Effects of Raw and Diluted olive Mill Waste Water on the Morphological, Physiological and Biochemical Features of Seed Germination and Seedling Development of Alfalfa (Medicago Sativa) and Sorghum (Sorghum Bicolor)
OMW disposal is harmful to the environment and human health and is being replaced by new approaches aiming to use it as a new source of pharmacologically active biomolecules and/or as an efficient substitute of mineral fertilizers leading to eco–friendly management of this type of waste and economical benefits to the farmers. Efficient use of OMW as a substitute to mineral fertilizers may be reached if the appropriate treatment that removes phytotoxicity and/or dilution that allows proper germination and vigorous growth of a tolerant crop relevant to human consumption or animal feed is efficiently established. However, the high variability of OMW composition and subsequently toxicity as well as differential sensitivity of different crops to OMW, hinder the efforts to generate a generic dilution factor for all crops. Therefore, aiming optimized use of local OMW produced in olive mill factories in the Sfax city (Tunisia) in ferti–irrigation of alfalfa and sorghum, we tested the use of 25, 50, 75, and 100% OMW to support the germination and growth of the plants. Our results clearly show that OMW had adverse effects on germination and seedling development of alfalfa and sorghum. These adverse effects are reflected during seed germination at the biochemical level by changes in soluble protein content, increased H2O2 levels, and increased Malondialdehyde (MDA) levels as well as decreased α–amylase activity. During seed development, biochemical effects include changes to chlorophyll and carotenoid contents. Our study reaches the consensus that suitable crop species have to be selected in order to establish a putative OMW dilution factor that supports seed germination and seedling development.