Arylsulfatase activity of microbial biomass in soils as affected by cropping systems |
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| Authors: | S Klose J M Moore M A Tabatabai |
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| Institution: | (1) Department of Agronomy, Iowa State University, Ames, IA 50011-1010, USA e-mail: malit@iastate.edu, Fax: +1-515-2943163, ML |
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| Abstract: | The impacts of crop rotations and N fertilization on different pools of arylsulfatase activity (total, intracellular, and
extracellular) were studied in soils of two long-term field experiments in Iowa to assess the contibution of the microbial
biomass to the activity of this enzyme. Surface-soil samples were taken in 1996 and 1997 in corn, soybeans, oats, or meadow
(alfalfa) plots that received 0 or 180 kg N ha–1 before corn, and an annual application of 20 kg P ha–1 and 56 kg K ha–1. The arylsulfatase activity in the soils was assayed at optimal pH (acetate buffer, pH 5.8) before and after chloroform fumigation;
microbial biomass C (Cmic) and N (Nmic) were determined by chloroform-fumigation methods. All pools of arylsulfatase activity in soils were significantly affected
by crop rotation and plant cover at sampling time, but not by N fertilization. Generally, the highest total, intracellular,
and extracellular arylsulfatase activities were obtained in soils under cereal-meadow rotations, taken under oats or meadow,
and the lowest under continuous cropping systems.Total, intracellular, and extracellular arylsulfatase activities were significantly
correlated with Cmic (r>0.41, P<0.01) and Nmic (r>0.38, P<0.01) in soils. The averages of specific activity values, i.e., of arylsulfatase activity of the microbial biomass, expressed
per milligram Cmic, ranged from 315 to 407 μg p-nitrophenol h–1. The total arylsulfatase activity was significantly correlated with the intracellular activity, with r values >0.79 (P<0.001). In general, about 45% of the total arylsulfatase activity was extracellular, and 55% was associated with the microbial
biomass in soils, indicating the importance of the microflora as an enzyme source in soils.
Received: 23 April 1998 |
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| Keywords: | Arylsulfatase activity Chloroform-fumigation method Biomass enzymes Crop rotations N fertilization |
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