Fertigation with KNO3 as a means of reducing salinity hazards was tested with peanut (Arachis hypogaea) plants grown on dune sand, resulting in a reduction of plant growth and yield. The objective of this work was to study the interactions between N, K+ and NaCl as well as the effects of the NH4 +/NO3 -ratio on vegetative and reproductive growth. Wheat (Triticum aestivum L.) plants were grown in polyethylene pots with fine calcareous dune sand with different proportions of NH4 + and NO3 -, under saline (60 mM NaCl) and non-saline conditions. Three replicates were harvested at the beginning of flowering, and one was grown to grain maturity. NaCl reduced shoot dry weight in all the treatments. Increasing the NH4 + proportion in the total of 6 mM N in the nutrient solution, increased shoot dry weight, did not change nitrogen concentration in the dry mass but increased P percentage, either with or without 60 mM NaCl. The number of tillers produced in each treatment was correlated with dry matter yield. The effect of the NH4 +/NO3 - ratio may be explained by alteration of the cation-anion balance on the nutrient uptake by roots,which lowered pH of the nutrient solution with increasing NH4 + concentration, by alteration of the cation-anion balance on the nutrient uptake by roots, which lowered pH of the nutrient solution with increasing NH4 + concentration.