Abstract: This study deals with the evaluation of olive mill wastewater spreading effects on the fertility of soil in the arid area of Marrakech-Morocco. Investigations were performed taking into account agronomic application of OMW (5, 10, 20 and 50 m3 ha-1) as compared to chemical fertilisation with a common fertiliser (225 kg ha-1 TSP (triple superphosphate) 45%, 200 kg ha-1 ammonium sulfate 21%, 100 kg ha-1 potassium sulfate 48%) under field conditions of Maize culture. Land spreading of OMW was conducted according to a fractionated application mode (the third of the dose at the beginning, then the rest one month after) during the vegetative stage of maize. Soil moisture, salinity, total organic carbon content, total nitrogen, phosphate and potassium increased proportionally to the amounts of untreated OMW. Plant growth didn`t show significant differences when the control was compared to the lower dose treatment by OMW (5 m3 ha-1). In parallel, plant growth was efficiently raised by OMW inputs at the rates of 10 and 20 m3 ha-1 compared to the control plot. Significant amelioration was obtained in term of shoot height and roots length (12 and 23%, respectively) in plots treated with OMW at 20 m3 ha-1 rate. In addition, spikes, stems, fresh and dry weight of maize grown in plot treated with 20 m3 ha-1 of OMW increased by 45, 46, 48 and 55%, respectively. However, leaf area decreased by 10% in the plot amended with 50 m3 ha-1 as compared to control. Plants in soil amended with 50 m3 ha-1 of OMW accumulated two times phenolics into leaves than did the control. The same tendency was observed in peroxidase activity that constitutes an ubiquitous parameter of stress. Principal Component Analysis (PCA) showed a positive correlation between soil physicochemical properties and treatment in one hand and stress indicators in the other hand. These results suggest a stimulation of plant stress metabolism and this is consistent with the presence of high amounts of ionic salts in soil treated with higher OMW dose (50 m3 ha-1).