Bulk stomatal resistance control on evaporation

Bulk stomatal resistances of a soybean crop were evaluated throughout a growing season as residuals in both the combination model and an Ohm's Law analogue. For a leaf area index exceeding unity, bulk stomatal resistances from the combination model compared well with estimates derived from leaf stomatal resistance and leaf area index measurements. Employing independent bulk stomatal resistances in the combination model yields evaporation estimates which agreed well with estimates from the Bowen ratio method. Leaf resistance was found to be related to global solar radiation during non-limiting soil moisture conditions. Although leaf resistance varied inversely with soil moisture, the relationship could not be used to provide predictive procedures. Procedures used by other workers which relate stomatal resistance to environmental influences were found to be of limited application.