A technique for controlling the soil moisture potential in the root zone of transpiring plants was developed. The method uses the principles of unsaturated flow through a porous media to develop the desired moisture potential. In the case of non-steady state transpiration, the maximum possible fluctuation in soil moisture potential can be determined by the techniques presented. Two implicit leaf temperature prediction equations were derived from the energy balance approach. The equations define sensible and latent heat transfer from a plant population as a two step process: (1) Transfer between the plant leaf and the canopy bulk air and (2) Transfer between the canopy bulk air and the atmosphere. Boundary layer concepts were applied to leaf heat transfer in both equations. Turbulent atmospheric transfer by free and forced convection were considered. Measurements of leaf temperature and wind velocity, temperature and humidity profiles for a cucumber plot were taken during ten tests. Richardson numbers to classify atmospheric stability were determined. The neutral wind velocity profile parameters, roughness height and zero displacement height were determined by a computerized least squares technique using data from the ten tests. (WRSIC abstract)