TABLE 4.

Leaf area index (LAI) at flowering (FL), aboveground total dry weight (TDW), radiation use efficiency (RUE), and related parameters at maturity for four treatments at Jingzhou.

Year (Y)	Treatment (T)	LAI at FL	IR (MJ m–2)	IPAR (MJ m–2)	LIP (%)	TDW (g m–2)	RUE (g MJ–1)
2017	CK	3.49 c	1,820	487.7 d	78.4 d	1,153.5 d	2.37 d
	FP	6.45 b	1,836	639.0 c	81.5 c	1,580.0 c	2.47 c
	OPT–N	6.60 b	1,836	661.8 b	84.5 b	1,675.2 b	2.53 b
	OPT+N	7.08 a	1,847	722.3 a	87.4 a	1,876.6 a	2.60 a
	Mean	5.9	1,835	627.7	83	1571.3	2.49
2018	CK	3.71 c	1,753	723.7 d	68.5 d	1,516.0 d	2.09 c
	FP	5.90 b	1,755	788.1 c	76.8 c	2,013.8 c	2.56 b
	OPT–N	6.63 b	1,795	822.4 b	84.3 b	2,134.8 b	2.60 ab
	OPT+N	8.49 a	1,847	853.3 a	87.9 a	2,288.6 a	2.68 a
	Mean	6.18	1,509	796.9	79.4	1,988.3	2.48
2019	CK	2.52 d	1,943	554.3 c	51.1 d	1,201.4 d	2.17 c
	FP	5.52 c	1,962	743.7 b	75.2 c	2,039.0 c	2.74 b
	OPT–N	7.34 b	1,987	764.2 ab	82.8 b	2,155.5 b	2.82 a
	OPT+N	8.66 a	2,163	783.3 a	86.2 a	2,240.5 a	2.86 a
	Mean	6.01	2,000	711.4	73.8	1,909.1	2.65
2020	CK	2.72 c	1,630	533.1 d	59.0 d	1,193.2 d	2.24 c
	FP	4.79 b	1,716	650.2 c	77.6 c	1,700.0 c	2.61 b
	OPT–N	5.78 a	1,741	737.0 b	83.5 b	1,993.2 b	2.70 ab
	OPT+N	6.10 a	1,763	770.4 a	86.5 a	2,147.5 a	2.79 a
	Mean	4.85	1,711	672.6	76.7	1,758.5	2.59
Analysis of variance	Year (Y)	1.82*	–	8.48**	5.88*	3.22*	7.85**
	Treatment (T)	12.33**	–	20.55**	12.54**	51.21**	61.77**
	Y × T	21.01*	–	55.88**	28.20**	11.24**	32.34**

IR, total solar radiation; IPAR, intercepted photosynthetically active radiation; LIP, light interception percentage; ns, not significant. Different lowercase letters within columns indicate significant differences at P < 0.05; *P < 0.05; **P < 0.01.