INTERACTIVE EFFECTS OF SALINITY AND NITROGEN NUTRITION ON WATER-CONSUMPTION AND TRANSPIRATION COEFFICIENTS OF APPLE-TREES

The interactive effects of N supply and salinity on water consumption of 'Golden Delicious' apple trees on M26 and M9 were investigated in a sand culture system during 1989-1991. Nutrient solutions differing in N level (4, 8 and 12 mM NO3-) were supplied during each growth period (April-November). Salinization of the growth medium was brought about by addition of NaCl or Na2SO4 (30 mM Na+). Water consumption per tree was markedly increased with increasing N supply from a low to a mediu m level. This effect was more evident in trees on M26 compared to thos e on M9 and in trees treated with NaCl compared to those treated with Na2SO4 medium. Trees on M26 consumed higher amounts of water than thos e on M9. Trees in the Na2SO4 medium used more water than those in the NaCl treatment. Values of transpiration coefficient decreased with inc reasing N supply, especially in NaCl-treated trees on M26. The amount of water consumed per fruit dry weight was reduced by increasing N sup ply, but that consumed per root dry weight was increased,