Study of Manganese Status and Management According to Growth Stages and Its Effect on the Yield and Quality of Citrus in East of Mazandaran

To study manganese (Mn) status and its effect on fruit yield and quality of Thomson navel oranges, two separate experiments were carried out in East of Mazandaran Province, Iran. The first experiment was conducted in citrus orchards of the region, and the second was conducted in an orchard of Thomson navel on sour orange rootstock, using a randomized complete block design with seven treatments and four replications. Treatments included: 1) First control (without manganese); 2) Second control (without manganese and with urea spray), 3) 300 g manganese sulfate per tree as soil application, before leaf development, 4) 300 g manganese sulfate per tree as fertigation, in the first stage of fruit growth, 5) 300 g manganese sulfate per tree as fertigation, in the first and second stages of fruit growth, 6) Manganese sulfate spraying in the first stage of fruit growth, and 7) Manganese sulfate spraying in the first and second stages of growth. The results showed that the orchards of Sari and Neka had the most deficiency symptoms. The results of the second experiment showed that soil application before leaf development had no effect on yield, fruit quality, Mn concentration in leaf, fruit and root, but its application as fertigation and spraying increased fruit yield, diameter, and weight, leaf and fruit manganese concentration. The highest leaf Mn concentration was obtained from the first and second stage of fruit growth treatment. Fertigation treatment significantly increased the root Mn concentration compared to the control. In general, according to the results of this experiment, for orchards with a history of mild manganese deficiency or probable manganese deficiency, application of manganese sulfate as fertigation or spray after the fall of petals in the first stage of fruit growth is recommended. However, for orchards that have severe symptoms of manganese chlorosis, two foliar applications or fertigations with manganese sulfate, after petal fall and second stage of the fruit growth, before the growth of the fall flash, is recommended.