轮作对土壤养分、微生物活性及细菌群落结构的影响

试验选择云南省具有代表性的烤烟-休闲-玉米(T-F-M)、烤烟-油菜-玉米(T-C-M)、烤烟-油菜-水稻(T-C-R)和烤烟-苕子-水稻(T-V-R)等4种轮作模式,通过测定土壤养分、酶活性及16S rDNA序列分析,研究了轮作对土壤养分、微生物活性及细菌群落结构的影响。结果表明,经过16年的不同轮作种植后,土壤pH值变化于6.2~7.1之间,有机质和有效氮、磷、钾提高或无显著变化,说明在高强度轮作种植条件下,辅以秸秆还田或冬季休闲均可保持或提高土壤肥力和生产力。土壤微生物量碳氮、蔗糖酶、脱氢酶、脲酶、磷酸酶和过氧化氢酶活性均以T-V-R最高,说明土壤生态环境改善,促进微生物繁衍,数量增加,活性增强。土壤细菌的16S rDNA读数依次为5395(T-F-M)、5864(T-C-M)、5528(T-C-R)和6614(T-V-R),分别代表885,973,969和987种(属)类的细菌,归属于变形菌、绿弯菌、放线菌、酸杆菌、拟杆菌等31个门,其中变形菌门的数量最多,占总量的24.69%~32.49%。此外,在4种轮作处理土壤中,前5种门类的细菌相同,15种优势菌株有6种(属)一样,均有较高的丰富度,但也因种植模式不同而变化,说明土壤是决定细菌组成的基本要素,种植模式可不同程度地改变它们的种群结构。从土壤有机质、有效养分、酶活性、微生物量碳氮、细菌种群结构和多样性等方面看,T-V-R 最佳,该种植模式具有潜在的推广应用价值。

Influence of crop rotation on soil nutrients,microbial activities and bacterial commu-nity structures

A 16-year field experiment has been carried out to investigate the influence of crop rotations on soil nutrients,microbial activities and bacterial community structures.The study includes 454 pyrosequencing anal-ysis of bacterial 16S rDNA.The experiment investigated four crop rotation treatments:1)flue-cured tobacco in summer,followed by winter fallowing and maize in summer (T-F-M);2)flue-cured tobacco in summer, canola in winter and maize in summer (T-C-M);3)flue-cured tobacco in summer,canola in winter and rice insummer (T-C-R);and 4)tobacco in summer,Vicia villosa in winter and rice in summer (T-V-R).After 16-years of crop rotation,soil pH had changed from 6.2 to 7.1.Compared with original soil levels,organic matter and available nutrients (such as nitrogen,phosphorus and potassium)either varied very little or significantly increased,suggesting the retention or growth of fertility under intensive rotations that return straw into soil and fallow during winter.There were higher microbial biomass carbon and nitrogen and enzyme activity (for example,sucrase,phosphatase,dehydrogenase,catalase and urease)in soils under the T-V-R treatment than in any of the other treatments.The readings of bacterial 16S rDNA sequences were 5395 for T-F-M soils,5864 for T-C-M,5528 for T-C-R and 6614 for T-V-R,representing 885,973,969 and 987 bacterial genera or species respectively,attributed to 31 phyla including Proteobacteria,Chloroflexi,Actinobacteria,Acidobacteria and Bacteroidetes.Proteobacteria were the largest group,accounting for 24.69%-32.49% of soil bacteria.5 of the 31 bacterial phyla and 6 of the 15 predominant bacteria were found in all the treatments’soils.It seems reasonable to suggest that crop rotation was a fundamental determinant of the abundance of soil bacterial com-ponents and community structures.Taking into account variations in organic matter,available nutrients,en-zyme activities,microbial biomass,bacterial community structures and biodiversity,our experiment suggests that T-V-R could be the best rotation model to promote in the flue-tobacco cultivation areas of Yunnan province.