Long-term test disproves assumption - CO2 inventory is optimized
Soils have great potential to retain CO2 from the atmosphere in the form of carbon. Agroscope researchers have now been able to show that in extensive cultivation systems significantly more carbon enters the soil via plant roots than previously assumed. Based on these findings, the estimated values for the national greenhouse gas inventory were adjusted.
With the greenhouse gas inventory, the federal government checks whether Switzerland is on track with its CO2 reduction targets. Soils play an important role in this, as they absorb CO2 from the atmosphere. Crop roots are the most important source of soil organic carbon in arable soils. These inputs are estimated in the greenhouse gas inventory based on aboveground biomass. Previously, carbon inputs through roots were assumed to increase as more aboveground biomass is formed. This means that for intensive cropping systems with high yields, higher carbon inputs were assumed than for extensive systems such as organic farming.
Long-term field tests disprove previous assumptions
Agroscope has now disproved these assumptions. Researchers studied the below-ground carbon inputs of maize and winter wheat in two of their most important long-term experiments, the DOK experiment (comparing organic and conventional farming systems since 1978, Therwil BL) and the ZOFE (the Zurich Organic Fertilization Experiment was started in 1949 and is the oldest long-term experiment in Switzerland). Carbon inputs are the sum of carbon supplied to the soil via the roots themselves on the one hand and via root exudates on the other. Surprisingly, below-ground carbon inputs remained constant in both crops, although above-ground biomass varied up to a factor of 3.5. The biological method in the DOK trial even had one third higher carbon inputs via root exudates than conventional cultivation in corn with 20% lower aboveground biomass.
As a quintessence, it can thus be said that more carbon is added to the soil via root biomass and root exudates in organic farming in relation to above-ground biomass than in intensive arable farming.
Field studies on practical farms confirm model studies
The results of another extensive study on 24 farms in Switzerland confirmed the findings from the long-term trials. Wheat yields on the organic farms were one-third lower than under conventional management, but root biomass was 40% higher. The results underscore the potential of extensive systems such as organic farming to contribute more carbon to the soil through the roots and thereby mitigate climate change.
Adjustment in the greenhouse gas inventory
Based on these findings by Agroscope, the estimated values in the model for calculating the greenhouse gas inventory were adjusted. The greenhouse gas inventory is used to check whether Switzerland is on track with the international and national reduction targets according to the Kyoto Protocol and the CO2 Act. CO2 emissions or the CO2 uptake of soils also play an important role. Both can be influenced by agricultural use. Since carbon inputs via the roots cannot be measured on a large scale, they have so far been estimated for cereals on the basis of above-ground biomass yields.
Source: Agroscope
Info: The results of the Agroscope researchers were developed within the framework of the National Research Program "Sustainable Use of Soil as a Resource, NRP68" and published in the following renowned scientific journals:
- "Agriculture Ecosystems and Environment.
(DOI: 10.1016/j.agee.2018.07.010, link. https://doi.org/10.1016/j.agee.2018.07.010)
- "Science of the Total Environment.
(DOI: 10.1016/j.scitotenv.2020.143551, link. https://doi.org/10.1016/j.scitotenv.2020.143551)
