The intensifying requirements for white clover cultivar change

For the last five years an average 14,761 ha of white clover has been grown for seed, with 77%, 8% and 15% sown in public cultivars, New Zealand and overseas proprietary cultivars, respectively. The area presently contaminated by proprietaries is estimated at 20,000 ha. New Zealand requirements for cultivar-change are more effective than OECD requirements. The five-year break period enables successful cultivar change in 90% of cases and is improved further when buried seed counts were used prior to sowing to indicate paddocks with unacceptable buried seed load. Current isolation distances appear adequate with virtually all foreign pollen deposition occurring within 24m of the pollen source. Capture of additional public cultivar area (77%) by proprietary cultivars will rely on increasing the seed yields of proprietary cultivars by approximately 25%. This is realisable through greater attention to the environmental requirements of each cultivar and through better technology transfer between head licencees and growers.