Temperatures in wheat during radiation frost

Abstract

Plant and air temperatures were measured during radiation frost within a crop of wheat (Triticum aestivum cv. Timgalen) grown in 1974 on the Liverpool Plains Field Station, Breeza, New South Wales. Observations were made at different heights within the canopy at several stages of crop development, and these were related to screen and grass minimum temperatures recorded in a meteorological enclosure adjacent to the crop. Coldest conditions were found near the surface of the crop where temperatures were as much as 2°C lower than those in middle regions of the canopy. The temperature just below the soil surface was between 4° and 6°C warmer than that of plant or air at 5 cm to 10 cm above its surface. Grass minimum temperature was linearly related to screen minimum and found to be 3°C lower. Either measurement was useful in estimating the lowest temperature within that canopy.