The effects of low N fertilizer on grain filling and yield in shennong 702 were studid through source-sink adjustment experiment of cutting leaves and glume flowers. The results were as follows: the yield was a little lower in low N fertilizer then in average N fertilizer, it showed tolerance of low N fertilizer. Low N fertilizer treatment made the export rate of stem and leaf sheath decrease a little. When the source was short, grain filling was delayed. When the sink was lack, grain filling was accelerated. Grain filling in Shennong702 was synchronous in average N fertilizer, so it was sink limiting type. Grain filling was asynchronous in low N fertilizer, so it was source limiting type. According to these results, we can ease up the conflict between source and sink, decrease environment pollution and improve production through adjust the level of N fertilizer.
