Some effects of annual applications of three growth-retarding compounds on the composition and growth of a pasture sward.
Maleic hydrazide and mefluidide significantly retarded growth of a mixed sward dominated by Festuca rubra, Agrostis spp., Poa spp., Dactylis glomerata and Holcus lanatus and reduced numbers of grass inflorescences. Paclobutrazol, a soil-acting compound, reduced growth of several grass species, but did not affect their flowering. Maleic hydrazide and mefluidide treatments resulted in swards dominated by F. rubra, while paclobutrazol plots were dominated by tall grasses and F. rubra was reduced. Treatment with a mixture of maleic hydrazide and paclobutrazol resulted in a sward with less F. rubra than that produced by maleic hydrazide alone. Numbers of dicotyledonous species were reduced by maleic hydrazide and paclobutrazol applied alone or as a mixture. Mefluidide treatments significantly increased numbers of species, some of the species occurring at increased frequencies. Numbers of perennial species were maintained, while annuals and biennials were able to establish. Retardants offer scope for the maintenance of amenity grassland. Where botanical interest is of concern, mefluidide may maintain species diversity. Paclobutrazol used alone will retard fine-leaved grasses but will encourage coarse grass species if these are present.