M. Kuhwald, W. Hamer, J. Brunotte, and R. Duttmann (2020)

Soil Penetration Resistance after One-Time Inversion Tillage: A Spatio-Temporal Analysis at the Field Scale

Land2020, 9(12), 482

An important component of SOILAssist is the involvement of stakeholders. To identify and investigate soil compaction under real conditions in farmers' fields, we ask farmers if there is compaction in their fields and what signs do they recognize.

The possibly compacted areas are located on the field and additionally a control area that shows no changes. These areas are investigated with our UAV to detect possible compaction patterns.

In addition, we carry out hand harvesting of the crop to detect any yield depressions. Soil sampling takes place in the control area and in the compacted area. The hydraulic conductivity is investigated directly in the field with infiltrators. We also examine the penetration resistance of the soil. With these methods we can determine soil structural deterioration due to compaction.

Due to the recurring summer drought, the soil investigation is planned for spring. Due to the corona pandemic, we unfortunately could not visit the farmers this year until summer. Under the required distance and hygiene rules we conducted interviews and sampled the fields. However, soil sampling was only possible at one of the farmers fields because the soil had dried out too much.

On-farm research is an important research component to study soil compaction under real conditions and determine the influence on yield.

The last field campaign this year was the sugar beet harvest in October 2020.

The focus of this field trial was the measurement with our tire measurement boxes, which are installed in each of the six rims of the Grimme Rexor beet harvester. They measure the tire deflection of each tire. This is directly connected to the wheel load. Portable field scales can be used to determine the static wheel load. However, the dynamic wheel load in the field can be many times higher, as it depends on the slope inclination and slip. The Rexor is a bunker machine and so the wheel load increases continuously during harvesting until the bunker is filled and the beets have to be debunkered.

The tire measurement boxes give information about the dynamic wheel load during the field operation. An RTK GPS is used to precisely locate the machine in the field during harvesting. The data from the tire measurement boxes is merged with the GPS data to provide a precise indication of the load applied by the harvester in the field.

Therefore we are able to indicate the exact influence of the harvesting machine on the soil. With the help of this information we can give recommendations for action, e.g. adjusting the bunker filling to the length of the field.

In September and October 2020, we were able to successfully complete the planned silo maize campaign on field 1 of the SOILAssist trial areas. In addition to an extensive manual harvest, we also took a large number of soil samples. Working outdoors enabled us to comply with the distance and hygiene rules, so that safe working under the current pandemic conditions was possible.

Soil sampling and manual harvesting is an essential validation component of the compaction detection carried out in the project by UAV images. For this purpose, soil samples are taken in the field at areas that were previously detected as conspicuous and are examined in our laboratories for soil-physical tests. Additional samples were taken at control areas and will then serve as a reference in the analysis.

In the SOILAssist project, the motto is: "After the sampling is before the harvest". This could also be accompanied and recorded despite current restrictions. This year, the Claas 970 maize chopper with a working width of 9 m was used. It was accompanied by five loading vehicles with silo trucks from the company Kaweco. During harvesting, care was taken to ensure that the loading vehicles followed the parallel running mulcher wherever possible. By using RTK-GPS, a high-resolution image of the driving sequences during the silo maize harvest of the different machines could be recorded.

Despite the current difficult situation concerning Corona, we were able to carry out measurements with the gamma spectrometer from the BonaRes project I4S (Intelligence for Soil) on the SoilAssist test fields with a reduced team and in compliance with all distance and hygiene requirements.

The aim was to derive heterogeneities and differences in soil parameters, such as clay content, from the measurement of natural radioactive radiation in the field. The measurements took place on field 1. Silage maize growing on the field was in an early stage of development (BBCH 10-12). On field 1, three different soil tillage variants (plough, cultivator, short disc harrow) were applied, so this aspect can be included in the evaluations.

Furthermore, extensive analyses, e.g. particle size distribution data are available from SoilAssist measurements and can be used for the evaluations. In addition, a further field with significant heterogeneities and a clay vein in the topsoil was included in the investigations and surveyed with the gamma spectrometer. The evaluations will be carried out together with I4S.

After a brief interruption of the flights, which was caused by the worldwide Corona Pandemic, SoilAssist was able to resume its work in the study areas Hohenschulen and Adenstedt in mid-April. For this purpose, the schedule of the investigations was adjusted so that it can be carried out by a single person. This meant that the digital terrain models (DTM) for the maize and sugar beet fields in the study areas could be produced in good time after sowing. In addition, a first survey of the cereal vegetation on the test fields was possible. 

The preparation of the DTM is essential for spatial analyses using an Unmanned Arial Vehicle (UAV) to determine plant growth.