Suggested:
What is the best way to build up humus - through direct seeding or partial crumb deepening? And how do these approaches affect long-term soil fertility? Two experts provide insight.
At a workshop on soil cultivation during the HumusKlimaTag, direct sower Burkhard Fromme and expert in partial crumb deepening Dr. Andreas Baur discussed with participants how soil organic matter content can be increased through specific cultivation methods. Despite the differences between the two approaches, they are not necessarily contradictory but rather complementary.
Burkhard Fromme and Dr. Andreas Baur presented two very different approaches to cultivation methods: direct sowing and partial crumb deepening. However, there were some parallels in their goals.
Direct Sowing
For farmer Burkhard Fromme, direct sowing is the ideal approach to increase soil fertility and build organic matter. It is important to the farmer from Scheppau, Lower Saxony, that the focus is not only on using direct sowing technology, but rather on thinking in terms of a system.
A central element for him is cover crop cultivation. Fromme relies on diverse mixtures with eight or more components that biologically stabilize soil structure. Planted within eight hours after harvest, they effectively reduce erosion and sludging on Fromme's fields. Ground cover with plant material also protects the soil from extreme temperature fluctuations and reduces water loss, which is particularly important in times of climate change.
Although cover crops can impress with their enormous aboveground biomass production, what happens in the soil is more crucial for the farmer. "To build organic matter in the long term, we need to promote root growth," says Fromme. This is not just about the roots themselves but mainly about the exudates they release to feed soil life. Constantly feeding soil life stimulates biological processes in the soil. For example, earthworm activity is promoted, which in turn improves water infiltration and increases soil fertility.
To avoid counteracting a stable soil structure, Fromme tries to minimize soil pressure. Therefore, the use of wide tires with low air pressure is as important to him as the specialized direct sowing technology.
Partial Crumb Deepening
Dr. Andreas Baur from the Leibniz Centre for Agricultural Landscape Research (ZALF) presented a completely different approach, which could be considered the opposite of direct sowing: partial crumb deepening (pKV). Nevertheless, Baur also focuses on soil structure, creating root space, and building organic matter or storing carbon. But what is behind partial crumb deepening?
A central element of this method is a (Carbon Farming) plow whose shares work at different depths. They mix low-carbon subsoil to some extent into the topsoil and simultaneously move humus-rich topsoil into newly created shafts in the subsoil. Ultimately, pKV aims to increase the carbon content in the soil.
Another advantage of this method, according to Baur, is that the melioration shares, which work up to 55 cm deep, break through compaction zones below the plow depth. This makes the water and nutrient reserves of the subsoil more accessible to the crops, increasing yields. The crumb soil in the shafts also reduces recompaction due to the higher organic matter content, as occurs with extensive deep plowing. The firm zones remaining between the loosening shafts maintain the soil's load-bearing capacity. Baur and his colleagues have been researching pKV for many years and consider a meliorative measure every ten years to be beneficial. An interesting aspect of the work of the ZALF researchers is that they examine areas that were processed with so-called segment plows during the GDR era. Back then, the focus was mainly on breaking up soil compaction. Since the working method of the plow used then is very similar to that of the current Carbon Farming plow, soil was also shifted back then. The shafts created about 40 years ago are still recognizable today and the subject of Baur's research. Studies have shown that the bulk density in the old shafts is still significantly lower than in the adjacent non-loosened areas. Researchers can also demonstrate that in 40 years, a maximum of 50% of the carbon from the humus-rich topsoil shifted into the shafts has been degraded.
According to Baur, with a one-time pKV operation, sustainable carbon storage can be achieved, ranging from 10t CO2/ha on sandy soils to 30t CO2/ha on loamy soils.
Both Baur and direct sower Fromme claim that their systems build organic matter and improve soil structure. This makes the soil more resilient to extreme weather conditions, providing protection against the effects of climate change and contributing to climate protection. The experts also agree that both approaches can be combined if the areas are transitioned to direct sowing after the Carbon Farming plow.
