#AgriChallenges
For the love of combining

05/26/2024

Straw is becoming increasingly relevant: as an energy source, building material and renewable material. At the same time, the harvest window is getting shorter; in 2023 combine harvesters were frequently confronted by green straw. Hybrid machines are known to fare well in these conditions. But is this at the expense of straw quality? This is what Rabea Renner investigated at the CLAAS Academy for her bachelor thesis – with surprising results. A profile.

Rabea translated her passion for combining into scientific facts. In her bachelor thesis she demonstrated that selected hybrid combine harvesters produce comparable straw quality to the straw walkers she investigated.

But even this finding proved hard to come by: Rabea had exams in June and was obliged to sit at a desk while the combine harvester worked outside.

"She was just itching get out there and drive it herself," recounted supervisor Klaus Schäfer, combine harvester instructor at the CLAAS Academy. For six months he has been supervising the thesis which Rabea had submitted to the Department of Agriculture at the South Westphalia University of Applied Sciences.

Title of the thesis, in scientific terms: "Investigation of the structure of long straw in relation to two different combiner harvesting systems in different types of cereal and at different harvesting times." In short, says the 24-year-old: "The straw quality is not negatively affected by the different combine harvesting systems under investigation."

Scientifically proven straw quality

In times of accelerating climate change and increasing scarcity of resources, efficient straw management is becoming more and more relevant. As a renewable resource, straw is used in many different areas: from animal husbandry to energy generation and the production of sustainable construction materials.

There is still a misconception that only straw walkers produce good straw, because they shake the straw and subject it to less mechanical stress. "People see perfect box-shaped straw and regard it as a sign of quality," explains Rabea. In contrast, a hybrid combine harvester draws the straw through the rotor and throws it together more compactly. But does this affect the quality?

"Rabea first had to define in scientific terms what characterises high-quality straw," explains her supervisor Klaus Schäfer. Not all straw has to be the same quality, it depends on how it is used, so ultimately it comes down to its commercial value. In short, can the straw be picked up by a baler?

Study trials in two federal states

Barley and wheat were mown and threshed on different trial fields in Saxony Anhalt and North Rhine-Westphalia for Rabeas' study – with a hybrid combine harvester and a straw walker.

"The straw was baled and weighed, and we also collected samples to measure straw fragmentation," the graduate explained. The findings from the investigation of the combine harvesting systems are set out in detail in the 83-page study, but the heart of the matter comes at the end: "In summary, it can be concluded that the hybrid system is on a par with the straw walker system we tested in terms of long straw quantity and quality." A very good result!

On a par with straw, way ahead of the rest

On her parents' farm, the 24-year-old still drives a conventional straw walker machine. "But we actually would have preferred a hybrid combine harvester given the weather last year," she says, referring to the 2023 harvest. "They are much more versatile and achiever higher throughputs."

In addition to faster handling of larger crop volumes for greater harvesting efficiency, hybrid combine harvesters ensure good grain quality with less damage, lower losses due to more efficient separation – and greater energy efficiency: "It costs less than 1.5 litres of diesel to harvest one tonne of wheat with a hybrid combine," calculates combine harvester instructor Klaus Schäfer.

For Rabea Renner, the moment in summer when she does the final pass with the combine harvester at the end of a long day is still priceless. At that stage it doesn't matter how the straw is handled, whether it is shaken or rotated. Her eyes light up as she remembers "that final pass before the sun goes down."

#AgriChallengesFor the love of combining

Scientifically proven straw quality

Study trials in two federal states

On a par with straw, way ahead of the rest

#AgriChallenges
For the love of combining