Field zones with different soil moisture measured by TerraSAR-X in October as basis for soil drivability or variable-rate seeding maps


“How are we supposed to generate satellite image maps for precision agriculture if we do not carry out our development work with the highest precision from the very start?” said Dr. Katrin Kohler, Head of Research and Development at SBI.

The fact that meticulous work leads to success is evidenced by the soil moisture maps investigated by SBI for the SARfields project. Farmers will soon be able to use these maps to decide on the drivability of the soil with heavy machinery and on the variable application of seeds, growth regulators or herbicides – all depending on the individual moisture zones of the field. These maps complete SBI’s portfolio of satellite image maps for field management, which includes, among others, biomass level, yield potential, and nitrogen maps.

In this project, particular emphasis was placed on the precise recordings of soil moisture in on-farm trials, which were then used as “ground truth” data and compared to the radar data from satellite images. It turned out that soil moisture can be precisely determined using radar images if the soil is still unvegetated or the plants are small. In Germany, this applies to the period from autumn until April and May for fields cultivated, i.e., with cereals. After that period, the growing biomass covers the ground and certain short-wave radar signals can no longer reach the surface. “With radar, however, it is also possible to record properties of the plant canopies, so that from May onwards radar images can be used for crop analysis and as a basis for application maps,” said Layth Sahib, the hydrogeologist responsible for the data analysis in this project at SBI. Sahib and Kohler will present the results on June 22nd in Montreal.

The research project SARFields was launched a year and a half ago within the framework of the “Development of new applications, products, and services under integrative use of X and C band SAR data” programme of the German Federal Ministry of Economics and Energy that is also co-financing the project under 50EE1508. The project is carried out in cooperation with TRE Altamira Inc., Vancouver, and is coordinated by the German and Canadian Space Agencies, DLR and CSA. The main aim of the project is to advance the application of SAR satellite images in measuring the soil moisture of agricultural land using X- and C-band SAR data, and thus promote the use of data taken from satellites RADARSAT-2, Terra-SAR-X and Sentinel-1.