Different fields in a farm often have very different soils – which means differences in average yield potential. Crops in fields with a lower yield potential require less fertiliser than crops in fields with an above-average yield potential. Farmers already learn this in their training in order to reduce over-fertilisation or under supply. However, there are also large differences in yield potential within a single field. The amount of fertiliser distributed within a field is just as important as between fields. We have summarised for you the ways in which you can capture and pick up on the differences.
Humus-rich depressions, sandy knolls, boggy areas – many farmers are roughly familiar with the different zones in their fields. Smart farming technologies are more popular than ever in this area. Most farms are introduced to this type of management through the use of application maps based on satellite photos. These application maps specify a certain application quantity for an exact point of the field. The system then applies the corresponding quantity when spreading fertiliser, for example. However, the creation of these application maps is very time-consuming. What’s more, these do not always reflect the exact nitrogen requirements of the plants, especially in the case of fertiliser spreading. Often no current satellite photos are available at the desired time or satellite photos are distorted by peripheral influences such as forest edges or crops on neighbouring fields. ISARIA plant sensors are more precise in this respect. The sensors measure the current and actual nitrogen nutrient condition of the plants as they pass over them. The entry-level variant here is the single-point mode, which can be used to detect crops at different stages of development within a field and supply them with the optimum application quantity. In single-point mode, the farmer carries out a calibration. This involves assigning a desired application quantity to the mean calibration value. This amount is then varied depending on the selected gradient and the crop in question.
Identifying the yield potential
However, the best way to determine and classify the different yield potentials within a field is to use a yield potential map. A yield potential map is based exclusively on historical data. Possible bases for this are multi-year satellite maps for the same crop at the same vegetation stage (in wide crop rotations, satellite maps are required every 6-8 years). In addition, information from a soil rating, TPI maps, yield maps from the combine or forage harvester, soil sample maps (usable field capacity) or a soil conductivity measurement can be included in a yield potential map. Extremely precise information about the different zones within a field can also be generated by sensor scans over several years. However, it is important to bear in mind that data from comparable crops and for the same vegetation period must always be compared. A relative yield potential map is created from all the above georeferenced information. This map has an average of 100% across the board and deviates from the mean depending on the yield potential of the respective zone.
Why not just rely on yield potential maps?
Yield potential maps indicate the different yield potentials per zone of a field in percentage terms. The quality of the yield potential map depends on the quality and abundance of the historical information taken into account.
BUT: These are exclusively historical values, which do not always correspond to the current crop. In spring, for example, cereals often develop faster on sandy south-facing slopes because the soil warms up more quickly. The plants’ water needs can still be met by the winter moisture. However, this location is actually one of the low-yield zones, as there is insufficient water for good yield development in the summer months.
It is therefore important to consider both historical data and current crop information when determining the correct amount of fertiliser to apply. ISARIA implements this technically with the MAP OVERLAY process.
How does that work?
A yield potential map is added to the job in ISARIA Connect. The job can then be imported into the terminal. As a further option, the user can also transmit the relative yield potential map directly to the ISARIA terminal in shape format via a USB stick. As the tractor passes over each area, the optimum application quantity is then calculated and applied on the basis of the yield potential (from the yield potential map) and the current nutrient condition of the crop (from the measurement with the ISARIA sensor-based system).
When map and plant sensor merge
ISARIA offers the benefits of both strategies – historical yield potential maps and current ISARIA sensor measurements. The different yield requirements of a field are shown on the map. With the sensor, it is now possible to individually evaluate and treat the crop within a defined yield zone. As a result, the different yield zones are supplied with different amounts of fertiliser according to need and potential, and the fertiliser is distributed correctly within a yield zone. ISARIA offers two solutions for this:
- Single point mode with yield potential map
- ISARIA expert systems with yield potential map
The first option, as described above, is a good way to promote zones with high yield potential while achieving homogeneous crops within the zones. The second variant, i.e. the combination of map and ISARIA expert system, is clearly the ideal solution. In this case, fertiliser is applied even more precisely and in line with requirements. With the ISARIA expert systems, the total amount of fertiliser is determined by the system, not the user. The amount of fertiliser is always based on the current crop’s nutrient condition. If the crop’s nutrient condition is ideal, only as much fertiliser is applied as is needed until the next fertiliser application or until harvest. If the crop’s nutrient condition is inadequate, the amount of fertiliser required to bring the crop’s nutrient condition up to the ideal level is applied. Pre-determined yield expectations and quality parameters to be achieved on the respective sub-field determine when a crop’s nutrient condition is ideal.
Good to know
With all ISARIA systems, the fertiliser is applied to the field as required and the specifications of the German fertiliser regulations are complied with. After the work is done, the measurement and application data can be quickly and easily transferred to ISARIA CONNECT and stored or processed there for documentation purposes. This saves additional work on documentation.
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