Effect Of Different Potassium Levels On The Micro-ecology Changes At Rhizosphere And Tobacco’s Quantity&Quality

Tobacco is one of the typical crops with potassium preference.The accu-mulation of potassium will affect not only the quantity but also the qual-ity of it.So the changes of rhizosphere environment must be studied at different potassium supply level in order to improve the efficiency of manuring and the content of potassium in tobacco.The study was carried out in Jian’ou Nanping,which consisted with six treatments and three repeats from potassium-free to potassium-overdose.The complex’ system was studied which composed with microbiota,planta and soil,by means of measuring the quantity and composition of bacteria&fungi,the microbial biomass carbon&nitrogen,the available potassium at rhizo-sphere&bulk soil and the soil enzyme activity of rhizosphere.Specific results are as followed.First,the different supply level of potassium would affect the community of bacteria but not of fungi.As the time goes,the diversity and richness of bacteria was increase in high potassium supply and decrease in low potassium supply which indicated that the community had the adaptation to high potassium supply and the soil nutrition was deficiency in low.In the growing period,1.82 kg per hectare of potassium applied would help the microflore community developing and the tobacco growing.In the maturing period,3.04 kg per hectare of potassium applied would help the microflore community developing and the quality of tobacco improving.Second,by measuring the factors relate to azote,it’s most suitable by applying 1.82 kg to 2.44 kg per hectare in the growing period.The nitrat-ase and urease activity was relatively low and the main PGPB(Plant Growth Promoting Bacteria)of azote was nitrobacteria.It meant the azote was changed to niter from ammonia,and helped the growth of tobacco.In maturing period,the urease activity decreased,the growth of tobacco inhibited and efficiency of dilution effect decreased when 3.04 kg per hectare applied.It would promote the saccharides accumulation and the quality of tobacco.Third,by measuring the factors of potassium,the content of available potassium in rhizosphere would be affected by the abundance of potas-sium PGPB,but would not affect the content of potassium in tobacco caused by dilution effect and transport of potassium in tobacco.Properly increasing the supply of potassium was advised to promote the growth of tobacco and increase the content of potassium in tobacco leaf.Fourth,in the maturing period,pathogenic fungi were decrease firstly and then increase slowly with the increase of potassium supply level.The correlation analysis showed that pathogenic fungi was significant nega-tive correlation with average price of tobacco and highly significant negative correlation when partial correlation being taken and controlled by shannon index of bacteria.Pathogenic fungi also correlated with antagonistic bacteria negatively.It indicated that pathogenic fungi would affect the quality of tobacco and be affected by antagonistic bacteria,so exogenous PGPB would improve the quality of tobacco.Fifth,overall consideration of microflore community,factors of azote,phosphorus&potassium and the quantity&quality of tobacco,1.82kg of potassium per hectare applied in the growing period was suggested to promote the microflore community,environment of soil,growth of to-bacco and final output.Topdressing was required when topping to offer a stabilized potassium supply,promote the saccharides accumulation,inhibit the growth of tobacco and improve the quality of tobacco...