Effect of Training on Branches Strength of Thomson Navel Orange

To evaluate the effect of training from on strength of branches of Thomson prange on poncirus rootstock, an experiment was conducted in Astara Citrus Station during 2008-2014, using factorial on the basis of randomized complete block design with five replications. The first factor was crotch angle (45, 65 degree and check) and number of branches (3, 4 and 5) was considered as the second factor. In the first two years, budding plants were produced and during the growth of buddingplants in the third year, treatments were applied. Trees were transplanted to the land according to the planting plan at the end of the third year. Heavy snow in February 2013 broke many of the branches in all treatment so that the perfect analysis of data could not be done according to the plan. However, analysis by chi-square method showed only significant correlation between the number of bloken branches and up trunk diameter of crotch. No correlation was detected between number of broken nranches and number of branch and crotch angle. Correlation between broken branches due to heavy snow, crotch angle and branch number was not also observed pulling of remaining limbs showed significant difference between maximum stresses at breaking and crotch angle. Branches with 65 degree crotch angle could handle more pressure than those with 45 degree crotch angle.