| Summary: | 碩士 === 國立中興大學 === 農藝學研究所 === 79 === Attempts were made to outlined the influence of fertilizer-N applied at different growth stages on the dynamics of N absorption and partitioning in rice plants. In the 2nd crop season of 1988 and the 1st crop season of 1989, a Japonic rice variety, Tainung 67, was tested in paddy-tank (1x1x1 m3) experiments using a cuboctahedron design with three N application rate (i.e.20,40 and 60 Kg.N ha(-1)) each at the basal dressing and the first (at early tillering stage) and the second (at young panicle stage) top dressings. The results indicate that:
In the 2nd crop, N uptake increased linearly with increasing N application rate were estimate as 45, 37 and 75 percents for the basal dressing, the first and the second top dressing, respectively. In the 1st crop, however, only the N applied at the second top dressing showed significant effect on N uptake. And the recovery rate was aboult 77 percent.
The partitioning pattern of the current absorbed N among plant organs did not differ much across the range of treatments. During vegetative period, the absorbed N was allotted with largest proportion to leaf blade, lesser to stem and sheath and the least to root.
After heading, the proportion of current absorbed N that was distributed to vegetative organs declined rapidly and panicle soon became redistribution and thus formed a second source for the H remobilization were more prominent in the 2nd crop season than in the first.
In the 2nd crop, the amount of N remobilized from stem and sheath to panicle decreased as application rate of basal dressing increased. And both the absolute and relative contribution to panicle by the current absorbed N during grain filling period increased linerly with increasing application rate at the second top dressing. In the 1st crop, both the N applicated at basal dressing and the second top dressing had positive effects on the amount of N remobilized from stem and sheath to panicle.
Grain yield and panicle number per m(2) increased linerly as H appiication rates increased at the first and the second top dressings in 2nd crop season. However, fertility responded negatively to the N applied at the second top dressing.
Both spikelet number per panicle and 1000-grain weight did not vary significantly across the range of treatments. In the first crop, only the N applied at the second top dressing showed significant effect on grain yield.
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