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ARS Home » Research » Publications at this Location » Publication #154549


item Colvin, Thomas

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2004
Publication Date: 12/10/2004
Citation: Boyd, P.M., Hanna, H., Baker, J.L., Colvin, T.S. 2004. Field evaluation of anhydrous ammonia manifold performance. Applied Engineering in Agriculture. 20:(6):745-756.

Interpretive Summary: Anhydrous ammonia is a major source of nitrogen as a fertilizer for corn and other crops. The loss of nitrogen from croplands has been targeted as a heavy contributor to environmental problems related to hypoxia in the Gulf of Mexico. Several research projects have shown that reducing the application rate of nitrogen to minimize the amount of nitrate nitrogen in the soil at any point in time and particularly the end of the growing season is one of the best ways to limit off-site environmental damage. Historically, anhydrous ammonia applicators have been difficult to check for uniformity of application across the width of the machine because the nitrogen is put into the soil as a gas/liquid that is dangerous to humans if it escapes before it is captured by the soil. This led to some over-application of nitrogen to ensure that the lowest rate of application would be adequate for the crop. This project used a system developed by the project team that is capable of measuring the amount of anhydrous ammonia going to individual knives. A conventional manifold was tested against several recently developed commercial manifolds and one new manifold developed by the team. Results showed that all of the new manifolds were an improvement over the conventional manifold in terms of uniformity of application across the width of the machine. This should allow for the lowering of application rate to more closely match the need of the crop and reduce loss of nitrogen from the soil. These results should have both economic and environmental benefits if newer types of manifolds are adopted.

Technical Abstract: Experiments conducted between August 1999 and April 2002 evaluated anhydrous ammonia manifold distribution during field application at 84 kg N/ha (75 lb N/ac) and 168 kg N/ha (150 lb N/ac) application rates. The conventional, Vertical-Dam, Rotaflow [tm], Equa-flow [tm], FD-1200 prototype, and a new prototype manifold named the Impellicone manifold were tested. Temperature and pressure data was collected along the flow path. Results showed high distribution variation by the conventional manifold at both application rates. At the 84 kg N/ha (75 lb N/ac) rate, all other manifolds tested had significantly lower application variation. At the 168 kg N/ha (150 lb N/ac) rate, the conventional manifold grouped with the Vertical-Dam with a corn ring and the FD-1200 prototype. All other manifolds had significantly lower application variation. The Impellicone, Rotaflow [tm], and Equa-flow [tm] manifolds performed with the lowest measured variation at both rates. Analysis of recorded temperature and pressure data indicates that NH3 flowing through the system very closely follows the saturation line and acts as a saturated mixture. Predictions of NH3 quality based on published values would be acceptable. Investigation for correlation between coefficient of variation (CV), air temperature, and percent of volume in the vapor phase of NH3 resulted in only a trend of decreased CV with lower percent of volume in the vapor phase at the higher application rate for the manifolds examined. Results suggest that replacement of a conventional manifold with a Vertical-Dam manifold or any of the other manifolds tested could reduce application variation, and as a result reduce application rate by eliminating the need for over-application to compensate for variations.