Response Of Drought-Tolerant Cultivar Jinhuang And Its Rhizosphere Nitrogen-Fixing Bacteria To Glyphosate Use

The Inner Mongolia Autonomous Region is located in arid and semi-arid climate area,which is one of the regions with serious desertification in China.Returning farmland to grassland is one of the effective measures to prevent land desertification and protect the ecological environment.Medicago sativa has strong drought tolerance and is a common forage variety for returning farmland to grass in Inner Mongolia Autonomous Region.However,glyphosate is often used in farmland herbicide,and unreasonable use and long degradation time lead to a large amount of glyphosate left in the land.Excessive glyphosate not only affects the normal growth of alfalfa,but also affects the nitrogen fixation capacity and the diversity of nitrogen-fixing microorganisms in the soil.Therefore,high-throughput sequencing technique was used to study the growth of the drought-tolerant cultivar Jinhuang after treatment with different concentrations of glyphosate,the change of soil chemical properties,the nitrogen-fixing microbial community diversity in the rhizosphere soil,the abundance and structure were analyzed,in order to provide a reasonable planting method for returning farmland to grassland.The results of the following research were finally obtained:(1)The results of plant growth index determination showed that the use of glyphosate at high concentration could significantly reduce the height,stem diameter,fresh plant weight and root fresh weight of alfalfa plants,and inhibit the formation of root nodules in the roots of alfalfa plants,and then affecting the normal growth of plants.(2)The effect of high-concentration glyphosate on nitrogen-fixing microbial diversity in rhizosphere soil of alfalfa was much greater than that of inoculation,and the diversity and richness of nitrogen-fixing microorganisms in alfalfa rhizosphere soil samples treated with high concentration glyphosate decreased significantly.The community structure,?-diversity and species difference of these nitrogen-fixing microorganisms were significantly affected.(3)It was found that different concentrations of glyphosate had no significant effect on soil pH,but inoculation of rhizobium could significantly increase the amount of alkaline hydrolyzed nitrogen in soil,and with the increase of glyphosate concentration,the amount of alkali-hydrolyzed nitrogen in soil decreased gradually.Inoculation of rhizobium had no significant effect on the content of available potassium in soil,but the content of available potassium in soil treated with high concentration glyphosate had an increasing trend.At the same time,the content of available phosphorus in soil treated.with high concentration glyphosate increased significantly,but the response of soil organic carbon to inoculation condition and glyphosate use concentration was not significant.