The Effect of Nitrogen Fertilization on Tree Growth, Fruit Yield and Quality of Clementine Nules on Two Citrus Rootstocks in the Gharb Region (Morocco)

The objective of the current study is to evaluate the effects of nitrogen rate N on tree growth, fruit yield and quality of clementine Nules variety, budded on Flhorag and Carrizo citrange rootstocks, grown on clay soils at the Experimental station of Sidi Allal Tazi, INRA Morocco, over five seasons. The experiment has been carried out in a split-plot design with three replications, including the nitrogen doses as the main plot and rootstock the subplot. Three fertilization treatments of the rates of N (g/tree) (T0: control (native nutrient), T1: 270, T2: 540 in g/tree) and 135 P2O5, 270 K2O g/tree have been applied to citrus trees in field conditions. The study found that nitrogen rate and rootstock genotype had significant effects on vegetative growth, yield, and fruit quality of Nules clementine. As N rate increased, vegetative growth improved significantly, with the trees grafted on Carrizo citrange and fertilized with T2 (540 N g/tree) showing the best results. A strong positive correlation was also observed between canopy volume and fruit yield for both rootstock genotypes. Carrizo citrange proved to be a more efficient rootstock for Nules variety than Flhorag, with higher yield and better fruit quality. As a conclusion, the recommended NPK rate for obtaining an optimal yield and good fruit quality of Nules clementine fruits was 540 N-135 P2O5-270 K2O g/tree/year under Sidi Allal Tazi–Gharb (Morocco) conditions.