培養液のNO<sub>3</sub>/NH<sub>4</sub>比と液温がトマトの生育, 収量ならびに尻腐れ果発生に及ぼす影響

Abstract

Tomato plants were grown in nutrient solution four times in two years on a practical scale in order to study the effects of NO3/NH4 ratios and temperature of the nutrient solution on growth, yields, and blossom-end rot (BER) incidence.In spring season crops, growth was best at 25°C. Combined application of NO3 and NH4 produced better growth than did NO3 alone except when plants were grown at low solution temperature and high NH4 ratio. However, the incidence of BER increased with the combined application of NO3 and NH4, and especially, the yields of normal fruits which had no BER were significantly decreased at high solution temperature and high NH4 ratios because of increased incidence of BER. Without exception, leaf Ca concentration was lower when plants were supplied with NO3 and NH4 than with NO3 alone; this seemed to be related to the incidenceof BER.In fall season crops, the yields of normal fruits were proportional to plant growth because of a low rate of BER incidence. Namely, in the low solution temperature the growth was better with a combination of NO3 and NH4 than with NO3 alone, and the yields of normal fruits were higher when plants were supplied with 12 me/l of N as a mixture (10/2 or 8/4) rather than the same amount of NO3. However, in the high solution temperature, increased ratios of NH4 to NO3 resulted in reduction of plant growth and of the yields of normal fruits. Leaf Ca concentration was decreased with increasing ratios of NH4 to NO3 in the solution, but no relationship between leaf Ca concentration and plant growth or BER incidence was observed.Thus, in practical hydroponic production of tomato, the nutrient solution should exclude NH4 in the warm season when BER may easily occur. In the cool season with low light intensity, however, solutions containing NH4 up to about one-third of total N may be recomended for promoting plant growth, keeping plant vigor, and increasing the yields of normal fruits.