Under temperate climate, soil liming in apple orchards is necessary to avoid excessive soil acidification. A critical factor inducing soil acidification is the use of nitrogen (N) as ammonium. The aim of this study was to examine the impact of different liming strategies on tree responses in an ammonium nitrate-fertigated apple orchard. The study was conducted from 2010 to 2015, in a commercial apple orchard. ‘Red Delicious’ trees/M.9 rootstocks were planted in the spring of 2010 on coarse-textured soil. The trees were annually drip-fertigated with N in the form of ammonium nitrate at a dose of 10-15 g N plant-1 applied weekly over a 12-week period, commencing at the full bloom stage. Ground calcitic limestone was applied annually at doses of 200, 300 or 400 kg CaO ha-1 (referred to as AL1, AL2 and AL3 treatments, respectively) or periodically, once every 3 years at a standard dose or doses increased by 50% and 100% (referred to as PL1, PL2 and PL3 treatments, respectively). After 6 years of the growth of apple trees, the soil pH values beneath the emitters down to the 40-cm in depth were lower (4.6-6.0) than those found 30 cm from the drippers (5.3-6.3). The lowest pH values at the 0-20 cm layer were beneath the emitters in AL1, AL2, PL1 and PL2 treatments (4.6-4.9) and at the 21-40 cm depth in AL1 and PL1 treatments (5.0-5.1). In most of the years, tree leaves in AL3 treatment contained the most N, magnesium and calcium and the least manganese. The leaf concentrations of these nutrients in each year were above the critical values. Over the 6-year period, the leaf concentrations of phosphorus, boron, iron, zinc and copper did not differ among the liming combinations. The trees in AL3 treatment were the only ones that did not exhibit symptoms of internal bark necrosis (IBN). The trees in AL1, AL2, PL1 and PL3 treatments had moderate IBN symptoms. The strongest growth and highest aggregated yield of the trees were observed in AL3 combination. However, the yield efficiency of the trees from this combination was comparable to that in the other liming treatments. No liming treatment affected the mean fruit weight. The results indicated that in the ‘Delicious’ group apple orchards fertigated with ammonium-N and planted on coarse-textured soil, liming should be applied annually at a dose enabling the neutralization of fertigation-induced soil acidification.  

23.3.2018