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| The effects of different fertilization treatments on paddy soil microbial communities were characterized using several techniques. Treatments included no fertilizer (NF), inorganic fertilizer only (CF), pig manure in combination with inorganic fertilizer (CFM) and straw manure in combination with inorganic fertilizer (CFS). Assessments included determination of microbial population counts by soil dilution plating on various general and selective culture media, microbial activity by community level physiological profiling using Biolog sole carbon source utilization tests (Biolog) and phospholipid fatty acid (PLFA) profiles. Soil populations with organic manure tended to have higher levels of culturable bacteria and fungi and lower levels of actinomycetes. Biolog plates indicated that the soil microbial metabolism quotient (AWCD), Shannon index and McIntonsh index all increased significantly in CFS- and CFM-treated soils relative to NF-treated soil. Soil phospholipid fatty acid (PLFA) analysis demonstrated the monounsaturated fatty acids 18:1ω9c, 18:1ω7c, 16:1ω7c, 16:1ω9c, 15:1ω6c and 18:2ω6,9c were most prevalent in CFM- and CFS-treated soils. The saturated straight chain lipids 14:0, 17:0, 18:0, 19:0 and 20:0 were most enriched in NF- and CF-treated soils. Fertilization increased the PLFA biomarkers for bacteria and fungi, but reduced the markers for actinomycetes. The ratio of Gram-positive to Gram-negative bacteria was significantly higher in the NF- and CF-treated soils relative to the CFS- and CFM-treated soils (P<0.05). However, further studies are required to understand how these changes in microbial community structure might actually impact soil microbial community function. |
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| Keywords:Paddy soil;Fertilization;Soil microbial community;Biolog;Phospholipid fatty acid (PLFA) |
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