Abstract
The amount of N in plants increased exponentially at the early growth stage (y=abx) and linearly at the middle and late growth stages (y=a+bx). The crossing point of the two equations coincided with the maximum tiller number stage. Narrow spacing shortened the exponential phase. On the other hand, wide spacing and slow release fertilizer lengthened the exponential phase. Parameter 'b' at the linear phase was not affected by spacing and rate of basal fertilizer. However, it varied with the kind of basal N and with soil chemical characteristics. Sink size and potential sink size were correlated with the amount of N in the plant at the late spikelet initiation and flowering stages. However, contribution of N in the plant to sink formation varied with spacing and growth duration of varieties. This can be explained by the duration of the vegetative lag phase of the plant.
