Flood-Tolerant Pastures for Dairying in Northland

Much flood-prone land in Northland consists of fertile alluvial flats which are or could be used for dairy production. Heavy rainfall from subtropical cyclonic dislurbances have caused severe pastoral damage to these areas by flooding during late summer and early autumn. A range of pasture species were screened to ascertain plant surviv_al under depleted oxygen levels and warm temperatures which occur in flood water during summer. Subtropical grasses screened tended to survive immersion better than temperate species. Creeping grasses such as Hemarthria altissima and Paspalum distichum were more tolerant than P. dilatatum. Of the temperate species, Phalaris arundinacea, Phleum pratense, Agropyron elongatum and A. repens were the species best able to survive. All legumes screened were intolerant of flooding. Lotus pendunculatus was the best of the perennial legumes screened. Annual Lotus species present in soil as seed germinated and grew after immersion. Spaced-plant trials indicated that grasses with greatest potential in flood-prone situations tended to be frost sensitive; as a consequence pasture mixtures will be required to alleviate winter feed deficits.