Evaluation of different fertilization strategies on orange.

The effects of timing and modes of nutrient application on yield, vegetative and nutritional status of 30-year old ‘Valencia late' sweet orange trees [Citrus sinensis (L.) Osbeck] grafted on sour orange (C. aurantium L.) were evaluated. The treatments compared were: A — single nutrient fertilizers (N, P, K) topsoil dressed in March; B — single nutrient fertilizers topsoil dressed in July; C — fertigation from the 2nd decade of March to the 1st decade of September. A simple randomized scheme was adopted. Trees in all treatments were spray-irrigated and received in each of the trial years the following nutrient supplies: 450, 400 and 600 g per plant of N, P2O5 and K2O, respectively. No significant differences between the various treatments were observed regarding yield, fruit regreening, fruit drop, some fruit quality parameters and trunk circumference. Earlier ripening was observed in treatment C, due to significant differences in acidity and TSS/Acidity ratio. Trees in treatment A showed a lower fruit weight, probably due to the significantly lower K level in leaves. Higher leaf N levels in treatment A were noted, whereas trees in treatment C were found to have lower levels of Fe. No differences were observed in the leaf contents of the other nutrients. [ABSTRACT FROM AUTHOR]