biomass (50 g DM m-2) was produced by US1 in all variants, while the biomass of US2 was significantly lower with 32 g DM m-2. As a result of a successful mechanical weed control as well as a good development of the main crops, the weed pressure in 2014 was generally low. Nevertheless, the results show that undersown crops can reduce weeds substantially. While the significantly highest weed biomass was recorded in the plots without undersown crops, it was reduced by 70% with US1 and by 80% with US2 on average respectively.

The possibility of annual and perennial legume crops to be used for undersowing of degraded pasture stands and alfalfa seed production stands was studied in the conditions of the Northern Bulgaria. The direct undersowing of degraded pasture stands was done after harvest with these legumes: birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifoliumpratense L.), black medick (Medicago lupulina L.), arrowleaf clover (Trifolium vesiculosum Savi), and common vetch (Vicia sativa L.). The undersowing of degraded seed production stands of alfalfa was done in autumn of the fourth year of using with subterranean clover (Tr. subterraneum ssp. brachycalicinum cv. Antas). Red clover showed the best results in terms of suitability for the direct undersowing of degraded pasture stands. Subterranean clover could be used for the direct undersowing of the degraded alfalfa seed production stands due to its self-seeding ability.

Mixed farming systems have traditionally incorporated subterranean clover (Trifolium subterraneum L.) and lucerne (Medicago sativa L.) as key components of the pasture phase across south-eastern Australia. However, poor adaptation of subterranean clover to acidic soils, insufficient and inconsistent rainfall, high input costs, soil acidification and the emergence of herbicide-resistant weeds have reduced efficacy of some traditional clover species in recent years. To overcome these challenges, numerous novel pasture species have been selectively improved and released for establishment in Australia. Despite their suitability to Australian climate and soils, limited knowledge exists regarding their weed-suppressive ability in relation to establishment and regeneration. Field trials were therefore conducted over 3 years in New South Wales to evaluate the suppressive potential of selected pasture legume species and cultivars as monocultures and in mixed stands against dominant annual pasture weeds. Pasture and weed biomass varied significantly between pasture species when sown as monocultures, but mixtures of several species did not differ with regard to establishment and subsequent weed infestation. Arrowleaf clover (T. vesiculosum Savi.) and biserrula (Biserrula pelecinus L.) cv. Casbah showed improved stand establishment, with higher biomass and reduced weed infestation compared with other pasture species. Generally, weed suppression was positively correlated with pasture biomass; however, yellow serradella (Ornithopus compressus L.) cv. Santorini exhibited greater weed suppression than other pasture legumes while producing lower biomass, thereby suggesting a mechanism other than competition for resources affecting weed-suppressive ability. Over the period 2015–17, arrowleaf clover and biserrula cv. Casbah were generally the most consistent annual pasture legumes with respect to yearly regeneration and suppression of annual pasture weed species. Results of 3 years of field experimentation using a variety of annual pasture legumes demonstrated that arrowleaf clover and biserrula were the most consistent and competitive annual legumes with respect to stand establishment, yearly regeneration and consistent suppression of common pasture weed species. Multivariate analysis revealed weed suppressive potential of annual pasture legumes including biserrula cv. Casbah and yellow serradella were due to mechanisms other than competition for resources. [ABSTRACT FROM AUTHOR]

