In this work, the impact of nitrogen (N) and potassium (K2O) fertilizers rates and application scheduling on “Nules” Clementine variety yield, size and quality was evaluated for two consecutive years (2014 and 2015). The experiment was carried out in a commercial citrus orchard located in Taroudant province in Morocco where a randomized complete block design was adopted. Among 6 treatment programs tested, the treatment N°6 appeared to be the most suitable as fertilization program for citrus clementine “Nules” grown under the semi arid climate of southern Morocco. This program is a combination of 240 kg/ha of N and 160 kg/ha of K2O scheduled as follow: Nitrogen 15% before bud initiation (BB), 30% between bud growth (BG) and full blooming (FB), 35% from FB to the physiological fruits dropping of June (PD), 20% between PD and fruit color changing (CC) and 0% from CC to the end of harvesting (EH). Potassium: 15% (BB), 20% (BG-FB), 15% (FB-PD), 25% (PD-CC) and 25% (CC-EH). Statistical analysis showed highly significant differences between the treatments. Treatment 6 showed the highest results in terms of fruit yield, size and juice content, whereas treatments 1 and 2 showed the lowest results respectively. However, no significant differences were recorded in term of total soluble solids and TSS/TA ratio even titrable acidity was higher in the case of treatment 6.