The role of nutritional management in improving the symptoms of citrus decline

Abstract

Citrus decline is developing in the southern part of Iran. NH4–N form and factors that limit the uptake of calcium, magnesium and micronutrients by root cause increased citrus decline severity. In this study, the effect of nutritional management on the control of the complication of citrus loss in Valencia orange trees (Citrus scinensis L. Osbeck) was investigated. The experiment was conducted in a randomized complete block design with seven treatments in four replications and four trees per each plot, during 2016 and 2018. - Control (nutrition based on soil test and with ammonium sulfate nitrogen source) - Supplementary soil fertigation with micronutrients iron + zinc + copper + manganese EDDHA chelates at three times during the growth of shoots in the spring; calcium nitrate; magnesium nitrate - Foliar nutrition with micronutrients zinc sulfate + manganese sulfate + boric acid + copper sulfate; potassium nitrate and magnesium nitrate. The results showed that, leaf potassium concentration had a positive correlation with root decay and shoot dieback. Supplemental soil fertigation with micronutrients, calcium and magnesium nitrate caused a significant increase in fibrous root density and reduction of root decay percentage. Supplemental soil fertigation with calcium nitrate and foliar nutrition with magnesium nitrate resulted in significant improvement of citrus decline indices in Valencia oranges, including leaf fall, shoot diebacks, leaf special weight, leaf water content, and quantitative and qualitative of fruits. Due to the negative effect of excessive potassium concentration on aggravation of citrus decline, balanced consumption of potassium in citrus orchards is recommended.