Spectral Sensors by Carl Zeiss

M e a s u r in g C r o p P la n t Q u a lit y in t h e F ie ld

INTR ODUC TION
F or the s hort period between harves ting and the next
sowing, plant breeders need rapid, cost-effective andmeaningful analytical techniques to be able to develop
crop plants with improved quality. T he advances
achieved obtained in, for example, the dry matter
content of forage gras s , the oil content of oils eed rapeand the protein content of feed barley depend directlyon the intens ity of s election from a s tarting material
which cons is ts of thous ands of foundation s tocks .
Instead of conventional „wet chemical“ analyticalprocedures, spectroscopy in the near infrared (NIR S )has proved to be s ucces s ful for this purpos e and can
now be trans ferred from the laboratory to the field as aconsequence of newly developed instruments.

F ig.1 MMS NIR

THE ME THOD

F ig.2 F orage harves ter from the company Haldrup (Denmark).
0,7fres h gras s
0,6

A bs orption (L og 1/R )T he water content of field crops determines theirs tability during s torage, partially characterizes theirnutritional value and is als o a crucial factor in fixing
their trading price. Water is the cons tituent which canbe mos t eas ily determined in the near infrared Whileother cons tituents of economic importance s uch asprotein, oil and carbohydrates dis play lower
abs orptivity in the near infrared , their contents cannonetheles s be determined with high analyticalprecis ion by a single, non-des tructive measurement offreshly harvested grains and seeds.

0,50,40,30,20,1
dry gras s
0,0
960

1028

1101

1173

1245

1318

1390

1462

1534

1607

1679

W avelength (nm)F ig.3 Absorption spectra of grass with different
levels of mois ture.

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Spectral Sensors by Carl Zeiss

THE SYSTEM
On the basis of the equipment devised and the chemometric research carried out by Norris in the USA, spectroscopy in
the near infrared (NIR) has now made its way into plant cultivation. So far, however, the current status of the NIRS
instrument technology has limited this analytical procedure to stationary use in the laboratory. The availability of diodearrays for the spectral range of the near infrared now makes it possible to the use NIRS directly on agricultural harvest
machines. The company Carl Zeiss, the Danish agricultural engineering company Haldrup and the Institute of Crop andGrassland Science of the German Federal Agricultural Research Center have jointly developed a forage harvester fortrial plots which allows NIRS measurements on representative samples of the crop during harvesting. The CORONANIR sensor module installed in the harvester is based on the MMS-NIR 1.7 diode array spectrometer (Fig. 1) and has
been specially designed for the rough conditions of field use.
The particular benefits of the CORONA NIR result from the high measuring speed of the MMS-NIR 1.7, its hightemperature stability, small size and total insensitivity to vibrations and shock. These features clearly distinguish thisunit from the NIR measuring instruments used in the laboratory which are unsuitable for mobile use in the roughconditions of field cropping, not only because of their slow measuring speed but also because of their moving, shocksensitive gratings or filter wheels required for the dispersion of polychromatic light. In the summer of 1999, the firstHaldrup forage harvesters of the new „NIRS harvest line“ for such forage plants as grass and clover were purchased by
the German plant breeding companies Deutsche Saatveredelung (DSV) and Norddeutsche Pflanzenzucht (NPZ) andtested in the field (Fig. 2). The chemometric calibration of the sensor in field conditions is being continued together withthese plant breeding companies. In addition, a combine harvester equipped with a CORONA NIR will be available forsuch grain crops as cereals, oil seeds and grain legumes for the first time in the year 2000.
The integration of NIR diode array spectrometers in agricultural combine harvesters will initially increase the efficacy ofplant breeding and testing aimed at creating cultivars with improved properties. In addition, it should not be overlookedthat this type of „mobile analysis” can also be transferred to practical agriculture where a wide variety of approaches toso-called „precision farming” are increasingly being tested. Thus, the NIR diode array spectrometers could one day
make an effective contribution to quality assurance in environmentally compatible plant production.

Autors:Dr. Christian Paul and Michael Rode work at the Institute of Crop and Grassland Science of the German Federal
Agricultural Research Center (FAL), Bundesallee 50 in 38116 Braunschweig/Germany.

Carl Zeiss
Spektralsensorik

D-07740 Jena
Telefon:(03641)64 2838
Telefax:(03641)64 2485
E-Mail:info.spektralsensorik@zeiss.de
Internet:
http:// www.zeiss.de