ALLELOPATHIC EFFECTS OF EUCALYPTUS CAMALDULENSIS ON GERMINATION RATES OF THREE ECONOMIC CROPS

Abstract

Field investigation on allelopathic effects of Eucalyptus camaldulensis was carried out at 3-year-old plantation in Rayong Province, East of Thailand. Three economic crops selected were Vigna radiata Linn., Vigna mungo Linn., and Impomoea reptans Poir. 2x2x2 factorial experiments of randomized block design were employed having 3 treatments as follows: A: germination site (a₁: inside eucalypt plantation, a₂: outside eucalypt plantation), B: eucalypt leaf litter (b₁: seed covered by leaf litter, b₂ seed uncovered by leaf litter) and C: surface soil collected from two plantation spacings (C₁: 1.7x.1.7 m², C₂: 1.5x1.5 m²). It was found that maximum germination rates of V. radiata, V. mungo and I. reptans were recorded from a₂xb₁xc₂, a₁xb₂xc₁ and a₂xb₁xc₁, respectively. The findings revealed that there was no negatively allelopathic effect of Eucalyptus camaldulensis on germination rates of three economic crops tested. Variation in germination rate among treatments as well as among species was the results of other germination factors rather than allelopathy. Again, unexistent vegetation beneath the canopy of Eucalyptus camaldulensis plantation could be explained in the same manner.