Experimental Study On The Improvement Of Pisha Sandstone By Microbial Flora And Plants

With the rapid development of China's economy and urbanization,environmental problems such as water pollution,soil desertification and soil erosion become increasingly prominent.A series of engineering and biological measures have been carried out for soil erosion control and ecological restoration in Pisha sandstone area of the Yellow River Basin,but there are many limitations and difficulties to overcome.As one of the important ways of soil and rock improvement,microbial measures have a certain application potential in soil improvement and vegetation restoration in Pisha sandstone area.In this paper,functional strains were used as the research object to prepare microbial agents and investigate the effects on the soil properties of Pisha sandstone and the plant growth under the joint action of microorganisms and plants,so as to provide experimental reference for the application of microbial measures in the improvement of Pisha sandstone.In this paper,12 strains of Bacillus were isolated from Pisha sandstone,coal mine reclaimed soil and Alfalfa root samples.All of them have the ability of producing indoleacetic acid and siderophore and have certain plant growth promoting characteristics,meanwhile they can produce biofilm for good resistance.The effects of these 12 Bacillus strains on soil properties and plant growth in the environment of Pisha sandstone were studied.The results showed that all the 12 Bacillus strains could affect the soil properties of Pisha sandstone to a certain extent and promote the growth of plants.Among them,Bacillus sp.P75 could increase the organic matter content of Pisha sandstone soil by 24.7%,the available phosphorus content by 11.9%,the available potassium content by 21.0%,the invertase activity by 58.8%,and promote the growth of Alfalfa and Ryegrass effectively.According to the ability of 12 Bacillus strains to produce indoleacetic acid,siderophore and biofilm,and their effects on the soil properties of Pisha sandstone soil and the plant growth,Bacillus sp.P75 was selected as the target functional strain.According to the results of 16 S r RNA gene sequence analysis,the strain P75 belongs to the Bacillus halolerans.In order to improve the Pisha sandstone soil quality and restore the vegetation,it is usually necessary to use a variety of functional bacteria to prepare composite microbial agents.Therefore,Sinorhizobium meliloti D10,Bacillus megaterium H3 and Bacillus subtilis HB01 were introduced after systematic investigation,and they were prepared into a variety of microbial agents with the Bacillus halolerans P75,and then mixed with Pisha sandstone to study the effects of microbial agents on the soil properties of Pisha sandstone and the growth of plant seedlings.The results showed that the soil properties of Pisha sandstone were improved and the growth of Alfalfa seedlings was promoted by the microbial agents,and the microbial agent A4 containing strains P75,D10,H3 and HB01 had the best effect.A pot experiment of Alfalfa,Ryegrass and Caragana was carried out by using the mixture of microbial agent A4 and Pisha sandstone as soil matrix.The effects of the combination of bacteria and plants on the improvement of Pisha sandstone was studied,and the mechanism of soil improvement was discussed.The results showed that the combined action of complex bacteria and plants could reduce the alkalinity of the soil,increase the content of soil organic matter,alkali hydrolyzed nitrogen,available phosphorus and available potassium to a certain extent,enhance the activities of soil invertase and urease,increase the number of soil bacteria and the water stability of soil agglomerates,improve the nutritional conditions and structural composition of the Pisha sandstone soil,thus promoted the growth of Alfalfa,Ryegrass and Caragana.In addition,through high-throughput sequencing technology,the dominant microflora of Pisha sandstone soil were Proteobacteria,Bacteroidetes,Actinobacteria and Firmicutes,etc.Adding microbial agents could significantly change the diversity and compositon of soil bacterial community,such as the abundance of Bacteroidetes and Firmicutes was significantly increased in treatment groups.However,the effects of different plants and microorganisms on the soil properties and bacterial community composition was different,and the growth of different plants was also different,which showed that the interaction relationship between microorganisms and different plants in the environment of Pisha sandstone was obviously different.