Effect of fall-applied nitrogen on growth, nitrogen storage, and frost hardiness of bareroot Larix olgensis seedlings

Abstract

Nursery response of evergreen trees to fall fertilization has been studied widely, but little attention has been given to deciduous trees. Bareroot Olga Bay larch (Larix olgensis Henry) seedlings were fertilized in the nursery with urea at four rates (0, 30, 60, 90 kg N ha-1), with half of each rate applied on two dates (September 16 and October 1, 2009). The seedlings were excavated for evaluation on October 15. In the unfertilized (control) treatment, root and shoot dry mass increased by 100% and 57% respectively, while N concentration in the roots and shoots increased by 43% and 40% during the 30 day period. This indicated that substantial biomass growth during this period did not lead to internal nutrient dilution. Root dry mass increased when fall fertilization rates were ≥ 60 kg N ha-1. Fall fertilization increased N concentrations in root tissue by 48-73%. Compared with the control, shoot tissues of fall fertilized seedlings had slightly higher N concentration and content and significantly higher frost hardiness.