In-Field Assessment of Single Leaf Nitrogen
Status by Spectral Reﬂectance Measurements
V. ALCHANATIS AND Z. SCHMILOVITCH email@example.com
Institute of Agricultural Engineering, ARO, the Volcani Center, POB 6, Bet Dagan 50250, Israel
M. MERON firstname.lastname@example.org
Galilee Technology Center, Migal, P.O.B. 90000, Rosh Pinna 12100, Israel.
Abstract. Commercial agriculture has come under increasing pressure to reduce nitrogen fertilizer inputs
in order to minimize potential non-point source pollution of ground and surface waters. This has resulted
in increased interest in site-speciﬁc fertilizer management. This research aimed to develop techniques for
real time assessment of nitrogen status of corn using a mobile sensor with the potential to regulate nitrogen
application based on data from that sensor. Speciﬁcally, the research attempted to determine the system
parameters necessary to optimize reﬂectance spectra of corn plants as a function of growth stage and
nitrogen status. An adaptable, multi-spectral sensor and the signal processing algorithm to provide real
time, in-ﬁeld assessment of corn nitrogen status were developed.
Keywords: variable rate application, spectroscopy, optical sensor, fertilization, NIR, minispectrometer
Precision agriculture is based on using the inherent spatial and temporal variability
in a ﬁeld as a basis to manage farm operations. This is a site-speciﬁc approach and
can reduce input costs, result in higher crop productivity and decrease environmental
There are two basic methods of implementing site-speciﬁc management (SSM) for
the variable-rate application (VRA) of crop production inputs: map-based and
sensor-based. The map-based SSM method is based on the use of maps to represent
crop yields, soil properties, pest infestations, and VRA plans. The sensor-based SSM
method provides the capability to vary the application rate of crop production inputs
with no mapping involved.
The sensor-based method utilizes sensors to measure the desired properties, soil
properties or crop characteristics, on the go. Measurements made by such a system
are then processed and used immediately to control a variable-rate applicator. At
this point, the major challenge is to develop sensors that will work accurately in ﬁeld
conditions at realistic working speeds. Sensor-based application systems must be
capable of accomplishing the sensing, data processing, and application rate adjust-
ment steps in one machine pass.
The present work describes the development of an optical sensing system for in-
ﬁeld detection of leaf nitrogen status in corn.
Precision Agriculture, 6, 25–39, 2005
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