Nowadays, conventional farming systems work with narrow crop rotations or even without any rotation. Conventional crop rotations commonly consist of 2-3 crops of which usually 2 are cereals. In particular conventional cattle farms are characterized by a high percentage of maize cropping, used as livestock feed. These cereals are cultivated with high inputs of synthetic nitrogen fertiliser, requiring a high-energy use to be produced and leading to direct nitrogen emissions when being applied on the crops. Further, as most of the cropped cereals, such as maize, are additionally associated with the problem of soil organic matter losses, a new approach is needed which reduced GHG emissions and other associated problems of the common crop rotation systems.
In organic livestock farms grass-legume (alfalfa, red and white clover, etc.) leys are a relatively common element, as the grass-legume mix can be used as fodder and the positive effects on soil fertility, pest management and nitrogen fixation in the soil are well known. But for stockless farms even under organic management, the grass-legume biomass would have to be mulched, which involves a loss of financial value, nutrients and evokes nitrous oxide release.
What is the SOLMACC practice
In order to reduce GHG emissions on the farms, SOLMACC farmers implement different changes in their crop rotation systems, depending on their farm structures, size and technical/financial possibilities.
Increased share of grain legumes
Some of the farms introduce grain legumes, such as soya, beans, winter peas and lupines into their crop rotation or extended their share. These legumes substitute cereals cropped and help to fix nitrogen (reducing of N2O emissions) and additionally sequester carbon.
Increasing forage legumes/grass-legume leys
Some of the farms introduced forage legumes or extended their share in the crop rotation. This was done by enriching the proportion of N fixing plant specie in the current green manure mixture. The grass-legume biomass is harvested as hay or silage as livestock feed. Stockless farms also implemented optimized crop rotations with grass-legume leys and their harvested biomass was used by agreed cooperating livestock or biogas producing farms, respectively. The farm residues of the livestock/biogas farm, be they farmyard manure or biogas rest substrate, are brought back to the cropland of the stockless farm in amounts equivalent to the amount of nitrogen in the grass-clover biomass.
Two different cooperation models were established:
- Cooperation between stockless and livestock farms (stockless farm exports grass-legume, imports manure) are established
- Cooperation with biogas producing farms: Biogas plants are often associated with intensive maize monocultures with all related negative environmental effects (soil erosion, fertiliser application, biodiversity decline); the use of grass-legume in biogas plants can help to increase the sustainability of biogas plants (increased carbon stock in soil under grass-legume mixtures, higher biodiversity, soil structure improvement and increased resilience to extreme weather events, biological nitrogen fixation)
What are the positive climate effects
The optimized crop rotation practices of the SOLMACC farms provide measures to reduce GHG emissions of conventional and organic farms by:
- N fixation, which helps to reduce N2O emissions and additionally helps to replace energy-intensive synthetic fertilizers
- Grain/forage legumes help to sequester carbon by increasing the soil organic matter. This will also help farmers to maintain or increase soil fertility.
Additionally, the cooperation between livestock and stockless farms will demonstrate a win-win situation for both farms, environmentally but also economically. As the grass-clover biomass will not be left anymore as much on the field but be removed instead, the associated nitrous oxide emissions will decrease along with an overall increase of the N-fixation performance of the grass-legume system. The livestock and/or biogas farm receives additional feedstuff and can therefore increase its intensity without further land use expansion. The cooperation is also economically viable since biogas can be produced by using the grass-legume and thereby improving nitrogen fixation by the legume and increase the overall efficiency of the system.