Current trends of intensification of olive cultivation including irrigation and fertigation have dictated a need to reconsider fertilization management practices. We evaluated the long-term effect of nitrogen (N) fertilization level on the productivity of field grown olive trees in an intensively cultivated orchard in order to optimize N fertilization and achieve maximum yields and profits with minimal negative environmental impact. Deficient N fertilization reduced vegetative growth and lowered fruit and oil yields, attributed to down-regulation of flowering intensity and reduced rate of perfect flowers and fruit set. In addition, under low N availability trees appeared to be more susceptible to alternate bearing. The highest N level was the most effective in promoting vegetative growth, but did not induce an increase in yield. An intermediate annual level of 150 kg N hectare−1 was optimal for maintaining highest long-term yield and reducing alternate bearing. The results correspond to previous findings from container-grown trees that N availability significantly affects tree reproductive traits. Proper N fertilization is concluded to be fundamental to successful management of intensive cultivated olive orchards. © 2018 Elsevier B.V.