Abstract
The lower critical leaf concentration for nickel (Ni) has not been fully determined for commercial pecan [Carya illinoinensis (Wangenh.) K. Koch.] orchards. In a two-year study, foliar Ni was applied to orchard trees in early spring beginning at the parachute stage of leaf development and followed by two additional applications at two week intervals. Yield, yield efficiency (ratio of yield to trunk area), trunk growth, leaf area, specific leaf weight, nut weight, nut quality, and kernel percentage were unaffected by treatment. Leaf Ni was increased, but leaf zinc (Zn) and manganese (Mn) concentrations were reduced by foliar Ni application. The lack of a detectable response to Ni treatment indicates that a July leaflet Ni concentration in the control (2.87 μg g−1) met this pecan orchard's Ni requirement, establishing a lower critical threshold for leaf Ni than proposed elsewhere.
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