Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/25/2012
Publication Date: 7/1/2013
Citation: Myers, T., Dell, C.J., Beegle, D. 2013. Evaluation of ammonia emissions from manure incorporated with different soil aerator configurations. Journal of Soil and Water Conservation. 68(4):306-314. Interpretive Summary: Incorporation of manure into soil with a rolling-tine aerator has the potential to reduce the emission of ammonia from soil in no-till systems, where incorporation by conventional tillage practices is not possible. We tested several aerator configurations to determine the impacts on ammonia emissions, plant-available N, and corn grain yield. Ammonia emissions were only reduced when the aerator toolbar was angled (increased soil erosion risk), however corn grain yield was generally increased when the soil was aerated with either a straight or angled toolbar. We do not recommend the aerator as a tool to provide low-disturbance manure incorporation if reducing ammonia emissions is the goal, but the potential to increase grain yield with aeration should be studied further.
Technical Abstract: The incorporation of swine manure with tillage effectively reduces ammonia emissions and conserves crop available N but is not compatible with no-till and many other conservation tillage programs. Rolling-tine aerators potentially provide a means to enhance manure infiltration with limited disruption of the soil surface, however the impact of the range of aerator configurations and manure placements have not been widely studied. We measured ammonia emissions, conducted pre-side dress nitrate tests (PSNT), and monitored corn grain yield when swine manure was incorporated with combinations of two aerator toolbar offset angles (0 and 10 degrees) and two manure placements (broadcast before aeration and banded behind aerator) and compared those measurements to unincorporated surface application and an unmanured control. Additional plots were established with five rates of mineral N fertilization to determine N response curve and estimate fertilizer N equivalent of the applied manure. Measurement of cumulative ammonia emissions using a dynamic chamber method showed that offsetting the aerator toolbar by 10 degrees reduced emissions by 65-75% , with both manure placements, compared to surface application. However, no consistent reductions in ammonia emissions were observed when the toolbar was not offset. While reduction in ammonia with the offset toolbar could conserve substantial amounts of plant available N, the soil disturbance caused by the offset tines would not be compatible with most conservation tillage programs. PSNT values increased when ammonia emissions were reduced. In 2009, both the angled and straight aerator treatments with manure banded behind the aerator resulted in significantly higher corn grain yield than all other treatments despite reductions in ammonia emissions only when the toolbar was angled. Correlation of yield from manure application treatments with the N response curve for multiple mineral N application rates showed a greater than expected response to manure application. Yield responses are an indication that aeration has benefits in addition to N conservation. We do not recommend the rolling-tine aerator if reducing ammonia emissions in conservation tillage is the primary goal, but future study into other yield increasing benefits of aeration is needed.