Three-River-Plain is a typical dry farming agricultural region.Investigation shows that solum structure pattern is:internal factor of drought and waterlogging resistance of soils.The difference in drough and waterlogging resistibility of the solum patterns depends on presence or absence of block soil layer in the soil profile of 0-100 cm.In the soil without block soil layer,the capacity of water storage and supply is higher,the drought and waterlogging resistibility of the soil and crop yield are generally high and stable.In the soil with block soil layer,the drought and waterlogging resistibility varies with the depth of block soil layer in profile and its properties.With well development of block soil layer,the soils of Three-River-Plain belong to those of the pooz solum pattern which are unfavorable for resistance of drought and waterlogging of the soil.It is of practical significance to improve these soils with proper measures in combination with reasonable management of water for the control and regulation of soil water and the alleviation of disaster of drought and waterlogging and the ncrease of cmp yield.