Table 2.

Relative chlorophyll content (SPAD) after PBZ application in Year 1 and 4 in consecutive years of slow-release N application.

Species	Nitrogen rate (kg N/100 m2)	PBZ (g a.i./cm dbh)	SPAD after each annual N application
Species	Nitrogen rate (kg N/100 m2)	PBZ (g a.i./cm dbh)	Year 1	Year 2	Year 3	Year 4
Bur oak	0	0	42.36a^{^z}	40.42a	41.75a	42.23a
	0.96	0	44.83a	45.28ab	45.51ab	47.08b
	2.88	0	46.68a	46.92b	47.93b	48.05b
Bur oak	0	1.2	45.82	51.96	46.65	44.57
	0.96	1.2	46.33	45.54	45.81	41.57
	2.88	1.2	45.42	44.61	46.18	47.06
White oak	0	0	40.34	39.78	39.44	39.98
	0.96	0	41.12	42.60	42.93	42.01
	2.88	0	41.31	40.56	42.80	41.74

↵^z Values in the same column for the same species and treatment combination followed by different letters were significantly different at P ≤ 0.05.