The movement characteristics of three kinds of weed seeds in ploughed layer of corn field

The movement characteristics of redroot amaranth(amaranthus retroflexus),common crabgrass(digitaria sanguinalis),barnyardgrass(echinochloa crusgalli) in ploughed layer of corn field are studied. The results show that weed seeds are mainly distributed in 0～20cm ploughed layer of corn field and most weed seeds are in 0～5cm soil layer. However,weed seeds are distributed in 0～5cm surface layer,and a few weed seeds in 5cm soil layer downwards founded. ploughing is one of driving force which made the weed seeds to move upwards and downwsrds in the ploughed layer. After ploughing,about 30 percent of the seed on soil surface is moved down to the bottom of the ploughed layer and about 10 percent of them on the bottom moved up to the surface.