The application of NH4NO3to a light sandy loam and a heavy silty clay loam revealed that irrespective of whether soil was limed or unlimed, NH4‐N was neither nitrified nor lost during winter but NO3‐N was completely removed from the light soil and substantially reduced in the heavy. Under simulated summer weather much of the NH4‐N was nitrified when either the sandy loam or the silty clay loam was limed and it was in the NO3‐N form that most of the losses occurred, probably by denitrification.