Citrus nutrition in Iran: lessons from calcareous soils.

The history of effective citrus nutrition programs is as old as the cultivation of citrus, regardless of the nature and properties of the soil. Citrus cultivation in Iran is predominantly confined to calcareous soils with a minimum of 5% calcium carbonate equivalent calcareousness. Citrus raised on such calcareous soils is exposed to altogether different dynamics of lime-induced multiple soil fertility constraints such as large-scale deficiencies of essential nutrients under the dominating influence of pedogenic/geogenic accumulation of calcium carbonate, chronically deteriorating the soil tilth through dispersion of clay particles with a cascading influence on soil water relations and microbiological properties, compared to either acid or other alkaline non-calcareous soils. Incidentally, calcareous-linked boron toxicity is another pedological problem, yet so formidable to deal with in sustaining an uninterrupted production. Rootstocks (Carrizo, Citranges, Cleopatra) have though played a very handful role in moderating the impacts of soil calcareousness on citrus yield, but still, long-term studies are missing, besides changes in rhizosphere microbiome concerning citrus decline, an analog to negative rhizosphere effect. The authors have attempted analysis of different issues relating to diagnosis (coupled with test interpretations) and management of nutrient constraints (dynamic synergy between citrus-microbes–organics-inorganic) exclusively on calcareous soils with emphasis on Iranian citrus. Finally, the outcome of such analysis has provided a solid blue-print as future researchable issues. [ABSTRACT FROM AUTHOR]