| Rice is one of the most important food crops in China.In recent years,the food production has been steadily improved by usage of high-yielding crop varieties,modem fertilizer,irrigation and pesticides.But the food crisis situation is still grim.In the process of rice growth,soil microbial activity was closely associated with the growth of the crops.Soil microorganisms were involved in the whole process of soil biochemical substance circulation and energy flow,and its species,richness and biological activity had a positive effect in improving soil fertility,inhibition of plant diseases and ultimately increasing crop yields,while its structure and function diversity was an important index of soil quality.Hence,the research on difference of diversity of microbial commuruty structure system in rice root and the changing rule with the soil environment factors may provide a more comprehensive theoretical basis for formulating reasonable fertilization measures,promoting soil fertility,increasing rice yield and improving the farmland soil environment.A long-term soil transplant experiment was conducted in two agricultural experiment stations which separated only two kilometers.In 2013,the annual yield of Zhangbang Village plots was 8.46 t/ha,while ZhouGan Village plots annual output reached 9.43 t/ha,higher than the annual output of Zhangbang Village by 0.97 t/ha,which is consistent with the statistical results of this and for several years before.Both villages are in Daikin town of Wuxue,Hubei province.However,the two villages used the same organic fertilizer and chemical fertilizer during the process of the rice planting.Therefore,in order to explore the influence of microbial activity on rice growth of two pieces of farmland,under the condition of same fertilization but the different rice production,the experiment was performed using a five-point sampling method of rice rhizosphere and non-rhizosphere soil of Pre-plant background,Retuning-green stage,Tillering stage,Panicle differentiation stage,Full-heading stage,Maturity period,Post-harvest background.A total of 24 soil samples were collected.The basic physicochemical properties and soil enzymatic activities of paddy field soils were determined.The phospholipid fatty acid determination and 16S rDNA high-throughput sequencing were analyzed to observe the change of microbial activity in different growth stage,and then comprehensive analysis of the above data was accomplished by using the statistical analysis software,such as SPSS,CANOCO and R.The main results were as follows:(1)Surface soil of lowyield field Zhangbang Village is clay,while highyield field ZhouGan Village is sand clay.ZhouGan Village soil had a better soil fertility maintenance capacity.During the whole reproductive period,the average of pH,total C,total N of Zhougan Village were significantly higher than that of Zhangbang village while total P,total K,valid P,valid K,alkali solution nitrogen were significantly lower than Zhangbang village.Therefore,ZhouGan Village may had a higher efficiency of soi1 effective fertility.Significant difference was found in different growth period of rice soil physical and chemical properties,and the change tendency of soil physical and chemical properties in two village paddy soil are different.(2)Through determination of soil enzyme activities which involved in the circulation of carbon,nitrogen,phosphorus and sulfur elements,significant difference was found in two village paddy soil enzyme activity,and the response of soil enzymatic activities to the rice growth and rhizosphere effect were different.The change of soil enzyme activity was closely related to the physical and chemical factors,and soil enzyme activity in lowyield field Zhangbang Village was mainly affected by the AP,TP,TK while soil enzyme activity in highyield field ZhouGan Village is mainly aflfected by pH,AK.(3)PLFAs results show that the different production paddy soil have significant different soil microbial community structure,and different types of microorganisms vary with growth period.The PLFA biomass of highyield field ZhouGan Village is significantly higher than lowyield field Zhangbang Village and reached its highest in tillering stage.Gram-positive bacterial and actinomyces biomass(oligotrophic)in lowyield field Zhangbang Village were significantly higher than that of highyield field ZhouGan Village soil samples,however,Gram-negative bacterial abundance(eutrophic)was below ZhouGan Village,suggesting that soil of ZhouGan Village was more fertile than Zhangbang Village.(4)RDA analysis results show that soil microbial community structure is closely correlated with envirounent physical and chemical factors and soil enzyme activity in two villages,and a stronger correlation was found in highyield field Zhougan Village.The soil microbial community in lowyield field Zhangbang Village was mainly affected by C and N while soil microbial community in highyield field ZhouGan Village is mainly affected by P,K and pH.Different microbial groups also present different correlation with the physical and chemical factors in different places.Urease,aryl?sulfatase and phosphatase activities were positively correlated with GP and AMF in RDI,and were negatively correlated with the GN in RD1.Invertase activities is positively related to the Euk,negatively related to the Act.(5)High throughput sequencing results showed that the bacterial community diversity showed obvious difference in lowyield field Zhangbang Village and highyield field Zhougan Village.The Alpha diversity of soil microbial communities in highyield field ZhouGan Village was significantly higher than lowyield field Zhangbang Village.Both village soil bacterial community structure was significantly affected by the growth stage of rice,and the change of lowyield field Zhangbang Village is more obvious than highyield field ZhouGan Village,which indicated that the soil bacterial community structure of Zhangbang Village are more vulnerable to the effects of other crops.(6)Different kinds of bacteria in two villages were markedly changed along with the variation of growth stage,and the diflference between two villages is obvious.Acidobacteria,Actinobacteria,Chloroflexi and Planctomycetes were significant changed along with the variation of the growth stage,and different soil bacteria groups showed different response to the rice growth stage.A more stable core OTUs was observed in highyield field ZhouGan Village during the growth period,the advantage bacterium groups of different growth stage in lowyield field Zhangbang Village showed more obvious community dominance.However,The soil bacteria groups in highyield field ZhouGan Village was relatively balanced,thus the highyield field ZhouGan Village soil had a better ability to adapt to environmental disturbance.(7)The correlation of soil enzyme activity and bacterial community structure was small,but different enzyme activities were significantly associated with the dominated OTUs which were belonged to the Planctomycetes,Chloroflexi and Proteobacteria.These bacteria may probably promote the function of soi1 enzymes in the soil environment.The soil microbial diversity was closely correlated with rice growth stage,soil fertility status and soil enzyme activity.The change of soil physiochemical properties and enzyme activities influenced the diversity of soil microbial community structure and function.Multiple-factor analysis results of experimental data showed that the most significant impact factor to soil microbial community diversity was the rice growth stage,and the rice growth stage is the main cause that affect paddy soil internal environment and the change of the soil microbial community.In general,from the point of the experimental results,high yield field ZhouGan Village soil fertility factors of soil N,P,K were lower than the low yield fields Zhangbang Village,but a higher soil C/N ratio,suggested that the organic matter content is higher in high yield field ZhouGan Village,which was conducive to the growth of microorganisms.PLFA and high-throughput sequencing structure show that,on the one hand,the high yield field ZhouGan Village had a higher richness and diversity of the microbial community,the community structure is more stable,which was conducive to the full play of ecological function of microorganisms;On the other hand,the higher activity of soil enzyme activity and a more closely relation of microbial comm1nity with the soil invertase,urease,phosphatase,and aryl acid esterase enzyme activity indicated that high-yield field ZhouGan Village had more active soil enzyme activity and soil microbial community,and the active microbial community were more advantageous to promote the improvement of soil enzyme activity and more beneficial to develop its ecological function on specific microbial groups,thereby to promote the soil substance circulation of C5 N,P,S,increase the effectiveness of soil nutrients,promote rice crop to efficient utilization of N,P,K fertility factors,ultimately promote rice production. |
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