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Physicochemical soil parameters can be found in Table 2. Soil pH decreased for all treatments during the growth period. This acidification was expected due to hydrolysis of urea to bacterial NH4+ (Udert et al. 2006), which can exchange with protons in plant roots (Bouman et al. 1995). Soil fertilized only once with urine (treatment B) had a much higher CEC than control soil and soil regularly fertilized with urine. CEC is a relevant soil parameter because it has been demonstrated to increase yield due to more adsorption sites available for concentrating macronutrients and micronutrients near plant roots (Liang et al. 2006). With weekly applications, changes in CEC due to urine application and corn growth may have equilibrated; with a one-time application later in the experiment, urine fertilization had a separate and additional effect on CEC. In implementation, waiting 5 weeks to fertilize corn may lead to higher soil CEC values, which can increase corn yield. This same phenomenon may explain how soil magnesium concentrations were highest for one-time urine fertilization although much more total urine was added in the weekly regime.

Table 2

Soil physicochemical properties before and after the corn was fertilized with urine

ParameterBefore treatment
After treatment
AB CA: 25,000 L/ha neat urineB: 10,800 L/ha diluted urineC: control (no urine)
pH 6.7 6.8  6.9 5.8 6.1 
Organic matter (g dm−377 78  94 100 102 106 
Mg (mmol dm−330  26  28 26 45 30 
S (mg/dm−3191 187  247 21 19 24 
CEC (mmol/dm−3125 114  118 134.4 153.5 137.5 
P (mg dm−394 105  96 171 129 177 
K (mmol dm−319  18  17 19 14.5 14.5 
Ca (mmol dm−3) 61 56  60 75 79 78 
Mg (mmol dm−330  26  28 26 45 30 
Al  0 
Potential acidity (mmol dm−316 14 13 15 15 15 
ParameterBefore treatment
After treatment
AB CA: 25,000 L/ha neat urineB: 10,800 L/ha diluted urineC: control (no urine)
pH 6.7 6.8  6.9 5.8 6.1 
Organic matter (g dm−377 78  94 100 102 106 
Mg (mmol dm−330  26  28 26 45 30 
S (mg/dm−3191 187  247 21 19 24 
CEC (mmol/dm−3125 114  118 134.4 153.5 137.5 
P (mg dm−394 105  96 171 129 177 
K (mmol dm−319  18  17 19 14.5 14.5 
Ca (mmol dm−3) 61 56  60 75 79 78 
Mg (mmol dm−330  26  28 26 45 30 
Al  0 
Potential acidity (mmol dm−316 14 13 15 15 15 

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