Subterranean clover (Trifolium subterraneum) is an important forage legume in Mediterranean regions worldwide. Aphanomyces damping‐off and root disease (Aphanomyces trifolii) poses significant threat to its persistence and productivity. Studies were conducted to define how environmental explanatory variables (temperature, soil type, moisture, nutrition) and variety influence disease severity and consequent forage productivity and persistence. Relationships were modelled using linear and generalized linear models and boosted regression trees. Linear modelling highlighted complex relationships between environmental variables and each dependent variable (emergence, tap and lateral root disease, dry shoot and root weight). All environmental variables produced significant interaction and/or main effects within each dependent variable. Boosted regression trees supported the complex nature of relationships in linear models, with temperature and either soil or variety most, and nutrition least, influential. Heat maps showed more disease for low temperatures. Least tap root disease was under high temperatures, while least lateral root disease was under medium or high temperatures, low moisture, and in sand‐based soil. These are the first studies using modelling approaches to reveal the complexities of how fluctuating soil temperature, moisture and nutrition conditions, and soil type and variety, determine aphanomyces damping‐off and root disease severity and resultant adverse impacts on forage legume productivity and persistence. Outcomes are widely applicable across soilborne oomycete pathogens of forage legumes. Studies highlighted how warming temperatures and drying climate associated with climate change should reduce future impact and importance of this and other soilborne oomycete diseases of forage legumes favoured by cold temperatures and wet and waterlogged conditions. [ABSTRACT FROM AUTHOR]

Annual pasture legumes with a superior ability to acquire soil phosphorus (P) and a low external critical P requirement could reduce the need for P fertiliser. Roots of pasture legumes grown in field soil will commonly be colonised by arbuscular mycorrhizal fungi (AMF). However, recent research suggests a second community of arbuscule-forming root-colonising fungi may be present: fine root endophytes (FRE). AMF are known to enhance P acquisition by plants under certain conditions, whereas very little is known about FRE and their impact on plant P status. We, therefore, grew plants at seven levels of P supply to determine and compare the external critical P requirements of two species of Ornithopus and two cultivars of Trifolium subterraneum when colonised predominantly by FRE (FRE-dominant treatment) or both FRE and AMF (mixed treatment). As expected from previous studies, the Ornithopus species had a lower critical P requirement than the T. subterraneum cultivars. However, for the Ornithopus species only, the FRE-dominant community had a significantly lower external critical P requirement (24–31 mg P kg −1 soil) than the mixed community (50–58 mg P kg −1 soil). Moreover, at low-P supply (≤15 mg applied P kg −1 soil), Ornithopus species in the FRE-dominant treatment had longer specific root length, smaller average root diameter, 45–128% greater total root length, and lower shoot and root P concentration than in the mixed treatment. We concluded that comparisons among experiments of root morphological traits and external critical P requirements can be affected by the presence of different communities of arbuscule-forming root-colonising fungi and that these effects may vary among plant species. [ABSTRACT FROM AUTHOR]

In connection with the dilution of seed production birdsfoot trefoil stands the possibility of under-sowing them with self-seeding crops was studied. The trial was carried out on the experimental field of Institute of Forage Crops, Pleven, Bulgaria with birdsfoot trefoil (Lotus corniculatus L.) Targovishte 1 variety. In autumn after the fourth year of use of the stands (for seed production direction) an under-sowing with three subterranean clover subspecies was done as follows: Trifolium subterraneum ssp. brachycalicinum (Antas variety), Trifolium subterraneum ssp. yaninicum (Trikkala variety) and Trifolium subterraneum ssp. subterraneum (Denmark variety). The capacity of self-sowing of subterranean clover in birdsfoot trefoil stands was assessed. It was found that subterranean clover effectively used the autumn-winter soil moisture, formed a sufficient number of seeds for self-seeding and germinated plants occupied the sites of the dropped birdsfoot trefoil plants. Trifolium subterraneum ssp. brachycalicinum showed the best self-seeding ability. Thus, after under-sowing with subterranean clover, degraded seed production birdsfoot trefoil stands could be used for forage. [ABSTRACT FROM AUTHOR]

