Phosphorus, copper and zinc supply levels influence growth and nutrition of a young Populus trichocarpa (Torr. & Gray)×P. deltoides (Bartr. ex Marsh) hybrid.

Abstract

Growth and nutrient responses of a P.trichocarpa × P. deltoides hybrid to phosphorus(P), copper (Cu) and zinc (Zn) were examined in a 4P× 3Cu × 3Zn factorial experiment conducted in anunheated greenhouse from 20 May until 25 August, 1997. Increase of growth medium P concentration from 37 to356 mg kg-1 resulted in a mean increase in treedry weight of 53%, and increase of P concentrationfrom 37 to 500 mg kg-1 was associated with a stemvolume increase of 47%. Increase from 0 to 0.32 µM Cu in solution applied thrice weekly wasassociated with a 61% increase in tree dry weight anda 59% increase in stem volume. There was also asmaller increase in stem volume (9.4%) resulting fromincrease in concentration of Zn from 0 to 0.31 µMin nutrient solution. Mean minimal leafconcentrations for satisfactory stem growth were foundto be 2.5 g kg-1 P, 2.4 mg kg-1 Cu and 74 mgkg-1Zn. Visual deficiency symptoms wereassociated with mean leaf P concentrations below 1.6 gkg-1, and Cu concentrations below 1.7 mgkg-1. Increase in leaf P concentration wasassociated with decreases in leaf Cu and Znconcentrations, and high leaf Zn appeared tocompensate in some degree for low leaf Cu. Totalplant dry weight was satisfactorily predicted by stemvolume (r2 = 0.85), but not by mean leaf weightor area.