Effects of soil tillage and weed control on weed species composition and winter wheat yield in North China

Field experiments were conducted during 2008–2009 and 2009–2010 winter wheat growing seasons to examine the effect of five tillage systems: zero tillage (Z), harrow tillage (H), rotary tillage (R), subsoil tillage (S), and conventional tillage (C) and two weed managements: weedy treatment (W) and weed controlled by herbcide treatment (C) on weed species composition and winter wheat grain yield. Dominant weed species included Descuminia sophia (L.) Webb ex and Capsella bursa-pastoris (L.) Medik. Relative weed density and dry weight were greater in W+R treatment than in other treatments in 2009 and 2010. At winter wheat heading stage, weed dry weight was reduced by 88% (2009) and 61% (2010) in weed control treatments compared to weedy treatments. Maximum weed control efficiency (WCE) in weed control treatments ranged 96–98% for zero tillage, harrow tillage, and rotary tillage in 2009, and rotary tillage in 2010, compared to conventional tillage. Winter wheat grain yield in weedy treatments was 13% (2009) and 20% (2010) lower than those in weed control treatments. Winter wheat grain yield in C+S treatment was greater than in the other four weed control treatments. Winter wheat yield in C+R was highest whereas C+C had the lowest yield among the five tillage treatments. Under different soil tillage systems, the species, density, relative density, dry matter, and WCE of weeds were changed differently. Among the 5 soil tillage systems, harrow and rotary were relatively superior to other treatments for weed control. As a whole, weedy treatment had a negative effect on winter wheat grain yield, which is the indirect reason.