Study on the effects cropping systems of continuous corn,corn-soybean and corn-oat-clover,and fertilization on the properties of the soils was made on Morrow plots which are the earliest agronomic experiment station established in 1876 at Urbana,filinois in U.S.A.Continuous cropping of corn decreased the organic matter and total nitrogen contents of the soils by more than 50% and other nutrients in different amounts,and it also decreased the porosity,increased the bulk density and deteriorated the structure and water retention ability of the soils.While rotation of corn and other crops in combination with application of orgynic manure and chemical fertilizers were favorable for the improvement of chemical and physical properties of the soils and growth of crops and the increase of crop yields.