Examination the possibility of bearing regulation of Siahoo mandarin (Citrus reticulata Blanco) by using chemical thinning components

In order to evaluate the different concentrations of Naphthalene Acetic Acid (NAA) on alternate bearing of ‘Siahoo’ mandarin (Citrus reticulata Blanco) was performed an experiment as factorial arrangement in randomized complete block design with two factors. First factor was spray time (30 or 50 days after flowering) and different concentration of NAA (0, 200, 300 and 400 mg/L) with three replications and two trees in each replications during four successive years. Application of treatments was only in high-yield (ON) years. Evaluated characters were consisting: yield, fruit weight average and alternate bearing index. Results showed that 200 mg/L NAA 50 days after flowering could be regulated alternate bearing and decreased fluctuation of yield production during different years. Also application of 200 mg/L NAA in both times spray led to production of larger fruits than other treatments. Evaluation the alternate bearing index showed that application of 200 mg/L NAA 50 days after flowering had the highest influence on alternate bearing reducing. Increase the NAA concentration had no influence on alternate bearing reducing.