China contributes a large part to rice production, one of the most important crops in the world. It is estimated that in China rice constitutes about half of the total food production, covering an area of about 30 % of \08 hectares of cultivated land of the whole country. Owing to the peculiar water regime, paddy soils possess quite different properties physically, chemically and biologically as compared with those of upland soils. Such properties have a conspicuous effect on fertility and management practice of paddy field. For the purpose of summing up the past work and opening up new prospects, a "Symposium on Paddy Soils" was organized under the auspices of Academia Sinica, held on October 19-24, 1980 in Nanjing, which was followed by a seven-day paddy soil excursion in the lower Changjiang Delta. In addition to 120 Chinese soil scientists, 56 guests coming from America, Asia, Europe and Oceania attended the symposium on invitation. A total of 110 papers were presented either orally or by poster. All these are collected and published in the present proceedings which we hope may be helpful to the scientific exchanges between soil scientists of China and other countries.

International networks; Varietal improvement; Soil, crop, and water management; Pest management; Technology transfer.

Revised and updated selected papers from the 1992 International Rice Research Conference.

The key to sustaining the soil resource base is to maintain, or enhance, soil quality. Soil quality cannot be seen or measured directly from the soil alone but is inferred from soil characteristics and soil behavior under defined conditions. In essence, the quality of soils is analogous to the health of humans, and just as there is no single characteristic that can be measured to quantify a person's health, there is no single measurement that can quantify soil quality. However, there are certain characteristics, particularly when considered together, that are good indicators. Soil quality, just as human health, can be maintained or enhanced by good management practices; and seriously degraded-sometimes irrevers ibly-with poor practices. Soil quality is also important because it has direct and indirect effects on air quality and water quality. While the enhancement of soil quality does not always assure parallel improvements in the quality of air and, particularly, water resources, this is often the case. However, soil deg radation is invariably accompanied by degraded qualities of both air and water resources. The consensus among many scientists is that the greatest challenge is not increasing production, but preventing serious deterioration of the soil and water resource base so that the production level can be sustained.