oil properties
Four years after planting, the pH of the soil in the ‘Pre-PK + Post-N’ treatment was lower than for the other treatment groups (Table 3); however, this value was higher than the critical value of 5.5 proposed by Gajek (2005) for blackcurrants. Increased soil acidity as a result of the ‘Pre-PK + Post-N’ treatment can be attributed to the use of ammonium nitrate because it acidifies the soil environment (Wójcik, 2001). It is worth noting that in the ‘Pre-Manure + Post-N’ and ‘Pre-Manure + Post-N + Foliar Fertiliser’ treatment groups, the soil pH values were higher than in the ‘Pre-PK + Post-N’ treatment. This indicates that incorporation of swine manure into soil neutralised the acidification caused by the use of ammonium nitrate. Application of swine manure can stabilise soil pH through the complexation of aluminum ions in the soil solution generated by the decomposing organic matter of manure and through the presence of considerable amounts of basic cations and carbonate ions in manure