Ermelinda Silva acknowledges the financial support provided by national funds through
FCT -Portuguese Foundation for Science and Technology (PD/BD/128274/2017), under the Doctoral
Programme “Agricultural Production Chains—from fork to farm” (PD/00122/2012) and from the
European Social Funds and the Regional Operational Programme Norte 2020. This research was
funded by the Operational Group “Novas práticas em olivais de sequeiro: estratégias de mitigação e
adaptação às alterações climáticas”, funded by PT2020 and EAFRD (European Agricultural Fund for
Rural Development). The authors are grateful to the Foundation for Science and Technology (FCT,
Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UIDB/00690/2020)
and CITAB (UIDB/04033/2020) and also to AgriFood XXI Project, No. NORTE-01-0145-FEDER-
000041, co-financed by the European Regional Development Fund (ERDF) through NORTE 2020
(North Regional Operational Program 2014–2020). Ermelinda Silva also acknowledges the present financial
support throughout project NORTE-06-3559-FSE-000103 funded by the Fundo Social Europeu
(FSE) and FCT research unit Centre BIO R&D Unit (UIDB/05083/2020).
The effects of mineral fertilizers on the physicochemical properties of olives and oil under
rainfed conditions is scarce. In this three-year study, the results of a nitrogen (N), phosphorus (P),
potassium (K) and boron (B) fertilization trial carried out in a young rainfed olive grove and arranged
as a nutrient omission trial are reported. The control consisted of the application of N, P, K and
B (NPKB) and four other treatments corresponded to the removal of one of them (N0, P0, K0 and
B0). Olive yield and several variables associated with the physicochemical properties of olives and
oil were evaluated. The NPKB treatment increased olive yield compared to the treatment that did
not receive N (N0). Although dependent on the climate conditions of the crop season, the NPKB
treatment increased fruit weight and the pulp/pit ratio and its fruits tended to accumulate more
oil than K0. However, the phenolics concentrations on fruits and oil tended to be lower. All olive
oil samples were classified in the “extra virgin” category and all showed a decrease in its stability
between 3 and 15 months of storage, regardless of treatment, especially in N0, P0 and B0 treatments.
The results of the sensorial analysis indicate that all the oils fell into the medium fruitiness and
greenly-fruity category. Only in P0 and B0 were defects detected, namely muddy sediment. Thus,
this study seems to indicate the importance of N application, but also a balanced nutrient application
and that further studies are needed, given the difficulty in finding clear trends in the response of
measured variables to fertilizer treatments.
