Soil factors that contribute to the abundance and structure of the diazotrophic community and soybean growth, yield, and quality under biochar amendment

Chemical and Biological Technologies in Agriculture

Table 1 Soil physicochemical properties and nutrient contents in biochar-amended soil

Treatment	Soil physicochemical properties			Soil nutrient contents
Treatment	θ/%	γ_d/(g/cm³)	pH	TOC/(g/kg)	AP/(mg/kg)	AK/(mg/kg)	TN/(g/kg)	NH₄⁺-N/(mg/L)	NO₃⁻-N/(mg/L)
B27	17.90 ± 0.27a	1.28 ± 0.02c	8.23 ± 0.04a	13.38 ± 0.55a	18.02 ± 0.47a	152.17 ± 2.25a	1.02 ± 0.01a	1.23 ± 0.03b	0.38 ± 0.01a
B18	17.50 ± 0.02a	1.31 ± 0.02bc	8.18 ± 0.02b	11.43 ± 0.37b	17.99 ± 0.55a	151.25 ± 1.50a	0.95 ± 0.02b	1.21 ± 0.01b	0.24 ± 0.02c
B9	17.40 ± 0.28a	1.34 ± 0.02ab	8.15 ± 0.01b	9.93 ± 0.36c	16.20 ± 0.34b	151.00 ± 3.25a	0.90 ± 0.01c	1.13 ± 0.02c	0.32 ± 0.02b
B0	17.30 ± 0.06a	1.37 ± 0.03a	8.16 ± 0.01b	8.43 ± 0.32d	15.00 ± 0.53c	150.85 ± 1.87a	0.86 ± 0.02d	1.52 ± 0.02a	0.31 ± 0.01b

B27, 45 t hm⁻² biochar addition; B18, 30 t hm⁻² biochar addition; B9, 15 t hm⁻² biochar addition, B0, no biochar added. θ, water content; γ_d, soil bulk density; TOC, total organic carbon; AP, available phosphorus; AK, available potassium; TN, total nitrogen. Values are means ± standard deviation. Different lowercase letters within columns indicate significant (p < .05) differences among treatments