Response of olive tree to ammonium nitrate fertilization under saline conditions

Abstract

Water scarcity and salinity are major concerns for the new intensive olive groves in arid and semi-arid areas in Tunisia. Furthermore, an inadequately applied fertilization program should aggravate the problem of salinity. The main aim of the present study is to assess the effects of salinity and ammonium nitrate (AN) on the behavior of olive plants (Olea europaea L.var. Arbequina). The experiment was performed with four NaCl levels (0.5, 50, 100, and 150 mM) combined with three levels of NH4 NO3 (0, 50, 100 g) by adding the nutrient solution of ½ Hoagland. Salinity had a statically significant negative effect on the considered responses, although the severity of the effect varies among treatments. High concentrations of salt (100, 150 mM) decreased vegetative growth, the production of fresh and dry biomass, leaf area, chlorophyll concentration, and increased leaf succulence. Similarly, salinity induced an accumulation of toxic ions and loss of electrolytes in the leaves. The use of ammonium nitrate is noticed to be ineffective in improving various growth and physiological parameters of olive plants grown under saline conditions, and it depressed all studied parameters mainly at the highest dose. This depression could be attributed to an increase in leaf sodium concentration after ammonium nitrate application, in spite of the increase of leaf nitrogen concentration. A better management of nitrogen fertilization in saline conditions should be considered mainly in relation to the right source.