Background and aims: The growth and root morphology responses to soil phosphorus (P) fertility by five cultivars of Trifolium subterraneum (a temperate annual pasture legume) were examined to assess whether differences in root morphology and/or root acclimation to P stress influenced P-acquisition by the clover varieties, or their critical P requirements (i.e. the rate of P supply needed for maximum shoot yield).Methods: The clovers were grown as microswards in soil with P stratified in a topsoil layer to mimic growth conditions and soil P availability in a pasture. Yield and P content of shoots, and roots from the topsoil and subsoil layers was determined after 5 weeks growth in a controlled-environment cabinet. The lengths, diameters, and root hair lengths of nutrient foraging roots from the topsoil layer were quantified.Results: The shoot yield of the cultivars was similar when grown with high soil P fertility. However, the cultivars varied up to 1.5-fold in their ability to yield at low levels of soil P supply, and by 1.6-fold in their critical P requirements. All cultivars acclimated to low P soil by increasing root length density in the topsoil but those that yielded relatively well did so by maintaining a large root hair cylinder volume (i.e. they explored more soil) under low soil P conditions. This was associated with maintenance of dry matter allocations to topsoil roots and higher specific root lengths. Both factors assisted development of high root length density for nutrient foraging. Root acclimation responses to P were compared among the cultivars at equivalent relative shoot yields to assess the influence of plant P stress as a trigger for nutrient foraging. The least P-efficient cultivars slowed their allocation of dry matter to foraging roots at lower levels of P stress.Conclusions: The results suggest variation within T. subterraneum for root proliferation and specific root length could be targeted in breeding for improved P-acquisition efficiency. [ABSTRACT FROM AUTHOR]

Nitrogen content in plant biomass yield of subterranean clover (Trifolium subterraneum L.) and cocksfoot (Dactylis glomerata L.) was determined as related to the different concentrations of nitrogen supply. Plants were grown sole and in mixture as symbiotrophic or heterotrophic cultures under controlled mineral elements concentration in the media and inoculation with rhyzobial strain. Two concentrations of inorganic nitrogen were tested: 0.125 mM (N1) and 1.25 mM (N2). Experimental variants: subterranean clover (100%) + N1; subterranean clover (100%) + N2; cocksfoot (100%) + N1; cocksfoot (100%) + N2; subterranean clover + cocksfoot (50:50%) + N1; subterranean clover + cocksfoot (50:50%) + N2. Inorganic nitrogen concentration had greater effect on shoot yield nitrogen content than on root yield nitrogen content for both crops. Nitrogen content in whole plant biomass yield of subterranean clover grown either sole or in mixture with cocksfoot was almost three times greater under high nitrogen concentration. Nitrogen use efficiency was highest in the mixture.

Subterranean clover (Trifolium subterraneum) is a critical pasture legume in Mediterranean regions of southern Australia and elsewhere, including Mediterranean-type climatic regions in Africa, Asia, Australia, Europe, North America, and South America. Pythium damping-off and root disease caused by Pythium irregulare is a significant threat to subterranean clover in Australia and a study was conducted to define how environmental factors (viz. temperature, soil type, moisture and nutrition) as well as variety, influence the extent of damping-off and root disease as well as subterranean clover productivity under challenge by this pathogen. Relationships were statistically modeled using linear and generalized linear models and boosted regression trees. Modeling found complex relationships between explanatory variables and the extent of Pythium damping-off and root rot. Linear modeling identified high-level (4 or 5-way) significant interactions for each dependent variable (dry shoot and root weight, emergence, tap and lateral root disease index). Furthermore, all explanatory variables (temperature, soil, moisture, nutrition, variety) were found significant as part of some interaction within these models. A significant five-way interaction between all explanatory variables was found for both dry shoot and root dry weights, and a four way interaction between temperature, soil, moisture, and nutrition was found for both tap and lateral root disease index. A second approach to modeling using boosted regression trees provided support for and helped clarify the complex nature of the relationships found in linear models. All explanatory variables showed at least 5% relative influence on each of the five dependent variables. All models indicated differences due to soil type, with the sand-based soil having either higher weights, greater emergence, or lower disease indices; while lowest weights and less emergence, as well as higher disease indices, were found for loam soil and low temperature. There was more severe tap and lateral root rot disease in higher moisture situations.