The growth and seed production potential of white clover (Trifolium repens L.) was studied in field plots in 2 years, with and without a companion grass (Lolium perenne L.). Three rates of grass suppressant, fluazifop-butyl (Fusilade), applied in early June, were compared on plots sown with the companion grass. Two clover varieties, Aberystwyth SI84 and Olwen, were compared.
Sowing a companion grass reduced the amount of clover in the sward in both the first and second harvest years, but did not affect the vigour of individual clover growing points or the number of clover inflorescences when the crop was ready to be harvested for seed.
Fluazifop-butyl, at the highest rate used (125g/ha), reduced the rates of leaf emergence and extension, and the numbers of reproductive tillers, in Lolium, without reducing the rate of leaf emergence in clover, although the weight per clover leaf was somewhat reduced. In the first harvest year, the numbers of SI84 inflorescences in June and July were increased by fluazifop-butyl, but the effect had worn off by harvest (24 August). Seed yield potential was not increased by fluazifop-butyl at the rates used.
Olwen produced heavier leaves, but fewer leaves and fewer growing points/0·1 m2 than SI84. In the first harvest year, Olwen had fewer and smaller inflorescences than S184.
It proved feasible to measure the weight of new leaf produced per week and the nett additions to stolon and inflorescence dry matter (DM). The estimate of nett addition to stolon DM was increased by increasing the number of visible internodes included in the calculation, up to the maximum number recorded (nine). The rate of leaf emergence was slower on young branches than on main axes.