Table 2.

The soil catalase activity (SCA (0.1 mol L⁻¹ KMnO₄ g⁻¹ h⁻¹)) in different irrigation amounts (W), fertilizer rates (F), and potato varieties (V) during S1 (the germination and seedling stage), S2 (the tuber formation stage), S3 (the tuber enlargement stage), S4 (the starch accumulation stage), and S5 (the tuber maturity stage).

Treatments	Soil layer (cm)	S1	S2	S3	S4	S5
T1	0–20	3.61 b	3.46 ab	3.26 a	3.08 ab	3.10 bcd
	20–40	3.67 c	3.81 a	3.41 bc	3.22 abcd	3.26 abc
	40–60	5.12 ab	3.95 a	3.64 a	3.36 a	3.11 a
T2	0–20	4.26 ab	3.43 abcd	3.28 b	3.23 a	3.19 abc
	20–40	4.56 a	3.68 ab	3.76 a	3.29 abc	3.52 a
	40–60	5.10 ab	3.79 a	3.31 c	3.21 a	3.19 a
T3	0–20	4.14 ab	3.65 a	3.18 ab	2.94 ab	3.03 bcd
	20–40	3.87 bc	3.68 ab	3.57 abc	2.96 d	3.22 abcd
	40–60	4.45 cd	3.75 a	3.39 bc	3.04 ab	3.20 a
T4	0–20	3.98 ab	3.44 abc	3.19 ab	3.08 ab	2.85 de
	20–40	4.34 ab	3.85 a	3.53 abc	3.12 cd	3.14 bcd
	40–60	5.18 ab	4.13 a	3.69 a	3.07 ab	3.16 a
T5	0–20	4.77 a	3.35 abcd	3.15 ab	3.36 a	3.41 a
	20–40	4.56 a	3.57 abc	3.67 ab	3.49 a	3.38 ab
	40–60	5.29 a	4.15 a	3.69 a	3.41 a	3.30 a
T6	0–20	3.77 b	3.02 d	2.99 bc	3.07 ab	3.23 ab
	20–40	4.23 abc	3.27 c	3.56 abc	3.45 ab	3.54 a
	40–60	4.69 abc	3.80 a	3.56 ab	3.09 ab	3.32 a
T7	0–20	3.86 b	3.03 cd	3.00 bc	2.52 b	2.82 de
	20–40	4.50 ab	3.47 abc	3.38 c	3.17 bcd	2.94 cd
	40–60	4.61 bc	3.68 a	3.40 bc	2.96 b	3.11 a
T8	0–20	4.34 ab	3.31 abcd	3.02 bc	3.05 ab	2.91 cde
	20–40	4.64 a	3.78 a	3.54 abc	3.08 cd	2.97 cd
	40–60	4.39 cd	3.88 a	3.30 c	3.14 ab	3.21 a
T9	0–20	3.65 b	3.06 bcd	2.86 c	3.02 ab	2.66 e
	20–40	3.66 c	3.30 bc	3.31 c	3.32 abc	2.87 d
	40–60	3.99 d	3.77 a	3.40 bc	3.17 ab	3.09 a
	Significance test
W		**	ns	**	ns	**
F		**	ns	**	ns	*
V		ns	ns	ns	ns	ns

Different letters indicate significant difference at P < 0.05. ** indicates a remarkably significant difference (P < 0.01), * indicates a significant difference (P < 0.05), and ns indicates no significant difference (P > 0.05).