Infrared Radiation Shields for Cold Protection of Young Citrus Trees1

Abstract

Abstract Aluminum-foil-surfaced shields were evaluated with individual citrus trees. These shields, highly reflective in the infrared, moderated leaf temperatures by interrupting their radiant heat loss. A horizontal shield over an individual tree provided about 1°F of cold protection on clear and relatively calm nights. Temperatures of shielded and unshielded leaves were not affected by moderate wind drift or position on the tree. Radiant cooling may induce air flow over the tree that tends to convectively equalize leaf and air temperature. Large differences did not occur between leaf temperatures on adjacent trees. Neither position nor replication produced large temperature differences between leaves at night. Analysis of the heat balance in quasi-steady state indicated that 1° differences were reasonable and that small radiation shields cannot be expected to provide more protection than the amount that leaves are radiantly cooled below air temperature.