Distribution of Microorganisms,Biomass ATP,and Enzyme Activities in Organic and Mineral Particles of a Long‐Term Wastewater Irrigated Soil |
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| Authors: | Zdenek Filip Shinjiro Kanazawa Jacques Berthelin |
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| Abstract: | The aim of the study was to elucidate the spatial distribution of soil microorganisms and enyzme activities in a long‐term wastewater treated soil. Soil was sampled from a plough layer of the Ah horizon of a sandy Haplic Luvisol which was either (1) irrigated with municipal wastewater for almost 100 years, or (2) no more irrigated since 20 years, or (3) never received wastewater. The samples were fractionated by wet sieving to obtain seven size fractions of organic and mineral soil particles, and a separate silt+clay fraction. The individual soil samples contained between 1.2% (never irrigated) and 4.1% (long‐term irrigated) organic particles by weight, but these particles harboured up to 47.8% of the total soil carbon and 41.7% of nitrogen, and thus represented an important storage of energy and nutrient for microorganisms. In total, however, the highest C and N amounts were accumulated in the silt+clay fraction, whereas coarser mineral particles which dominanted by weight in the Haplic Luvisol were low in C and N. The highest numbers of bacteria, actinomycetes and fungi per gram of the individual soil fractions were found in organic particles of the long‐term irrigated soil. Less nutrient‐dependent oligotrophic bacteria were for the most part associated with the silt+clay fraction, irrespective of the soil treatment with wastewater. Similar to microbial counts, also the ATP content, as a measure of active microbial biomass, and the activities of β‐glucosidase, β‐acetylglucosaminidase, and proteinase were higher in the long‐term irrigated soil than in that which was never irrigated. In most cases slightly enhanced values of microbiological and biochemical parameters were still detectable 20 years after the wastewater irrigation was terminated. The values of the individual parameters decreased in all soil samples under testing in general gradually with decrease in size of the organic soil particles. In conclusion, the coarse soil organic particles > 5 mm and the silt+clay fraction < 0.05 mm represent the sites with the highest microbial inhabitance, ATP contents and enzyme activities in the Ah horizon of an Haplic Luvisol. Long‐term wastewater irrigation resulted in an increase of microbial counts, total biomass and soil enzyme activities. |
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| Keywords: | soil microorganisms biomass ATP soil enzymes spatial distribution wastewater irrigation Haplic Luvisol |
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