vor 6 Monaten

XtraBlatt Issue 01-2022

  • Text
  • Xtrablatt
  • Carbon
  • Farmers
  • Machinery
  • Contractors
  • Germany
  • Grassland
  • Slurry
  • Biogas
  • Agricultural
  • Krone

TITLE TOPIC and have

TITLE TOPIC and have increasingly become the focus of political efforts to mitigate climate change. Raising the water table to a natural level (re-wetting) can almost entirely eliminate emissions from peatland while at the same time increasing biodiversity and protecting bodies of water from nutrient inputs. However, since this would mark the end of the drainage-based grassland use that we know today, alternative forms of use and concepts for restoring wet peatlands are currently being explored in numerous research and modelling projects. TOP PRIORITY ON GRASS- LAND MANAGEMENT We need to consider how mineral soils are used too, since farming practices have a major impact on carbon (C) storage. For instance, there are significant differences in the carbon content of arable and grassland soils. Year-round vegetation cover, intensive root penetration and the regular use of organic fertilisers means that grassland soils store more organic carbon than arable soils. This has been confirmed by several scientific studies and by the results of the soil status survey in Germany. Surveying mineral soils in arable land, the measurements produced an average of 96 tonnes of organic C per hectare at a depth of 1 metre. This compares to 135t/ha on grassland, an increase of 31%. Accounting for around 4.7 million hectares and 30% of the agricultural land, grassland is a defining landscape element in Germany. Overall, it is safe to assume that grassland cultivation on mineral soils results in a net carbon sequestration. Increasing amounts of carbon are stored in grassland over time until the point of saturation is reached after several decades. By comparison, mechanical intervention (e.g. cultivating or ploughing) can cause the soil carbon that has accumulated over several years to be released far more rapidly than it was sequestered. Against this background, it should be the top priority to preserve the grass sward in the long-term by applying grassland management practices that are adapted to local conditions, such as harrowing and overseeding in order to avoid ploughing and resowing. Another primary political focus is the retention of areas under permanent grassland and the ban on ploughing environmentally sensitive permanent grassland, for example in water conservation areas or areas at risk of water or wind erosion. Yet not only is the retention of permanent grassland important for sequestered carbon levels in agricultural land, the type of land management can also be important for the sequestration of carbon. 1 BALANCING USE INTENSITY Intensively managed grasslands play an important role in the sequestration of carbon. This is because they fix high rates of carbon in the form of abundant aboveground biomass, which can also have a positive impact on belowground root growth. After all, a branching root system can store enormous quantities of carbon. Furthermore, increasing the yield level or the cutting frequency can have a favourable effect on root growth and thus on carbon fixation. Similarly, locally adapted intensive grazing regimes increase shoot density, which in turn can have positive impacts on root growth. However, it is worth bearing in mind that stepping up the intensity of use can have a negative impact on other key parameters such as biodiversity and soil compaction. It is also important to understand that increasing carbon sequestration by intensifying the use often brings climate trade-offs. For instance, higher yields translate into higher demands for nutrients, most of which are provided in the form of mineral fertiliser. Higher fertiliser application rates mean higher CO 2 emissions in fertiliser production (energy-intensive Haber-Bosch process for nitrogen production). After an application, there is also the risk of increased releases of soil-borne greenhouse gas emissions such as nitrous oxide (N 2 O). This highlights the importance of increasing the amount of legumes in the grass mix (white clover, red clover) to fix atmospheric nitrogen. In view of the current high cost of nitrogen fertilisers, it makes sense to establish legumes, if only in pursuit of a more resilient grassland management strategy. BENEFITS OF GRASS LEYS Integrating grass leys into arable crop rotations is another means of increasing the grassland area and the amount of 2 1 Mechanical interference in the soil, such as by a rotavator, may lead to a rapid release of carbon that was sequestrated over long periods of time. 2 Intensively managed grass stands play an important role in the sequestration of carbon. carbon stored in the soil. Especially in intensive cropping systems, long-term grass leys have enormous potential to improve soil fertility and increase the amount of organic matter in the soil. By providing year-round vegetation, they can reduce nitrogen losses through leaching as well as the risk of soil erosion, especially in regions with high autumn rainfall and high fertiliser inputs. Furthermore, grass-legume leys have an outstanding pre-crop value and their inclusion in the crop rotation can suppress weeds such as black grass. In conclusion, grassland soils – mainly peaty but also mineral soils – are important “natural” carbon sinks. This is because deep cultivation doesn’t normally take place in grassland. Consequently, we find less humus depletion than in intensive cropping systems. Thus researchers and policymakers focus on arable soils as a potential carbon sink or carbon source. This said, grass leys play a key role in intensive crop rotations. Whether in arable farming or permanent pasture, grassland plays an important role in climate protection – and at the same time it can provide high-quality forage for livestock. « Tammo Peters, Schleswig-Holstein Chamber of Agriculture 16 17