The effect of Zn and Mn micronutrients spraying on some quantitative and qualitative characteristics of Washington Navel orange (Citrus sinensis CV. Navel)

Micronutrient deficit is the one of major factors in reduction of citrus yield and quality. This study was conducted to investigate the effect of pre harvest treatments of zinc and manganese sulfate on quantity and quality characteristics of Washington Navel orange fruit at harvest time as factorial experiment based on randomized complete block design with three replications. Experimental factors were spraying of zinc sulfate (0, 2, 4 and 6 g lit-1) and manganese sulfate (0, 1, 2 and 4 g lit-1) in two stages, the first stage,15 days before full bloom (March 2nd) and second stage15 days after full bloom (April 9th). Results indicated that both zinc sulfate and manganese sulfate could improve the quality of orange fruit in the time of harvest as compared to control. Although, sprayed fruits had higher fruit number, length, diameter and weight, juice content, total soluble solid (TSS), Vitamin C as compared to control. Most effective treatments in all factors were obtained in 4 g lit-1 zinc sulfate + 1 g lit-1 manganese sulfate. Over all, results showed that combined treatment including 4 g lit-1 zinc sulfate + 1 g lit-1 manganese sulfate, 6 g lit-1 zinc sulfate + 1 g lit-1 manganese sulfate and 6 g lit-1 zinc sulfate + 4 g lit-1 manganese sulfate had better results. Generally, both zinc sulfate and manganese sulfate improved fruit quality and quantity during the harvest time compared to the control.