Effects Of Microbial Agents On Soil Properties And Plant Physiology Under Stress Conditions

Soil microbial properties can be used as the most sensitive and potential indicator for evaluating changes in soil quality and fertility.Plant resistance can reflect the ability of plants to resist damage under adversity conditions.In order to reveal the effects of microbial agents on soil properties and plant physiological characteristics under stress conditions,Medicago sativa L.was used as the test plant,the soil of the Haizhou open-pit dump field was used as the substrate,under the conditions of separate application of Trichoderma harzianum rifai,Bacillus subtilis and mixed application of two microbial inoculants,pot experiment methods were used to study different gradients of drought,salinity and heavy metal stress to determine their soil microbial properties and plant leaf resistance.Research indicated:(1)As the degree of drought stress increased,soil microbial properties gradually weakened.The application of the three microbial agents generally had a promotive effect on improving the soil microbial properties.According to the comprehensive index of each soil index determined,the effect of applying Bacillus subtilis alone was the best.The content of plant proline,plant soluble sugar,and plant malondialdehyde increased with the increase of drought;the activity of plant antioxidant enzymes showed a trend of first increasing and then decreasing.It could be seen from the comprehensive index of plant resistance indicators that the application of microbial agents could further improve the resistance of plants,and the application of Bacillus subtilis alone was more conducive to improving the resistance of plants than other treatments.(2)The soil microbial indicators generally decreased with the increase of salt stress,and the various soil microbial indicators of the application of microbial agents were higher than CK.Under no salt stress,the effect of single application of two microbial agents on improving soil comprehensive index was the same,and both were the best;under mild stress,single application of Trichoderma harzianum rifai had good effect;under moderate stress,single application of fungus was effective best;and under severe stress,the effect of applying Bacillus subtilis alone was better.The changing trend of plant resistance indexes under salt stress was basically the same as that under drought stress.From the comprehensive plant indexes under salt stress,it could be seen that the mixed application of two microbial agents had the best effect on improving plant resistance.(3)Under heavy metal Cd stress,the soil microbial properties were lower than those of no heavy metal stress.Under heavy metal Cd stress,the effect of mixed use of microbial agents was better than single application;under no stress,single microbial agents were better than mixed application.The application of microbial agents could reduce the content of plant proline,soluble sugar and malondialdehyde,and increased the content and activity of plant antioxidant enzymes.The mixed application of two microbial agents had the best effect on improving plant resistance when Cd stress was present.