Investigation of crop canopy temperature in apple orchard

The paper shows a sophisticated case study for a possible determination of transpiration in apple orchard. The trial measurements were carried out in the Study Orchard of Horticultural and Food Industry University situated in Szigetcsep situated South of Budapest. The main tool of the investigation was a 'Scheduler' type water stress instrument originally developed for crops. The instrument measures the air and crop canopy temperatures, the relative humidity and the radiation simultaneously. The aim of the investigation was to determine the influence of these factors at different levels of the canopy, with various exposures of the tree crowns. The measurements were made on several trees in certain selected rows and on those planted in concentric rows in a round field. The relationship between crop canopy and air temperatures appeared to depend primarily on the illumination. This can be greatly affected by shading conditions, but air motion cannot be neglected, the effect of which increases when its direction is in agreement with the direction of the rows. Its efficiency also has a significant effect on air humidity conditions. The relative humidity and air temperature values were used to calculate the equivalent temperature, also considering latent heat flux, and finally the evapotranspiration of plantation was calculated. From differences in the equivalent and air temperatures, conclusions can be drawn on the intensity and daily course of transpiration. According to the results, transpiration is the strongest in the morning, later it decreases significantly by the afternoon and becomes more intense again early at the night. (C) 2004 Published by Elsevier Ltd.