Effects Of Nitrogen-fixing Cyanobacteria And Endophytic Bacteria SM13 On Rice Seedling Quality And Yield

The increasing requirement for high rice yields is an inevitable trend accompanied with population growth.Increasing amount of chemical fertilizers for increasing rice yield will lead to aggravate ecological environmental pollution and restrict the sustainable development of agriculture.The development and application of microbial fertilizers is one of the important ways to relieve the contradiction between crop nutrition demand and chemical fertilizer pollution.A group of nitrogen-fixing cyanobacteria and a strain of rice root Promoting-Growth bacteria SM13 were screened in our laboratory.Both of them have the potential to improve the yield of rice.In order to clarify the effects of nitrogen-fixing cyanobacteria and SM13 on the quality,yield and quality of rice seedlings,seedling experiment,pot experiment and field experiment were carried out.Single factor experiment design was used,Kenjing 8 and Longyang 19 as tested varieties,treatments were set up: the application of only nitrogen-fixing cyanobacteria(LZ),the application of only endophytic bacteria SM13(SM),mixed application of both LZ and SM13(SL)and application of water control(CK).The effects of the two microbial inoculums on rice seedling quality,yield,quality,photosynthetic material production characteristics and soil microbial diversity were studied comprehensively.To provide a theoretical basis for the application of microbial fertilizer in fertilizer reduction and farmland ecological protection.The main results contents are as follows:1.At the two-leaf and one-heart stage,compared to CK,LZ significantly increased seedling fullnessand dry matter weight aboveground;SM significantly increased stem base width,dry matter belowground weight,seedling strength index,R/S and root length;SL significantly increased dry matter aboveground weight,total dry matter weight and fullness.At the three-leaf and one-heart stage,compared with CK,LZ significantly increased plant height,stem base width,dry matter aboveground weigh,dry matter belowground weight,total dry matter weight,seedling strength index,root length,root connections,root nodes and root bifurcation.SM significantly increased stem width,dry matter aboveground weight,dry matter belowground weight,total dry matter weight,seedling strength index,root length,root connections,root nodes,root tips and root bifurcations;SL significantly increased stem base width,dry matter aboveground weight,dry matter belowground weight,total dry matter weigh,fullness,seedling strength index,root shoot ratio,root length,number of root connections,number of root nodes and number of root bifurcations.2.The yield of potted plants showed SM>LZ>SL>CK,and the theoretical increased by3.22%～6.14%,respectively,but there was no significant difference compared with CK.Rice quality analysis,compared with CK,SM could improve the processing quality;SL can reduce appearance quality;l Z,SM and SL all decreased the protein content of brown rice;no significant effect of different treatments on taste quality.The investigation of rice growth and development showed that compared with CK,the application of two microbioal inoculums could promote the increase of plant height and total tiller number of rice.The dry matter weight of LZ,SM and SL at maximum tillering stage and filling stage increased by 19.91%,18.33%,18.1% and 21.11%,15.65%,15.88%,respectively.The effective leaf area and total leaf area of LZ at filling stage increased by 17.5% and 20.87%,respectively.The total leaf area of SM at full heading stage increased by 12.77%.LZ could significantly reduce the transpiration rate at full heading stage,stomatal conductance and transpiration rate at filling stage,which was conducive to improving water use efficiency of plants.In the analysis of soil characteristics,compared with CK,LZ could significantly increase the soil phosphatase activity at full heading stage,reduce the soil sucrase activity at filling stage,reduce the bacterial abundance of Rhodanobacter(sensitive to soil p H)and Bryobacter(improving soil properties and enhancing plant resistance),and increase the abundance of Sulfurivermis(nitrogen fixation and carbon fixation ability).SM could significantly reduce the invertase activity in the soil at the filling stage,increase the abundance of Nocardioides(soil bioremediation and inhibition of pathogen growth),and reduce the abundance of Cylindrocarpon(plant pathogenic bacteria).SL can significantly reduce the soil invertase activity at tillering and filling stages,and reduce the abundance of Rhodanobacter and Cylindrocarpon;correlation analysis showed that phosphatase and dehydrogenase at full heading stage and dehydrogenase at filling stage were the key to yield change.3.Compared to CK,the theoretical yield of SM,LZ and SL increased by 9.41%,7.35% and4.94% respectively,and the actual yield of SM and LZ increased by 8.58% and 8.34%respectively.In quality analysis,the application of two inoculums had no significant effect on processing quality;LZ can reduce appearance quality;LZ significantly reduced protein content in brown rice;each treatment had no significant effect on taste quality.In rice growth and development,SM significantly increased total leaf area index by 30.45% at maximum tillering stage,SL significantly increased total leaf area index and dry matter weight by 45.92% and23.83% at full heading stage,and LZ significantly increased dry matter weight by 27.21% at filling stage.In conclusion,the application of nitrogen-fixing cyanobacteria and endophytic bacteria SM13 can significantly improve the quality of rice seedlings,promote rice yield,help to increase dry matter accumulation and leaf area of rice,and have a certain impact on rice nutrition and appearance quality.The effect of single endophytic bacteria SM13 is better than that of other treatments.