PHOSPHORUS-INDUCED MICRONUTRIENT DISORDERS IN HYBRID POPLAR .1. PRELIMINARY DIAGNOSIS

Growth and nutrition of four clones (DN 17, DN 125, NM 2, Jac 4) of hybrid poplar in a sandy loam nursery soil, were examined for fertilization response to P at four rates (0, 288, 576, and 1152 kg ha-1) in 1986 and 1987. Except for clone NM 2, fertilization reduced height growth and caused various degrees of leaf symptoms suggesting nutrient disorders. Height of DN 17, the most sensitive of the four clones, was decreased 23 and 47% by the highest P treatment in the first and second year, respectively. Foliar vector diagnosis indicated that P addition induced Zn and/or Cu deficiencies rather than a direct P toxicity, since P vectors were smaller than Zn and Cu vectors. Available P levels in soil were raised proportionally by fertilization, but DTPA-extractable micronutrient status was not affected except for Mn. Differences in leaf P/Zn and P/Cu ratios among clones suggested that the clonal variation in growth performance may be related to maintaining nutritional balance in plants. © 1990 Kluwer Academic Publishers.