Joanne J. M. Wisdom’s research while affiliated with University of Western Australia and other places

High levels of the phytoestrogen formononetin (F) in green leaves of older cultivars (cvs) of subterranean clover (Trifolium subterraneum)-notably Dinninup, Dwalganup, Geraldton and Yarloop-can cause both transient and permanent fertility issues in ewes, as well as increased lamb and ewe mortality (known as clover disease). Cultivars bred for low F were released to solve this problem. To investigate if old, high-F cvs have persisted in pastures we examined leaf samples submitted by producers from across southern Australia. Cultivars were identified by morphological characters and F concentration. Isoflavones (F, genistein, biochanin A) were measured with thin-layer chromatography and leaf P and S concentrations were measured by inductively coupled plasma-optical emission spectrometry. Of 577 samples analysed, 60% contained F above the current 'safe' concentration of 0.20% of leaf dry weight, with the highest average F (0.90%) measured in samples from South Australia. Concentrations of F varied greatly among samples of individual cvs but were not related to leaf nutrient concentrations suggesting impacts of management or environment. The most common cv submitted was Dinninup, particularly for South Australia and Western Australia. The paucity of relatively modern low-F cultivars suggests producers submitted samples they suspected to be high-F cvs, possibly due to evidence of ewe reproductive health issues. Due to this bias, these results do not provide a quantitative assessment of the occurrence of old high-F cvs, but they do suggest a much greater prevalence than desirable and a need for pasture renovation with new low-F cultivars.

Societal Impact Statement Humans and honey bees have a long history of interaction to yield valued products and services. However, honey bees are under pressure from changes in vegetation, agricultural practices and climate change. We investigate if pasture legumes can be harnessed to support honey bees. We use a diverse set of species that originated from the Mediterranean and western Europe but are now developed as commercial cultivars for the southern Australian livestock industries. We find that pasture legumes show great promise as a means to support honey bees and suggest that further targeted research is warranted. Summary Globally, humans and honey bees (Apis mellifera) have a long history of interaction and this is now under pressure. In temperate southern Australia, exotic honey bees rely on an unstable native floral resource base, yet a diverse set of exotic pasture legume species are sown as staple rotational or permanent crops. We investigated if these pasture legumes could be strategically used to support honey bee populations for the apiary and horticulture industries in this region. A literature review on temperate pasture legumes and honey bees was undertaken and integrated with data from an Australian industry case study. Comparisons were made to the widely‐grown red clover (Trifolium pratense) and white clover (T. repens). We found that many southern Australian pasture legumes could provide significant floral resources as well as enhanced temporal and spatial stability for honey bees due to phenological variability and broad adaptation. Honey bees will likely recognise and be attracted to their flowers and other characteristics are comparable, or potentially superior, to red and white clover, such as floret number per inflorescence, floret length, nectar volume and sucrose‐dominance and pollen protein. The floral resource diversity from pasture legume mixes could aid honey bee health and support pollinator services for adjacent crops. We conclude that the exotic pasture legumes of temperate Australia show promise for development as a sown floral resource for honey bees. Globally, further investigation is merited to maximise benefits from the integration of a diverse range of pasture legumes into agricultural landscapes.

The use of acid soil-tolerant annual legume pasture species and liming to raise soil pH can have legacy effects that improve subsequent wheat crop growth in acid soils. We established a two-year experiment in a semi-arid environment with and without historical lime application to investigate how acid soils (±lime) influence the legacy effects of annual legume pastures. We measured legume and cereal growth and yield, soil-borne disease incidence, rhizosheath organic acid type and amount, legume biological nitrogen fixation (BNF) and soil moisture in Year 1, and soil microbial biomass carbon (MBC) and wheat yield and quality in Year 2. Minor differences in soil moisture and soil-borne diseases occurred between cereals and legumes, and the poor BNF contribution of all pasture legumes improved in lime treatments. Pasture legumes produced more organic acids than cereals, which increased in limed treatments. Soil MBC in Year 2 was greater following legumes than cereals. Year 2 wheat grain yield increased following pasture legumes, more so in limed treatments. The contribution of organic acid exudation by annual legume pastures to microbial community legacy effects warrants further scrutiny in semi-arid environments, particularly when acid soils limit typical rotational benefits. KEYWORDS alfalfa, crop rotations, disease, nitrogen fixation, organic acids, wheat