Claas (Germany) has developed the Isaria crop sensor featuring a CAN interface compliant to ISO 11783 (Isobus). It has been tested successfully by AEF (Agriculture Industry Electronics Foundation).
The capabilities of modern farming technology depend today on compatibility between the various parts such as tractors, terminals and implements. Interfaces defined according to the ISO 11783 standard series handle communication between the CAN-connectable devices. The AEF nonprofit association has tested the optical crop sensor by Claas on Isobus conformity and listed in its Isobus database. Farmers or contractors planning to invest in Isobus technology can access the database to check the compatibility status of the offered products.
The sensor can be connected to Isobus virtual terminals. It makes an online, plot-specific calculation of the crop's optimum nitrogen uptake. The product can be used for any crop, does not depend on daylight, and is compatible with any method of production. It requires just one operation to perform automatic measurements, calculations and adjustments while travelling. This means according to the supplier that the optimum fertilizer quantity and its application rate are calculated almost at the same time.
The crop sensor is an optical sensor with two sensor heads, fitted on the right and left hand side of a carrier frame, which is mounted on the tractor's front linkage at a defined height above the crop. The system is fitted with active lighting (LED) so that the sensor can be used both during the day and at night. The measuring frequency automatically adjusts to the environmental conditions such as the intensity of ambient light.
A measurement is taken of the light reflected by the crop under the sensor head. This is used to calculate the IRMI vegetation index, which states the current nitrogen supply to the crop. The sensor measures the quantity of nitrogen which has already been absorbed by the crop until then, compares this measurement with the target value of the current EC stage, and then calculates the nutrient shortfall that needs to be compensated.
In addition, crop density is measured using the IBI biomass index. If the IBI falls below a particular threshold value, for instance 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.
If the sensor needs to be calibrated on-site, Claas allows single-point calibration in addition to tried-and-tested two-point calibration. This is equivalent to common farming practice: A representative supply status for the crop is calculated based on selected points. The sensor responds to deviations by increasing or decreasing the applied quantity correspondingly. Furthermore, while travelling the tried-and-tested Isaria fertilizer system measures the nutritional status of the crops without prior calibration, therefore ensuring that the crop receives the optimum nitrogen supply. In 2016, Claas offers automatic calibration: The user simply adjusts the average quantity of the chosen fertilizer, and the sensor distributes this amount each time.
As experience has shown that the yield over the total area can fluctuate greatly, there is a risk of over- or under-fertilization. This is where the sensor utilizes the map-overlay process. In addition to the actual and calculated N supply, this process considers the yield potential to ensure application of the optimum plot-specific spread rate in kg/ha or l/ha. Among others, the valuable Claas yield mapping data can be used to help calculate the yield potential.
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