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United States Department of Agriculture

Agricultural Research Service

Research Project: CONSERVATION SYSTEMS RESEARCH FOR IMPROVING ENVIRONMENTAL QUALITY AND PRODUCER PROFITABILITY Title: Measuring Soil Nitrogen Mineralization under Field Conditions

Authors
item Balkcom, Kipling
item Blackmer, A - DECEASED
item Hansen, D - UNIV. OF DELAWARE

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 7, 2007
Publication Date: April 1, 2009
Citation: Balkcom, K.S., Blackmer, A.M., Hansen, D.J. 2009. Measuring soil nitrogen mineralization under field conditions. Communications in Soil Science and Plant Analysis. 40:1073-1086.

Interpretive Summary: Land application of animal manure is known to change rates of nitrogen (N) mineralization in soils, but information concerning intensity and duration of these effects has been difficult to obtain under field conditions. Scientists from the National Soil Dynamics Laboratory, Iowa State University, and University of Delaware estimated net effects of liquid swine manure on N mineralization in soils under field conditions in a completely randomized design, at six field sites across Iowa, by comparing liquid swine manure treatments to plots receiving no manure. Soil samples were collected immediately after manure application to determine inorganic N concentrations and those samples were also incubated 28 d under controlled conditions to determine amounts of N mineralized from the soil. Differences in inorganic N concentrations were significant among treatments at all six locations. In comparison, significant differences in inorganic N concentrations measured after 28 d of laboratory incubation were observed for only two of the six sites. Our results also illustrate how to distinguish between the effects manure has on rates of N mineralization in soils and rates at which manure N is mineralized. These findings indicate that liquid swine manure has an inorganic N fraction that behaves like commercial fertilizer and an organic N fraction that is relatively inactive.

Technical Abstract: Land application of animal manure is known to alter rates of nitrogen (N) mineralization in soils, but quantitative information concerning intensity and duration of these effects has been difficult to obtain under field conditions. We estimated net effects of manure on N mineralization in soils under field conditions in a completely randomized design, at six field sites, by comparing liquid swine (Sus scrofa) manure treatments to plots receiving no manure. Soil samples were collected immediately after manure application to determine inorganic N concentrations and those samples were also incubated 28 d in the laboratory to determine amounts of N mineralized from the soil. Analyses and incubation were repeated on a second set of samples collected after various times, depending on the site. Differences in inorganic N concentrations were significant among treatments at all six locations for the first sampling and five of the six locations for the second sampling. In comparison, significant differences in inorganic N concentrations measured after 28 d of laboratory incubation were observed for only two of the six sites for each sampling time. Our results illustrate how to distinguish between the effects manure has on rates of N mineralization in soils and rates at which manure N is mineralized.

Last Modified: 11/28/2014
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