Author
 |
Miller, Daniel |
|
Varel, Vincent |
|
Submitted to: Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting
Publication Type: Abstract Only Publication Acceptance Date: 6/28/2010 Publication Date: 10/31/2010 Citation: Miller, D.N., Varel, V.H. 2010. Potential for nitrate and Fe(III) additions to control indicator bacteria, retain nitrogen, and reduce odors in beef cattle feedlot soils [abstract]. Agronomy Society of America, Crop Science Society of America, Soil Science Society of America International Meetings. p.89 Paper No. 102-4. Available: http://a-c-s.confex.com/crops/2010am/webprogram/Paper59416.html. Interpretive Summary: A wide variety of odor compounds are associated with livestock wastes. These odor compounds are easily degraded in other environments when alternate electron acceptors (compounds other than O2) are available. In this study, nitrate and oxidized iron, two common alternate electron acceptors, were added to a cattle feedlot manure and soil mixture. Over several days, odor compounds and other soil constituents were monitored before and after a simulated rainfall event. Adding alternate electron acceptors affected many of the measured soil parameters including pH, ammonia content, fecal coliforms, gas production, and odorous volatile fatty acids. Compared to the standard manure & soil control, iron treatments had a three to four-fold increase in certain odor compounds, increased fecal coliform bacteria (fecal indicator microorganisms), and increased acidity. However, one positive for the iron treatment was its greater ammonia content compared to controls which retained no ammonia. The nitrate treatment was deemed superior to controls (and iron treatments) based upon its 100-fold lower fecal coliform content, lower soil/manure acidity, and its low content of certain odor compounds (branched chain volatile fatty acids). We conclude that nitrate amendment was the most effective for short-term control of many manure issues, while application of iron amendment may not prove to be a viable odor solution without further research because of the excessive accumulation of certain odor compounds and coliform bacteria. Technical Abstract: A wide variety of volatile odor compounds accumulate during the anaerobic fermentation of livestock wastes. Since these compounds are easily degraded in other environments when alternate electron acceptors (compounds other than O2) are available, we evaluated the use of amending NO3- and Fe(III) into mixtures of cattle feedlot manure as a way to minimize the production and persistence of odor compounds. Pan incubations were conducted with dry feedlot waste amended with Fe(III), NO3-, or no electron acceptor (fermentative control). Over several days, odor compounds and electron acceptors were monitored before and after a simulated rainfall event. Addition of alternate electron acceptors affected many of the measured soil parameters including pH, ammonia content, fecal coliforms, H2 gas production, total VFA, and branched-chain VFA. Compared to the standard fermentative control, iron treatments exhibited a three to four-fold increase in malodorous VFA content (6 to 8 mg VFA/g dry soil), increased fecal coliform content (10-fold higher), and decreased pH (2 unit decrease), which would greatly enhance VFA emission. However, one positive for the iron treatment was its greater ammonia content (>3 mg N/g dry soil) compared to controls which retained no ammonia. The nitrate treatment was superior to controls (and iron treatments) based upon its 100-fold lower fecal coliform content, high final pH (9.9), and its low content of branched-chain VFA. We conclude that nitrate amendment was the most effective for short-term control of many manure issues, while application of iron amendment may not prove to be a viable odor solution without further research because of the excessive accumulation of branched-chain VFA and coliform bacteria. |
