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United States Department of Agriculture

Agricultural Research Service

Title: The Potential Bioavailability of Organic C, N, and P Through Enzyme Hydrolysis in Soils of the Mojave Desert

Authors
item Nadeau, Jeffrey - UNIV. OF NEVADA, RENO
item Qualls, Robert - UNIV. OF NEVADA, RENO
item Nowak, Robert - UNIV. OF NEVADA, RENO
item Blank, Robert

Submitted to: Biogeochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2007
Publication Date: March 15, 2007
Citation: Nadeau, J.A., Qualls, R.G., Nowak, R.S., Blank, R.R. 2007. The potential bioavailability of organic C, N, and P through enzyme hydrolysis in soils of the mojave desert. Biogeochemistry. 82:305-320.

Interpretive Summary: Aspects of global change may decouple plant/soil nutrient relationships in the Mojave Desert. We measured potentially bioavailable nutrients in soils of the Mojave Desert using a novel procedure employing buffered solutions of an excess of various enzymes. In interspace and shrub microsite soils, respectively, 14.5 and 9.7% of the organic C in the form cellulose, 60.0-97.8 and 61.2-100.0% of the organic N in the form protein, and 44.0 and 57.5% of the organic P was hydrolysable. Refinement of our methods could lead to a valuable tool for the assessment of potential bioavailability of nutrients in a variety of soils.

Technical Abstract: Increases in the growth rate of plants and microbes in the Mojave Desert in response to predicted increases in precipitation and CO2 due to global climate change may induce nutrient limitations. This study was designed to measure the pool of potentially bioavailable nutrients in soils of the Mojave Desert. Soils were collected from shrub and interspace microsites and then subjected to amendment with buffered solutions of an excess of various enzymes. The products of each enzyme reaction were then measured and the maximum quantity of hydrolysable substrates calculated. In interspace and shrub microsite soils, respectively, 14.5 and 9.7% of the organic C in the form cellulose, 60.0-97.8 and 61.2-100.0% of the organic N in the form protein, and 44.0 and 57.5% of the organic P was hydrolysable. There were significant differences between microsites for hydrolysable substrate using all enzyme amendments except for protease. We propose that accumulations of hydrolysable organic C, N, and P in the Mojave Desert could be a result of the persistently dry soil conditions often found in desert ecosystems and the immobilization of enzymes, which may result in low diffusivity of soil substrates and enzymes and, accordingly, little degradation of organic C, N, and P. Alternatively, rapid nutrient cycling and immobilization by soil microorganisms could account for accumulations of organic C, N, and P. Further refinement of the methods used in this study could lead to a valuable tool for the assessment of potential bioavailability of nutrients in a variety of soils.

Last Modified: 8/21/2014
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