Compost and Biochar to Promote Soil Biological Activities under Sweet Potatoes Cultivation in a Subtropical Semiarid Region

Table 4

Soil pH and sodium concentration during the growing season of sweet potatoes at preplanting and 39, 48, and 92 days after planting.

	Treatments	Preplanting	39	48	92
			Days after planting
pH	Control	7.7 ± 0.02	7.82 ± 0.1 aB	7.84 ± 0.09 aB	9.23 ± 0.19 aA
	NPK		7.95 ± 0.11 aB	7.89 ± 0.02 aB	8.96 ± 0.26 aA
	RC		7.88 ± 0.14 aB	7.91 ± 0.1 aB	9.21 ± 0.24 aA
	AC		7.99 ± 0.14 aB	7.93 ± 0.1 aB	9.05 ± 0.06 aA
	Biochar		7.98 ± 0.21 aB	7.94 ± 0.11 aB	9.18 ± 0.2 aA
Na^+ (cmol kg^−1)	Control	0.09 ± 0.01	0.07 ± 0.02 aA	0.07 ± 0.01 aA	0.12 ± 0.05 aA
	NPK		0.08 ± 0.03 aB	0.08 ± 0.03 aB	0.15 ± 0.05 aA
	RC		0.07 ± 0.02 aA	0.08 ± 0.01 aA	0.11 ± 0.03 aA
	AC		0.07 ± 0.01 aB	0.08 ± 0.02 aB	0.15 ± 0.02 aA
	Biochar		0.07 ± 0.02 aA	0.07 ± 0.01 aA	0.12 ± 0.05 aA

Values are means ± standard errors (n = 3). Values within a column and variable followed by the same lowercase letter or within a row followed by the same uppercase letter are not significantly different ( > 0.05). Values followed by asterisk () are significantly different than preplanting values ( < 0.05). Control: no amendment; NPK: synthetic fertilizer; RC: regular compost; AC: accelerated compost; biochar: biochar produced from walnut shell feedstock.