Table 1. Means and standard errors of eucalyptus growth measured at four different time points in Guangxi, China; Different lowercase letters show the statistically significant differences at ɑ = 0.05 level among the three different soils (BF-treated, FS-treated, and control soils). Significances are indicated in bold for p < 0.05. * = significant different.
Treatments Diameter (cm) Height (m) Stem volume (m3 tree–1)
M3
  BF 0.83 ± 0.021 a 0.56 ± 0.035 0.010 ± 0.00045
  FS 0.73 ± 0.015 b 0.55 ± 0.025 0.0092 ± 0.00032
  Control 0.79 ± 0.035 a 0.60 ± 0.023 0.010 ± 0.00049
  p 0.047* 0.17 0.061
  Cohen’s f 0.6 0.44 0.51
M6
  BF 2.78 ± 0.062 a 2.10 ± 0.061 a 0.045 ± 0.0013 a
  FS 2.57 ± 0.20 a 1.97 ± 0.081 b 0.041 ± 0.0015 b
  Control 2.22 ± 0.067 b 1.85 ± 0.029 b 0.036 ± 0.0010 c
  p 0.039* 0.037* 0.027*
  Cohen’s f 0.25 0.61 0.67
M9
  BF 4.99 ± 0.04 a 6.70 ± 0.046 a 0.12 ± 0.0011 a
  FS 4.31 ± 0.11 b 6.33 ± 0.17 b 0.11 ± 0.0033 b
  Control 3.52 ± 0.17 c 5.23 ± 0.20 b 0.083 ± 0.0038 b
  p 0.027* 0.027* 0.02*
  Cohen’s f 0.69 0.69 0.7
M12
  BF 7 ± 0.21 a 10.32 ± 0.39 a 0.19 ± 0.0073 a
  FS 6.09 ± 0.10 b 9.27 ± 0.15 ab 0.16 ± 0.0012 ab
  Control 5.04 ± 0.18 b 6.68 ± 0.22 b 0.12 ± 0.0046 b
  p 0.027* 0.03* 0.027*
  Cohen’s f 0.69 0.7 0.69
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Fig. 1. Means and standard errors of soil enzyme activity variables (a, Catalase; b, Urease; c, Sucrase) three, six, nine, and twelve months after planting in soil treated with filtered sludge (FS) and bacterial fertilizer composed of filtered sludge + plant growth-promoting rhizobacteria (BF). ** indicate statistically significant differences among treatments and CK at α = 0.01, “ns” indicates “no significance”. View larger in new window/tab.

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Fig. 2. Means and standard errors of soil nutrients (a, total N (TN); b, available K (AK); c, available N (AN); d, available P (AP)) three, six, nine, and twelve months after treatments with filtered sludge (FS) and bacterial fertilizer composed of filtered sludge + plant growth-promoting rhizobacteria (BF). *, ** indicate statistically significant differences among treatments and CK at α = 0.05, α = 0.01, and “ns” indicates “no significance”. View larger in new window/tab.

Table 2. Coefficients of fixed effects model for panel data to determine the relationship between eucalyptus stem volume and soil fertility in our study. Significances were bold when p < 0.05. * = significant different; *** = extreme significant different.
Soil quality parameter Estimate Std. error Pr (> |t|)
(Intercept) 0.18 0.024
CAT –0.1 0.041 0.02*
Urease 0.002 0.002 0.29
Sucrase 0.003 0.001 0.000***
Total N –0.044 0.006 0.000***
Avail K –0.001 0 0.025*
Avail N –0.001 0.001 0.53
Avail P 0.032 0.051 0.53
F = 35.26, p = 0.000***, R2within = 0.91, R2between = 0.77, R2overall = 0.81