Abstract: An in situ field experiment combined with the brilliant blue staining tracer was conducted to study the distribution of soil nutrients and its response mechanism to fertilization and straw return under no fertilization (CK), conventional chemical fertilizer (T₁), NPK reduction plus straw return (T₂), and NPK reduction with straw return and organic manure (T₃) in maize croplands in black soil region of Northeast China. The results showed that compared with CK, the treatments with fertilization and/or straw return significantly increased maize yield. There was no significant difference in total nutrient content of plough layer among different treatments. Treatment T₁ increased soil nitrate content of at the 40-80 cm layer, while  T₃ increased available K content of in 0-100 cm soil layers and nitrate content in 0-40 cm and 80-100 cm soil layers. There was no significant difference in soil matrix flow among different treatments. Organic manure and straw return affected soil preferential flow, but without difference among the three fertilization treatments. Application of organic manure can promote the increase of soil porosity and the formation of preferential flow, facilitating the vertical transport of soil nutrients.

Key words: fertilization practice, straw return, profile distribution of nutrient, brilliant blue staining tracer.