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DEVELOPMENT AND TESTING OF DYNAMIC FERTILIZER MODEL TO ASSESS THE EFFECT OF CNMPS IN THE NORTH BOSQUE WATERSHED
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Pp. 019-026 in Total Maximum Daily Load (TMDL) Environmental Regulations–II Proceedings of the 8-12 November 2003 Conference (Albuquerque, New Mexico USA), Publication Date 8 November 2003. .(doi:10.13031/2013.15533)
Authors: J. B. Houser, A. Saleh, and L. Hauck
Keywords: Comprehensive Nutrient Management Plans, Manure management, SWAT, Phosphorus, ARCVIEW SWAT
Manure and litter management currently uses some form of phosphorus indicator to determine
the correct amount of fertilizer and/or manure to be applied to a field. Therefore, the manure
application rate to a field can be variable from year to year, and the maximum allowable
application rate is a function of some phosphorus indicator.
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The watershed model SWAT and the field-level model APEX allow the user to specify a priori
multi-year management by application field; however, interaction of manure management in a
dynamic manner with phosphorus indicators is limited. Though APEX has been recently
modified to adjust manure and fertilizer application based on soil test P levels, management
adjustments do not include accounting for changing application area requirements with changing
application rates and a fixed quantity of manure for disposal. The watershed model, SWAT, was
altered using algorithms already developed for APEX to allow manure application rates to
change dynamically within the simulation as a function of soil test P. In addition, ARCVIEW
SWAT (AVSWAT) output and SWAT were modified to adjust the area receiving fertilizer in
response to dynamically changing application rates, and the amount of manure requiring land
application each year based on simple constraints (such as mandated manure haul-off).
Initial testing of the modified SWAT gave indications that the modifications were performing as
expected. This modified SWAT will be used to assess the effect of comprehensive nutrient
management plans (CNMPs) in a watershed.