These are the results of annual variation of production and composition of 6-7 months-old leaves from a fertilizer experiment of a scion-rootstock combination of Navel orange on sweet orange. The experiment was planted in 1947 on Ortho Dark Red Latosol transition to Textural B Terra Roxa Soil in Cordeiropolis, State of São Paulo. During the 19 years the levels of NPK utilized per plant in a factorial experiment were 0, 250, and 500 g of N; 0, 200, and 400 g of P2O5 and 0, 150, and 300 g of K2O as sodium nitrate, superphosphate and potassium chloride respectively. Starting 1970 nitrogen was furnished as ammonium sulphate instead of sodium nitrate. Water balance was calculated by the method of Thornthwaite & Mather every two months and these data were correlated with the fruit production and leaf analysis. The effects of fertilization on yield were evaluated. Various correlations among nutrient levels in the leaves and between nutrient concentrations and fruit production were established. The results showed that there was no correlation between water balance (excess or deficiency) and production and slight correlation between water balance and percentage of nutrients in leaves. This indicates that under the conditions of the experiment supplementary water supplied by irrigation would not affect the production. Both nitrogen and potassium fertilization increased the production, while phosphorus had small and less frequent effect. A positive N x P interaction on production was observed in several years. Leaf analysis showed positive correlation between N and Mg, P and K, P and Ca, P and Mg. Negative correlation was observed between N and P, N and K, N and Ca, K and Ca, K and Mg. The average annual leaf percentage variation was from 2.20% to 2.81% for N, 0.086% to 0.158% for P; 0.82% to 1.74% for K; 2.37% to 4.76% for Ca and 0.19% to 0.37% for Mg. The responses to fertilization can be explained by the increase in the percentage of N, K and Ca (from superphosphate) in leaves and positive correlation between these elements and production. It was accepted that contents of 2.61% of N, 0.122% of P, 1.56% of K, and 4.20% of Ca in the leaves, corresponding to the higher fertilization level, represent adequate nutritional status.