Yellow loessial soils are infant soils developed on lossial material,without distinct development of genetic horizons and aonal characteristics of profile.The soils are similar to their parent material.The profile pattern is mainly composed of horizons of A_p-C or A-C.Based the diegnostic horizon and profile,the soils are divided into two subgroups,i.e.primary yellow cultivated loessial soils and Lightly yellow cultivated lossial soil.Based on the hydrothermal regimes of the soil in crop growing season (April to Sept.),the soils are subdivided into such soil families as warm-moist,warm-irrigated,warm-wet,warm-dry,cool-moist yellow cultivated lossial soils etc.Based on the texture and O.M.content,the soils are further subdivided into 28 soil species.The soil are mainly distributed in northern Shaanxi with an altitude of lower then 1200 m.