LAUSR

Abstract Experiments during 2018 and 2019 seasons, were carried out to investigate the allelopathic potentiality of Ocimum basilicum extract as a biodegradable herbicide against broad-leaved and grassy weeds. Leaves and flowers of Ocimum into flower were used to prepare extracts by three solvents (methanol, acetone and distilled water) to assay their effects on maize and soybean seedlings and dominant weeds in pots at Giza and fields Sids Stations. The inhibitor of 50% reduction (ID50) values on germination percentage for Amaranthus was about 0.2 to 0.9 mg, whereas for maize and soybean were 10 to 30 and 17 to 23 mg fresh weight of Ocimum equivalent extracts ml−1 respectively. Pots experiments showed that Amaranthus and Portulaca weeds were affected by extracts when applied post emergence which gave 33-68% reduction in fresh weight of Amaranthus/Portulaca mixture by the three studied extracts. Field experiment at Sids Station showed that the effect of different formulations, crude extract by acetone alone and extract plus camphor oil were more effective against broadleaved and grassy weeds than using its formulation with adjuvant where about 40.48 kg fresh weight of Ocimum equivalent extracts ml−1/ha when applied post emergence gave 97 to 99% control of weed biomass, which equal the recommended herbicide (glufosinate ammonium) effect. The chemical compositions of extracts were analyzed by GC–MS to determine chemical compositions of the developing new bio-herbicide. Thus, the present results suggest clearly that farmers can use easily extract 40.48 kg/ha of Ocimum to control weeds in horticulture orchard fields during summer season.