Why create soil maps?
In order to create application maps (fertiliser, seeding, soil tillage), you need basic data. Yield maps or aerial photographs are often used for this. However, the disadvantage is that it is only possible ro react to data with a significant time delay. NDVI (Normalized Difference Vegetation Index) and aerial photographs also do not really allow any conclusive statements to be made about the soil structure, but instead describe the current vegetation situation at the time the image was taken. They only actually show symptoms rather than the causes.
Electrical conductivity, on the other hand, is affected by soil type, compaction, moisture content, organic residues and salt content. This means soil parameters can also be calculated from conductivity values using appropriate algorithms and displayed in map form.
The following maps can be produced automatically with the TSM:
- Electrical conductivity
- Soil zones
- Relative water content
- Vertical horizon depth
Acquire data and generate maps quickly and at any time
A field should be treated in a way that preserves the soil and crops as much as possible. Sensors with direct soil contact (disk harrow, slides) are therefore usually only used on empty surfaces.
The TSM, on the other hand, can be installed on any towing vehicles and is also able to record data during a conventional tillage cycle without another pass being required. As the TSM functions contact-free, the crops will not be affected.
Users can create soil maps from the recorded data file immediately after the pass with the TSM. The zones are mapped to begin with so that more precise and therefore fewer soil samples can be taken.
Reduce the number of soil samples
Soil zone maps simplify soil sampling and significantly reduce the work load compared to the grid method.
An example for a 40 ha field for comparsion:
With the TSM - navigate at a distance of 12 m and at 25 km/h, on-site creation of a soil zone map and subsequent collection of 4 soil samples (time taken 2 hrs 15 min).
Without the TSM - 40 samples (10 min per sample): 6 hrs 40 min; plus manual map creation using GIS software (time taken approx. 8 hrs).
Generate more accurate results
Arguably more important than the speed of the entire process is that the soil sampling delivers considerably more accurate results, especially with heterogeneous soils. Nobody wants to produce inaccurate application maps in precision agriculture.
Figure 1 & 2 below are field zone maps that were created by measuring the conductivity (Fig. 1) and through grid samples (Fig. 2). It is noticeable that the map created with grid samples has a significantly coarser resolution. In this example, only 8 (marked in green) of the 40 grid fields would actually have homogeneous soils. All other zones
(orange-red shades) would actually be mixed zones. The average values obtained in the grid would, of course, be less relevant for site-specific applications.
While the zonal borders can be determined relatively precisely using sensor technology, in grid sampling the grid size is a limiting factor in practice. The more soil samples are taken, the more precise the maps will be, but there is also an exponentially rising work load involved (below example: over 26 hours for 160 samples vs 6 hrs 40 mins for 40 samples). However, the total area of the grid cell with homogeneous soils is increased 20 % to 32 % (again displayed in green).
Benefits compared to other technologies
Sensor types commercially available are based on contact or non-contact methods. Measurements by both sensor types have given comparable results. Ground contacted sensors use coulters as electrodes to make contact with the soil and to measure the electrical conductivity. In this approach, two to three pairs of coulters are mounted on a toolbar; one pair provides electrical current into the soil (transmitting electrodes) while the other coulters (receiving electrodes) measure the voltage drop between them.
Non-contact EC sensors work on the principle of electromagnetic induction (EMI). EMI does not contact the soil surface directly. The instrument is composed of a transmitter and a receiver coil, usually installed at the opposite ends of the unit. A sensor in the device measures the resulting electromagnetic field that the current induces.
The Topsoil Mapper belongs to the family of non-contact sensors. By installing the sensor on the tractors front linkage, the sensor can be operated on any field work of the farmers daily business. This provides the user with the highest flexibility The fact that no ground coupling is needed extends the operational period within the agricultural cycle. The Topsoil Mapper is designed as a non-expert system – it operates autonomously and does not require any expert knowledge in setup or operation.
The Top Soil Mapper is manufactured by Geoprospectors.
AGree Decision Ag by Emmetts are exclusive distributors for Australia & New Zealand. For more information, phone 03 5382 9456 or email firstname.lastname@example.org