Formation of dew and the drying process withincrop canopies

Abstract

AbstractOutdoor dew profiles within a plant canopy have been measured after dewy nights in a maize canopy and in a barley canopy. It is found that dew profiles can have a similar shape for various dew events. Clear unique dew profiles occurred when the plants are stiff, the stems as well as the leaves. This result suggests that it is likely that the similar profiles are a consequence of the more‐or‐less constant foliage area distribution of a plant canopy during a growing season. Flexible plant canopies, however, have more complex behaviour depending on the structure of the canopy and on the wind regime during the early hours. The drying process within the plant canopy has also been monitored until the free liquid water that had collected within the canopy through the night was evaporated. Initially, the drying process was faster in the upper layers of the canopy. Later, when the moisture distribution became more‐or‐less even through the whole canopy, the drying rate became approximately uniform. The amount of dew and the drying rate during the morning hours have also been estimated by making simple model simulations. For the inflexible maize canopy, the calculated total amount of dew agreed with the measured amount to within 6%. The measured drying process, however, lagged about one hour behind the calculated one. Possible causes of this difference are the dripping effect and drainage down the stems, which were not included in the calculations. These causes, however, are difficult to model, especially for a flexible canopy like a barley crop.