Effect of Deep tillage before winter coming on vertical distribution of root activity and senescence of flag leaf in wheat plant

P-tracing method was used to investigate the effect of deep tillage (cut off some roots) before winter coming on the vertical distribution of root activity and senescence of flag leaf in wheat plant from 1996 to 1998.The result shows that deep tillage (cut off some roots) can improve the mass root activity significantly at late development stage,and increase root activity remarkably in deeper soil horizon, which leads to delayed senescence of plant organs above ground and increases in grain yield.