Effects of Olive Mill Wastewater on Seed Germination and Seedling Growth

Olive mill wastewater (OMW) is considered as phytotoxic and thus an environmentally hazardous material. Therefore, alternative areas of application have been discussed; one of these might be its use as an additive in growing media for agricultural purposes. However, phytotoxic responses might occur at higher concentrations. The objective of the present study was to determine threshold levels for application of OMW in agriculture. The hypotheses were that (i) high concentrations of OMW are detrimental to seed germination and seedling growth, (ii) toxicity caused by OMW may be removed through sedimentation in a settling basin prior to addition. Data obtained showed that low concentrations of OMW did not reduce seed germination and seedling growth. However, higher concentrations showed significant differences in almost all the evaluated parameters. The addition of raw OMW at high concentrations (over 50%) reduced strongly in vitro seed germination, - and β-amylase activities. The great toxicity of the OMW observed in an in vitro experiment decreased drastically when the same OMW was utilized onto soil in microcosm, showing a decrease at about 35% in germination for fava (Vicia faba L.), sulla (Hedysarum coronarium L.), chicory (Cichorium intybus L.) and wheat (Triticum durum Desf.) seeds. These mean that the phytotoxic effects of OMW might be modified by chemical and biological processes in soil.