Abstract
The size of today’s agricultural machinery is one of the major contributors to the soil compaction problem (Schjønning, van den Akker et al. 2015). As agriculture adopts new technologies and advances towards automation, lightweight agricultural robots have been suggested as a possible solution to minimize soil compaction (Bluett, Tullberg et al. 2019, McPhee, Antille et al. 2020). Lighter and smaller machinery imply less capacity and as a result, less efficiency. To compensate for it, agricultural robots are being developed to work collaboratively in fleets. More vehicles on the field and narrower working widths will inevitably increase the area affected by traffic and repeated wheeling. Whether, it is less damaging to pass once with a heavy machine or multiple times with a lighter machine is still not clear and fully understood (Pulido-Moncada, Munkholm et al. 2019).
In this project, the ROBOTTI 150D (Agro Intelligence ApS) is being used as a lightweight autonomous field robot in different field experiments related to soil compaction and repeated wheeling. The objectives of the project are (i) to understand and characterize the stresses from the robot at the soil-tyre interface, (ii) to assess their impacts on soil structure and soil physical properties and (iii) to evaluate the influence of time and environmental factors on those impacts.
The ROBOTTI 150D (2020) is equipped with 320/65 R16 tires. It has a total mass of 3100 kg and it can carry 750 kg of extra load. It has two modules each of them having two wheels and one 55 kW diesel engine. The two modules are joined by a boom, which also serves as a suspension by using a revolute joint in one of the extremes. This type of suspension, although simple, differs substantially from traditional tractors and influences how the load is distributed among the wheels, especially when moving while loaded.
An initial experiment was conducted in April 2021 at Foulumgård (Denmark). Stress transducers were installed on a loamy sand soil close to field capacity at 10 cm depth. The robot was driven 10 times over the transducers while measuring the stresses. Penetration resistance down to 30 cm and 100 cm3 soil cores at 10 cm depth were respectively measured and excavated after one, five and ten passes to assess the effect of repeated wheeling on soil properties. From the stress transducers, we obtained the maximum vertical and horizontal stresses and the dynamic mean ground pressures. In the laboratory, we measured air permeability and air-filled porosity on the soil cores after equilibrating them to -100 hPa matric potential.
Due to the use of relatively small tires, mean ground pressures were found around 100 kPa which are similar to those from light and medium size tractors. For the same reason, mean maximum vertical stresses at 10 cm depths were close to 200 kPa, also similar to maximum stresses found on larger machinery. The high ground pressures resulted in topsoil compaction. After ten passes with the robot, air permeability and air-filled porosity were reduced to 8 μm2 and 0.14 cm3 cm-3 respectively. These values although low, are not critical for crop growth but might be worth considering in terms of risk of erosion or gas emissions. No changes were observed in penetration resistance below 25 cm depth for the different number of passes. Thus, showing the potential of using lightweight machinery to protect subsoils.
A second experiment was held on sandy loam soil at Flakkebjerg (Denmark). In October 2021, the robot was equipped with a sowing implement to establish a winter wheat crop on a fresh seedbed (prepared by a tractor) close to field capacity. In May 2022, under dry conditions with water contents close to the wilting point, mechanical weeding was conducted using a weeder attached to the robot. The same wheel tracks were followed for both operations. Before and after each operation, 8 x Ø10 cm soil cores were excavated from the middle of the wheel track starting at 10 cm depth. The samples were equilibrated to -100 hPa matric potential and air permeability and effective air-filled porosity were measured. After the laboratory measurements, the samples were X-ray CT scanned on a medical scanner. The voxel size of the resulting images was 0.3 x 0.3 x 0.5 mm. The images were segmented and analyzed with the software ImageJ to obtain, among other parameters, the total number and volume of macropores larger than 1 mm3.
The preliminary results show a significant (non-critical) decrease in macroporosity and air permeability from 0.09 cm3 cm-3 and 200 μm2 to 0.025 cm3 cm-3 and 100 μm2 respectively, as a consequence of passing with the robot on a moist seedbed (low soil strength). No changes were observed on the wheel track from the first to the second operation using the observed parameters. Thus, suggesting no effect from the environmental factors after 7 months. Due to the dry conditions (increase in soil strength) during the mechanical weeding, passing with the robot had no significant effect on the wheel track. These results highlight the importance of considering soil strength for timing field operations.
In conclusion, lightweight autonomous robots might help to avoid subsoil compaction but can potentially cause considerable topsoil compaction. Despite the light wheel loads, the number of wheeling events and operations should not be disregarded. Monitoring and estimating soil strength is still a key aspect to minimize the risk of soil compaction, even when using lightweight machinery.
