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07.07.2020 - Wolfgang Rudolph (Send email to Wolfgang Rudolph)

Precise fertilising with tradition

Frank Erdenbrecher steers the Unimog U 530 along the tracks at about 16 km/h. The tracks lead through the wheat field "Eiche" near the town of Hildburghausen in Thuringia. They lead through the 38 ha wheat field "Eiche" of Milch-Land GmbH Veilsdorf near the Thuringian town of Hildburghausen. The crop has reached the flag leaf stage (EC 37 to 39) and receives the second application of nitrogen via the mounted GDK 500A fertiliser spreader from Güstrower. The stainless steel large-area spreading unit with a working width of up to 40 m allows part-width section control and, via the slide adjustment, a one-sided reduction of the throwing width at the edges of the field. The Yara N-Sensor ALS 2 on the roof of the driver's cab controls how much calcium ammonium nitrate is deposited on the individual sections of the field based on the measured chlorophyll concentration and thus the nitrogen content of the plants. The exact calibration of the sensor takes place immediately before application.

Fertiliser management for 15 farms in the region

"The N-sensor on the Unimog works actively, i.e. with its own LED light source, and can therefore also be used at night or when there is dew," emphasises Gerhard Langguth at the edge of the field during an appointment with the Bauernzeitung. The 57-year-old is head of the agricultural division at Raiffeisen Warengenossenschaft Hildburghausen e. G., whose technology park includes the Unimog agrotruck. "The Milch-Land Veilsdorf farm is one of our main customers," adds board member Peter Harenberg. In addition to trading in a rural range of goods, including fertiliser and pesticides, the cooperative has been acting as a service provider for 15 mainly larger agricultural enterprises in the region since 2000. The offer includes the complete fertiliser management from the determination of the basic fertiliser requirement by means of soil sampling, to the lime and phosphorus application based on this, to the site-specific nitrogen fertilisation of the crops with the N-sensor. "The majority of the agricultural enterprises we serve take advantage of this complete package," says the 49-year-old business economist.

In the field of basic fertilisation, this is done in cooperation with Maschinenring Hildburghausen. "We carry out soil sampling on 6,000 ha every year and repeat it every five years. This allows us to keep an eye on the nutrient supply on the entire arable land," says Maschinenring managing director Manfred Müller. Sampling is carried out on a 3-ha grid using semi-automatic units mounted on the rear of off-road vehicles. A soil sampler N 2012 from the manufacturer Nietfeld was recently added to the two custom-built units from a machine construction company in Pulsnitz.

Successful in precision farming for two decades (from left): Manfred Müller, Peter Harenberg and Gerhard Langguth. Photos: Carmen Rudolph

Basic fertilisation on the basis of regular soil samples

The vehicles move in a Z-shape in each of the grid sub-areas previously defined on the computer. The track is recorded with a GPS device the first time the field is sampled and serves as a template for the route to be followed when the field is repeated. During short stops, the lance of the sampling device pierces up to 30 cm deep into the soil. The mixed samples from about 20 soil samples per grid, each filled into bags, are analysed by AGROLAB Agrarzentrum GmbH in Leinefelde. To avoid confusion, each bag is marked with a barcode.

The results of the nutrient analysis are recorded in the digital map of the field. The application map derived from this forms the working basis for the ISOBUS control of the spreader on the Unimog of the Hildburghausen service provider during basic fertilisation in the months of July to October. "Due to recruitment problems, the machinery ring will dissolve next year," regrets Müller, who will retire in a few months. "As far as fertiliser management is concerned, however, this has no consequences for the agricultural enterprises," assures Ivon Häußer as she empties the container for the composite sample at the soil tester. The 43-year-old business economist for agricultural business management takes over soil sampling as an employee of the Raiffeisen Warengenossenschaft, which will offer this service in future.

Less damage in the inventory due to steerable rear axle

The effect of lime application in autumn on nutrient availability in the soil is determined by the farms and the Hildburghausen service provider in spring on selected areas using the Yara N-tester. "The chlorophyll values of the plant leaves and taking into account an increase or decrease according to the annually updated variety table result in the guideline value for the required amount of nitrogen," explains Langguth. The second and third application of nutrients is carried out on a site-specific basis. To do this, the Unimog first drives through the crop and scans the average fertiliser requirement with the N sensor. The fertiliser is then applied according to the naturally varying requirements in the field areas during the passes by the online control of the spreader based on the measurement results of the N sensor on the cab roof.

When manoeuvring on the headland, it is noticeable that none of the Unimog's wheels leave the tracks created. Equipping the Agrotruck with a steerable rear axle is thanks to the persistence of the former head of the Raiffeisen Warengenossenschaft, Eberhard Tanzberger. Like his customers, he wanted as little fruit as possible to be destroyed when turning and manoeuvring in the crop. To suggest a technical solution for this, he personally went to the Mercedes-Benz plant in Wörth. The first U 530 fitted as standard with all-wheel steering then also went to Hildburghausen in 2017. The equipment features of the Unimog, which is also used for winter service in the low mountain region, also include a tyre pressure control system, a special arrangement of the radiators for extremely dusty conditions, and an interface for data transmission to and from the large-area spreader.

The Unimog with N-sensor and fertiliser spreader during a measurement drive in wheat. The Hildburghausen service providers acquired the ALS 2 N-sensor in the so-called "dissolved design". The anodised aluminium construction is 3,000 euros cheaper than the conventional version. Photo: Carmen Rudolph

Coordination with customers via agriPORT management software

"The fertiliser management measures on behalf of our customers generate huge amounts of data, which we have been managing with Agricon's agriPORT software since 2012," Langguth reports. All those involved can access the web-based system via the farm computer or mobile devices. In this way, the farms would create the application maps with the corresponding software modules, taking into account the planned crop rotation. The basis for this are the results of the soil samples entered into the system so far by the machinery ring and, from 2021, by the Raiffeisen Warengenossenschaft. The maps are then sent by email to the on-board computer in the service provider's fertiliser spreader. In the shared order management system, in turn, the farms can find out about the progress of the application. "This has worked very well. Otherwise, the coordination of site-specific fertilisation between the various farms and service providers on the many individual fields would hardly be feasible," the agricultural engineer is convinced.

Target value fertilisation facilitates compliance with the DVO

In order to be able to make full use of the programme's possibilities, to keep up to date with new functions after updates, but also to inform himself about current solutions in crop production, he maintains the exchange of experience in a working group organised by Agricon. "Recently, one of the topics was the so-called target value fertilisation", Langguth informs us. This is a software extension to improve the accuracy of variable nitrogen fertilisation.

According to the Fertiliser Ordinance (DVO), only limited amounts of nitrogen may be fertilised on a field-by-field basis. With the conventional and agronomically correct approach of N-sensor fertilisation, the farmer does not know at the beginning of the work what total amount will be applied to the respective field at the end. This is only determined during application, depending on the agronomic and economic optimum. Unfortunately, this is pushed into the background by the DVO. Instead, a target value is aimed for, which usually corresponds to the remaining residual N fertiliser quantity. The user specifies this quantity in the software module Target value fertilisation. The N sensor then automatically adjusts to the target. This gives the farmer legal security.