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Does
Choice of Response Function Matter in Setting Maximum Allowable N-Application
Rates in Danish Agriculture? Jorgen R. Mortensen and Bruce R. Beattie |
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Abstract | |
Response
research during the last couple of decades tends to support agronomic
knowledge pointing to decreasing marginal yield response up to a point
where additional nitrogen does not result in further yield increase but
rather a yield plateau. In contrast to a non-linear response with plateau
model (NLRP) a cubic polynomial specification is generally used by those
responsible for recommending/setting nitrogen norms in compliance with
Danish environmental policy. The flexibility of the cubic polynomial ensures
a relatively good fit to observed nitrogen/yield data and, surprisingly,
often renders a close emulation of the NLRP model. Unfortunately, the
cubic also often produces unrealistic optimal nitrogen application estimates.
In those cases, Danish authorities use a simple quadratic specification
as a fallback. We argue that an NLRP specification would be a better first
choice model than the cubic – among other things, avoiding the need
for a fallback model. Further progress in response research and choice
of proper model specification could possibly be achieved by accounting
for total nitrogen supply by including nitrogen provided in the form of
mineralized nitrogen from soil sources. |
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© 2007 Dept. of Agricultural & Resource Economics, The University of Arizona
Send comments or questions to arecweb@ag.arizona.edu
Last updated February 10, 2005
Document located at http://ag.arizona.edu/arec/pubs/researchpapers/abstract2005-01.html