Effects of soil tillage and straw returning on weed biodiversity in summer maize (Zea mays) field

To investigate the effects of different soil tillage methods on weed density,dominant species,bio-diversity indices and yield of summer maize,the experiment was conducted using a summer maize cultivar Zhengdan 958 in 2008 growing season at the Agronomy Station of Shandong Agricultural University.The five soil tillage methods were zero-tillage,rotary-tillage,harrow-tillage,subsoil-tillage,and conventional tillage,respectively.All these soil tillage methods were conducted from 2003 to 2008.A total of 13 weed species were recorded in this investigation.Under the conditions of total crop straw returned,zero-tillage could significantly(LSD,P0.05)increase the weed diversity;In contrast,under the conditions of no crop straw returned,the weed diversity in conventional tillage was much higher than those in zero-tillage,rotary tilling,plowing and raking,and sub soiling,respectively.After total crop straw returned,the weed dominant species in no-tillage and subsoil-tillage were Ditaria sanguinalis(L.)Scop.and Echinochloa hispidula(Retz.)Nees,respectively;in rotary-tillage tilling and harrow-tillage were Ditaria sanguinalis(L.)Scop.,Echinochloa hispidula(Retz.)Nees,and Eleusine indica(L.)Gaertn,respectively;in conventional tillage were Ditaria sanguinalis(L.)Scop.,Abutilon theophrasti Medic.,Echinochloa hispidula(Retz.)Nees,and Cyperus rotundus L.,respectively.Under the conditions of no crop straw returned,the weed dominant species in zero-tillage and conventional tillage were enhanced.Under the conditions of total crop straw returned,zerotillage,harrowtillage,and subsoiltillage could increase species richness and evenness of weed community.The results revealed that long term crop straw returned could significantly(LSD,P0.05)increase the summer maize yield and the weed biomass,especially under the conditions of conventional tillage.The weed biomass above the ground surface was negative correlated with the summer maize.