“Not a single field on earth is homogeneous”

Upon arrival at the ‘Neuwiesenhof’ farm in Baden-Württemberg in southwest Germany, the first thing that catches the eye is a Fritzmeier Isaria crop sensor. It was just used to sidedress nitrogen fertiliser variable rate in winter wheat. “Shall I show you the rest of my precision farming equipment,” says Oliver Martin. The equipment includes an Amazone mounted sprayer, a brand-new Amazone Primera direct seed drill, a Claas Lexion combine harvester, an Amazone ZA-TS twin disc fertiliser spreader with Argus Twin radar system, a Lemken Karat cultivator and a Kubota UTV with Fritzmeier soil sampler and the Geoprospectors Topsoil Mapper soil scanner.

Oliver Martin demonstrates the soil scanner at a field next to his farm. While hovering it between 20 and 45 cm above the ground, the soil electrical conductivity (ECa and ECt) is measured to determine various soil characteristics. Photo: René Koerhuis

All machines are (made) Isobus compatible and capable of working variable rate (including the cultivator). “Some of the machines were modified on our request. Others we modify or upgrade ourselves to suit our needs. There’s not a single machine or tractor on our farm that wasn’t modified!” All tractors and the combine harvester are equipped with interchangeable Topcon RTK-GPS sets and electric auto-steering systems, and the combine harvester is (of course) equipped with yield mapping. He tries to apply controlled traffic farming (CTF) where possible and uses 21m wide tramlines for spreading granular fertiliser and crop protection. The spreading width was lowered from 24 to 21m to more accurately apply granular fertiliser. Crop protection is always done between 2 and 7am to avoid evaporation and drift as much as possible and to be able to apply just 70% of the standard doses of chemicals. And if the wind catches up, his weather station aboard the tractor tells him to stop spraying… “I can also use it if necessary to afterwards prove that I was not violating the environmental rules during spraying.”

This is the new design of the Topsoil Mapper soil scanner from Geoprospectors. Photo: Geoprospectors

Very heterogenous soils

The soil sample points on the 160-ha farm with an average field size of 2.03 ha and loess soil types differ from 24 to 94 with 100 points being the best arable soil type. “So, all my fields are heterogenous to very heterogenous and that triggered me to start with site specific application.” Ploughing was banned in 1988 and since 2015, where possible, direct drilling is used instead of mulch drilling. “In arable farming, the soil is the starting point of everything. If you know what happens there, you can act with the right measures. If you spoil your soil, it will reward you with homogenous and good quality crops.”

In order to understand what is happening in his soil, Mr Martin started searching for a soil scanner some years ago. “I wanted a continuous on-the-go soil scanner that did not necessarily require an extra pass over the field to avoid (extra) soil compaction. I also did not want it to require soil contact and I wanted to be able to use it at any time, including on frozen or snow-covered soil and in (very) dry and (very) wet conditions. When I read about the Topsoil Mapper (TSM) from Austrian manufacturer Geoprospectors somewhere in 2014-2015, so before it was officially introduced, I knew I wanted to have the TSM.” Geoprospectors was founded in 2014 and the TSM soil scanner was introduced at the 2015 Agritechnica exhibition in Hanover (Germany). Mr Martin currently deploys one out of three TSM scanners in Germany and out of 56 sold worldwide (see box below for more info).

“I’m a data nerd”

If you were already amazed by the above, then you’re probably going to be flabbergasted when Mr Martin starts taking about remote and near sensing and data (processing)! “I would consider myself to be a data nerd.” Surprisingly enough, he uses satellite images instead of the soil scanner to create so-called yield potential maps. “The ESA Sentinel 1 and 2 provide very accurate 10x10m resolution images. I use radar infrared satellite images from the past five years. These are not for free, but worth the € 6/ha I’m paying.” With his own algorithms, the satellite images are processed into yield potential maps. Mr Martin can do this for any field on earth and as he points out: “Many farmers usually tend to think their fields are homogenous. But based on my experience, I can guarantee you that not a single field on earth is homogeneous!” The yield potential maps (standard) consist of five different zones between low yield potential, average yield potential and high yield potential. The zones are used to create variable rate fertiliser application as well as variable rate drilling maps. “My target is homogenous (quality) crops, saving on inputs not necessarily is. I apply them variable rate to match the site-specific yield potential. Experience shows that, based on a common 70 kg N per ha dosage, I for instance vary the application rate between 40 and 100 kg/ha and on average I apply 71 kg/ha. My profit/gain shows in the crops that are much more homogenous.”

During the growing season, Mr Martin uses the Isaria crop sensor, drones with a Parrot Sequoia thermospectral camera as well as satellite imagery (the NDVI-indices) to determine the site-specific dosage of sidedressing granular fertilisers as well as growth regulators. “I use the satellite generated NDVI-maps, since I experienced that crop sensors can be at their limits at the end of the growing season. This pays off during harvesting because the homogenous crop just requires one single optimal setting of the combine harvester. Therefore, I simply don’t need a cruise control option and I can even save fuel as well.”

Topsoil Mapper usage

The TSM soil scanner is used on the Neuwiesenhof farm to determine site specific soil texture, compaction and soil horizons, relative water content, organic matter content, and in combination with the soil sampler, the phosphate, manganese and calcium content in the top 110cm of the soil. The field maps created with the soil scanner are used to generate variable rate seed drilling maps. “In winter crops, I increase the number of seeds per hectare on parts with a low relative water content (equals lower quality soil types) to compensate for non-emerging seeds. In summer crops like seed grain maize, I use the opposite strategy as on the parts of the field with a relative low water content, water is going to be the limitation. I usually vary the number of maize seeds between 7 and 11 per square meter.”

The TSM is not (yet) used for variable depth cultivation at the farm. “Our three-point linkage cultivator is not perfectly suitable for that. A semi-trailed version would be more suitable.” The TSM is used on about one third (63 ha) of the farms fields. It was also used to determine the (deep) soil compaction caused by heavy slurry application equipment. “The compaction by self-propelled machines is so severe, even with lowest tyre pressures in crab steer, that I banned all slurry equipment from my farm. I use compost instead.”

“As the TSM soil scanner, compared to other soil scanners, measures the delta (or change) in soil conditions, it’s not necessary to scan fields more often than once every 5 to 7 years,” he concludes.