Risultati preliminari di una prova di concimazione nell'arancio «Washington navel»

In this paper are reported the results of 4-year research on the effects of differential N, P, K treatments on young «Washington navel» orange trees. The following treatments were compared: A - Control; B - Nitrogen fertilization at rate of 60 Kg/ha per year (N); C - Nitrogen and phosphorus fertilization at rates, respectively, of 60 Kg/ha and 120 Kg/ha per year (NP); D - Nitrogen and potassium fertilization at rates, respectively, of 60 Kg/ha and 90 Kg/ha per year (NK); E - Nitrogen, phosphorus, and potassium fertilization at rates, respectively, of 60 kg/ha, 120 kg/ha, and 90 Kg/ha per year (NPK). The results evidenced that 4 year later the start of the research the different treatments did not influence tree growth, while N and Mn content of the leaves was increased by NP and NPK treatments. No difference was found between N, NK, and NPK treatments on the average yield, that was reduced in NP treatment and in the control trees. As for as the fruit quality is concerned, a higher juice percentage was found in fruits from the control trees, while total soluble solids were increased by treatments NP and NPK.