In this project, the ROBOTTI 150D (Agro Intelligence ApS) is being used as a lightweight autonomous field robot in different field experiments related to soil compaction and repeated wheeling. The objectives of the project are (i) to understand and characterize the stresses from the robot at the soil-tyre interface, (ii) to assess their impacts on soil structure and soil physical properties and (iii) to evaluate the influence of time and environmental factors on those impacts.
The ROBOTTI 150D (2020) is equipped with 320/65 R16 tires. It has a total mass of 3100 kg and it can carry 750 kg of extra load. It has two modules each of them having two wheels and one 55 kW diesel engine. The two modules are joined by a boom, which also serves as a suspension by using a revolute joint in one of the extremes. This type of suspension, although simple, differs substantially from traditional tractors and influences how the load is distributed among the wheels, especially when moving while loaded.
An initial experiment was conducted in April 2021 at Foulumgård (Denmark). Stress transducers were installed on a loamy sand soil close to field capacity at 10 cm depth. The robot was driven 10 times over the transducers while measuring the stresses. Penetration resistance down to 30 cm and 100 cm3 soil cores at 10 cm depth were respectively measured and excavated after one, five and ten passes to assess the effect of repeated wheeling on soil properties. From the stress transducers, we obtained the maximum vertical and horizontal stresses and the dynamic mean ground pressures. In the laboratory, we measured air permeability and air-filled porosity on the soil cores after equilibrating them to -100 hPa matric potential.
Due to the use of relatively small tires, mean ground pressures were found around 100 kPa which are similar to those from light and medium size tractors. For the same reason, mean maximum vertical stresses at 10 cm depths were close to 200 kPa, also similar to maximum stresses found on larger machinery. The high ground pressures resulted in topsoil compaction. After ten passes with the robot, air permeability and air-filled porosity were reduced to 8 μm2 and 0.14 cm3 cm-3 respectively. These values although low, are not critical for crop growth but might be worth considering in terms of risk of erosion or gas emissions. No changes were observed in penetration resistance below 25 cm depth for the different number of passes. Thus, showing the potential of using lightweight machinery to protect subsoils.
A second experiment was held on sandy loam soil at Flakkebjerg (Denmark). In October 2021, the robot was equipped with a sowing implement to establish a winter wheat crop on a fresh seedbed (prepared by a tractor) close to field capacity. In May 2022, under dry conditions with water contents close to the wilting point, mechanical weeding was conducted using a weeder attached to the robot. The same wheel tracks were followed for both operations. Before and after each operation, 8 x Ø10 cm soil cores were excavated from the middle of the wheel track starting at 10 cm depth. The samples were equilibrated to -100 hPa matric potential and air permeability and effective air-filled porosity were measured. After the laboratory measurements, the samples were X-ray CT scanned on a medical scanner. The voxel size of the resulting images was 0.3 x 0.3 x 0.5 mm. The images were segmented and analyzed with the software ImageJ to obtain, among other parameters, the total number and volume of macropores larger than 1 mm3.
The preliminary results show a significant (non-critical) decrease in macroporosity and air permeability from 0.09 cm3 cm-3 and 200 μm2 to 0.025 cm3 cm-3 and 100 μm2 respectively, as a consequence of passing with the robot on a moist seedbed (low soil strength). No changes were observed on the wheel track from the first to the second operation using the observed parameters. Thus, suggesting no effect from the environmental factors after 7 months. Due to the dry conditions (increase in soil strength) during the mechanical weeding, passing with the robot had no significant effect on the wheel track. These results highlight the importance of considering soil strength for timing field operations.
In conclusion, lightweight autonomous robots might help to avoid subsoil compaction but can potentially cause considerable topsoil compaction. Despite the light wheel loads, the number of wheeling events and operations should not be disregarded. Monitoring and estimating soil strength is still a key aspect to minimize the risk of soil compaction, even when using lightweight machinery.
| Originalsprog | Engelsk |
|---|---|
| Titel | Book of abstracts : NJF Seminar: Advances and Innovations in Agriculture |
| Forlag | NJF, Nordic Association of Agricultural Scientists |
| Publikationsdato | nov. 2022 |
| Sider | 32-33 |
| Status | Udgivet - nov. 2022 |
| Begivenhed | Advances and Innovations in Agricultural Engineering.: 4th NJF - Agromek- EurAgEng joint seminar - Sydsalen, Entrance Agromek West, Herning, Danmark Varighed: 29 nov. 2022 → 30 nov. 2022 https://www.nmbu.no/forside/agromek |
Konference
| Konference | Advances and Innovations in Agricultural Engineering. |
|---|---|
| Lokation | Sydsalen, Entrance Agromek West |
| Land/Område | Danmark |
| By | Herning |
| Periode | 29/11/2022 → 30/11/2022 |
| Internetadresse |