Fertilization, cover cropping and harvest date: Their effects on foliar nutrient concentrations in olive trees on a farm in Southwest Buenos Aires

Abstract

The effects of different fertilization treatments in areas with or without a cover crop on leaf nutrient concentrations were compared in an olive farm in southwestern Buenos Aires, Argentina. In each studied growth cycle (from 2020 to 2023), sampling was carried out in spring, summer, autumn, and winter. Fertilization treatments included (1) organic fertilization to the soil; inorganic fertilization with macronutrients (N, P, and K) (2) to the leaves or (3) to the soil; and (4) an unfertilized control. The interaction between fertilization treatment and cover crop was only significant for foliar N concentration, but it accounted for less than 1.5% of all evaluated sources of variation. The most important component of all sources of variation for N, P, and K was sampling date [month, period (year)], which accounted for > 80% of the model. The seasonal variation in the concentration of N, P, and K was nutrient-dependent. Within each fertilization treatment, the highest or lowest leaf N concentrations varied with the season of the year. The highest (p<0.05) % P was obtained in the control and inorganic soil fertilization, and the lowest (p<0.05) in inorganic foliar fertilization. Finally, fertilization treatments did not differ (p>0.05) in foliar % K.