Climate change impacts and sustainability of farming systems - assessments in a network of pilot farms
Agricultural activities of farms and the activities’ contributions to climate change are highly complex. Organic and conventional farms are different in methods, input and yield level. It is unknown if and how environmental effects and sustainability of farms differ systematically with respect to farming system and region. Climate [change] impacts of agricultural production in 80 organic and conventional dairy farms and cash crop farms in Germany are analyzed and modelled.
Research methods on sustainability analyses based on whole farm approaches are only rarely available, particularly with regard to real farms acting in the actual economic and legal setting. This is where the project focuses on: A network of organic and conventional so-called pilot farms is established in Germany to facilitate long-term systemic research. . Two research topics are addressed:
a) Greenhouse gas emissions of farming systems: Organic and conventional farming systems are analysed with respect to emissions of CO2, N2O and CH4 on the farm level. Greenhouse gas emissions in plant and milk production are modelled, the main drivers of emissions are identified and from this, mitigation strategies are deducted. b) Sustainability of farming systems: Indicators that describe and compare soil fertility, soil protection (soil erosion, soil compaction, humus content), water protection issues, biodiversity and landscape aspects are analysed to describe environmental sustainability of farming systems.
40 organic and 40 conventional German farms were explored with respect to dairying and cropping from 2009 to 2014. Whole-farm greenhouse gas balances were calculated on basis of farm and analytical data. All relevant pre-chain and farm processes and emissions as well as energy, nitrogen and carbon flows and land use changes were considered.
To include a wide range of site and management conditions 80 organic and conventional farms were selected from four German regions in a paired approach (one organic and one conventional farm located close to each other form a pair of dairy farms or cash crop farms, respectively). Farm management data were assessed from 2009 to 2014 by interviews with the farmers and their available records. In the first years, samples of feedstuff, livestock manure, soils and plants were taken and analysed. Wheat yields and clover grass yields were determined on the farms. Greenhouse gas emissions were modelled with the software REPRO. Additionally, the effects of different modelling approaches in milk production on greenhouse gas emissions from enteric fermentation and manure were studied in detail.
The results show a high variability of greenhouse gas flows depending on site conditions, farm structure, intensity and management. Critical emissions points and insecurities in modelling were identified. First steps to develop an advisory concept on climate smart agriculture were done.
In detail, we found:
In all parameters and all results the group of organic farms showed to be far more diverse than the group of conventional farms. The annual milk yield also varied widely between the organic farms which increased heterogeneity in all product related results.
On average, the organic dairy cows had lower milk yileds than the conventional dairy cows. For this reason, all average product related emissions were higher for the organic farms.
Comparing CO2 balances of the organic and conventional farms in the South and in the West as opposed to the emission only, the picture changed. The CO2 balance also takes pre-chain emissions into account (such as production of chemical-synthetic fertilizers or buying feedstuffs form abroad) and also considers CO2 storage in soils. The CO2 balance revealed that on average, organic farms work with lower energy input (predominantly because they do not use chemical-synthetic fertilizers for feedstuff production) and bind more CO2 in their soils (mainly because of a high share of clover-grass in the crop rotations). Conventional farms reached their higher milk yields by feeding maize silage and concentrates produced on farm and off farm (using large inputs of chemical nitrogen fertilizers). Using soy bean extraction feeds, which are banned from use in organic farming, leads to CO2 emissions from soils (due to land use change from rain forest to arable land). On average, the animal related CO2 balance was lower for organic than for conventional farms, while the product related CO2 balance was not different per kg of energy corrected milk.
Enteric methane emissions had the largest share on the emissions (both animal related and product related). To a large extent, enteric emissions are genetically given but can nevertheless be decreased by offering high quality roughage and a ration adequate for the cows’ milk yield. The method by which enteric emissions are determined largely effects the level of results. For that reason, one and the same method must be used if comparisons are made (e.g. comparing farms or systems).
Emissions from dairy cow excreta also had a high share on the overall emissions. No differences were found between straw based and slurry based systems. While some of these emissions from excreta are inevitable, the largest share can be reduced considerably by applying well-established methods during storage and application of manures.
12.2008 - 7.2014
Project funding number: 06OE353 (Thünen-Institut), 06OE353 (TUM)
Funding program: Bundesprogramm Ökologischer Landbau und andere Formen nachhaltiger Landwirtschaft (BÖLN)
Project status: finished