Abstract: The effects of straw chopper on the straw length and inhomogeneity were studied. The vertical distribution characteristics of returning straw among four kinds of mechanical combination treatments were compared. The results showed that the horizontal distribution of straw was more uniform in treatment of the straw chopper. Straw mostly distributed in soil layer of 10 cm to 30 cm, espectivelly 20 cm to 30 cm layer in treatment of hydraulic amplitude modulated reversible plow added straw chopper, the effect of mixing soil was better than others.

Key words: mechines for straw returning to the field, inhomogeneity, vertical distribution, spatial distribution characteristics, effect of mixing soil