To explore the effect of returning crop straw to the field structure improvement. In this experiment

we adopted in two factor split plot design that of main factor fertilization (F): F1 (NPK compound fertilizer)

F0 (no fertilizer); and that of the auxiliary factor crops (B): B1 (rape)

B2 (corn)

B3 (potato)

B4 (oats)

B5 (buckwheat). Unplanted and without fertilization used as the control (CK). We measured several parameters that of soil bulk density

porosity

capillary porosity

field water holding capacity

aggregate size and MWD

GMD

D values. The results showed that straw mulching of 5 crops reduced soil bulk density

increased capillary porosity and field water retention in 0—60 cm soil layer

and 20—60 cm soil layer was the main improvement. At the same time

the content of soil >0.25 mm granular aggregates was increased

and the MWD and GMD values of aggregates in the 0—20 cm soil layer were increased

while the D values were decreased and the stability was increased. When straw was returned to the field with chemical fertilizer

the content of >0.25 mm granular aggregates in 0—60 cm soil decreased

MWD and GMD values decreased

and D values increased

and the stability decreased. We confirmed that rape straw returned treatment would improving soil density

porosity

filed water-holding capacity and aggregate stability

buckwheat straw returned treatment would increasing filed water-holding capacity

oat straw returned treatment would increasing soil aggregate stability. We concluded that returning crop straw to field would improving the soil structure and achieved different effects to differ crop types. In general

the rape straw returning to field is better improvement for soil structure.