Analysis of the phospholipid fatty acids upland light colored andosol and the relationship among the size of biomass based on phospholipid fatty acid analysis, microscopical counts and chloroform fumigation-incubation
1998
Arao, T. (National Agriculture Research Center, Tsukuba, Ibaraki (Japan)) | Okano, M. | Kanamori, T.
In order to analyze the microbial biomass and community structure in soil, we investigated the amounts and composition of phospholipid fatty acids which had been annually applied with rice straw compost (0, 20, 40, 80 Mg ha(-1)) and extracted from the upland light colored andosol of experimental plots. The phospholipid content increased with increasing compost application levels. The major fatty acids were 16:0, 18:0, 18:1omega7, 18:1omega9, 18:1omega5, 16]1omega7, 16:1omega5, 16:1omega9, i17:1omega8, p11-19:1, 20:1, 18:2omega6, 20:4, 17:Ocyc, 19:Ocyc, p10-17:0, i15:0, a15:0, i16:0, i17:0, a17:0, p10-19:0 and 24:0-2OH. The phospholipid fatty acid composition indicated that the main origin of the soil phospholipids was bacterial membrane lipids. The proportion of the branched chain fatty acids heightened as amount of applied compost was increased. Their proportions in soils in March and April were lower than in October and December, however, the proportions of cyclopropane fatty acids, 16:1omega7 and 18:1omega7, in soils in March and April were higher than in October and December. These results suggest that the ratio of Gram-positive bacteria to Gram-negative bacteria increased under cultivation of wheat. The phospholipid fatty acid content was closely correlated with the available N; the amount of N mineralized during four weeks of incubation at 25 degrees C. Correlation coefficients betweenavailable N and soil content of fatty acids were 0.94 for i15:0, 0.93 for p10-17:0, 0.90 for p10-19:0, 0.76 for 16:0, 0.70 fro 18:2omega6 and 0.64 for 18:1omega7. There were also significant correlations between the counts of bacteria by microscopical method and phospholipid fatty acid content. The proportion derived from soil microbial biomass seemed to be high in soil phospholipid because 23-41% of the soil phospholipid content declined after chloroform fumigation
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