Study On The Impacts Of Tillage Methods On The Weed Communities And The Soil Physicochemical Properties In A Winter Wheat-summer Maize Rotation Farmland

Conservation tillage,marked by no-tillage,reduced tillage and straw mulching,is a new tillage methods widely applied in agricultural production in recent years.The change of tillage methods would not only affect on the crop yield but also cause the variation of farmland ecological environment.Therefore,to explore the impact of conservation tillage on farmland ecological environment becomes a hot issue in modern ecological agriculture.In this study,one wheat-maize rotation field locating in Jinan city,Shandong province,was selected as the studying site.The different tillage methods(rotary tillage,deep tillage,no-tillage)have been carried out for 4 years.Influence caused by the tillage methods on weed community characteristics,density of seed bank,vertical distribution and the soil physicochemical properties were studied.The main content includes the following aspects:During the study of the impacts of different tillage methods on weed community,the influence caused by the tillage methods on weed density,weed community characteristics and weed biomass were studied.As the results shows,there were 15 species in the weed communities in the test filed.Digitaria sanguinalis was the dominat species,which occupied the highest weed density of 72.3%.All three indexes of the community species richness,the community diversity and the community evenness were the highest,however the community dominance index was the lowest in the plot under no-tillage.In terms of weed biomass,the plots under no-tillage had significantly higher weed biomass,than those under rotray tillage and deep tillage in the four times community investigation.During the study of the impacts of different tillage methods on weed seed bank,the influence caused by the tillage methods on weed seed density,weed seed bank in0-15 cm vertical distribution of soil layer were studied.As the results shows,there were7 main species in the weed seed bank in the test,among which Digitaria sanguinalis,Echinochloa crusgalli and Setaria viridis became dominant species in different seasons.The change of total weed seed bank density was not obvious between two years,grew just by 6.3%.Compared with the plot under rotray tillage and deep tillge,the seed density of the weed seed bank was the highest in the plot under no-tillage.Meanwhile,the proportion of dominant species in weed seed bank was the lowest.Spring andautumn were the peak season of weed seeds.Weed seeds mainly gathered in the upper soil layer(0-7.5 cm)under the no-tillage.By contrast,rotary tillage led to the weed seeds gethered in the deeper soil layer(7.5-15 cm),deep tillage had no impact on vertical distribution of weed seed bank.During the study of the impacts of different tillage methods on the soil physicochemical properties,the influence caused by the tillage methods on moisture content,bulk density,porosity and SOC in 0-15 cm soil layer were studied.As the results shows,all of the average moisture content,bulk density,porosity and SOC in0-15 cm soil layer under no-tillage were higher than rotray tillage and deep tillage.No-tillage would lead to a significant difference between the upper and deeper soil layer in moisture content,porosity and SOC.Rotray tillage would lead to a significant difference between the upper and deeper soil layer in bulk density.Deep tillage would lead to a significant difference between the upper and deeper soil layer in SOC.