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The effect of fertilization with different forms of nitrogen on yield and nitrate metabolism in leaves of greenhouse lettuce. I. Yield and content of selected components in lettuce leaves

Włodzimierz Sady*, Stanisław Rożek**, Józef Gregorczyk*

**Institute of Vegetables and Ornamental Plants
**Chair of Plant Physiology
**Faculty of Horticulture, Agricultural University
**29 Listopada 54, 31-425 Kraków, Poland

The effect of different nitrogen forms (100% N-NO3, 50% N-NO3 + 50% N-NH4, 100% NH4, 50% N-NO3 + 50% N-NH2, 100% N-NH2) on the yield and content of selected components in lettuce leaves was determined. The applied forms of nitrogen did not significantly affect the weight of lettuce plants grown in nutrient solutions of pH 6.0, but the effect of these forms was manifested in the content of nitrates and nitrites in the leaves. As compared with the nitrate form, fertilization with reduced forms of nitrogen decreased the content of nitrates in lettuce plants by 12.2-35.2% in plots with urea form and by 64.2-71.3% in those with the ammonium form. Application of the urea form also decreased the content of nitrites in lettuce plants.

Reduced forms of nitrogen distinctly increased the content of dry weight and sugars in the leaves. The application of ammonium nitrogen decreased the amount of acid used for lowering the pH of solutions prepared from tapwater ("hard" water).

Sady W., Rożek S., Gregorczyk J., 1990. The effect of fertilization with different forms of nitrogen on yield and nitrate metabolism in leaves of greenhouse lettuce. I. Yield and content of selected components in lettuce leaves. Folia Horticulturae II/1: 65-76.