Investigation of Reducing Alternative Bearing in Siaho Mandarin by Changing Time of Nitrogen Foliar Applications and Harvest Time in Haji Abad (Hormozgan)

Alternate bearing is a common phenomenon in most commercial perennial fruit trees and negatively impacts the net returns to producers. Alternate bearing is the most important problem in “Siaho” mandarin production. In order to alleviate this problem, treatments including different times of nitrogen foliar application and harvest time were investigated for five years on 36 bearing Siaho mandarin trees in Haji Abad, Hormozgan province. Results showed that yield fluctuations were more in early years of the experiment than later years. Reduction in alternate bearing was observed with nitrogen spraying in November: foliar nitrogen with 0.5 % urea in November reduced alternate bearing index (range: 0-1) significantly compared to one and two months later. Alternate bearing index value for November was half (0.062 compared with 0.113) and about one-third (0.062 compared with 0.160) in comparison with January and February spraying time, respectively. Harvest time had no significant effect on alternate bearing index. In order to alleviate alternate bearing in “Siaho” mandarin, November is the best time of nitrogen foliar application.