| With the development of agriculture,the proportion of chemical fertilizer in agricultural production is more and more large,soil acidification,hardening and various environmental problems are increasingly serious.Rice is the largest food crop in China,and chemical fertilizer is widely abused in rice fields.Soil physical and chemical properties and microbial community structure are important indicators for evaluating soil quality,which have received extensive attention in recent years.Organic fertilizers contain a large amount of OM and a variety of nutrients.Long-term use of organic fertilizers can significantly improve the soil quality and environmental conditions,but the shortcoming of slow fertilizer effect seriously restricts its development.The use of partial organic fertilizers instead of inorganic fertilizers can make up for the shortcomings of separate application of each other,and has the advantages of environmental friendliness,remarkable effect and easy to be accepted by people.However,the effects of organic replacement fertilization on rice yield,physicochemical indices and microbial community structure in paddy soil are still unclear.The organic alternative fertilization localization experiment started in 2015.The experiment was carried out in a paddy field in Gao 'an,Jiangxi Province,and it was managed according to local conventional rice management methods.In this study,soil samples were collected before late rice harvest in November 2018,and physicochemical characteristics and bacterial communities in the soil were detected,meanwhile,the yield was statistically analyzed.The main results of this study are as follows:(1)Substitution of organic fertilizer with different proportions could significantly affect the physical and chemical characteristics of paddy soil.Soil acidification can be significantly reduced by using a high proportion of organic substitution fertilizer;the application of medium and high proportion of organic substitution fertilizer could significantly increase the contents of total organic nutrients(total nitrogen,total phosphorus,total potassium)and available nutrients(hydrolyzed nitrogen,available phosphorus,available potassium)in soil,the highest improvement effect of organic substitution on OM was 26.56% higher than that of inorganic fertilizer alone,reached 28.02 g/kg;the activity of urease,catalase,acid phosphatase and ?-glucosidase was significantly increased by organic substitution of fertilizer,among them,the activity of ?-glucosidase was enhanced most significantly,the highest value appears in D100,which is 141.76% higher than D0.(2)Substitution of organic fertilizers with different proportions had significant effects on bacterial diversity and community structure.The results of ?-diversity and ?-diversity showed that there was a significant difference in bacterial community diversity between organic fertilizers and chemical fertilizers;The results of difference analysis showed that organic substitution could significantly increase the abundance of Actinobacteria,Firmicutes,Rokubacteria and Gemmatimonadetes;The results of correlation analysis showed that some dominant phyla(Nitrospirae,Actinobacteria and Firmicutes)and dominant genera(Bacillus,Pseudarthrobacter,Aquisphaera)were significantly correlated with fertilization treatment;the results of structural equation model showed that the substitution of organic fertilizer for chemical fertilizer had a very significant effect on the core OTUs of bacteria,and the explanation rate of core OTUs reached 42%.(3)The substitution of organic fertilizers for chemical fertilizers can affect the metabolic functions of soil bacterial communities.Organic substitution fertilization can enhance the ability of soil bacteria related to carbon and nitrogen metabolism.Among 17 different functions related to carbon and nitrogen metabolism,most of the functions related to carbon metabolism and all of the functions related to nitrogen metabolism were significantly enriched in organic substitution.(4)The physical and chemical characteristics of soil were closely related to the structure of bacterial community.The results of RDA showed that the total OTUs of bacteria were significantly affected by OM,cation exchange capacity,pH and acid phosphatase,however,the core OTUs were significantly affected by OM,pH,rapidly available potassium,?-glucosidase and acid phosphatase,and the interpretation rate of OM is the highest for both total OTUs and core OTUs;the results of correlation analysis showed that the bacterial genera which has the significant correlation with organic matter and acid phosphatase were the most,and the Proteobacteria has the largest number of genera which has the significant correlation with physicochemical properties,while the genera that has the significant correlation with pH were all significant correlation.(5)Different fertilization treatments had significant effects on rice yield.Rice yield was significantly affected by soil total nutrients,available nutrients and soil bacteria.The organic substitution ratio of 25% and 50% is similar to the yield of inorganic fertilizer application alone,but slightly higher than that of chemical fertilizer application alone,which is the recommended organic substitution ratio in this study;when organic substitution ratio is 75% or 100%,rice yield decreases significantly.In conclusion,organic substitution fertilization can reduce soil acidification,improve soil nutrients,soil physicochemical and microbial composition,and enhance soil metabolic function.Moreover,appropriate organic substitution also plays a positive role in increasing rice yield.These findings enhance our understanding of the effects of different organic alternative fertilizers and have important theoretical implications for the future use of organic fertilizers. |
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