Nitrogen nutrition diagnosis for olive trees grown in super-intensive cropping systems

Abstract

The results of a 4-year experiment combining irrigation, N, and K showed that to maintain productivity and tree growth it is necessary to attain a higher leaf N status than current diagnosis standards. To sustain high oil yield and quality and to avoid excessive vigor, a critical N concentration was established for olive trees of 1.94% for leaves sampled in July. A negative relationship was obtained between N leaf concentration and some quality parameters. Above 1.94% N, total phenolic content and oxidative stability fell below 220 mg kg−1 and 10 hr, respectively. In addition, above this N leaf concentration other factors including the alternate bearing index (ABI) and vegetative growth distorted productive and qualitative responses. Moreover, the differential productive response of trees related to alternate fruit bearing status implies that the interpretation of leaf nitrogen content can be more accurate when ABI suggests an ON tree status.