Nitrogen fixation by caucasian clover and white clover in irrigated ryegrass pastures

The N₂ fixation ability of caucasian clover was compared with that of white clover in irrigated ryegrass pastures over years 2 and 3 of a grazing experiment, using the ¹⁵N enrichment technique. ‘Endura’ caucasian clover was inoculated with the specific Rhizobium strain ICC148. The N concentration in clover herbage and the proportion of clover N derived from N₂ fixation (PN) were similar for both clovers at averages of 4.6%N and 50–60% respectively over the 2 years. The amount of N₂ fixed per hectare was directly related to the amount of clover dry matter (DM) produced by the two clover species. Caucasian clover produced four times the DM yield of white clover in year 2 (5400 cf. 1450 kg DM/ha) and four times the amount of N₂ fixed in herbage (136 cf. 36 kg N/ ha). In year 3, caucasian clover produced 50% more clover DM (3450 cf. 2370 kg DM/ha) and N₂ fixed (98 cf. 66 kg N/ha) than white clover. The increased N input from caucasian clover increased grass %N and N uptake from soil in caucasian clover pastures resulting in higher total pasture production compared with white clover pastures (15.7 cf. 14.2 t DM/ha) by year 3. In this study, caucasian clover demonstrated greater potential than white clover to meet the N demands of high-yielding perennial ryegrass in an intensive pastoral system.The authors acknowledge funding from the Struthers Trust for the development of the grazing experiment at Lincoln University and FRST funding for provision of ¹⁶N and N analyses. We thank the C. Alma Baker and Struthers Trusts for providing A.D. Black with financial support from post-graduate scholarships

Landscape genomic prediction for restoration of a Eucalyptus foundation species under climate change

As species face rapid environmental change, we can build resilient populations through restoration projects that incorporate predicted future climates into seed sourcing decisions. Eucalyptus melliodora is a foundation species of a critically endangered community in Australia that is a target for restoration. We examined genomic and phenotypic variation to make empirical based recommendations for seed sourcing. We examined isolation by distance and isolation by environment, determining high levels of gene flow extending for 500 km and correlations with climate and soil variables. Growth experiments revealed extensive phenotypic variation both within and among sampling sites, but no site-specific differentiation in phenotypic plasticity. Model predictions suggest that seed can be sourced broadly across the landscape, providing ample diversity for adaptation to environmental change. Application of our landscape genomic model to E. melliodora restoration projects can identify genomic variation suitable for predicted future climates, thereby increasing the long term probability of successful restoration

Nitrogen fixation by caucasian clover and white clover in irrigated ryegrass pastures

The N₂ fixation ability of caucasian clover was compared with that of white clover in irrigated ryegrass pastures over years 2 and 3 of a grazing experiment, using the ¹⁵N enrichment technique. ‘Endura’ caucasian clover was inoculated with the specific Rhizobium strain ICC148. The N concentration in clover herbage and the proportion of clover N derived from N₂ fixation (PN) were similar for both clovers at averages of 4.6%N and 50–60% respectively over the 2 years. The amount of N₂ fixed per hectare was directly related to the amount of clover dry matter (DM) produced by the two clover species. Caucasian clover produced four times the DM yield of white clover in year 2 (5400 cf. 1450 kg DM/ha) and four times the amount of N₂ fixed in herbage (136 cf. 36 kg N/ ha). In year 3, caucasian clover produced 50% more clover DM (3450 cf. 2370 kg DM/ha) and N₂ fixed (98 cf. 66 kg N/ha) than white clover. The increased N input from caucasian clover increased grass %N and N uptake from soil in caucasian clover pastures resulting in higher total pasture production compared with white clover pastures (15.7 cf. 14.2 t DM/ha) by year 3. In this study, caucasian clover demonstrated greater potential than white clover to meet the N demands of high-yielding perennial ryegrass in an intensive pastoral system.The authors acknowledge funding from the Struthers Trust for the development of the grazing experiment at Lincoln University and FRST funding for provision of ¹⁶N and N analyses. We thank the C. Alma Baker and Struthers Trusts for providing A.D. Black with financial support from post-graduate scholarships

Improving white clover for Australasia

Improving the genetic merit of temperate forage legumes helps ensure profitability and sustainability of our Australasian pastoral industries. Today’s plant breeders are supported by a range of underpinning research activities including genetic resources exploration and enhancement, plant physiology, plant health, feed quality, agronomy, quantitative genetics and plant biotechnology; and have collaborative interfaces with animal and farm systems science. Lifting the rate of gain by integration of molecular tools, innovative breeding strategies, and new genetic resources is the major objective of our white clover breeding network. This paper, presented at the Australasian Grassland Association’s recent Legume Symposium, focuses on the key research and development achievements in white clover breeding for Australasia, and on the success and future of an Australasian collaboration to breed improved cultivars for the region’s temperate environments. The paper reports on successful developments in the areas of improving white clover root systems for phosphate uptake, pest tolerance, development of novel inter-specific hybrids and marker-aided breeding. The successful trans-Tasman collaboration in white clover breeding and future work is also discussed