EN
The aim of research was evaluation of efficiency of air heating trailed machine for protection against spring frost in apple orchard with frost pocket. During the occurrence of night frost the machine was trailed along tree rows and the warmed air is distributed across the rows. The generated heat caused fluctuations of air temperature in the tree rows at the distance of 25 m from the machine. At the distance of 15 m, during the night frost -2 °C and at the height of 1 m the heat pulses of 1.7 °C were observed. The mean and minimal air temperatures at the protected area were slightly higher (up to 0.5 °C) than at non-protected area. The spring night frosts observed during evaluation period were not sufficiently severed to cause the frostbite of buds and blossom. The influence of use of air heating trailed machine on reduction of blossom frost damages was not proved. The air heating increased, however, the number of primordia and apple crop in the season 2011.