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Title: CHANGES IN ENZYME ACTIVITIES AND MICROBIAL BIOMASS OF TALLGRASS PRAIRIE SOIL AS RELATED TO BURNING AND NITROGEN FERTILIZATION

Author
item AJWA, HUSEIN
item DELL, CURTIS - KANSAS STATE UNIVERSITY
item RICE, CHARLES - KANSAS STATE UNIVERSITY

Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: A tallgrass prairie ecosystem is characterized by minimal additions or losses of nutrients. Cultivation of such a pristine land (e.g., crop rotation, mulching, and application of fertilizers and pesticides) greatly affects the fertility, microbial and enzyme activities of soils. Because many enzymes and microbial biomass respond immediately to changes in soil fertility status, they were evaluated as potential indicators of soil quality as affected by nitrogen fertilization and controlled burning practices. This study shows that long-term burning and N fertilization of tallgrass prairie soil has diverse effects on surface soil (0-5 cm) enzyme activities, and some enzymes are more sensitive indicators of disturbances in pristine ecosystems than microbial biomass. Long-term burning appears to alter the rate of organic matter turnover and therefore, affect microbial biomass and the production of enzymes. Because many soil enzymes and MBN are immediately responsive to soil disturbance or restoration, they can be used as indices of environmental stability and soil quality for sustainable management. This study also shows that enzyme activities should be accounted for when evaluating the sustainability of land management practices.

Technical Abstract: Microbial biomass and enzyme activities are affected by management practices and can be used as sensitive indicators of ecological stability. Microbial biomass C (MBC); microbial biomass N (MBN); and eight enzyme activities involved in the cycling of C, N, P, and S were studied in the surface (0-5 cm) of an Irwin silty clay loam soil (fine, mixed, mesic, Pachic Arguistoll) in a tallgrass prairie ecosystem. Treatments of annual spring burning and N fertilization were initiated in 1986 and encompassed: (1) unburned-unfertilized, (2) burned-unfertilized, (3) burned-fertilized, and (4) unburned-fertilized. Activities of dehydrogenase, beta-glucosidase, urease, deaminase, denitrifying enzyme, acid phosphatase, alkaline phospatase, and arylsulfatase were assayed. Long-term burning and N fertilization of the tallgrass prairie soil reduced MBC and MBN relative to the unburned-unfertilized treatment. The effects of burning and N fertilization varied among the enzymes and the time of sampling. Long-term burning significantly (P<0.05) increased activities of urease and acid phosphatase, but decreased activities of beta-glucosidase, deaminase, and alkaline phosphatase. Long-term N fertilization significantly increased activities of beta-glucosidase and acid phosphatase, but decreased urease activity. This study found that several soil enzyme activites can be used as indicators of ecological changes caused by N fertilization and long-term burning management practices. The relevance of these changes in surface soil to the long-term sustainability of this ecosystem needs further evaluation.