Appropriate nitrogen supply could improve soil microbial and chemical characteristics with Sophora davidii seedlings cultivated in water stress conditions

Figures & data

Table I. Physical and chemical characteristics of substrate soil.

pH	Bulk density (g cm^−3)	Graval content (%)	Water field capacity (%)	Organic C (g kg^−1)	Kjeldahl N (g kg^−1)	Total P (g kg^−1)	NH4-N (mg kg^−1)	NO3-N (mg kg^−1)	Available P (mg kg^−1)
8.06	1.36	52	24.68	55.29	2.01	0.81	9.55	17.63	9.25

Table II. Soil organic C (SOC), Kjeldahl N, total P, NH₄-N, NO₃-N and available P content (means±SD, n = 4) at different water and N supply regimes cultivated with Sophora davidii seedlings.

	SOC (g kg^−1)	Kjeldahl N (g kg^−1)	Total P (g kg^−1)	NH4-N (mg kg^−1)	NO3-N (mg kg^−1)	Available P (mg kg^−1)
W20N0	46.66±4.69	1.81±0.03	0.86±0.06	9.38±0.80	20.14±2.22	8.31±1.32
W20Nl	60.80±8.55	2.22±0.23	0.84±0.10	12.44±1.88	22.60±2.06	11.85±1.13
W20Nh	58.25±16.13	2.14±0.16	0.96±0.24	15.04±2.36	30.15±3.20	10.23±2.24
W40N0	58.96±3.16	2.36±0.18	0.87±0.04	9.56±1.74	22.38±1.25	11.34±0.80
W40Nl	70.61±10.36	2.47±0.13	0.90±0.12	23.66±2.28	30.12±2.15	14.21±1.08
W40Nh	64.83±14.92	2.60±0.20	0.83±0.07	24.76±1.79	36.62±4.58	12.39±1.97
W80N0	73.82±8.60	2.06±0.26	0.81±0.09	12.56±2.00	26.43±3.07	12.30±1.52
W80Nl	81.33±15.56	2.37±0.45	0.76±0.01	23.40±1.86	32.14±2.26	16.29±1.09
W80Nh	74.18±7.44	2.30±0.42	0.77±0.18	31.94±1.55	40.61±4.35	14.28±1.59
Fwater	11.42**	7.78**	2.66	99.15**	140.87**	8.69**
FN	0.95	4.27*	0.12	167.74**	91.07**	2.81
Fwater×N	1.36	0.41	0.81	19.12**	22.11**	7.59**
W80N0, W80Nl and W80Nh: zero, low and high N supply under 80% field capacity (FC) condition; W40N0, W40Nl and W40Nh: zero, low and high N supply under 40% FC condition; W20N0, W20Nl and W20Nh: zero, low and high N supply under 20% FC condition. *p < 0.05, **p < 0.01.

Figure 1.  Soil microbial biomass C (MBC), microbial biomass N (MBN) and microbial P (MBP) at different water (80%, 40% and 20% field water capacity (FC)) and N supply (control, N0; low N supply, Nl; and high N supply, Nh) regimes cultivated with Sophora davidii seedlings. Bars indicate SD (n = 4).

Table III. pH, the ratio of C to N (C/N), C to P (C/P), microbial biomass C to organic C (MBC/SOC), microbial biomass C to N (MBC/MBN), and microbial biomass C to P (MBC/MBP) of soils (means±SD) at different water and N supply regimes cultivated with Sophora davidii seedlings.

	pH	C/N	C/P	MBC/SOC	MBC/MBN	MBC/MBP
W20N0	7.95±0.16	25.77±2.95	54.25±3.65	0.0076±0.0004	12.82±1.49	45.31±2.17
W20Nl	7.84±0.33	27.38±10.70	72.38±13.59	0.0068±0.0015	9.42±1.06	49.19±1.31
W20Nh	7.72±0.32	27.21±9.27	60.67±22.82	0.0078±0.0013	13.23±0.52	56.61±3.12
W40N0	7.82±0.32	24.98±5.14	67.77±4.13	0.0068±0.0019	9.97±2.54	49.71±2.86
W40Nl	7.58±0.05	28.58±4.43	78.46±3.68	0.0050±0.0048	6.74±2.86	37.05±13.07
W40Nh	7.50±0.23	24.93±15.06	78.11±14.77	0.0063±0.0049	10.76±3.70	47.08±11.24
W80N0	7.84±0.20	35.83±7.53	91.13±21.43	0.0069±0.0051	15.87±1.61	72.06±19.05
W80Nl	7.71±0.04	34.31±17.18	107.01±10.17	0.0086±0.0008	12.23±2.99	87.87±23.47
W80Nh	7.51±0.20	32.25±10.97	96.34±14.69	0.0061±0.0049	14.49±3.57	59.52±22.97
Fwater	0.26	13.01**	14.24**	8.96**	7.37**	20.37**
FN	4.38*	0.01	1.80	0.80	1.26	0.83
Fwater×N	1.67	1.01	0.85	0.34	1.30	1.56
W80N0, W80Nl and W80Nh: zero, low and high N supply under 80% field capacity (FC) condition; W40N0, W40Nl and W40Nh: zero, low and high N supply under 40% FC condition; W20N0, W20Nl and W20Nh: zero, low and high N supply under 20% FC condition. *p < 0.05, **p < 0.01.

Figure 2.  Soil invertase, urease, proteinase, alkaline phosphatase, neutral phosphatase, acid phosphatase and catalase activity at different water (80%, 40% and 20% field water capacity (FC)) and N supply (control, N0; low N supply, Nl; and high N supply, Nh) regimes cultivated with Sophora davidii seedlings. Bars indicate SD (n = 4).

Table IV. Pearson's correlation between soil chemical and microbiological characteristics.

	Soil organic C	Kjeldahl N	Total P	NH4-N	NO3-N	Available P
Invertase	0.423**	0.341*	−0.393**	0.717**	0.721**	−0.518**
Urease	0.060	0.346*	−0.043	0.675**	0.562**	0.207
Proteinase	−0.383*	0.132	0.219	−0.135	−0.418**	0.149
Alkaline phosphatase	0.190	0.309*	−0.448**	0.259	0.250	0.414**
Neutral phosphatase	0.124	0.075	0.189	0.268	0.437**	−0.116
Acid phosphatase	0.082	0.226	−0.244	−0.132	−0.028	−0.187
Catalase	0.200	−0.611**	−0.021	−0.430**	−0.277	−0.240
Microbial biomass C	0.352*	−0.042	−0.473**	0.310*	0.557**	−0.392**
Microbial biomass N	0.199	0.153	−0.247	0.065	−0.134	−0.125
Microbial biomass P	−0.272	0.420**	−0.005	0.150	−0.022	0.092
n = 36, *p < 0.05, **p < 0.01.