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United States Department of Agriculture

Agricultural Research Service

Title: Seasonal Variations on Denitrifying Enzyme Activity of Feedlot Soil

Authors
item Woodbury, Bryan
item Nienaber, John
item Eigenberg, Roger
item Miller, Daniel

Submitted to: American Society of Agri Engineers Special Meetings and Conferences Papers
Publication Type: Other
Publication Acceptance Date: July 11, 2000
Publication Date: N/A

Interpretive Summary: A very high amount of nitrogen contained in cattle manure is lost from the feedlot surface. Ammonia is an important form of nitrogen lost to the atmosphere, but it is being closely studied. There is a second form of nitrogen loss to the atmosphere that has not been studied, but may be important. This paper describes a preliminary study to find out the importance of feedlot surface conditions, location in the feedlot and effects of climate on this form of nitrogen gas. Control of this may become an important method to reduce nitrogen loss and control some forms of odor from the feedlot.

Technical Abstract: Animal waste nutrient models have been used by producers to develop best management practices. These models use crude approximations for nitrogen lost from the feedlot. Ammonia loss has been widely studied and accounts for the majority of gaseous nitrogen lost from a feedlot soil; however, denitrification has not been thoroughly investigated, particularly for feedlot soil environment. The objectives of this study were to determine the seasonal denitrification enzyme activity (DEA) of a feedlot soil and explain potential controlling mechanisms. Three locations were identified as having varying levels of microbial activity by using electromagnetic induction mapping techniques. Three depths (unconsolidated surface soil, 0 - 10 cm, 10 - 20 cm) were isolated at each location and analyzed for DEA, nitrification activity, denitrifier most probable number, soil moisture, and pH. Denitrification enzyme activity varied from 0.0 to 132.2 mmol/g/hr rbased on season, depth, and spacial location within the feedlot. However, no single factor correlated with DEA across all locations and depths. The DEA of the unconsolidated surface soil furthest from the feedbunk maintained the highest level when compared to all other locations and depths, even when soil temperatures were near 0 deg C and soil moisture was very low. Also, the relative DEA below 10 cm for all locations and depths were very low during the entire investigation.

Last Modified: 10/23/2014
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