Autumn urea application and cold hardiness of apple trees

Abstract

Effect of autumn urea application on cold hardiness of apple trees was investigated at Experimental Orchard in Dąbrowice on four apple cultivars ('Szampioii'. ´Jonagold´, ´Elstar' and 'Spartan´) of different sensitivity to low temperature injuries. During three-years experiment (2000-2002) no changes in frost resistance of apple trees after urea treatment in the end of October (during leaves fall) were noted. After the earlier application of urea, at middle of October. significantly more damages of annual shoots of cv. ´Jonagold' occurred only in the season 2001. These damages did not influence later growth of apple trees. Spring observations indicated that for all apple's cultivars setting of buds was better on treated with urea than on untreated ones. Electrolyte leakage determinations confirmed the field results that urea did not cause decrease in low temperature resistance of apple trees.