Clonal Differences in Yield Response of Populus deltoides to Nitrogen Fertilization

Abstract

Abstract Trees propagated from cuttings of 22 clones of Populus deltoides were grown under unfertilized and nitrogen‐fertilized conditions. Large increases in growth resulted from fertilization. A strong clone × fertilizer interaction was observed for diameter, height, and volume growth. Wood specific gravity was reduced by fertilization but no interaction between clones and fertilizers was noted for that character after 2 years. The presence of the genotype‐environment interaction indicated that it would be unwise to select eastern cottonwood from a nutritional environment other than the one in which it will ultimately grow. Frequently a clone which performed poorly under unfertilized conditions excelled when fertilized and in several instances the reverse was true. This suggests the possibility that selection can be made specifically for fertilizer response in tree improvement programs. Caution should be exercised when interpreting fertilizer response of experimental populations which might contain genetic bias.