EFFECT OF DIVERSE LONG-TERM MINERAL FERTILIZATION ON FRUIT YIELD AND MINERAL CONTENT IN THE LEAVES OF HIGHBUSH BLUEBERRY PLANTS

Abstract

Since 1923 a long-term fertilization experiment has been carried out in one of the fields of the Experimental Station of the Warsaw Agricultural University in Skierniewice. Until now, this field has not been fertilized with organic fertilizers and no legumes have been grown there. Mineral CaNPK fertilizers have been applied each year according to the following scheme: O, CaNPK, NPK, PK, PN, KN. Since 1976, 90 kg N/ha in the form of (NH(4))(2)SO4, 60 kg P2O5 in the form of Ca(H(2)PO(4))(2) and 110 kg K2O in the form of KCI has been applied. The experiment with high-bush blueberry was set up in 1976 and carried out in 3 replications with 9 plants of each cultivar per plot. This paper presents growth and fruit yield of the blueberry plants in three periods: the first one from 1976 till 1988, the second one till 2005 and the third one till 2011. In the third period of the experiment, the rejuvenation pruning was additionally introduced by cutting back the plants at various heights. The greatest negative influence on yielding of blueberry plants was obtained from plants with liming plots (CaNPK) and without nitrogen fertilization (PK). The blueberry plants reaction to potassium fertilization was very weak. Despite of the low K content in the PN combination, the yield was only about 10% lower than in the NPK combination. On the plots without phosphorus fertilization, the yield was similar to that obtained from the plots fertilized with this component. The annual fertilization with P and K increased the levels of these components in the leaves, while liming increased the levels of Ca and Mg and decreased those of Fe, Zn and Mn.