Influence of nitrogen supply on the growth and branching habit of Pinus radiata seedlings

Authors: P.J. Knight
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 1973, Issue N.Z.J.For. 18(2) 1973, pp 273-278, Aug 1973
Publisher: New Zealand Institute of Forestry

---

Abstract: In a glasshouse pot trial, radiata pine (Pinus radiata D.Don) seedlings raised and grown in a nitrogen (N)-deficient soil for 16 months were grown for the next 17 months with five levels of N supply, namely, 0, 25, 50, 75, and 100 ppm N.

Nitrogen supply markedly affected the form of the seedlings through its effect on branch development. The net length of lateral branches per seedling, as well as the mean number of whorls and branches per seedling, increased with increasing level of N supply. Lateral branching in the N-deficient control seedlings was minimal with net mean branch length of about 2 cm/seedling — i.e., 7% of mean stem height. By contrast, the heavily branched seedlings of the highest N treatment produced branches totalling nearly 67 cm in length — i.e., 100% of mean stem height.

Seedling height at time of harvest was positively correlated with N supply up to the 75 ppm level of supply. While seedlings grown with 100 ppm N supply attained only three-quarters of the mean height of the crop grown with the 75 ppm N rate, the crop yields of dry matter were comparable.

---