Proper Application of Fertilizers May Lead to More Consistent Olive Harvests

A study finds that periodic fertilization with nitrogen, phosphate and potassium decreases the alternate bearing pattern of olive trees.

A recently published study has found that alternate bearing characteristics in olive trees can be mitigated by appropriate nutrient supplements.

The study, which was carried out in conjunction by scientists from the University of Sfax in Tunisia and the University of Bari in Italy, found that well-timed and systematic applications of certain fertilizers can prevent yield fluctuations while minimizing resource inputs.

Alternate bearing is a common trait of fruit trees and widely considered to be a homeostatic mechanism. In ‘on’ years, trees produce a higher yield of fruit, which depletes their reserves of nitrogen, phosphate and potassium. Fruit trees then produce less fruit in ‘off’ years in order to expend those same nutrients on seed production and leaf and shoot growth.

“Our data of the four-year trial could be very useful to reduce alternate bearing in olive trees by means of an appropriate fertilization management,” Saida Bedbabis, the lead researcher from the University of Sfax, wrote in the study. “Nutrients would be applied to olive trees when required, taking into account if trees are in ‘on’ or ‘off’ years.”

According to the study, the application of certain fertilizers at particular times of the year is also a more cost-efficient and environmentally friendly way of mitigating the effects of alternate fruit bearing than the alternative: super-intensive cropping.

“Correct fertilization is an appropriate way to face and reduce alternate bearing whereas the super-intensive system is a different way of cultivation,” Giuseppe Ferrara, the corresponding author of the study, said. “With an appropriate schedule of fertilization, we try to face the real requests of [what nutrients] the trees [need to produce olives]. The super-intensive system forces the trees to produce at a maximum rate.”

The study tracked the seasonal changes in nitrogen, phosphate and potassium in the leaves and stems of trees in a Tunisian olive grove over four years. More