Abstract:A long-term field experiment was conducted for 19 years to investigate the effects of chemical fertilizer and wheat straw return on soil fertility and quality of grain under the condition of wheat-wheat continuous rotation on castanozems soil in Hehuang irrigation region of Qinghai province. The results show that compared with the control treatment, soil bulk densities and soil water contents are decreased by 1.2%–7.1% and 4.7%–13.5% under the N and P chemical fertilization combined with potash addition fertilization and/or straw return treatments, and the contents of soil water-stable aggregate (>0.25mm) are increased and stability of soil aggregate is improved. Regard to improving soil physical properties, the straw return is superior to the chemical N, P and K fertilization. The light fraction of soil organic matter, soil total organic matter, soil N, P and K contents are increased as well, especially soil available K content which reaches to 279.5mg/kg in the NPK+100%ST treatment and is about 2.6 times of the control treatment. The yield of spring wheat is also increased under the chemical N, P and K fertilization treatment combined with straw and chemical fertilizer. On base of the N and P fertilization, straw return and/or potash addition treatments except for the NPK+100%ST treatment improve protein content of wheat seed and have no negative effects on grain quality. Conclusions: suitable amounts of potash and/or straw application with chemical N and P fertilization can improve soil fertility and spring wheat yield and quality, and half amount of straw return can replace potash application in local agricultural practice.