Improved growth of white clover in hill grasslands by mycorrhizal inoculation

Field trials in a hill grassland area of mid-Wales showed that growth of white clover could be improved by inoculation with selected vesicular-arbuscular (VA) mycorrhizal fungi. After one growing season mycorrhizal inoculation had approximately doubled shoot dry weight, runner number and nodulation at two sites previously improved by adding lime and fertiliser and by replacing the native vegetation mainly with rye-grass and white clover. At a previously unimproved site, limed at the time of planting, mycorrhizal inoculation increased shoot dry weight by up to two and a half times, almost doubled runner formation, and increased nodulation up to five-fold where 90 kg P/ha as basic slag had been applied. Responses to mycorrhiza at this site were smaller with 22-5 kg P/ha as basic slag and were absent where no P was added. After two growing seasons inoculation responses were even more pronounced at this previously unimproved site; where clovers were being overgrown by adjacent native grasses only those given both 90 kg P/ha and mycorrhizal inoculation survived well.