Effects of Ratios of NO3 to NH4 and Concentrations of each N Source in the Nutrient Solution on Growth and Leaf N Constituents of Vegetable Crops and Solution pH

Abstract

Two experiments were carried out in order to investigate the effects of ratios of N03 to NH4 and concentrations of each N source in the nutrient solution on growth and leaf N constituents of vegetable crops and solution pH. In the first experiment, 10 kinds of vegetables such as cucumber, lettuce, etc. were grown with nutrient solution containing total N of 3 (low-N series) or 12 me/l (high-N series). Seven ratios of N03 to NH4 were employed at each N concentration. In the second experiment, lettuce, cabbage, garland chrysanthemum and spinach were grown with nutrient solution in which N was supplied as follows; N03 (124 me/1) series, NH4 (1.12 me/1) series, N03 4 me/i+ NH4 (1-.12 me/1) series and N0312 me/i+ NH4 (2-..12 me/1) series. In both experiments, solution pH was daily checked and adjusted to 6.0. Vegetable crops were grown in a greenhouse for about 3 weeks. In general, NH4 nutrition resulted in higher leaf NH4 N concentration and reduced plant growth compared with N03 nutrition. This toxic effect of NH4, however, was reduced or alleviated and leaf NH4-N concentration was decreased with combined application of small amount of N03. The obvious enhancement of growth rate was observed from the addition of NH4 to nutrient solution containing 4 or 12 me/1 N03. The concentration of leaf N03-N was increased with increasing N03 concentration in the nutrient solution. In the low-N series, leaf N03-N concentration of all leaf vegetables was lowered with increasing ratio of NH4 in the nutrient solution. In the high-N series, however, lowering of leaf N03-N concentration was hardly recognized in such vegetables as Chinese cabbage, spinach, etc. which absorbed N03 dominantly, even if the ratio of NH4 in the nutrient solution increased. Solution pH increased under N03 nutrition and decreased severely under NH4 nutrition. When plants were grown with N03+NH4, solution pH decreased irrespective of the ratio of N03 to NH4 in the nutrient solution in vegetables which absorbed NH4 dominantly (for example cucumber, lettuce, etc.). While in vegetables which absorbed N03 dominantly (for example tomato, spinach, etc.), solution pH was kept relatively constant for a long period when plants were grown in the suitable ratio of N03 to NH4. •• OE¾ '˜ ŽÒ‚ç‚Í ‚±‚ê ‚Ü‚Å,20•" Ží ‚Ì ‚¼•Ø‚ð ‹ŸŽŽ‚µ‚Ä,NOE`NOE`'Ô ‚É'Î ‚· ‚é • ¶ˆç "½‰ž ‚ð •… •k-@ ‚É ‚ae ‚èOEŸ "¢ ‚µ‚Ä‚«‚½.‚» ‚Ì OE‹ 11983"N3OEŽ17"ú Žó-• ‰Ê,NOE¹ ‚AE‚µ‚ÄNH4‚Ì ‚Ý‚ð Ž{-p ‚· ‚é ‚AE • ¶ ˆç ‚ð 'j ŠQ‚³ ‚ê ‚é ‚» •Ø‚ª '½‚¢ ‚ª,NO3‚AENH4‚ð "™-Ê •¹-p ‚· ‚é ‚AENO3 ‚Ì ‚Ý‚ðŽ{-p‚µ‚½•ê • ‡ ‚ae ‚è‚à-Ç •D‚È• ¶ ˆç ‚𠎦 ‚· ‚à ‚Ì ‚ª ‚ ‚é ‚± ‚AE ‚ð•ñ •• ‚µ‚½(4,5,6).‚Ü ‚½ˆê "Ê‚É"|-{ ‰t ‚ÌpH‚Í, 159