Microbial biomass estimations in soils from tussock grasslands by three biochemical procedures |
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| Authors: | DJ Ross KR Tate Annette Cairns Elizabeth A Pansier |
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| Institution: | Soil Bureau, Department of Scientific and Industrial Research, Lower Hutt, New Zealand |
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| Abstract: | Microbial biomass was determined by three biochemical procedures in nine topsoils from a climosequence in tussock grasslands. The pH values of the samples ranged from 4.4 to 6.2 and organic C contents from 2.5 to 20.0%. When determined by a chloroform-fumigation procedure, contents of biomass C and mineral-N (Min-N) flush ranged from 530–2780 and 59–167 μgg?1 dry soil respectively. Adenosine 5'-triphosphate (ATP) content ranged from 2.2 to 10.7 μg g?1 dry soil. All three estimates were significantly correlated with each other and with several soil properties, including organic C and total N contents and CO2 production. They were not significantly correlated with any climatic factor.In spite of these significant correlations, the ratios of the biomass estimates varied appreciably in the different soils. The ratios of biomass C/Min-N flush ranged from 7.8 to 22.8 (average 12.5), biomass C/ATP from 163 to 423 (average 248) and Min-N flush/ATP from 12 to 35 (average 22). These ratios were mostly higher than those found elsewhere for Australian and English soils. The high biomass C/ATP and Min-N flush/ATP ratios did not appear to originate from inefficient extraction of “native” ATP or from the soils' P status. Based on these results, care in the use of factors for obtaining soil microbial biomass content from Min-N flush or ATP values is indicated. |
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