Influency of etephon concentration and spraying pressure on the amount of reserve substances in tangerines 'Montenegrina'

Abstract

This experiment was carried out with the purpose of evaluating the effect of chemical thinning and spraying pressures on fruit production, production alternance, and leaf/root reserve substances of nine-year-old trees of tangerine 'Montenegrina' (Citrus deliciosa Tenore) of a commercial orchard in Viamão, RS, Brazil. The Treatments were: 1 = control (water spraying); 2 = Etephon 100 ppm + urea 3%, weight water solution (wws); 3 = Etephon 200 ppm + urea 3% (wws), and 4 = Etephon 300 ppm + urea 3% (wws). The solution of Etephon + urea was applied using four spraying pressure regimes: 50, 100, 150 and 200 pounds/square inch. Treatments were applied by the time of shedding. The increase of Etephon concentration caused a decrease in fruit production. Best results on avoiding alternance were obtained with Etephon 200 ppm + urea 3%. The amount of root reserve substances was directly related to the amount of mineral nutrients of leaves, and this was considered as likely cause of alternance. Increasing spraying pressure up to 150 pounds/square inch improved the effect of Etephon, reducing both total production of fruits in the year of treatment and alternance in the year after, without effects on root reserve substances. There was no effect of Etephon concentrations and spraying pressures on leaf reserve substances.