Replicability of nitrogen recommendations from ramped
calibration strips in winter wheat
David C. Roberts
•
B. Wade Brorsen
•
Randal K. Taylor
•
John B. Solie
•
William R. Raun
Published online: 3 December 2010
Ó Springer Science+Business Media, LLC 2010
Abstract Ramped calibration strips have been suggested as a way for grain producers to
determine nitrogen needs more accurately. The strips use incrementally increasing levels of
nitrogen and enable producers to conduct an experiment in each field to determine nitrogen
needs. This study determines whether predictions from the program Ramp Analyzer 1.2 are
replicable in Oklahoma hard red winter wheat (Triticum aestivum). Predictions are derived
from 36 individual strips from on-farm experiments—two pairs of adjacent strips at each of
nine winter wheat fields in Canadian County, OK. The two pairs of strips within each field
were between 120 and 155 m apart. Each strip was analyzed three times during the
2006–2007 growing season. Nitrogen recommendations from Ramp Analyzer 1.2 are not
correlated even for strips that were placed side by side, and recommendations from strips
in the same field show no more homogeneity than randomly selected strips throughout the
county. The results indicate that ramped calibration strips are unlikely to produce accurate
nitrogen requirement predictions at any spatial scale, whether at the county level or for
subsections of a single field. In contrast, a procedure that uses only measures from the plot
with no nitrogen and the plot with the highest level of nitrogen applied does show repli-
cability. Thus, improvements in the ramped calibration strip technology are needed if it is
to become viable.
D. C. Roberts (&)
Department of Agribusiness & Applied Economics, North Dakota State University,
NDSU Dept. 7160, P.O. Box 6050, Fargo, ND 58108-6050, USA
e-mail: david.c.roberts@ndsu.edu
B. W. Brorsen
Department of Agricultural Economics, Oklahoma State University, 414 Agricultural Hall,
Stillwater, OK 74078, USA
R. K. Taylor Á J. B. Solie
Department of Biosystems and Agricultural Engineering, Oklahoma State University,
111 Agricultural Hall, Stillwater, OK 74078, USA
W. R. Raun
Department of Plant and Soil Sciences, Oklahoma State University,
044 N. Agricultural Hall, Stillwater, OK 74078, USA
123
Precision Agric (2011) 12:653–665
DOI 10.1007/s11119-010-9209-y
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