POTASSIUM, NITROGEN, AMMONIUM-NITRATE RATIO, AND SODIUM-CHLORIDE EFFECTS ON WHEAT GROWTH .2. TILLERING AND GRAIN-YIELD

The objectives of this project were to study the interactions among N, K+ and NaCl and the NH4+/NO3- ratio and their effect on vegetative and reproductive growth of wheat (Triticum aestivum L.). Plants were grown in polyethylene pots with fine calcareous dune sand with and without 60 mM NaCl, two nitrogen concentrations (2 or 6 mM), two K+ concentrations (0.5 or 5 mM) and four NH4+/NO3- ratios (0:1, 1:1, 3:1 and 1:0). Three replicates were harvested at the beginning of flowering, and one grown to grain maturity. Shoot and root growth, and mineral composition of the leaves, were reported in part I of this series (1). Number of tillers per plant was correlated with dry matter yield. It also increased with nitrogen concentration and with NH4+/NO3- ratio, with or without 60 mM NaCl. Mean grain weight was negatively correlated with NH4+/NO3- ratio (and consequently with the number of tillers per plant). This reduction of grain weight was more pronounced with than without 60 mM NaCl. Consequently grain production of plants grown with a relatively high NH4+/NO3- ratio was more susceptible to NaCl than their vegetative yield, than plants grown with NO3- nitrogen only.