REPORT ON THE INTERNATIONAL HDP TRIAL IN POLAND

The trial was planted in November 1980 at the Experimental Station Dabrowice near Skierniewice on light sandy-loam podsolic soil. Trees for the four standard systems of the HDP International Trial were produced in Polish nurseries by budding M.9 and M.27 rootstocks and were without feathers. For the fifth, local, system Golden Delicious and Gloster trees on Antonovka rootstocks with Budagovsky (B.9) dwarf interstocks were chosen. These trees were planted at a distance of 3.5 m between the rows and 1.5 m in the rows. Soon after planting, in December 1980, the temperature dropped to -23°.

Most of the well grown, strong trees were damaged by the frost. Shoots, the graft union and the upper parts of the rootstocks were damaged. Most of the damage was visible in early spring at pruning time, some appeared later during the growing season. As a result the following percentages of the trees were lost: Golden Delicious on M.9: 21%, M.27: 20%; Gloster on M.9: 8%, M.27: 8%. Gloster and Golden Delicious with B.9 interstock only 3%. These last trees, obtained by grafting, were more hardy.

The upper parts of most of the trees were frozen and died so it was necessary to head all the trees to 50 cm above ground level.

The growth of the trees was slow due to extremely dry weather in 1981–83. Tree irrigation was limited to one or two waterings because of water shortage. Only in treatments 4p and 4q did the tree canopies fill their allotted space. There was much variation in growth between trees and replications due to frost damage and replanting. The strongest growth of stems and shoots was observed in the local (5) system. The heavy pruning of the bed-mini-bush system resulted in more strong shoot growth (tables 1 and 2).

A few flower buds were recorded in 1982 and a few fruits were harvested from the strongest trees. All the trees came into bloom in 1983. The differences between the treatments in number of flower buds and crop per tree were related to tree condition. The estimated yield per hectare was three to four times higher in the bed-mini-bush system than in most of the other systems.

The quality of the fruits was excellent in 1983. The apples were large, beautifully coloured and mostly free from russet.

Tree growth and cropping was more or less typical for Polish soil and climatic conditions. Dwarf trees in Poland usually start to grow very slowly and very seldom give their first yield before they are 3 years old.