Precision Agriculture, 3, 169–182, 2002
© 2002 Kluwer Academic Publishers. Manufactured in The Netherlands.
A Review of Combine Sensors for
P. REYNS, B. MISSOTTEN, H. RAMON AND J. DE BAERDEMAEKER
Laboratory for Agro-Machinery and Processing, K.U. Leuven, 3001 Heverlee, Belgium
Abstract. To maximize economic return from agricultural production units, costs have to be minimized and
beneﬁts maximized. For grain, kernel yield and quality have to be maximized while the use of seeds, fertilizer,
herbicides and fungicides have to be optimized.
The best location to evaluate productivity levels, by measuring yield and quality of grain and straw, is the
combine harvester. Moreover, other grain quality characteristics like density or test weight can be determined
for use as an evaluation tool. In this paper, an overview is given of the past and current research toward
the evaluation of currently available commercial sensors (e.g., for measuring grain yield and grain moisture
content) as well as toward the development of new sensors (e.g., grain protein content and straw yield).
Keywords: combine, sensors, grain yield, grain quality
One of the most important objectives of farmers is the optimization of proﬁt for each
ﬁeld. One approach is to minimize inputs. This beneﬁt is directly correlated to yield and
crop quality. For a long time, this improvement has been obtained through a thorough
crop selection for speciﬁc climates, and for an increased resistance to pest infections.
Better fertility management supported these improvements. Higher yields are sometimes
accompanied by an increased leaching of pollutants to the environment. Misapplication
of fertilizers and pesticides results in pollution and increased pressure on the environ-
ment. Farmers are under increasing legislative pressure to reduce fertilizer, pesticide and
Precision farming is likely to provide a solution for these problems. During the grow-
ing season, one can visually detect differences in a ﬁeld. Different growing conditions
result in varying grain yield, weed infestation etc. Fertilizer and herbicide application
can be adapted to this variation in a site-speciﬁc manner to obtain maximum economic
yield. To evaluate this proﬁt, yield has to be determined site-speciﬁcally. With cereal
grains, the only place to measure the latter is the combine harvester. So within precision
farming, combine harvesters play an important function.
About 15 years ago, research was initiated toward the site-speciﬁc measurement of
grain yield. The ﬁrst commercial sensors appeared ﬁve years ago. Nowadays, research
is focused upon the measurement of grain quality and yield of other crops (sugar beets,
forages, potatoes,), but also on the comparison and evaluation of existing technologies.
The following paper is meant to be a guideline through the research on different
commercial sensors available, new developments that can be expected with respect to