1981 Volume 49 Issue 4 Pages 563-570
In order to make comparison among vegetables in growth response to nitrogen source and accumulation of NH4-N and NO3-N in leaves, potato, carrot, radish (Raphanus sativus L. radicula group), turnip, and japanese radish (Raphanus sativus L. daikon group) were cultured in nutrient solution containing NO3, NO3+NH4(1:1), NH4, NO3+NO2 (1:1), and NO2 as nitrogen sources. The experiment consisted of 4 kinds of treatment conditions where 2 levels of nitrogen concentration (2meq/l designated as low-N and 12meq/l as high-N) and 2 levels of solution pH (5 and 7) were combined. Plants were grown under each treatment for about 3 weeks.
1. All root vegetables fertilized with NO3 and NO3+NH4 showed normal appearance with healthy leaves and grew well under all treatment conditions. The growth of root (edible portion) was often considerably better under NO3+NH4 than NO3 nutrition.
2. When plants were supplied with NH4, the top growth of potato and carrot was relatively good and the NH4-N concentration in their leaves was low. On the contrary, the top growth of turnip and japanese radish was inhibited extremely in NH4 nutrition and the NH4-N concentration in their leaves was high. The highest NH4-N concentration, however, was detected in leaves of radish which showed intermediate growth between aforesaid 2 groups. The concentration of NH4-N in leaves of plants which showed markedly restricted growth in NH4 was a few times as much as the concentration of amide-N.
3. Nitrite toxicities were more intensive under lower solution pH and higher N concentration. The difference of growth response of root vegetables to nitrogen sources was not clear under NO3+NO2 or NO2 nutrition.
4. The concentration of NO3-N in leaves was scarcely affected by solution pH but was affected markedly by N forms and levels in nutrient solution Under high-N treatment, the concentration of NO3-N in leaves of turnip and japanese radish was more than 2% on a dry weight basis. The concentration of NO3-N in leaves of NO3+NH4 plants was, in general, lower than NO3 plants under low-N treatment, while no difference was detected between them under high-N treatment. Apparently low NO3-N concentration was detected in roots(edible portion)as compared in leaves.
