Weed infestation of soybean (Glycine max L. Merr.) under different tillage systems

Direct drilling is one of the methods to reduce tillage costs. Low labor intensity of this system also makes it possible to grow crops in locations where it is a problem to maintain optimal sowing time. However, the use of no-tillage can cause increased weed infestation of crop plants and as a consequence a decline in crop yields. The present study investigated the effect of two tillage systems, plough tillage and direct drilling, on the species composition, density and air-dry weight of weeds in crops of two soybean cultivars (‘Aldana’ and ‘Augusta’). A three-year field experiment was set up on loess-derived gray-brown podzolic soil. The study showed that the use of direct drilling for soybean cropping resulted in a significant increase in the density and dry weight of weeds relative to plough tillage. The study also found richer floristic composition of weeds and an increase in the numbers of dominant species under no-tillage conditions. Elymus repens , Echinochloa crus-galli and Chenopodium album were dominant weed species in all experimental treatments. Chenopodium album and Galinsoga parviflora were characterized by the highest constancy (constancy classes V and IV) in crops of both soybean cultivars, whereas Echinochloa crus-galli showed the highest constancy value in the ‘Aldana’ crop. Under direct drilling, most weed species were found to exhibit higher constancy compared to plough tillage.