Comparison of adaptability to nitrogen source among vegetable crops 2. growth response and accumulation of ammonium and nitrate nitrogen of leaf vegetables cultured in nutrient solution containing nitrate ammonium and nitrite as nitrogen sources
Ikeda, H.; Osawa, T.
Journal of the Japanese Society for Horticultural Science 48(4): 435-442
Lettuce, spinach, cabbage, Chinese cabbage (pe-tsai), celery, seri (Oenanthe javanica DC.), garland chrysanthemum and Japanese honewort (Cryptotaenia japonica Hassk.) were grown in solution culture to compare their growth and accumulation of ammonium- and nitrate-N, using NO3, NO3 + NH4 (1:1), NH4, NO3 + NO2 (1:1), and NO2 as N sources. The experiment consisted of 4 kinds of treatment conditions where 2 levels of N (2 meq/l designated as low-N and 12 meq/l as high-N) and 2 levels of solution pH (5 and 7) were combined. Plants were grown under different treatments for about 3 wk. When plants were supplied with NO3, the growth of vegetables, in general, was excellent and plants showed normal appearance with healthy leaves except seri, which showed somewhat yellowish-green color leaves. In general, leaf vegetables fertilized with NO3 + NH4 grew well under all treatment conditions. Plant growth of the NO3 + NH4 treatment was almost equal to, or better than that of the NO3 treatment. In seri especially, the growth of NO3 + NH4-treated plants was sometimes 30-40% better than that of NO3-treated plants. In comparison with NO3, the growth of spinach and Chinese cabbage was most markedly inhibited with NH4, and cabbage also showed restricted growth in NH4. However, the growth inhibition in seri and lettuce was slight. When plants were cultured with NH4, a relatively close relationship was observed between response and leaf NH4-N concentration, i.e., low NH4-N concentration was detected in leaves of healthy plants, and high NH4-N concentrations was detected in leaves of injured plants. Under NO3 + NO2 or NO2 nutrition seri and lettuce showed the most marked growth reduction of all the leaf vegetables, but the tolerance of garland chrysanthemum and celery to NO2 seemed to be relatively high. They showed about 80% of the growth of the NO3 plants under low-N treatment. When plants were cultured with NO3 nutrition, concentratin of NO3 in leaves of tested plants varied with plant series. Even under low-N treatment, the concentration NO3-N in leaves of seri, celery, lettuce and Chinese cabbage was higher than 1.0% on a dry weight basis. Under high-N treatment, concentration of NO3-N in leaves of tested plants was also high and in general was higher than 1.2%. In particular, that of celery and Chinese cabbage was over 2.0% on a dry weight basis.