Effects of nitrogen fertilizer rates on uptake and distribution of nitrogen in ratoon rice

The effects of N fertilizer rates on uptake and distribution of N in ratoon rice were .studied. The results showed that the relationship between N uptake and its recovery rate with nitrogen application rates for promoting bud and tiller in main rice and its ratoon crop was a parabola curve. After nitrogen fertilizer was applied, the amount of N uptake decreased with the growing of crops. About 1/3 of N uptake from the nitrogen fertilizer applied to promote bud and tiller was deposited in the main rice stubbie. The total amount of N accumulated in the stubble was closely related to nitrogen application promoting bud and tiller, the relationship exhibited a parabola curve. The nitrogen source in the stubble of main rice was gradually transported to the tillers of ratoon crop after main rice was harvested,it played a great role in bud sprouting and tiller growing. N accumulation in the leaves and stem-sheath of ratoon rice increased with nitrogen application rate enhanced, a large amounts of N in the parts of ratoon rice were transported to the panicles after full heading. The apparent transportation rate was 57% -76% in consideration of N translocation from the stubble of main rice,. This indicated that the nitrogen transported from the stubble and the other parts including leaves and stem-sheath was the main nitrogen source deposited in grains of ratoon rice. The grain yield of ratoon crop had parabola correlation with the nitrogen application rate for promoting bud and tiller. The grain yield of ratoon crop up to 241. 3 kg· hm-2 was the highest.