FERTIGATION OF HIGHBUSH BLUEBERRY (Vaccinium corymbosum L.). PART I. THE EFFECT ON GROWTH AND YIELD

Fertigation in conjunction with traditional spread fertilization could improve the growth and yield of highbush blueberry. Study was conducted in the years 2002-2004 on a 10-year old plantation of highbush blueberry cv. 'Bluecrop'. The effect of fertigation with 3 nutrient solutions (F-1, F-2, F-3) was investigated in comparison to drip irrigation (F-0) on growth and yield of highbush blueberry. Fertigation with nutrient solution F-1 containing (in mg.dm(-3)): 100 (N-NH4+N-NO3), 30 P-PO4, 60 K, 30 Mg, 0.30 B and 0.03 Mo, and from the water contents of 84.5 Ca, 47.9 S-SO4, 4.8 Na, 6.6 Cl, 0.160 Fe, 0.054 Mn, 0.041 Zn and 0.009 Cu (pH 5.50, EC 1.10 mS.cm(-1)) had a positive effect (in comparison to the drip irrigation) on the fruit yield and single fruit mass of highbush blueberry cv. 'Bluecrop'. An increase of nutrient contents in nutrient solution F-2 to the level of (in mg.dm(-3)): 150 (N-NH4+N-NO3), 45 P-PO4, 90 K, 45 Mg, 0.30 B and 0.03 Mo (the others as in F-1; pH 5.50 and EC 1.45 mS.cm(-1)) did not reduce the yield in relation to F-1, while it lowered the mass of one fruit. Yields of highbush blueberry under the influence of drip fertigation in relation to drip irrigation (F-0), at the optimal soil fertility obtained on the basis of spread fertilization, increased as follows: F-1 at 17.3%, F-2 at 21.9% and F-3 at 5.3%. The greatest effect of fertigation on yield of highbush blueberry was found in the year of soil drought, in which the highest rates of nutrient solutions F-1 and F-2 were applied. Fertigation with the nutrient solutions F-1 to F-3 increased dry matter contents of fruits, however it was lower than in drip irrigation. No nitrates or nitrites were detected in fruits of highbush blueberry. Highbush blueberry cv. 'Bluecrop' is a plant with high nutrient requirement. Average yearly nutrient rates for 10-13 years old plantation applied with the treatments F-1 and F-2 (sum of spread fertilization and fertigation) were: 19-24 g N, 10-12 g P, 7-10 g K, 9 g Ca, 6-8 g Mg and 4 g S.m(-2)-bush(-1). For horticultural practice the nutrient solution F-1 could be recommended because of its advantageous effect on yield and the lowest fertilizer expenditure.