ABSTRACT Many native forests have been destroyed by the introduction and large-scale planting of fast growing exotic tree species. Consequently, some native species have become endangered and the ecosystem services provided by native forests are diminishing (For example, continuous monoculture planting of eucalyptus may caused accumulation of phytotoxins in soil which results in soil degradation and loss of productivity. In this study the allelopathic effect of Eucalyptus globulus aqueous leaf extraction on germination and early growth of two agricultural crops; Eragrostis teff and Cicer arietinum, which are commonly cultivated in Ethiopia particularly in South Gonder Dera district, were studied under laboratory room and field experimental conditions . At both conditions, seeds and seedlings were watered with 0% (control), 10%, 20%, 30% and 40% extractions of Eucalyptus globulus in every other days. Extraction above 10% delayed mean germination time of of Cicer arietinum at both laboratory room and field conditions. All extractions of Eucalyptus globulus delayed germination time of teff during laboratory room experiment . In field experiment the mean germinating time of teff was significantly affected by above 10% extractions of Eucalyptus globulus. Number of germinating seeds were only affected at laboratory condition of both crops by 40% extractions . Germination percentage of both crops significantly affected by 40% of extract solutions except laboratory experiment of teff which was not affected by all extracts. All extracttions inhibited the shoot length of chickpea and teff at both conditions. Root length of chickpea at laboratory room andexperiment were significantly inhibited by all extracts. But during field conditions it was affected by above 10% extract solutions. Seedling height reduction and vigor index of both crops were significantly affected by all extracts at both conditions.These shows the toxicity of Eucalyptus globlus to Teff and Chickpea. So, E. globulus tree is toxic to Eragrostis teff and Cicer arietinum , it must not be intercropped with these plants. Besides, increasing awareness of the farmers towards allelopathic effect of E. globulus against chickpea and teff is necessary so that they avoid intercropping and further studies must be done on allelopathic effect of E.globulus on Eragrostis teff and Cicer arietinum . KEY WORDS;- shoot length, root length, mean germinating time, Seedling height reduction, vigor index, Germination percentage

A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REUIREMENT FOR MASTE OF SCIENCE DEGREE IN BIOLOGY (BOTANY)