Abstract: Combined application of organic and chemical fertilioers to soils at different fertilily levels in the suburbs of Beijing resulted in the highest yield for wheat.Then the yield at the medium一and high一fertility test fields was higher.than that at low-Icrtility test liclds.The feet of increasing yield resulting from the combined application of the both types of fcrtiliicrs was equal to the sum of separate effects of the organic and mineral fertiliocrs in increase of yield, and no signilicant interaction was found between the two types of Icrtilicrs, but in soils at higher fcrtiiity levels negative interaction was }bscrvcd.On the basis of the fcrtilr expcrinvents, combined application rates of organic and mineral Icrtiliocrs for wheat which was grown in soil at different Icrtility levels in the suburbs of I3cijing were proposed.It was lound that N application rate increased and P application rate decreased in the soil wish low fertility to which the organic manurcs were applied, that N application rate decreased and P applica-lion rate increased as organic manurcs were applied to high-fertility soils; and that NP applicanon rates would increase to the medium一fertility soils, if the organic manurcs were applied to it combined with them.M15

Key words: Organic manurcs, Chemical fertilizen, Intcraction