Measurements of the temporal variations of the concentrations of O+2 ions, O+4 ions and electrons in krypton-oxygen afterglow plasmas at 180 K are described. From mass spectrometric observations of the time varying O+2 ionic wall current the rate coefficient for the forward ternary association reaction O+2+O2+Kr to or from O+4+Kr was measured to be (8.3+or-1.6)*10-30 cm6s-1 at 180 K. This result together with the known equilibrium constant for this reaction enabled gas and charge density conditions to be determined for which the O+4 ion was rapidly established as the dominant positive ion species in the afterglow. Electron-positive ion recombination coefficients, alpha , were deduced from measurements of the temporal decay rate of the electron number densities. From early afterglow time observations alpha (O+2) was measured to be (3.5+or-1.0)*10-7 cm3s-1, and from late afterglow time observations alpha (O+4) was measured to be (1.8+or-0.6)*10-6 cm3s-1. Possible ionospheric implications of the O+4 ion result are briefly discussed.