Combined Effects of N-NH4 Level and a Nitrification Inhibitor on the Performance of Blueberry in High and Low pH-Buffer Media

Abstract Purpose Application of nitrification inhibitor (NI) is considered as an efficient tool for optimization of N management. The main purpose of this study was to examine the combined effects of N-NH 4 level and NI on the performance of blueberry plants grown in low and high pH-buffered substrates. Methods Three levels of N-NH 4 (20, 40 or 80 mg L −1 ) were applied, with or without NI, to southern highbush blueberry plants ( Vaccinium corymbosum , cv. Springhigh) grown in sandy substrate with or without CaCO 3 (5% w/w). The pH and the nutrient element composition of the leachate, the concentrations of nutrient elements in the leaves and branches, biomass production, chlorophyll concentrations and canopy size were measured over two years of cultivation. Results An increase in the N-NH 4 level was accompanied by a decrease in the pH values of the leachates. The pH values of the leachate were higher in the CaCO 3 and NI treatments compared to those without CaCO 3 and without NI treatments. An increase in the level of N-NH 4 enhanced the biomass production in the substrate with CaCO 3 , whereas the opposite effect was obtained in the treatment without CaCO 3 . Addition of NI was associated with a decrease in biomass production compared to the treatment without NI in the treatments with and without CaCO 3 . No deficiencies of the measured nutrient elements were identified in any treatment. Conclusion Application of NI reduces the potential of contamination by NO 3 in high buffered-pH substrate, but it is not necessary in low pH-buffered substrate and it leads to a decrease of biomass production in low and high pH-buffered substrates.