A laboratory experiment was conducted on a Typic Ustochrept soil to study the transformation of a coal fertilizer ammonium polycarboxylate (AMP) and efficacy of coal acids (CA) and nitrohumic acid (NHA) as nitrification retardars. During 35 days (d) of incubation period, at field capacity AMP showed lower soil NH4+-N and NO3−-N than urea. Difference in NH4+-N and NO3−-N contents between urea and AMP gradually narrowed down with time. From 28d onwards AMP showed slightly higher (NH4+)-N than urea. Both CA and NHA inhibited effectively NH4+-N oxidation up to 28d. Under flooding, all the treatments showed maximum soil NH4+-N on 7d except AMP. Up to 14d NH4+-N content was in thefollowing sequence: urea + CA > urea + NHA ≈ urea > AMP > control. From 21d, AMP was superior to rest of the sources. The CA was more effective than NHA under flooding. Average soil NO3−-N content was <4 ppm on application of urea and < 1 ppm in AMP. Effects of CA and NHA were not reflected in NO3−-N content of the soil samples.
Urea transformation, ammonium polycarboxylate, coal acids, nitrohumic acid, nitrification inhibitors
