Effects of Aqueous Eucalyptus Extracts on Seed Germination and Seedling Growth of Phaseolus vulgaris L. and Zea mays L.

Allelopathic effects of Eucalyptus are widely reported and are considered the major factor limiting the cultivation of agricultural crops intercropped. However, reports of the allelopathic effects of Eucalyptus are mostly based on laboratory bioassay, not on field trials. The objective of the present study was to determine the effects of different leaves powder proportions of Eucalyptus species on agricultural crops as well as change in soil reaction. This research was undertaken in a pot experiment that haricot bean and maize grown in the nursery of Hawassa University College of Agriculture campus laid in a completely randomized design. Collected leaves of Eucalyptus camaldulensis and Eucalyptus grandis were prepared powdered by air drying and grinding. Results suggested that leaves powder of each tree species induced significant inhibitory effect on germination and seedling growth of each crops compared to the control treatments. Application of low-dose leaves powder of either tree species had low effect on both crops. Eucalyptus grandis has more inhibitory effect on both crops, and the negative effect of allelochemicals is more pronounced on haricot bean. This indicates that maize and haricot bean should not be planted very close to Eucalyptus trees and crops seed rate should be increased to get the maximum germination.