SEASONAL CHANGES IN MINERAL NUTRIENT CONCENTRATIONS OF OLIVE LEAVES IN AN ARID REGION OF ARGENTINA

The objective of this study was to determine the time of year when nitrogen (N), phosphorus (P), and potassium (K) are most stable in leaves from current season shoots in ‘Arbequina’ olive trees in San Juan, Argentina (31°58’06”S; 69°35’37”W). The concentrations of foliar N, P and K were evaluated monthly over 4 years in an 8-year-old commercial orchard with a density of 357 trees per hectare. Samples were taken from three replicate plots of 10 trees each. Leaf N concentration was highest in March (late summer in the Southern Hemisphere) and minimum values were found in the spring months of September, October, and November. For P, maximum concentra¬tions were found in August-September (late winter) and minimum concentrations in December-January (early summer). Lastly, the minimum concentrations of K were detected in October (spring) similar to N, while maximum values occurred in November. Statistical analyses indicated minimum values of standard deviation and coefficient of variation for both N and K in spring (October, November) and for P in winter. Nitrogen and K are more likely to be deficient than P in this region, and the period prior to flowering in the spring appears to be the most appropriate for foliar nutrition sampling given the stability of these nutrients at that time of year.