| Long-term use of reclaimed water irrigation may increase soil salinity.Bacillus subtilis can secrete metabolites that promote plant growth and prevent pathogen infection,which help bacteria survive in harsh environmental conditions;Soil yeasts are conducive to mineralization of organic matter and dissipation of carbon and energy,and have the ability to dissolve insoluble phosphate.In this study,pot experiments were carried out in greenhouse for two years（2018 and 2019）,in which shallow water and continuous irrigation（keep 0-5 cm water depth）,the effects of reclaimed water（Z）and fresh water（Q）controlled irrigation on rice reproductive development were compared and analyzed to evaluate the effect of the combination of reclaimed water and controlled irrigation.After 50 days of reclaimed water irrigation,fresh water irrigation was resumed and different proportions of Bacillus subtilis（B）and Saccharomyces cerevisiae（Y）were applied.The qualities of B and Y were 5 g and 0 g（J1）and 3.75 g and 1.25g（J2）,2.50 g and 2.50 g（J3）,1.25g and 3.75g（J4）,0 and 5g（J5）,respectively.B and Y are irrigated with water and no B and Y（J0）was also set.In 2019,two treatments of reclaimed water irrigation:the mass of B and Y are 3.75g and 1.25g（B3Y1）,2.50 g and 2.50 g（B2Y2）,respectively,the effects of the application of B and Y on the physical and chemical properties of soil,microbial diversity and the physiological and biochemical response characteristics of rice were analyzed,and the regulation mechanism of microbial on crop physiology was studied.The main research results are as follows:1)Under controlled irrigation,there was no significant difference in the early stage of plant height under reclaimed water irrigation compared with clear water irrigation,and the difference was between5-13 cm in the middle and later stage.In 2018,the plant height at S21-S41 treated with reclaimed water irrigation was higher than clean water irrigation for nearly 20 days,but with the extension of reclaimed water irrigation time,the plant height and plant height of rice were significantly inhibited.The tiller number of rice under of reclaimed water irrigation increased continuously,especially increased by 36.36%at the end of growth period in 2018;the tiller number of rice under fresh water increased gradually,and exceeded CK at the end of growth period in 2019;under reclaimed water irrigation,the photosynthesis was severely inhibited,and the photosynthetic rate decreased by nearly 50%,but the potential water use efficiency was increased by nearly one time,and the photosynthetic index was lower than that of fresh irrigation.2)Restoration of clear water irrigation could significantly increase plant height,and the increase was greater after adding B.subtilis and S.cerevisiae,and the increase was more obvious in 2018 than in2019;the application of B.subtilis and S.cerevisiae in 2018 can increase of rice tillers within 20 days,but inhibit the production of invalid tillers in the later stage;the application of B.subtilis and S.cerevisiae in 2019 increased rice tillers,but the tillers in the later stage was reduced by 5-10 compared with the J0.The application of B.subtilis and S.cerevisiae was beneficial to increase the dry weight of root,stem and root length of rice at the end of growth period;the application of B.subtilis and S.cerevisiae increased the leaf dry weight within 40 days,but the final leaf dry weight was lower than that of Z treatment;30 days after the application of B.subtilis and S.cerevisiae,the leaf area of rice increased significantly,and J3 treatment increased by 60.02%;the panicle dry weight of rice increased continuously after the restoration of clear water irrigation and application of B.subtilis and S.cerevisiae.B3Y1 treatment increased the stem quality,B2Y2 treatment increased the root,stem and leaf dry weight,but both decreased the ear dry weight.The application of B.subtilis and S.cerevisiae is conducive to increasing rice yield and enhancing lodging resistance.For example,in 2018,the application of B.subtilis and S.cerevisiae can significantly increase the dry matter quality,the number of full grains,the quality of full grains and the quality of 1000 grains of a single spike;In 2019,except for J4 treatment,other treatments all increased bending resistance,bending moment,decreased lodging index and enhanced lodging resistance of rice.Compared with clear water,B3Y1 treatment had a significant improvement effect,while B2Y2 had an inhibition effect.B.subtilis and S.cerevisiae could prolong the rapid dry matter accumulation period and increase the dry matter accumulation rate of rice based on logistic equation.3)The micro environment of soil was optimized by applying B.subtilis and S.cerevisiae.The