Nitrogen

Abstract

The response of melon and tomato plants exposed to different salinity levels, given as Cl salts, under a wide range of NO3 levels, was tested using an aero‐hydroponic system in the greenhouse. Even though the main effect of salinity on plants was due to the osmotic potential of the solutions, greater NO3 proportions at equisalinity levels resulted in a higher concentration of soluble solids in tomato juice and in greater melon and tomato yields. The effect of NO₃ was also detected at the high ion concentration (Cl+NO₃=115 mmol l^‐1); still, in this salinity range yields were already reduced by 50 to 60% The chemical composition of plants was strongly affected by the composition of the solutions. Lower Cl concentration was found in plants exposed to high NO₃ levels and vice versa. The addition of increasing Na and Ca levels resulted in a reduction of K and Mg contents in the plant tissue.

Key words:

• Ion concentration
• ion antagonism
• Cucumis melo L.
• Lycopersicon escuientum L.