Influence of Heavy Metals and Temperature on Urea Transformation in a Typic Ustochrept

Effect of four heavy metals, viz. Ni, Zn, Pb and Hg on urea hydrolysis at 15°C and life was studied in Hisar sandy loam soil (Typic Ustochrept). Irrespective of the metal added, urea was completely, hydrolysed within 7and 14 days at life and 15°C, respectively. NH₄-N persisted for a longer time in the soil at low temperature; higher concentration (400 mg kg⁻¹ soil) of the metal ions further delayed the nitrification in the order Hg > Zn >Ni > Pb. Transformation of NH_4⁺-N to NO₄⁻-N was affected both by the temperature and metal ions. At 15°C, 104.2 mg kg⁻¹ soil, NO_3⁻-N was recovered in control while 85.0 and 68.5 mg kg⁻¹ soil NO_3⁻-N obtained when Hg and Zn were applied at the rate of 400 mg kg⁻¹ soil respectively, after 42 days.