Alfalfa cropping is superior to cotton and rapeseed cropping in improving the quality and microbial diversity of reclaimed saline soils

Figures & data

Table 1. Soil properties under the reclamation of abandoned salinised farmlands by planting different crops.

Samples	pH	EC (mS·cm^−1)	TK (g·kg^−1)	TP (g·kg^−1)	TN (g·kg^−1)	TC (g·kg^−1)	C/N ratio
CK	9.13 ± 0.08a	1.64 ± 0.13a	57.64 ± 2.81c	0.81 ± 0.05d	0.18 ± 0.01d	2.05 ± 0.12c	11.39 ± 1.52a
Cot	8.37 ± 0.05b	1.12 ± 0.06b	80.89 ± 2.27b	0.92 ± 0.05c	0.28 ± 0.01c	2.20 ± 0.16b	7.86 ± 0.61b
Alf	8.30 ± 0.14b	0.93 ± 0.038c	85.68 ± 4.18b	1.55 ± 0.05a	0.63 ± 0.02a	3.04 ± 0.11a	4.83 ± 0.25b
Ra	8.48 ± 0.08b	1.00 ± 0.03bc	114.46 ± 6.11a	1.25 ± 0.05b	0.47 ± 0.01b	2.82 ± 0.16b	6.00 ± 0.23c

Notes: Cot, Cotton cropping; Alf, alfalfa cropping; Rap, rapeseed cropping; EC, electrical conductivity; TK, total potassium; TP, total phosphorus; TC, total carbon; TN, total nitrogen; C/N ratio, total carbon/total nitrogen ratio; CK, abandoned farmland. Different lowercase letters in each column indicate significant difference between groups (Tukey’s test, p < 0.05).

Figure 1. Relative abundance of dominant bacterial (a) and fungal phyla (b) (relative abundance >5%) under the reclamation of abandoned salinised farmlands by planting different crops. Cot, Cotton cropping; Alf, alfalfa cropping; Rap, rapeseed cropping. The same below.

Figure 2. Hierarchical clustering analysis (a, bacteria; b, fungi) and PCA analysis (c, bacteria; d, fungi) of bacterial phyla and fungal phyla at the OTU level.

Figure 3. Venn diagram of unique and common OTUs.

Figure 4. α-diversity of soil bacterial (a, b) and fungal communities (c, d) during the reclamation of abandoned salinised farmlands by planting different crops. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Figure 5. Redundancy analysis (RDA) between bacterial community and soil properties (a) as well as canonical correspondence analysis (CCA) between fungal community and soil properties (b). EC, electrical conductivity; TK, total potassium; TP, total phosphorus; C/N ratio, total carbon/total nitrogen ratio.

Figure 6. Correlation between soil factors and bacterial (a)/fungal (b) community at the phyla level. TC, total carbon; TN, total nitrogen. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Table 2. Correlation between soil factors and RDA axes.

Soil factor	RDA1	RDA2	R^2	p-value
EC	−0.8065	−0.5913	0.7656	0.007
TK	−0.9879	0.1551	0.0612	0.756
TP	−0.0659	0.9978	0.6806	0.01
C/N ratio	−0.6746	−0.7382	0.8082	0.002

Notes: EC, electrical conductivity; TK, total potassium; TP, total phosphorus; C/N ratio, total carbon/total nitrogen ratio.

Table 3. Correlation between soil factors and CCA axes.

Soil factor	CCA1	CCA2	R^2	p-value
EC	−0.9976	0.069	0.9268	0.004
TK	0.6739	0.7389	0.0113	0.929
TP	0.637	−0.7709	0.6655	0.013
C/N ratio	−0.9671	0.2546	0.916	0.001

Notes: EC, electrical conductivity; TK, total potassium; TP, total phosphorus; C/N ratio, total carbon/total nitrogen ratio.

Table 4. PERMANOVA analysis of the effects of soil factors on soil bacterial and fungal community.

Classification	Soil factor	Sums of Sqs	Mean Sqs	F Model	R^2	p-value
Bacteria	pH	0.766	0.766	8.413	0.457	0.001
	TN	0.610	0.610	5.712	0.364	0.001
	C/N ratio	0.718	0.718	7.494	0.428	0.001
	EC	0.703	0.703	7.213	0.419	0.004
	TP	0.484	0.484	4.057	0.289	0.008
	TC	0.250	0.250	1.752	0.149	0.171
	TK	0.205	0.205	1.391	0.122	0.252
Fungi	pH	1.266	1.266	5.709	0.363	0.001
	TN	1.064	1.064	4.396	0.305	0.001
	C/N ratio	1.208	1.208	5.306	0.347	0.001
	EC	1.257	1.257	5.645	0.361	0.002
	TP	0.893	0.893	3.447	0.256	0.011
	TK	0.843	0.843	3.191	0.242	0.013
	TC	0.870	0.870	3.329	0.250	0.013

Notes: EC, electrical conductivity; TK, total potassium; TP, total phosphorus; TC, total carbon; TN, total nitrogen; C/N ratio, total carbon/total nitrogen ratio; Sums of Sqs, Sum of squared deviations; Mean Sqs, Mean variance; F. Model, F test value; R², Interpretation of soil factors for sample differences; p-value, confidence level. Bold p values indicate p < 0.05.