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.

中文翻译：

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营养管理在改善柑橘衰退症状中的作用

摘要 伊朗南部的柑橘衰退正在加剧。NH4-N 形式和限制钙、镁和微量营养素吸收的因素的根本原因是柑橘衰退的严重程度增加。在这项研究中，研究了营养管理对控制瓦伦西亚橙树（Citrus scinensis L. Osbeck）柑橘损失并发症的影响。在 2016 年和 2018 年期间，以随机完整区组设计进行了 7 个处理，每个样地 4 次重复和 4 棵树。 - 对照（基于土壤测试和硫酸铵氮源的营养） - 用微量营养素铁补充土壤灌溉施肥+锌+铜+锰EDDHA在春季枝条生长过程中3次螯合；硝酸钙；硝酸镁 - 含有微量营养素硫酸锌 + 硫酸锰 + 硼酸 + 硫酸铜的叶面营养；硝酸钾和硝酸镁。结果表明，叶片钾浓度与根腐烂和茎秆枯死呈正相关。用微量营养素、硝酸钙和硝酸镁补充土壤施肥导致须根密度显着增加并降低根腐烂率。用硝酸钙补充土壤施肥和用硝酸镁进行叶面营养显着改善了瓦伦西亚橙的柑橘衰退指数，包括落叶、枝条枯死、叶片特殊重量、叶片含水量以及果实的数量和质量。由于钾浓度过高对柑橘衰退加剧的负面影响，