Cultivating for the climate
The harvest has been brought in, the winter grains are already slumbering in the ground. But in the time between harvest and new sowing, many fields lay fallow for months, some even remain uncultivated until spring. That could change in the future – for the sake of the climate. The cultivation of catch crops could help to reduce CO2.
“We notice that grain fields, for example, are harvested earlier and earlier in summer. The autumn or spring sowing also shifts forward, but not as significantly. Thus, fields lie fallow for longer periods of time. This means that the period in which arable plants convert CO2 using photosynthesis becomes shorter,” says Dr. Alexander Graf from the Institute of Bio- and Geosciences (IBG-3), who is investigating the CO2 exchange between soils, plants and the atmosphere.
After the harvest, some farmers cultivate catch crops which are not harvested but ploughed under later, such as mustard and oil radish. This prevents nitrate leaching into groundwater, saves fertiliser and improves soil quality. Catch crop sowing could apparently also help to slow down the increase in CO2 concentrations in the atmosphere and thus mitigate climate change.
days longerthan 50 years ago, fields lie fallow
Graf and his team have found that a field with repeated catch crop cultivation absorbed about 60 per cent more CO2 than a field that had been left fallow more often and for longer periods. They had collected data from two arable fields for four years. “The next step is to find out under which conditions plants and soils store and release which quantities of CO2,” he emphasises.
Not only the respective soil properties play a role here, but also the increasing amount of CO2 in the atmosphere, which acts as additional fertiliser for some plants, or global warming, which causes organisms in the soil to release more CO2 into the air. “When we understand these exchange processes better, we can pinpoint concretely whether and how which catch crops can be used specifically for climate protection,” says Graf.
REDUCING MORE CO2 WITH WINTER GRAINS
A field that is repeatedly tilled with catch crops between the sowing times of plants such as sugar beet and wheat absorbs 60 per cent more CO2 than ...
... a field that lies fallow until the next sowing. During fallow, a field emits about half of the CO2 it absorbed before.
Image: Forschungszentrum Jülich/Sascha Kreklau, Graphic: SeitenPlan GmbH