Microbial composition and diversity of an upland r

Authors: JiZheng He Yong Zheng ChengRong Chen YuanQiu He LiMei Zhang

Publish Date: 2008/08/20

Volume: 8, Issue: 5, Pages: 349-358

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Abstract

Fertilization is an important agricultural practice for increasing crop yields In order to maintain the soil sustainability it is important to monitor the effects of fertilizer applications on the shifts of soil microorganisms which control the cycling of many nutrients in the soil Here culturedependent and cultureindependent approaches were used to analyze the soil bacterial and fungal quantities and community structure under seven fertilization treatments including Control Manure Return harvested peanut straw was returned to the plot and chemical fertilizers of NPK NP NK and PK The objective of this study was to examine the effects on soil microbial composition and diversity of longterm organic and chemical fertilizer regimes in a Chinese upland red soilSoil samples were collected from a longterm experiment station at Yingtan 28°15′N 116°55′E Jiangxi Province of China The soil samples 0–20 cm from four individual plots per treatment were collected The total numbers of culturable bacteria and fungi were determined as colony forming units CFUs and selected colonies were identified on agar plates by dilution plate methods Moreover soil DNAs were extracted and bacterial 16S rRNA genes and fungal 18S rRNA genes were polymerase chain reaction amplified and then analyzed by denaturing gradient gel electrophoresis DGGE cloning and sequencingThe organic fertilizers especially manure induced the least culturable bacterial CFUs but the highest bacterial diversity ascertained by DGGE banding patterns Chemical fertilizers on the other hand had less effect on the bacterial composition and diversity with the NK treatment having the lowest CFUs For the fungal community the manure treatment had the largest CFUs but much fewer DGGE bands also with the NK treatment having the lowest CFUs The conventional identification of representative bacterial and fungal genera showed that longterm fertilization treatments resulted in differences in soil microbial composition and diversity In particular 424 of the identified bacterial isolates were classified into members of Arthrobacter For fungi Aspergillus Penicillium and Mucor were the most prevalent three genera which accounted for 466 of the total identified fungi The longterm fertilization treatments resulted in different bacterial and fungal compositions ascertained by the culturedependent and also the cultureindependent approachesIt was evident that more representative fungal genera appeared in organic treatments than other treatments indicating that culturable fungi were more sensitive to organic than to chemical fertilizers A very notable finding was that fungal CFUs appeared maximal in organic manure treatments This was quite different from the bacterial CFUs in the manure indicating that bacteria and fungi responded differently to the fertilization Similar to bacteria the minimum fungal CFUs were also observed in the NK treatment This result provided evidence that phosphorus could be a key factor for microorganisms in the soil Thus despite the fact that culturedependent techniques are not ideal for studies of the composition of natural microbial communities when used alone they provide one of the more useful means of understanding the growth habit development and potential function of microorganisms from soil habitats A combination of culturedependent and cultureindependent approaches is likely to reveal more complete information regarding the composition of soil microbial communitiesLongterm fertilization had great effects on the soil bacterial and fungal communities Organic fertilizer applications induced the least culturable bacterial CFUs but the highest bacterial diversity while chemical fertilizer applications had less impact on soil bacterial community The largest fungal CFUs were obtained but much lower diversity was detected in the manure treatment The lowest bacterial and also fungal CFUs were observed in the NK treatment The longterm fertilization treatments resulted in different bacterial and fungal compositions ascertained by the culturedependent and also the cultureindependent approaches Phosphorus fertilizer could be considered as a key factor to control the microbial CFUs and diversity in this Chinese upland red soilSoil fungi seem to be a more sensitive indicator of soil fertility than soil bacteria Since the major limitation of molecular methods in soil microbial studies is the lack of discrimination between the living and dead or active and dormant microorganisms both culturedependent and cultureindependent methods should be used to appropriately characterize soil microbial diversity

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