Shandong, China, has a dry spring and rainy summer. In Linyi district, for example, mean annual rainfall is 872-949 mm, of which 125-150 mm (15%) occur in spring and 560-600 mm (65%) in summer. Because of waterlogging in the wet summer period, grain yields of rainfed crops such as maize, soybean, or sweet potato were often poor in low-lying farming regions. When rice was dry-seeded late in spring after fall wheat, the medium-duration rice varieties could not ripen because of the shortened growing period. It was difficult to grow rice seedlings because of the lack of water in spring. Therefore, only a fall wheat crop could be grown in the region.