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Crop sensor optimizes nitrogen fertilization

The Isobus-connectable Isaria crop sensor determines the nitrogen requirement of plants as the tractor drives along. In June, it was demonstrated at the Feldtage 2014 in Bernburg-Strenzfeld, Germany.

The Isaria system senses the plants, calculates the required amount of nitrogen irrespective of the crop type and variety, and sends the data to the farmer’s display via Isobus (Photo: Claas)

CLAAS' (GERMANY) LONG-TERM PARTNER Fritzmeier Umwelttechnik (Germany) has developed the measurement technology for the Isaria system. It consists of an optical sensor with two sensor heads. These are fitted on the right and left of a carrier frame, which is mounted on the tractor's front linkage at a defined distance from the crop. Due to active lighting (LED), the crop sensor can be used during the day and at night. Four LEDs emit light in specific wavelengths within the red and near-infrared range of the light spectrum. The reflected light is measured by a detection unit, which is situated 40 cm to 100 cm above the crop stand. Based on the detector’s signals a vegetation index is generated, which highly correlates with the nutrition status of the crop.

The measuring frequency automatically adjusts to the environmental conditions such as crop density, intensity of the ambient light, and nutrition level of the plants. The sensors are installed in the arm of the tractor add-on device. They are able to perform 500 measurements per second.

The light reflected by the crop under the sensor head is measured. This measurement is used to calculate the IRMI vegetation index, which reflects the current nitrogen supply to the crop. The product measures the quantity of nitrogen, which has already been absorbed by the crop up to that point-in-time, compares this number with the target value of the current European Community stage and then calculates the missing nutrient, which has to be balanced out.

In addition, crop density is measured using the IBI (International Biochar Index) biomass index. If the IBI falls below a particular threshold value, for example due to drought or frost damage in the field, the spread rate in these subplots reverts to the value defined by the farmer. This combination of the two indices prevents errors.

The sensor can be used for any type of crop, at any time and regardless of the application method. If the sensor needs to be calibrated on site, Claas offers a single-point calibration method alongside the proven two-point calibration method. This calibration works in a similar way to the existing practice: a representative nutrition level of the crop is determined at specific points of the field. The sensor responds to variations by regulating the application quantity up and down.

The Isaria system senses the plants, calculates the required amount of nitrogen irrespective of the crop type and variety, and sends the data to the farmer’s display via Isobus (Photo: Claas)

The crop sensor provides an Isobus interface. It is operated via the Cebis Mobile or other Isobus-capable control terminals. The Isobus standard allows the use of only one control terminal for the crop sensor and implement. With this, Claas has responded to customer demands to reduce the number of control terminals in the cab.

Since 2013 the Isaria system is available in two versions: the Isobus version as Isaria Crop Sensor distributed by Claas and the Fritzmeier Isaria, which can be operated using a Windows-based tablet computer and is sold by different partners in specific countries. Both versions use the same sensor technology. But only Claas uses Isobus communication, the Fritzmeier version communicates via Bluetooth.

The Isaria system senses the plants, calculates the required amount of nitrogen irrespective of the crop type and variety, and sends the data to the farmer’s display via Isobus (Photo: Claas)

Fritzmeier is a pioneer in precision farming: In the 1990s they introduced the Weihenstephan system, a portable lab kit and a laboratory system for quick, on-site analysis of nitrogen levels. Since 2010, the company has focused on the optimization and further development of the Isaria system. Thereby customers benefit from past intensive field research in collaboration with the Chair of Agronomy and Organic Agriculture at the Center of Life and Food Sciences Weihenstephan of the Technische Universität München (TUM) resulting in a fertilization system that is described as an “absolute fertilizing system following the principle online with map overlay”. According to the provider, this "online with map overlay" process generates 5 percent higher revenue above nitrogen costs compared to uniform fertilization of fields or purely sensor-based fertilization.

Fritzmeier also developed the Mini-Veg N laser system. It is Isobus-connectable, too. This saves farmers the time-consuming task of having to climb in and out of the tractor. The Isobus terminal is complemented by a control unit, a sensor pack, and holders for the device. What makes the "active" system of the Mini-Veg so interesting is that the signals are delivered solely by material containing chlorophyll. There is therefore no interference during measurements, for example caused by surface dirt on the leaves, the lower layers of leaves, or the soil.

These precise measurements mean that the fertilizer is applied exactly where it is needed and where the plants can absorb it. The technology laser systems causes the leaves of the crop to fluoresce. The light measured from the chlorophyll provides information on the plant's nutrient levels and requirements. Calibration in the field is not necessary, as the data, which was gathered over many years at the scientific institutions in Weihenstephan (Germany), is already stored in the system.

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