EFFECT OF BARK AND STEM EXUDATES OF Eucalyptus camaldulensis L. ON THREE AGRICULTURAL CROPS

Abstract

A study was conducted in the the Department of Agroforestry and Environment, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh during October 2016 to March 2017. There were two experiments in the study. Experiment 1 was conducted to find out the effect of bark and stem exudates of Eucalyptus camaldulensis on the three agricultural crops in laboratory condition. There were three concentrations of bark and stem seperately viz., 10%, 25%, 50% and a control (only water). Experiment 2 was conducted with 50% concentration of bark and stem exudates in the field condition of 1m x 1m plot size. In both experiments three agricultural crops namely Maize (Zea mays), Country bean (Lablab purpureus) and Bottle gourd (Lagenaria siceraria) were taken to satisfy the objectives of the study. Designs of laboratory and field experiments were CRD and RCBD with three replications, respectively. Results of laboratory experiment showed that 50% concentration of both bark and stem exudates of E. camaldulensis inhibited more in germination of all three tested crops compared to other concentrations. Bark exudates of E. camaldulensis showed germination percentage 24.74% in Maize, 31% in Country bean and 54.33% in Bottle gourd over control and stem exudates of E. camaldulensis showed germination percentage 35.36% in Maize, 37.33% in Country bean and 45.67% in Bottle gourd over control. The results indicated that inhibition increases with the increase of concentration. In case of field experiments, both bark and stem exudates of E. camaldulensis also inhibited the germination of the three tested crop. Application of 50% concentration of E. camaldulensis bark exudates showed germination percentage 52.0% in Maize, 34.33% in Country bean and 50.0 % in Bottle gourd over control and 50% stem exudates showed germination percentage 40% in Maize, 19.67% in Country bean and 40% in Bottle gourd over control. Morphological parameters like plant height (cm), collar diameter (mm),central root length (cm), no. of first order lateral roots showed significantly higher growth in control over bark and stem exudates in all the tested crops at both the laboratory and field experiments. Similar results were recorded for biomass allocation like shoot dry weight (g), root dry weight (g), total dry weight (g), shoot/root ratio and quality index. From the results of laboratory experiment it is also indicated that though both bark and stem exudates inhibited the germination of Maize, Country bean and Bottle gourd in different rates but inhibition by stem exudates is less compared to bark exudates of respective crops except bottle gourd. In the field experiment, inhibition by bark exudates is less compared to stem exudates of respective crops.Consequently, germination speed of tested crops was more in control than bark and stem exudates of E. camaldulensis due to the inhibitory effect. From the overall result it can be concluded that in addition to the allelopathic effect of leaf and root of E. camaldulensis, bark and stem have also allelopathic effect on the agricultural crops which inhibited more in laboratory compared to field condition. This effect may be minimized through proper management of the agroforestry field by removing the fallen bark and stem residues.