Comparative effect of human urine and ammonium nitrate application on maize ( Zea mays L.) grown under various salt (NaCl) concentrations

The present study investigates the effect of urine and ammonium nitrate on maize ( Zea mays L.) vegetative growth, leaf nutrient concentration, soil electrical conductivity, and exchangeable‐cations contents under various concentrations of NaCl in a soil substrate. The experiment was arranged in a completely randomized block design with eight replications under greenhouse conditions. The experimental soil substrate was made from a 1 : 1 : 1 volume‐ratio mixture of compost, quartz sand, and silty‐loam soil. Salinity was induced by adding 0, 15, and 30 mL of 1 M NaCl solution per kg of substrate to achieve an electrical conductivity (EC) of 1.3 (S0), 4.6 (S1), and 7.6 (S2) dS m –1 . Nitrogen sources were urine and ammonium nitrate applied at 180 and 360 mg N (kg soil substrate) –1 . Basal P and K were added as mono potassium phosphate in amounts equivalent to 39 mg P and 47 mg K (kg substrate) –1 , respectively. In the S0 treatment, a 3‐fold increase in EC was measured after urine application compared to an insignificant change in ammonium nitrate–fertilized substrates 62 d after sowing. Under saline conditions, application of 360 mg N (kg soil) –1 as urine significantly decreased soil pH and maize shoot dry weight. At the highest salt and N dose (S2, N360) 50% of urine‐fertilized plants died. Regardless of salinity there was no significant difference between the two fertilizers for investigated growth factors when N was supplied at 180 mg (kg soil) –1 . Leaf N and Ca contents were higher after urine application than in ammonium nitrate–fertilized plants. At an application rate of 180 mg N (kg soil) –1 , urine was a suitable fertilizer for maize under saline conditions. Higher urine‐N dosages and/or soil salinity exceeding 7.6 dS m –1 may have a deleterious effect on maize growth.