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Table 1 Effects of different forms of N addition on soil, plant and microbial properties

From: Nitrogen deposition experiment mimicked with NH4NO3 overestimates the effect on soil microbial community composition and functional potential in the Eurasian steppe

Indices Mean (± se) under each treatment General lineal models
Control NH4NO3 Slow-released urea Urea NH4HCO3 (NH4)2SO4 Block N addition
Soil total organic carbon content (g kg−1) 42.509 (4.332) 35.292 (1.609) 40.679 (2.912) 40.329 (2.287) 37.47 (1.409) 37.462 (0.622) 0.304 0.358
Soil total N content (g kg−1) 2.555 (0.070) 2.593 (0.137) 2.940 (0.169) 2.753 (0.072) 2.705 (0.038) 2.788 (0.104) 0.325 0.183
C/N 16.608 (1.578) 13.72 (0.895) 13.905 (0.923) 14.643 (0.697) 13.88 (0.702) 13.512 (0.677) 0.645 0.302
Soil total phosphorus content (g kg−1) 0.118 (0.008) 0.108 (0.001) 0.111 (0.003) 0.108 (0.003) 0.105 (0.002) 0.109 (0.002) 0.421 0.383
Soil NO3-N content (mg kg−1) 11.295 (1.556)c 29.540 (5.842)b 49.817 (2.790)a 45.975 (5.173)ab 29.924 (1.236)b 34.050 (5.987)ab 0.43 < 0.001
Soil NH4+-N content (mg kg−1) 1.673 (0.316)d 28.950 (6.953)b 22.750 (3.562)bc 6.513 (1.379)cd 2.213 (0.224)d 115.240 (12.247)a 0.237 < 0.001
Soil dissolved organic carbon content (mg g−1) 351.345 (61.620) 258.636 (50.380) 260.702 (39.512) 235.843 (34.609) 216.965 (28.755) 222.135 (16.549) 0.414 0.268
Soil available phosphorus content (mg kg−1) 6.450 (1.393) 6.775 (0.642) 7.050 (0.972) 6.650 (0.096) 6.900 (0.670) 6.275 (0.256) 0.486 0.984
Soil pH 6.888 (0.081)a 6.590 (0.079)b 6.735 (0.093)ab 6.548 (0.094)b 6.668 (0.029)ab 6.030 (0.094)c 0.111 < 0.001
Soil moisture (%) 15.392 (0.271) 15.414 (0.264) 15.705 (0.229) 14.791 (0.747) 15.401 (0.179) 15.799 (0.401) 0.791 0.633
Aboveground plant biomass (g m−2) 130.283 (11.184)b 240.610 (40.884)a 209.565 (25.066)ab 214.028 (27.775)ab 169.780 (19.101)ab 146.265 (23.029)b 0.178 0.040
Belowground plant biomass (g m−2) 110.650 (6.916)a 57.340 (5.901)b 115.420 (27.360)a 93.663 (6.534)ab 63.250 (6.680)b 48.168 (10.128)b 0.598 0.009
Plant species richness 14.750 (2.462) 16.500 (1.500) 13.000 (1.291) 11.250 (1.031) 13.750 (1.652) 15.750 (3.227) 0.638 0.408
Microbial biomass carbon (mg g−1) 0.927 (0.081) 0.779 (0.067) 0.957 (0.091) 0.873 (0.069) 0.993 (0.037) 0.810 (0.044) 0.988 0.313
  1. Different letters within a row indicate significant differences between treatments (P < 0.05)