Growth and nutrition of hybrid poplars over 3 years after fertilization at planting

A hybrid poplar plantation on eastern Vancouver Island was fertilized at planting with two readily soluble and four controlled-release fertilizers (CRF). The CRFs varied in their duration of release and in their ratio of N to other elements. Fertilizers were applied at rates supplying 0, 13.5, or 27 g N/tree (N0, N13.5, and N27 treatments). The plantation contained one Populus trichocarpa Torr. & Gray x Populus deltoides Bartr. ex Marsh. (T x D) and one P. trichocarpa x Populus maximowiczii A. Henry (T x M) hybrid. The T x D hybrid was consistently larger than the T x M hybrid. After 1 year, stem volumes were 24 and 35% greater in the N13.5 and N27 treatments, respectively; after 3 years, volumes were 9 and 21% greater, respectively. Volumes of trees fertilized with readily soluble fertilizers did not differ from those fertilized with CRFs, but volumes may have differed between CRFs. Growth of poplar on this site appeared to be limited by multiple elemental deficiencies, particularly of N, P, and S.