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Li Y. Z.1 and Y. M. Huang2
1: Fujian Academy of Agricultural Sciences. 350003. Fujian,
China
2: Xiamen International Trade Group. 361004. Xiamen, China
Rice is the largest area cereal crop cultivated in China. About 60% of Chinese population use rice for main staple food. The bumper harvest or bad harvest of rice affects the national economy and the people's live hood strikingly.
The rice distribution in China
The rice distribution in China is divided into 6 districts. About 91% of rice cultivation area is distributed in the 3 districts of southern China: I. Double rice crop district of southern China (amounting for 16% of total rice cultivation area in China); II. Single and double rice crop district of southern China (amounting for 68%); III. Single rice crop in plateau of south-western China, which is belong to tropic and subtropical zone with the mountain hilly land and flatland crisscrossed together. For lack of water resource, the 3 rice districts in northern China is small in area and scattered. For being brought under cultivation in the last ten years and more, the rice cultivation area in the early ripe single rice cultivation district of north-eastern China has increased to 6% of the total area in China.
The current situation of rice production China
There are about 22 x 106hm2 paddy rice field in China. The rice growing area is about 30.2 x 106hm2, with average grain yield 5.9 t/hm2 and 178 x 106t in total, which was accounted to 34.0% of total rice production in the world, 39.5% of total cereal production in China. The single rice crop yield in large area of sea land in Liaoning of north-eastern China and Yinchuan of Ningxia of north-western China have arrived to 9-10 t/hm2. The average yield of double rice crop in 4 counties of Guangdong and Fujian province of south-eastern China have arrived to 15 t/hm2. The super high yielding of 16.64 t/hm2 from single rice crop in plateau of Dali, Yunnan province has been got. But for the poor water conservancy facilities and unproductive soil, about 1/3 of rice grain yield in China is only 3-4 t/hm2.
Last 20 years, a great achievement of rice cultivation in China is breeding indica-indica hybrid rice and cultivating it in large scale. In 1996 year, hybrid rice was cultivated about 13.6 x 106hm2, accounted to 45% of total rice area in China. Hybrid rice usually can yield grain 1 t/hm2 higher than that of general rice variety can do.
The importance of rice root research
There are two type low yielding paddy soil in China. One is yellow paddy soil developed from red earth, yellow earth and brown yellow earth soil distributed in mountain area and sloping field of hills with thin plough layer, low organic matter and nutrient content, which inhibits root extended. The other is gleyed paddy soil with year-long submergence, cool, rotten and strong reduce, which was toxin to root growth. The gleyed paddy soils are distributed in mountain valleys, lake side lowland and low-lying plains. In the alluvial plain lying in coastal delta and along large river and lake, the paddy soil is fertile and with density river net which is high yielding rice production area. But a part of which is with poor drainage system or long-time submergence and not reasonable fertilized. The rice root do not develop well, the grain yield only in the level of 6-7 t/hm2. The table 1 is the data of rice root morphology measured from different eco-condition of Fujian for years. The results showed that the rice grain yield is highly positive interrelated to root development.
Consequently, researching rice high yielding system with improving root and regulating root development effectively showed great significance increasing grain yield for low producing area or for high producing area.
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