Effects Of Glyphosate On Soil Ecological Functions In Soybean Fields

Soil ecosystem consists of inanimate and animate materials,and the energy flow,material circulation and information transfer within the system together constitute the main functions of the ecosystem.When chemical pesticides enter the soil,they inevitably have an impact on soil ecological functions.Soybean is an important grain-cum-oil crop,and GM glyphosate-resistant soybeans are widely grown worldwide,and glyphosate has been used in production in large quantities for a long time.Exploring the effects of glyphosate application on soil ecological functions in soybean fields can provide basic data for the safe cultivation of GM glyphosate-resistant soybean.In this study,we used transgenic glyphosate-resistant soybean,Hujiao 06-698,and its recipient soybean,Mengdou 12,as research objects,and used a multi-year field locus test method to investigate the effects of glyphosate application on soil ecological functions at the same location of transgenic glyphosate-resistant soybean fields for three consecutive years,with a view to providing a theoretical basis for the sustainable use of farmland ecosystems and the safe commercial application of transgenic glyphosate-resistant soybean.The main findings were as follows.(1)Different glyphosate dosages were significantly negatively correlated with the amount of year-to-year variation in soil catalase and phosphatase activities,and significantly positively correlated with the amount of year-to-year variation in soil urease and cellulase activities.(2)Soil fast-acting potassium content was not affected by glyphosate,soil alkaline nitrogen and fast-acting phosphorus content were significantly reduced,soil catalase activity was significantly increased,and urease,cellulase,phosphatase and root nitrogen fixing enzyme activities were significantly reduced.(3)Soil urease was significantly and positively correlated with soybean rhizosphere nitrogen fixation enzyme activity;phosphatase was significantly and negatively correlated with fast-acting phosphorus content,in addition to peroxidase and cellulase activities;peroxidase activity was significantly and negatively correlated with fast-acting phosphorus content;cellulase activity was significantly and positively correlated with fast-acting potassium content;soybean rhizosphere nitrogen fixation enzyme was significantly and negatively correlated with fast-acting phosphorus content.(4)The optimum glyphosate concentration was 2.4 kg a.i./hm2 on soil N,P and K nutrients and their functional enzyme activities.(5)Glyphosate had no significant effect on the abundance,evenness index,Shannon index,and dominance index of arthropod communities of glyphosate-resistant transgenic soybean Hujiao06-698 step beetle,tiger beetle,spotted sheath bean leaf beetle,and golden turtle.There was no significant correlation between different glyphosate dosages and arthropod community indices in soybean fields.(6)Glyphosate reduced the number and density of weed occurrence in transgenic soybean fields,but did not destroy the diversity of weeds in the fields.