Effect of Urea and Ammonium Nitrogen Application on the Yield and Nitrate Ion Concentration of Hydroponically Grown Japanese Hornwort (Cryptotaenia japonica Hassk)

Abstract

　The aim of this study was to examine the effect of urea nitrogen or ammonium nitrogen a pplication on the nitrate ion concentration, product quality, yield of Japanese hornwort plants grown by deep-flow hydroponics. It is known that nitrate ions are one of the causes of high blood methemoglobin levels in humans. The growth of Japanese hornworts cultured with urea nitrogen or ammonium nitrogen was delayed compared with the growth obtained using a standard chemical fertilizer (90% nitrate nitrogen and 10% ammonia nitrogen). The nitrate ion concentration of Japanese hornworts grown with urea nitrogen and with ammonium nitrogen decreased by 20% and 80～90%, respectively, compared with those grown with the standard chemical fertilizer. There was no difference in the quality of plants grown with urea nitrogen and the standard chemical fertilizer; however, the quality of Japanese hornworts grown with ammonium nitrogen was inferior to that of plants grown with other nitrogen sources. The total chlorophyll content increased and leaf color darkened in Japanese hornworts grown with urea nitrogen.