Distribution and Transformation of Band-Applied Urea in Soil Following Incubation Under Isothermal and Temperature Gradient Conditions

Abstract

Urea was added as a band in the middle of 12-cm-long columns of Wellwood clay loam (pH 6.6) and the soil was incubated at constant uniform temperatures of 10, 15 and 20 C. A similar set of the soil samples was incubated in columns which had a temperature of 23 C at one end and 8.5 C at the other end. At uniform temperatures the rate of disappearance of ammonium and the formation of nitrate from the banded urea was found to increase with increasing temperature. Nitrite was found to accumulate during the incubation period but disappeared with the prolonged incubation at 15 and 20 C. At 10 C incubation, the maximum nitrite accumulation occurred at 12 wk, the longest incubation time used. Various ionic species, NH4+, NO2− and NO3− were found to be nearly symmetrically distributed from the point of placement. When the soil was incubated under a temperature gradient, NO3− and to a lesser degree NH4+ accumulated near the end of the column.

Potential and kinetics of nitrification in soils from semiarid regions of northwestern India

“…In waterlogged soils, nitrification is restricted or even completely inhibited, resulting in an accumulation of NH 4 + -N. High rates of nitrification have been reported around soil water potential of -33 kPa (Justice and Smith 1962;Malhi and McGill 1982). Most studies on the effect of temperature on nitrification have employed soils from temperate climates with temperatures in the range 0 to 30 °C (Frederick 1956;Campbell and Biederbeck 1972;Kowalenko and Cameron 1976;Pang et al 1977). Sufficient information is not available on the magnitude of this effect in the high-temperature ranges (tropical and subtropical regions) and at different substrate concentrations.…”