*2.1.3. Waste Water effects on the olive crop*

Many experiences have confirmed the possibility to distribute the WW on the olive grove more than over 400 m3 ha-1 without significant variations of vital parameters as the photosynthetic activity, transpiration, stomatic conductance, leaves carbohydrates and chlorophylls content. Conversely, improvements of the productivity on treated plants was frequently observed. A decrease of the vegetative development has been recorded only on young plants raised in pots and treated with higher WW doses (Proietti et al., 1988).

The organic matter content in WW treated soil always results greater in comparison to the untreated control, with greater nitrogen contents and more elevated C/N ratio.

In the soils treated with WW a greater presence of the total microflora was found (Fungi and other microbial groups), as well as an increase of respiratory and enzymatic activities. These findings showed the absence of toxicity of the WW towards the microorganisms, and the improvement of soil fertility. Moreover, the findings of different researches indicate the increase in organic matter and nutrient contents, an improvement in the aggregate stability and, as a consequence, a better physical soil properties.

In order to the possible ground water pollution, other results have shown that also up to 500 m3 ha-1 of WW application do not represent a pollution danger of the surface water in the clay soils. (Andrich et al., 1992; Ben Rouina et al., 1999; Briccoli-Bati & Lombardo, 1990; Lombardo et al., 1995; Palliotti & Proietti, 1992).
