Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: January 19, 2009
Publication Date: January 21, 2009
Citation: Wood, B.W. 2009. Nickel deficiency is influenced by the relative concentrations of Zn, Cu, and Fe to Ni within tree organs and cells. Pecan Grower. 20(3):22-23. Interpretive Summary: The cause of an increase in incidence and severity of nickel deficiency in pecan orchards, and emerging incidence in woody perennial crops is unknown. It was found that the relative concentration of Zn and/or Cu to Ni, probably Fe to Ni, within plant tissues can regulate expression of Ni deficiency symptoms via an antagonistic impact on the biological availability of Ni for metabolic and physiological processes. This work identifies a likely causal agent for occurrence of Ni deficiency and presents evidence for the lack of sustainability of long-term fertilizer applications of Zn and Cu in agricultural systems, and explains why pecan trees respond so well to foliar Ni applications even though they exhibit no visible symptoms of deficiency.
Technical Abstract: The occurrence of nickel (Ni) deficiency of pecan [Carya illinoinensis (Wangenh.) K. Koch] in orchards is an increasingly common problem. There is uncertainty regarding the primary cause of the problem, as orchard soils have plenty of Ni. The influence of essential micronutrients on the endogenous bioavailability of Ni is unknown and is a possible factor triggering Ni deficiency. This study examines the linkage between Ni deficiency and endogenous foliar concentration of Ni, Zn, Cu and Fe. Severity of Ni deficiency was unrelated to foliar Ni concentration, but strongly linked to foliar Zn:Ni, Cu:Ni, and Fe:Ni ratios. Deficiency symptoms increased sigmoidally with increasing Zn:Ni or Cu:Ni ratio, and were correctable, regardless of the Zn:Ni or Cu:Ni ratio, in seedling trees by foliar applications of Ni-malate extracted from Alyssum biomass. Thus, Zn and Cu in foliage can function antagonistically to reduce the bioavailability of Ni and therefore trigger expression of Ni deficiency. Soil Zn or Cu supplements did not detectably affect foliar Ni concentration; thus, root uptake does not appear to be inhibited by Zn or Cu. It is concluded that Ni deficiency in pecan orchards is likely to be partially due to either Zn or Cu fertilization induced reductions in the physiological availability of Ni, perhaps via either competitive inhibition or sequestration. It is also concluded that long-term or excessive Zn and/or Cu fertilization of crops potentially triggers Ni deficiency through endogenous antagonisms; thus, potentially threatening the sustainability of commercial pecan enterprises. Hidden hunger type of Ni deficiency is most likely to occur when tree organs are high in Zn, Cu, Fe or a combination of the three metals relative to that of Ni.