A one-dimensional, steady-state plant-atmosphere model using different formulae for the thermal stability function is applied to data for corn crops. There are two general types of formulae available. Those proposed by W. C. Swinbank, A. J. Dyer and B. B. Hicks, and E. K. Webb were derived from measurements taken hundreds or thousands of roughness lengths above grass fields. Formulae recently proposed by A. S. Thom, J. B. Stewart, H. R. Oliver and J. H. C. Gash were derived from measurements taken nine roughness lengths above a pine forest. Use of the latter formulae yields better agreement between predicted and measured values of thermal eddy diffusivity at canopy height in the corn crops. These improved diffusivity values result in improved temperature-profile predictions in the top metre of the canopy.