Alleviation of alternate bearing phenomenon in mango (Mangifera indica L.) trees using boron and nitrogen fertilization

This investigation was conducted during two successive seasons (2014/2015) and (2015/2016) using 15 years old productive mango (Mangifera indica) trees cv. Zebda. The trees were grown at AlMalak Valley Farm, El-Sharkeya Governorate- Egypt (30-51 degrees North; 32-53 degrees East). Trees were planted 8 x 8 meter within and between rows in sandy soil under drip irrigation system using the Nile water. The objective of this study is to alleviate alternate bearing in cv. Zebda using mineral nutrients (nitrogen in the on year and boron in the off year). Treatments included three concentrations of nitrogen (1000, 1250, 1500 g/tree/year) and three concentrations of boron (0.0, 250, 500 mg L-1). Nitrogen was applied to the soil as ammonium sulfate and boron was applied as foliar spray of boric acid. The extra amount of nitrogen fertilizer (250 and 500 g N/tree) was applied at three installments in (May, June and July). Treatment was arranged in a factorial Completely Randomized Block Design with three replicates for each treatment. Results show that the on-year nitrogen fertilization significantly increased mango tree vegetative growth (number of shoot/branch, shoot length, shoot thickness, number of leaves/meter and leaf area) and yield. The average yield in the on year is 85.5 kg/tree at 1250 g N/tree but 67.4 Kilogram/tree at 1000 g N/tree (the control treatment). While in the off year boron foliar application resulted in a significant increase in flowering, initial fruit set, final fruit set and fruit yield. The average yield in the off year is 47 kg/tree at 250 mg L-1 boron but 9 kg/tree at 0.0 mg L-1 boron rate (the control treatment).The interaction treatment of 250 mg L-1 boron + 1500 g nitrogen/tree is the best treatment as it resulted in the highest values for all the tested parameters. The average yield of this treatment is 53.5 kg/tree. This treatment helps alleviate alternate bearing phenomenon by 41% and obtain the highest economic yield in the off-year, i.e. increased yield by 5.9 fold.