INTERACTIVE EFFECTS OF SALINITY AND NITROGEN NUTRITION ON BIOMASS PRODUCTION AND DISTRIBUTION IN APPLE-TREES

The combined effects of constant (30 mM Na), but different salinities (NaCl and Na2SO4) and three different levels of nitrogen (4, 8 and 12 mM NO3.) on production and distribution of biomass in 'Golden Deliciou s' apple trees on M26 and M9 were examined in a sand culture experimen t during 1989-1991. Increasing N supply significantly enhanced total b iomass production. This ameliorative effect of N could be attributed t o increased nutrient and decreased salt uptake. The effect of N was gr eater in M26 than in M9 and under NaCl-salinity than under Na2SO4-sali nity. Production of dry matter by the roots, stems and shoots was high er in M26 than in M9, whereas fruit dry matter showed the inverse rela tion. The vegetative-reproductive balance of the trees under salt stre ss was sensitive to N availability. While the fraction of the fruit in the total dry matter was markedly increased by raising N supply, that of the roots, stems and shoots was decreased. These responses were pa rticularly distinct in trees on M26 and under NaCl-salinity conditions .