Table 1.

Level values of each factor in the Box-Behnken design

Treatment	IRRI	GD	TT
1	−1	0	−1
2	0	0	0
3	−1	0	1
4	1	0	1
5	1	1	0
6	1	0	−1
7	0	1	−1
8	0	−1	−1
9	0	0	0
10	0	0	0
11	−1	−1	0
12	0	−1	1
13	0	0	0
14	0	1	1
15	−1	1	0
16	1	−1	0

IR radiation intensity (IRRI): (−1):3000 W/m²; (0): 4800 W/m²; (1): 9000 W/m²

Emitter-sample gap (GD): (−1):0.2 m; (0): 0.15 m; (1): 0.1 m

Treatment time (TT): (−1):1 min; (0): 2 min; (1): 3 min