Effects Of Continuous Molybdenum Application On Soil Microbial Diversity And Ecological Stoichimetry

Molybdenum?Mo?is an essential microelement for plants,animals and microbial.Recently,more studies have been done about Mo physiological function in plants.However,it is not clear about the roles of Mo in soil microbial diversity and soil carbon,nitrogen and phosphorus cycles.In order to understanding the microbial mechanism of carbon,nitrogen and phosphorus cycling by Mo application,the effects of continuous Mo application on soil microbial diversity and soil carbon,nitrogen and phosphorus circles process were investigated.The main results are as follows:1.The soil bacterium diversity,population abundance and functional gene abundance were affected by the Continuous Mo application.Mo application significantly decreased the Chao1,ACE and Shannon index of root zone soil bacterium for ripening period tomato,but increased the relative proportions of Actinobacteria,Acidobacteria,Chloroflexi,etc,reduced the relative percentages of Proteobacteria,etc.There are 15 differential bacterial populations between Mo-deficient and Mo-application treatments.Among them,the abundance of six populations were increased and nine of them were decreased.These differential populations might participate in the cellulose decomposition process,phosphate solubilization,nitrogen fixation,nitrification,and soil nutrient cycle process.As for gene function classification,continuous Mo application significantly enhanced the gene abundance related to photosynthesis,and base excision repair,while the gene abundance related to fatty acid biosynthesis were decreased.2.The root zone soil carbon,nitrogen and phosphorus library and their dynamic were changed by Mo application.There is no difference in carbon library?TOC,LOC,MLOC and HLOC?of wheat and broad beans root zone soil between Mo deficiency and Mo application treatments.However,there is a decreased tendency for the ?G enzyme activity of broad beans root zone soil under Mo application.There is no difference in root zone soil nitrogen components?TN,NO₃^--N and NH₄⁺-N?of wheat and broad beans between Mo deficiency and Mo application treatments.But,the NAG enzyme activity in wheat tillering stage was decreased by Mo application.There is no difference in TP,Olsen-P and different forms phosphorus content of wheat and broad beans root zone soil between Mo deficiency and Mo application treatments.While the capacity of active phosphorus library in wheat and beans root zone soil was enhanced in Mo application treatment.Under the Mo deficiency treatment,root zone soil NH₄⁺-N,NO₃^--N content showed significant positive correlations with soil carbon library,phosphorus library andACP enzyme activity.In conclusion,the balance of carbon circle,nitrogen circle and phosphorus was disturbed under Mo-deficient soil,while less contradiction appeared under Mo-sufficient treatment.3.The C/N,N/P,and C/P were not sensitive to continuous Mo application in wheat and broad beans root zone soil.ln?G:lnACP and lnNAG:lnACP of wheat and broad beans root zone soil were increasing with the progress of growth period.In addition,the ln?G:lnACP and lnNAG:lnACP of broad beans root zone soil at seedling stage showed increased in continuous Mo application treatment.