Lithuanian Institute of Agriculture, Lithuania
Field and laboratory experiments involving Poa pratensis L., Lolium perenne L., Phleum pratense L. and Festuca pratensis Huds were carried out on a light gleyic loam soil (Cambisols). Aqueous extracts of air-dry mass of above ground part and roots were prepared at different grass growth stages. Trifolium pratense L seed was germinated in Petri dishes on filter paper moistened with the obtained extracts. Assessments of the effect of grasses on the undersown clover were carried out three times per growing season in field conditions. Our experimental evidence suggests that germination of clover seed was much more suppressed by the extract of above ground part of grasses compared with root extracts. The toxic effect of the three grass extracts, prepared at the stages of inflorescence emergence and flowering, was critical on clover. Clover undersown into grasses during the period of inflorescence emergence germinated and established more poorly under field conditions compared with the clover undersown in spring or summer. As per the allelopathic activity of extracts prepared at various growth stages, grass species ranked differently.
