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Table 2 Effect of N-fertilizer/application method and PGPM on root growth and rhizosphere pH, shoot nutrient content and dry matter (55 days after sowing)

From: Densely rooted rhizosphere hotspots induced around subsurface NH4 +-fertilizer depots: a home for soil PGPMs?

Source of variation RLD 5 × 5 cm to seed (8 cm radius) (cm cm−3) Rhizosphere pH 5 × 5 cm to seed (8 cm radius) δ15 N (o/oo)15N/14N N conc. (% DM) N content (mg N plant−1) P conc. (mg P g−1 DM) P content (mg P plant−1) Shoot DM (g plant−1)
 LS means N*BE
  14NO3 -mixed*NoBE 6.4 5.62 170 1.83 114.0 2.18 13.7 6.35
  14NO3 -mixed*Pro 6.2 5.89 148 2.22 130.1 2.32 13.6 5.91
  15NH4 +-depot*NoBE 10.5 4.41 25,260 2.47 137.1 2.93 16.2 5.60
  15NH4 +-depot*Pro 9.9 4.55 21,257 2.66 133.9 3.15 15.9 5.09
  Standard error 0.68 0.13 831 0.13 4.69 0.146 0.62 0.420
 Two-Way ANOVA
  N 0.001*** 0.001*** < 0.001*** 0.002 ** 0.014* < 0.001*** 0.002** NS
  14NO3 6.3 5.75 159 2.03 b 122.0 b 2.52 b 13.6 b 6.13
  15NH4 + 10.2 4.48 23,259 2.57 a 135.5 a 3.04 a 16.0 a 5.35
  BE NS NS 0.036 0.051 NS NS NS NS
  NoBE 8.4 5.01 12,715 2.15 125.7 2.56 15.0 5.97
  Pro 8.0 5.22 10,702 2.44 132.0 2.73 14.7 5.50
  N*BE NS   NS NS NS NS NS NS
  1. P values are in italics; NS no significant difference, P ≥ 0.1; P < 0.1 is italic; *P < 0.5; **P < 0.01; ***P < 0.001; Means not sharing the same letters are significantly different from each other, Tukey test α = 0.05; Factors and interaction is italic; 14NO3 -mixed, non-isotopically labelled Ca(NO3)2 homogenously mixed in substrate; 15NH4 +-depot, 15N-labelled stabilized (NH4)2SO4 +DMPP placed in substrate as a depot; BE, bio-effector; NoBE, no bio-effector; Pro, Pseudomonas sp. DSMZ 13134. ANOVA on δ15N (o/oo) 15N/14N was performed on square root transformed data. RLD, root length density