Effect of nitrogen composition in culture solution on the growth of rice seedlings raised on a cotton mat spread on hydroponic apparatus for vegetables

Effect of the form and composition of nitrogen in a culture solution on the growth of rice seedlings raised on a cotton mat spread on a hydroponic app aratus for vegetables was investigated. The nitrogen composition, NH4-N : N O3-N, in the Kimura B solution was modified as follows : 28% : 72% (plot 1) , 44% : 56% (plot 2), 72% : 28% (plot 3), 100% : 0% (plot 4). Plant length, root length and root dry weight were greatest in plot I followed by plot 2 , 3 and 4. In plots I and 2, the plant length was same level as that in see dlings raised in a box. However, the seedlings in plots I and 2 had longer roots than those raised in a box, and were suspected to be injured by trans planting. Thus, nutrient application was modified to change the plant form as follows: the culture solution was not applied during the first seedling- raising period, NO3-N-rich culture solution (NH4-N: NO3-N=28% : 72%) was a pplied during the second period, and culture solution containing only NH4-N as the nitrogen source was applied during the last period. The seedlings r aised by this method had nearly the same plant length and root length as th ose raised in boxes. Moreover, there was no distinctive difference in growt h characteristics after transplanting between the seedlings raised by this method including different nitrogen compositions and raised in box.