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

Potential of European Perennial Ryegrass Germplasm in Southern New Zealand

86 cullivars of perennial ryegrass from The Netherlands, Germany, Denmark, France and Britain together with 9 New Zealand (NZ) cultivars were evaluated for agronomic potential in the cool, temperate southern region of NZ. Spaced plants of each cultivar were established in 1989 and screened for seasonal growth, moiphological features, head emergence, foliar diseases and endophyte presence. Principal Component Analysis (PCA) was used to order the relative performance of the cultivars taking all characters into consideration. A group containing 5 elite tetraploid and 10 diploid European cultivars showed potential for improving the summer feed quality of ryegrass. These cultivars contained densely tillered plants with leafy growth, few reproductive heads in early summer compared with NZ material and were non-endophytic. These features are important for maximising animal intake, digestibility and growth over summer. The late-heading feature of European cultivars is usually linked to poor late winter­early spring growth but the growth of the tetraploids showed similar growth to NZ material in the second winter and good persistence.· The elite European material could be either hybridised with NZ material to incorporate summer quality features or selected and developed independently

Evaluation of White Clover Breeding Lines in the Australasian Region

The accuracy of predicting breeding line performance across target environments is a significant criterion in the development of cultivars with broad or specific adaptation. This paper characterises the type and magnitude of genotype-by-environment (GE) interactions estimated from a multi-site white clover (Trifolium repens L.) breeding line evaluation trial conducted across sites in New Zealand and Australia

Widening the Adaptation of White Clover by Incorporation of Valuable New Traits from Wild Clover Species

Although white clover (Trifolium repens) is the most widely used legume in grazed pastures of temperate and sub-tropical regions, it is severely restricted in genetic diversity for adaptive traits to low soil fertility and other stress environments, including drought. The objective of this research was to transfer traits for wider adaptation from other clover species by hybridisation. Eight Trifolium species with contrasting adaptations were shown by DNA sequence phylogenetics to be closely related to white clover. Interspecific hybridisation was undertaken among these species using embryo rescue, and an array of partially fertile F1 hybrids was obtained. Population development from these F1 hybrids showed that hybrids involving six taxa could be selected for high sexual fertility. Most showed strong inter-species chromosome pairing and the potential for introgression of exotic genomes into white clover. Several of the new genomic combinations, which do not occur in nature, will improve prospects for extending the adaptive range of white clover

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

Suitability of new subterranean clovers in the Canterbury region

The annual legume, subterranean clover, is adapted to permanent pastures in the summer drought-prone areas of eastern New Zealand. Dry summers over the last decade in Canterbury have renewed the interest from farmers in the use of sub clover. As the previously used cultivars Mt Barker and Tallarook are no longer available, a trial was established at AgResearch Templeton to evaluate a new series of cultivars and breeding lines from Australia together with recent New Zealand selections. The lines were sown in rows in May 1993 and assessed for seed set, autumn seedling regeneration and spring growth under sheep grazing for 4 years. The new Australian cultivars had improved seed set and consistently better seedling regeneration and herbage yield compared with older cultivars. The late-flowering, small-leaved and densely branched types were best adapted to the Canterbury environment. The late-maturity cultivars Denmark and Leura, selected from Sardinian germplasm, re-established 50% more seedlings and produced 25% greater late winter/ spring growth than Mt Barker and Tallarook in the third year. The New Zealand selection Ak 948 had similar performance to Denmark and Leura but the remaining selections were mediocre by the fourth year. The Sardinian ecotype breeding material appeared well-adapted to Canterbury conditions and future cultivars based on this material may be most suitable. Further trials are required in harsher sites to confirm these cultivar recommendations. Keywords: Australian cultivars, dry regions, herbage yield, seedling regeneration, subterranean clover, Trifolium subterraneum</jats:p

Reproductive potential of caucasian clover at four locations within New Zealand

Seedlings of KZ2 caucasian clover (Trifolium ambiguum) were grown at 4 sites within New Zealand (Kerikeri 36°S, Palmerston North 40°S, Lincoln 43°S and Gore 46°S) where they received natural daylight and temperatures during 1997. Northernmost plants produced more vegetative primary crown shoot buds than southernmost. In the first growing season numbers of flowering shoots formed per plant were: K 17.9, P 10.0, L 10.2 and G 5.7. In spring of the second growing season, mean numbers of primary crown flowering shoots per plant at peak flowering in December 1997 were: K 19, P 30, L 55, G 20. Fewer flowering shoots formed at upturned rhizome tips. Daylength was not the major factor controlling flowering, the results instead supporting the hypothesis that low temperatures provided the main flowering stimulus. Lincoln was the best of the four locations overall for flowering shoot production. Fewer flowering shoots at Gore probably resulted from slower growth in cooler conditions. Poorer flowering at Kerikeri in the second season might have resulted from the warmer northern winter or been linked to the overproduction of vegetative buds in the first season. Stronger flowering at Kerikeri during the first season raises the possibility, though, of growing caucasian clover as an annual crop for seed production in Northland if sown early in spring. Keywords: caucasian clover, daylength, flowering, low temperature, seed production, Trifolium ambiguum</jats:p