Terracing is one rational way to use slopeland in this humid subtropical region. In certain parts of this region the land is less productive, as in the many deeply dissected gullies where paddy fields suffer from waterlogging by underground cold springs, which reduces soil temperatures for rice plants and inhibits the aeration needed for their root development. In Yunnan and Guizhou Provinces and the Guangxi Zhuang Autonomous Region, limestone areas totalling about 400,000 km have been highly weathered and leached under the prevailing humid tropical conditions. Three types of karst landform are recognized in those regions. First are ridges and depressions characterized by round depressions distributed among high ridges and bare limestone outcrops.
Surface water is scarce and the watertable deep.
Rendzina and terra rossa, in the depressions, are the main soil types. They are characterized by a relatively thin solum and are used mainly to raise dry farming crops such as maize and beans. The problem of drought is quite severe and this type of land generally has a low productivity. Maize, beans and sorghum are raised in the valleys, and the steeply sloping pillars are either forested, or planted with tung oil trees or bamboo. Sheep and goats are grazed on the shallower slopes.