Effect of nitrogen and phosphorus fertilization on Pinus radiata hedges shoots phenology and growth

Abstract

The effect of nitrogen and phosphorus fertilization on shoot phenology and growth of Pinus radiata edges was evaluated during the productive growing season. A factorial design, considering nitrogen levels of 0, 100, 200 and 400 mg L^-1 and phosphorus levels of 0, 50, 100, 150 mg L^-1 as nutrient solutions, was applied considering water loss of 3 year old hedges grown in pots. Measurements of shoot elongation (± 0.1 cm) and diameter (± 0.1 mm) were made every 16 ± 1 days during five months for 9 shoots selected randomly. Total number of shoots qualifying for cutting production was evaluated at the end of the study for each selected plant. Nitrogen fertilization affected shoot elongation, but no response was observed to phosphorus fertilization. Nitrogen concentrations applied showed three groups (0, 100 - 200, and 400 mg L^-1 of nitrogen) of magnitude of elongation responses. No differences were observed for shoot diameter among treatments. Elongation growth showed an exponential development that increased with nitrogen concentration in the nutrient solution. Nitrogen concentration also caused a linear increase in the number of shoots per plant. Nitrogen fertilization level also increased nitrogen concentration in shoots tissue which ranged from 13 g kg^-1 with 0 mg L^-1 of nitrogen to 24 g kg^-1 with 400 mg L^-1 of nitrogen. However, as the concentration of nitrogen increased in the growing medium, foliar potassium and calcium concentration decreased.