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General soil properties at the experimental site.†

 
Soil property
pH 5.5
Olsen phosphorus (mg kg−1) 28.4
Potassium (cmolc kg-1) 0.84
Calcium (cmolc kg-1) 3.6
Magnesium (cmolc kg-1) 0.90
Sodium (cmolc kg-1) 0.12
Cation exchange capacity (cmolc kg-1) 14
Total base saturation (%) 39
Available nitrogen (kg ha−1) 45
Anaerobically mineralizable nitrogen (μg g−1) 31
Soil tests were performed commercially by Hill Laboratories, Hamilton, NZ. Soil sample depth was 0 to 0.075 m. Thirty soil cores were taken from the site, bulked, and submitted for analysis, n = 1.



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Biochar physical and chemical properties.

 
Analysis Result Method
Cation exchange capacity (cmolc kg-1) 8.0 1 g biochar:50 mL silver thiourea (Blakemore et al. 1987)
Anion exchange capacity (cmolc kg-1) 4.0 Compulsive exchange method (Sparks, 1996)
pH(H2O) 7.8 1 g biochar:10 mL water (Blakemore et al. 1987)
pH(CaCl2) 7.4 1 g biochar:10 mL 0.01 M CaCl2 (Blakemore et al. 1987)
Electrical conductivity (dS m−1) 0.5 1 g biochar:10 mL water (Blakemore et al. 1987)
Particle density (Mg m−3) 1.1 Using a conventional pycnometer (density bottle) and displacement with kerosene (Rasul et al., 1999)
Bulk density (Mg m−3) 0.4 Mercury displacement (Pastor-Villegas et al., 2006)
Surface acidity (moles H+ kg−1) 1.4 Boehm titration (Boehm, 1994)
Specific surface area (mg g−1) 127.4 Iodine absorption method (ASTM, 2009)
N content (mg g−1) 0.65 Total C and N were analyzed using a LECO CNS−2000 Elemental analyzer (LECO, Australia)
C content (mg g−1) 772 As for N content
C:N ratio 1187
Volatile organics found Ethanol As described by Clough et al. (2010)
Biochar particle size fractions 45 to 15 mm (24.1%), 15 to 7 mm (33.8%), 7 to 5.6 mm (1.13%), 5.6 to 4 mm (10.6%), 4 to 2 mm (15.2%), 2 to 1mm (4.7%), ≤ 1mm (10.6%)



View Full Table | Close Full ViewTable 3.

Biochar-urine treatment effects on dry matter yields, herbage N content, N uptake, 15N enrichment, and percent 15N recovery.

 
Variable Day Treatment† ANOVA result
Control 0U 15U 30U All treatments‡ Biochar-urine treatments only§
Dry matter yield (g m−2) 21 153 ± 67 199 ± 40 199 ± 31 242 ± 41 ns¶ ns
43 103 ± 15 224 ± 53 185 ± 57 182 ± 46 #
58 44 ± 15 91 ± 19 104 ± 31 82 ± 34 # ns
Herbage N content (%) 21 2.7 ± 0.3 4.5 ± 0.3 4.5 ± 0.2 3.3 ± 1.8 # ns
43 2.5 ± 0.2 4.1 ± 0.3 3.9 ± 0.4 3.7 ± 0.2 * ns
58 2.9 ± 0.2 4.3 ± 0.3 3.9 ± 0.3 4.1 ± 0.4 * ns
N uptake (g m−2) 21 4.0 ± 1.7 8.87 ± 1.60 8.89 ± 1.07 8.28 ± 4.77 # ns
43 2.5 ± 0.3 9.03 ± 1.73 7.27 ± 2.84 6.70 ± 1.73 * ns
58 1.3 ± 0.5 3.88 ± 0.81 3.97 ± 1.01 3.30 ± 1.99 * ns
Atom%15N 21 0.41 ± 0.02 3.62 ± 0.16 3.72 ± 0.11 3.55 ± 0.23 * ns
43 0.38 ± 0.01 3.94 ± 0.06 3.99 ± 0.10 3.89 ± 0.09 * ns
58 0.38 ± 0.01 3.72 ± 0.14 3.77 ± 0.12 3.69 ± 0.10 * ns
15N recovery (%) 21 6.85 ± 1.24 7.05 ± 0.99 6.11 ± 3.53 ns
43 7.63 ± 1.49 6.26 ± 2.54 5.60 ± 1.53 ns
58 3.09 ± 0.75 3.20 ± 0.82 2.60 ± 0.94 ns
* P < 0.05.
Treatments: Control (nil urine and nil biochar); 0U (urine and nil biochar); 15U (urine and biochar at 15 t ha−1); 30U (urine and biochar at 15 t ha−1).
ANOVA comparing all treatments.
§ ANOVA comparing only the urine treatments (0U, 15U, and 30U). Error beside mean values equals ± standard error of the mean.
ns, not significant.
# P < 0.10.