Phytotoxic Effect of Treated Wastewater on Seed Germination and Percent Root Elongation Inhibition in Some Vegetable Crops

Abstract

Aims: Summer irrigations for citrus fruits and fodder are considered as pre-irrigations for growing annual crops in Tunisia. However, given the quality of this treated wastewater, pre-irrigation effect on the seed germination capacity remains unclear. We propose to study the effect of different concentrations of treated wastewater on the germination of some vegetables. Methodology: This laboratory experiment investigates the effect of different concentration from 0 to 100% (0%, 20%,40%, 60%, 80% and 100%) of treated wastewater on seed germination (%), germination index (Ig), root elongation and root elongation inhibition index (REI%) for some vegetable crops, the most commonly used by farmers: Radish, Okra and Pea. Results: Pea germination rate (%G) dropped significantly from 60% to 30% with WW concentration. The germination index (Ig) decreased for Radish and Pea seeds with increasing WW concentration; it decreases from 1.03 to 0.72 and from 0.8 to 0.33 for radish and pea, respectively. While, the sprouting index for okra increased from 1.24 to 2.2 with increasing WW concentration. According to the REI% values, there is no effect of WW concentration on the root elongation of okra. On the other hand, the most pronounced REI% was noticed for Pea which has shown positive REI% values for all the concentrations with an inhibition effect of about 67% for the 100% WW treatment. For the radish, the root elongation inhibition started from the 40% WW concentration. Conclusion: The crops tested have been arranged in the following order: Okra>Radish>Pea depending on the tolerance to treated wastewater. We conclude that the effect of treated wastewater on seed germination is depending on crops species and we should take care before using the treated wastewater for pre-sowing irrigation purposes.