Precision Agriculture, 3, 81–94, 2002
© 2002 Kluwer Academic Publishers. Manufactured in The Netherlands.
Error Sources on Yield-Based Fertilizer Variable
Rate Application Maps
C. W. CHAN email@example.com
Malaysian Agricultural Research and Development Institute, P.O. Box 12301,
50774 Kuala Lumpur, Malaysia
J. K. SCHUELLER
Department of Mechanical Engineering, University of Florida, P.O. Box 116300,
Gainesville, FL 32611, USA
W. M. MILLER, J. D. WHITNEY, AND T. A. WHEATON
University of Florida, Citrus Research and Education Center, Lake Alfred, FL 33850, USA
J. A. CORNELL
Department of Statistics, University of Florida, P.O. Box 110339, Gainesville, FL 32611, USA
Abstract. Spatially-variable application of inputs to agricultural ﬁelds is dependent upon accuracy of the
input variables. The effects of boundary determination, interpolation method, and GPS location errors were
studied for determining a variable rate nitrogen application map based upon yield maps of a 3.6 ha Florida
citrus block. A general linear model for the mean absolute error approximated the error effects.
Keywords: spatially-variable, precision agriculture, yield mapping, fertilizer application, GPS, GIS, errors
Spatially-variable crop production (SVCP) can improve economic returns and reduce the
introduction of undesirable residues into the environment. Yield mapping is a logical
starting point in SVCP providing valuable insights into potential farm problems and the
starting point for spatially-variable fertilizer or pesticide application. Both yield mapping
and variable rate application have been widely studied and commercially implemented,
particularly in agronomic crops.
Most SVCP research and development has been directed towards hardware and soft-
ware development and system implementation. However, there have also been some con-
cerns expressed about accuracy, particularly for variable rate application of pesticides and
fertilizers based on an application map (Goense, 1997). A map-based spatially-variable
rate technology application (VRT) system usually consists of an applicator ﬁtted with
a differential Global Positioning System (DGPS) receiver, where the machine’s ﬁeld
location determines application rates from a digital map.