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Alternate bearing in Satsuma mandarin and the ways of its reduction in north of Iran

Akhlaghi Amiri, N., Asadi Kangarshahi, A.
Acta horticulturae 2012 no.928 pp. 291-292
Citrus unshiu, alternate bearing, auxins, budbreak, diet-related diseases, foliar application, fruit set, harvest date, leaves, nutrition, sucrose, urea, Iran
In the last decade (1999-2008), methods of reducing alternate bearing of citrus east of Mazandaran was investigated. Most of these methods decrease fruitlet number in "on years" or increase fruit set and fruitlet number in "off years". Investigated methods include: 1) nutritional disorders and their effect on alternate bearing; 2) balanced nutrition based on leaf analysis and yield forecast; 3) foliar application of synthetic auxins in "on years"; 4) foliar application of sucrose in "on years"; 5) winter foliar application of urea about two weeks before bud break in "off years"; 6) urea foliar application before and after harvest in "on years". Results showed that balanced nutrition reduced alternate bearing index significantly. Auxins and sucrose reduced sink competition in "on years", so fruit size increased in "on years". Winter application of urea, increased fruit set in "off years". Urea application at harvest time almost eliminated the alternate bearing cycle. In fact most treatments adjusted the alternate bearing cycle by reducing number of "off years" or by increasing average yield in "off years" therefore decreasing differences between "on years" and "off years". Also most treatments increased fruit average weight and diameter in “on years”.