This experiment was carried out as a part of the studies on reasonable application of nitrogen in rice plant to determine: (Ⅰ) Nitrogen absorption. and rooting of rice seedlings as affected by urea foliar application at late seedling stage (Ⅱ) Effect of leaf prunning and foliar application of urea at late heading stage on the maturation and yield of rice (Ⅲ) Effect of foliar application of urea and its time during the stage of ear formation on yield of rice plant. Results obtained are summarized as follows.
Exp.I: Nitrogen absorption and rooting of rice seedlings as affected be urea foliar application at late seedling stage.
1 : The foliar application of urea plots(T₁,T₂) snowed mare N-content than non-urea foliar application plot(T0) at lane seedling stage, being significant among treatments and foliar application of urea seemed more effective in increasing the N-content of seedlings. and promoted root settlement and early growth alter the transplanting.
2 : The carbon contents of the plants of T₁, and T₂ at late seedling stage increased than T_0, and the carbon contents. of T₁ and T₂ plots became higher in amount in proportion to the nitrogen absorption as compared with those of T0.
3 : C/N ratio appeared significant among soil application plots(N₁, N₂) and foliar application of urea plots (T₁, T₂ and T_0). C/N ratio was lower in case of increased amount of nitrogen. The higher contents of nitrogen and carbon and lower C/N ratio resulted in the increment of root numbers and root lengths.
Exp.II: Effect of leaf prunning and foliar application of urea at late heading stage on the maturation and yield of rice.
1 : There was a highly significant decrease in the maturing rate by severe leaf prunning. In the mean time, significant increase in maturing rate was observed with urea foliar application and it was found the more frequent application the more effective for higher maturing rate with a moderate significance.
A correlationship between the level of prunning and maturing rate was enumerated to 0.961 of correlation coefficient, which indicated an increased maturing rate by the increased number of remaining leaves.
2 : The 1.000 grain weight, grain weight and hulled rice yield increased by leaf prunning in order (plot a$lt;b$lt;c$lt;d$lt;e) at the plots where upper single(a), two(b), three(c), four(d) and five leaves(e) remained, respectively, as compared with control plot(f), thus the high significance were observed among the leaf prunning. Correlation coefficient(r) of 0.925, 0.971 and 0.989, respectively, showed highly significant corrlationship between the level of leaf prunning.
In the mean time, the 1000 grain weight, gram weight and hulled rice yield increased in oder at one time urea foliar application plot(B) and two times foliar application plot (A) as compared with the .yield of control plot (C), and the high significance were observed among those treatments. Hulling ratio also showed the same tendency among those treatments(C,B and A plots in order).
3 : The nitrogen and carbon contents of both panicles and leaves in the foliar application of urea were increased. C/N ratio showed a higher level only in the leaves at the urea spray plot. In the mean time, it was found a higher degree of correlationship between the hulled rice yield(0.937),the contents of nitrogen(0.952) and carbon(0.946), and C/N ratio, indicating that the higher the contents of nitrogen and carbon, and C/N ratio the higher the yield of hulled rice.
Exp. III: Effect of foliar application of urea and its time during the stage of ear formation on yield of rice plant.
1 : The difference in average number of grains per ear was significant between the time of ear fertilization, showing a tendency of increase of grain number in accordance with earlier treatments although no significance was seen between methods of ear fertilization. Number of grain of 2.0% urea solution foliar application plot, 10% urea solution soil application plot, 2.0% urea solution soil application plot and the control are 65.9, 65.6, 64.4 and 63.9 grains, respectively, indicating the largest grain number in the 2.0% urea foliar application plot among the others.
2 : Maturing rates showed a significance between time of ear fertilization, showing a tendency of increase in the rate with the time lagging until 7 days before Baring. Those of A₁, A₃, A₂ and A_0 were 89.8%. 89,4% 87.8% and 87.5% respectively, showing the highest of rate in A₁ and A₃ in methods of ear fertilization and being highly significant between its treatment.
3 : 1000 grain weights were highly significant between time of application, showing a tendency of increase of weights with the time lagging until days before earings as that of maturing rates. High significance was recognized between methods of ear fertilization, showing the highest in A₂ 23.18 gr.
4 : Yields per 3.3㎡ were not significant between time of ear fertilization, whereas were highly significant between methods of ear fertilization.
Those of A₁, A₃, A₂ and A_0 were 1.486 ㎏, 1.491 ㎏, 1.381 ㎏ and 1.328 ㎏, respectively, showing the highest in A₁ and A₃.
5 : Hulling ratios showed significant different between time of ear fertilization, showing the highest in T₂, whereas those of methods of ear fertilization were highly significant between its treatment, Those of A₁, A₃, A₂ and A_0 were 84.72%, 84.06%, 83.29%, and 82.56% respectively, showing the highest m A₂ and A₃ among others.
6 : Yields of hulled rice per 3.3 ㎡ showed significant different between time of ear fertilization, showing the highest in T₁, 1.192 ㎏. Whereas, those were highly significant between methods of ear fertilization. Those of A₁, A₃, A₂ and A_0 were 1.259 ㎏, 1.254 ㎏, 1.149 ㎏ and 1.095 ㎏, respectively, showing the highest in A₁ and A₂.
7 : Contents of nitrogen on rice plant increased in case of nitrogen application as ear fertilizer and showed that the case of urea foliar application was more effective than that of soil application, showing the increased nitrogen content of rice plant was accompanied by carbon content.
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