Table 3. The δ ¹³C values of soil fractions (0–20 cm) under long-term fertilization.

Fractions	N	NPK	δ13C (‰)	SNPK	CK
			MNPK
>2000 μm	−20.01 ± 0.27b	−20.43 ± 0.68b	−20.16 ± 0.09b	−19.11 ± 0.32a	−21.47 ± 0.49c
LF	−21.84 ± 0.78bc	−20.72 ± 1.77ab	−21.72 ± 0.66bc	−19.41 ± 0.54a	−22.67 ± 0.59c
iPOM	−20.07 ± 0.12b	−20.27 ± 0.47b	−19.94 ± 0.14b	−19.22 ± 0.49a	−21.20 ± 0.22c
mSOM	−17.51 ± 0.51cd	−16.01 ± 0.87ab	−16.38 ± 0.98bc	−14.97 ± 0.84a	−18.17 ± 0.52d
2000–250 μm	−20.21 ± 0.38ab	−20.69 ± 0.01ab	−20.26 ± 0.09ab	−19.28 ± 0.29a	−21.04 ± 1.80b
LF	−21.72 ± 0.77a	−21.96 ± 0.90a	−21.69 ± 0.92a	−21.31 ± 1.48a	−22.94 ± 0.19a
iPOM	−19.50 ± 0.93ab	−20.17 ± 0.12b	−19.69 ± 0.28ab	−19.15 ± 0.53a	−21.30 ± 0.43c
mSOM	−16.85 ± 0.38c	−15.98 ± 0.04ab	−16.38 ± 0.81bc	−15.36 ± 0.37a	−20.74 ± 0.22d
250–53 μm	−19.16 ± 0.07c	−18.59 ± 0.03bc	−17.74 ± 0.19b	−14.61 ± 1.49a	−20.71 ± 0.61d
LF	−21.36 ± 0.55a	−21.93 ± 0.08ab	−21.20 ± 0.05a	−21.68 ± 0.78ab	−22.24 ± 0.22b
iPOM	−20.61 ± 0.19b	−20.52 ± 0.49b	−20.26 ± 0.15ab	−19.72 ± 0.10a	−21.48 ± 0.58c
mSOM	−20.03 ± 0.67a	−21.11 ± 0.38bc	−20.64 ± 0.32ab	−20.34 ± 0.37ab	−21.82 ± 0.55c
<53 μm	−20.34 ± 0.38ab	−20.86 ± 0.15bc	−20.19 ± 0.27a	−19.84 ± 0.18a	−21.19 ± 0.56c

Data are expressed as mean ± SE, n = 3. Different letters indicate statistical significance at P < 0.05 among fertilization treatments. Abbreviations: LF, Light fraction; iPOM, intra-aggregate POM; mSOM, mineral associated SOM; The abbreviations for fertilization treatments are the same as presented in Table 1.