The fate of fertilizer nitrogen applied to the paddy field and its absorption by rice plant : 4. Distribution of basal and top-dressed nitrogen in rice plant

Abstract

The distribution of absorbed nitrogen derived from basal and top-dressed fertilizer was investigated by tracing ¹⁵N. In the basally fertilized plots, at rooting stage, nitrogen derived from fertilizer was distributed apparently more in leaf sheaths than in laminae, and in the top-dressed plots, it was distributed apparently more in leaf sheaths than in laminae just after top-dressing, because there were new growing organs in leaf sheaths. The nitrogen derived from fertilizer in rice plants translocated gradually from sheaths to laminae with emergence of new laeves. So, it could be assumed that a large amount of absorbed nitrogen distributed in new growing organs. At the later growth stage the rice plants were top-dressed, it took the less number of days to accumulate the maximum amount of nitrogen in the laminae. Nitrogen applied at the ear emergence was firstly found in leaf sheaths, culms and laminae, and it translocated to ears with the progress of ripening. At maturity, nearly 70 percent of absorbed top-dressing nitrogen was found in the ear. At the earlier growth stage of rice plants fertilizer was applied, the higher ratio of tagged nitrogen in the laminae to that of the whole plant was there at the ear emergence, and the lower ratio of tagged nitrogen in the cars to that of the whole plant was there at maturilty.