Effects of foliar application of urea on olive leaf nitrogen, growth, and yield

'Mission' table olive (Olea europaea) trees in each of ten replicates were blocked by uniform 1993 pre-treatment yields. Trees had adequate leaf N, 1.6-2.0% N by dry weight. Foliar nitrogen application at 0.18 kg per tree was made once to separate trees at five treatment timings, mid April, June, July, August and November for two sequential years. The foliar urea sprays significantly increased leaf N levels within three days. The applications did not affect parthenocarpic fruit set (shotberries). Shoot growth, number of flowers per node, and the percentage of perfect flowers the year following application were unaffected. Fruit yield per tree, fruit size and calculated crop value per tree were not significantly increased by any treatment during the season of application or during the following season. The yield of N sufficient trees was not improved with previous or current season foliar urea sprays. Such applications are not an effective tool for combating alternate bearing of nitrogen sufficient olives. Our results demonstrated that olive leaves did efficiently absorb foliar applied nitrogen. Foliar urea application during the growing season can quickly boost olive leaf nitrogen levels when necessary.