number of bacteria,actinomycetes,coliforms and coliforms in different soil layers was increased,and the number of fungi was reduced（except J4 treatment in 0-5 cm and 5-15 cm soil layers）.The quantity of Bacillus subtilis in 0-25 cm soil was increased by applying Bacillus subtilis alone,but the quantity of fungi in soil was not increased by applying yeast alone.The application of B.subtilis and S.cerevisiae promoted the increase of redox potential of soil,which increased by 37.34%in J2 treatment at S119;Na+was decreased in soil after the restoration of fresh water irrigation,further decreased by 48.32%and63.46%in 0-5 cm soil layer of J1 and J2 treatment at S127,and K+was decreased at 10 days after the application of B.subtilis and S.cerevisiae.Soil EC was significantly reduced at S127 under B.subtilis and S.cerevisiae treatments.The pH value of soil decreased with the application of B.subtilis and S.cerevisiae for 10-30 days,and increased significantly by 5-25 cm at S127.The application of Bacillus subtilis alone increased 0-25 cm available P,while the application of S.cerevisiae（J4,J5 treatment）decreased 0-25 cm available P,but increased soil organic mass.At the time of harvest,the diversity of soil bacteria did not change significantly,but there were significant differences in bacterial abundance at the class and genus levels among different bacterial agent treatments.For example,in 2018,the Germplasms of J3 treatment decreased by 35.92%,and in 2019,the Alphaproteobacteria of J0 treatment increased by 33.77%;and the composition and functional abundance of soil fine bacteria also changed significantly in two years.Soil NO3--N and available potassium are the main factors influencing soil bacterial structure,organic matter and pH are the main i factors nfluencingsoil bacterial KEGG function abundance.4)The recovery of fresh water irrigation was conducive to the improvement of Chl a,Chl b and carotenoid content,and B.subtilis and S.cerevisiae played an enhanced role,with a large increase in J2,J4 and J5 treatments.The combination of B.subtilis and S.cerevisiae can also promote the increase of chlorophyll in rice.The application of B.subtilis and S.cerevisiae can increase the soluble sugar content of leaves and increase the activity of roots.The activity of superoxide dismutase（SOD）and catalase（CAT）in the leaves at S71 was increased by the application of B.subtilis and S.cerevisiae,especially in J2,J3 and J4.The photosynthetic capacity of rice was restored after the restoration of fresh water irrigation.B.subtilis and S.cerevisiae was more conducive to improving the photosynthetic capacity of rice,and B.subtilis and S.cerevisiae under the reclaimed water irrigation is also conducive to improving the photosynthetic capacity of rice.5)B.subtilis and S.cerevisiae improved the anatomical structure of root tip,basal nodes and leaves of rice,and provided good physiological conditions for the transportation of water and nutrients and the enhancement of photosynthetic capacity.In 2018 and 2019,there were no mass air cavities in the external roots of J0 and J1 treatment,which delayed root senescence.In addition to J4 treatment,the application of B.subtilis and S.cerevisiae increased the internal and external diameter;the application of B.subtilis and S.cerevisiae increased the number of main vein air cavity of leaves,and increased the perimeter and area of small vascular bundles,with the largest increase in J2 treatment.Restoration of fresh water increased the number of large vascular bundles,small vascular bundles and vesicles in the lateral leaves,and the application of fungicides could further promote the number of large vascular bundles in J2,J3,J4 and J5 treatments,but the circumference and area of small vascular bundles decreased;except for J4 treatment,other treatments were beneficial to increase the area of vesicles.It can be seen that the application of B.subtilis and S.cerevisiae improved the anatomical structure of root tip,basal nodes and leaves of rice.In conclusion,the application of B.subtilis and S.cerevisiae can reduce soil EC and pH value,increase soil available phosphorus,available potassium and organic quality,promote the reproduction of soil microorganisms,and effectively alleviate the physiological disorder of rice caused by soil salt stress;they also increase the activity of antioxidant enzymes,photosynthetic rate of rice leaves and the number of the main vein air cavity and the large vascular bundle of the basal stem node,which provide good soil environment and physiological state for dry matter accumulation and yield formation of rice.The results provide a theoretical basis for the regulation of soil microenvironment by B.subtilis and S.cerevisiae. |
