STUDY ON THE ALLELOPATHY OF ALFALFA (MEDICAGO-SATIVA L) .1. OBSERVATION OF ALLELOPATHY AND SURVEY FOR SUBSTANCES INDUCING GROWTH-INHIBITION

Allelopathic effects of alfalfa (Medicago sativa L.) plants were inves tigated using soil previously grown with alfalfa (alfalfa soil). Alfal fa soil inhibited the emergence of alfalfa seeds and also the growth o f alfalfa and radish. Methanol extracts from the alfalfa soil markedly inhibited the elongation of radish hypocotyl and alfalfa radicle, sug gesting the presence of allelopathic substances. The incorporation of cut pieces of alfalfa shoots in the soil reduced seed emergence, hypoc otyl elongation and dry weight in radish seedlings to 65, 73 and 81%, respectively, compared to the control. Aqueous extracts of alfalfa pla nts inhibited the elongation of radish hypocotyl and alfalfa radicle. Inhibition increased with increasing concentrations. Inhibition of rad ish hypocotyl and alfalfa radicle elongation was greater in root extra cts than in shoot extracts. The presence of phenolic compounds as alle lopathic substances in alfalfa soil, as well as in the alfalfa plant, was suggested using color reaction with diazotized sulfanilic acid.