Responses of active bacterial and fungal communities in soils under winter wheat to different fertilizer and pesticide regimens

• Published in: Applied and Environmental Microbiology Vol. 70; no. 5; pp. 2692 - 2701
• Main Authors: Girvan, M.S, Bullimore, J, Ball, A.S, Pretty, J.N, Osborn, A.M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01-05-2004
• Subjects: agricultural soils; Agriculture; application rate; Bacteria - genetics; Bacteria - growth & development; Bacteria - isolation & purification; biological activity in soil; Biological and medical sciences; Colony Count, Microbial; community ecology; Comparative analysis; denaturing gradient gel electrophoresis; DNA, Ribosomal - analysis; Ecology; Ecosystem; Electrophoresis - methods; fertilizer application; Fertilizers; Fundamental and applied biological sciences. Psychology; Fungi - genetics; Fungi - growth & development; Fungi - isolation & purification; gel electrophoresis; Gigaspora; Glomales; Glomus; good agricultural practices; grain crops; low input agriculture; Microbial Ecology; Microbiology; nitrates; pesticide application; Pesticides; Pesticides - pharmacology; phosphates; population density; Reverse Transcriptase Polymerase Chain Reaction; ribosomal RNA; RNA, Ribosomal, 16S - genetics; RNA, Ribosomal, 18S - genetics; soil bacteria; soil fertility; soil fungi; Soil Microbiology; Soils; species diversity; Triticum; Triticum aestivum; vesicular arbuscular mycorrhizae; Wheat; winter wheat; England; Fungi; Soils; Monocotyledones; Gramineae; Angiospermae; Pesticides; Bacteria; Spermatophyta; Microbial community; Triticum aestivum; Thallophyta
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.70.5.2692-2701.2004

The composition of the active microbial (bacterial and fungal) soil community in an arable wheat field subjected to different management practices was examined at five times during a 1-year period. Field sections were fertilized either at good agricultural practice (GAP) levels or at reduced levels (0.5x GAP) and were inoculated with vesicular arbuscular mycorrhizae (VAM) at the same time. Field subsections were treated either with or without pesticides. Changes in the active microbial communities were investigated by denaturing gradient gel electrophoresis analysis of reverse transcription-PCR-amplified 16S and 18S rRNA. Microbial community structure was primarily determined by season, and the seasonal trends were similar for the fungal and bacterial components. Between-sample microbial heterogeneity decreased under a mature crop in the summer but increased following harvesting and plowing. Although similar overall trends were seen for the two microbial components, sample variability was greater for the fungal community than for the bacterial community. The greatest management effects were due to GAP fertilization, which caused increases in the bacterial numbers in the total and culturable communities. Microbial biomass similarly increased. GAP fertilization also caused large shifts in both the active bacterial community structure and the active fungal community structure and additionally resulted in a decrease in the heterogeneity of the active bacterial community. Pesticide addition did not significantly affect bacterial numbers or heterogeneity, but it led to major shifts in the active soil bacterial community structure. PCR primers specific for Glomales 25S rRNA genes were used to monitor the VAM population following inoculation. Glomales were detected initially only in VAM-inoculated field sections but were subsequently detected in noninoculated field sections as the season progressed. After plowing, the level of Glomales was reduced in noninoculated field sections but remained high in VAM-inoculated field sections. Inoculation of VAM correlated with elevated soil phosphate and carbon levels.