Root Growth Response to Fertilizers

Granular nitrogen, potassium and phosphorous fertilizers were applied in 5 cm diameter, 60 cm deep holes near honeylocust {Gleditsia triacanthos var. inermis) and pin oak (Quercus palustris) trees. Each was applied separately and also together as a balanced fertilizer. After two years, root development near the holes was assessed. No evidence of phytotoxicity from the concentrated source of fertilizer salts was evident. Nitrogen, alone and in combination with the other two elements, significantly increased density of the honeylocust roots near the application holes. Pin oak root densities were only increased in the presence of nitrogen alone. Phosphorous had no effect on the roots of either species.