Natural reseeding of caucasian clover (Trifolium ambiguum) in tussock grasslands

Abstract

The potential of natural reseeding to increase the density of caucasian clover (Trifolium ambiguum M.Bieb.) swards in tussock grassland environments was investigated. Rates of pollination were high on all sites and viable seed was produced by mid March on sites ranging in altitude from 600 to 1100 m a.s.l. Hard seed, expected to survive passage through the grazing animal and germinate in the dung, was present. Rhizobia that effectively nodulate caucasian clover are absent from New Zealand soils and nodulation of seedlings and rhizome roots is dependent on spread of inoculant rhizobia in the soil. Lateral movement of rhizobia in soil did not exceed 6 cm per year, only slightly less than recorded rates of rhizome expansion. There was no evidence of movement of rhizobia in wind-blown dust or on sheep's hooves. Natural reseeding has the potential to 'thicken-up' swards of caucasian clover, but the slow spread of rhizobia indicates that nodulation failures will limit the extent of spread into unsown areas. Keywords: caucasian clover, reseeding, rhizobia, rhizomes, Trifolium ambiguum