Organic farming systems contribute to ecosystem services such as the maintenance of soil quality and biodiversity. Reduced tillage and green manures are efficient conservation agriculture tools that can be adapted to further improve organic crop production systems. The overall goals of this project are to design improved organic cropping systems with: (a) enhanced productivity and nutrient use efficiency, (b) more efficient weed management and (c) increased biodiversity, but (d) lower carbon footprints (in particular increased carbon sequestration and lower greenhouse gas emissions from soils). These goals will be achieved by adapting and integrating conservation agriculture techniques (in particular reduced tillage and improved use of green manures) into organic farming systems to intensify biological soil functions like nutrient cycling, soil carbon build-up and biological nitrogen fixation, while optimising weed management protocols (weeds being the main challenge when introducing reduced tillage systems). Optimum techniques for organic systems will be identified using an integrated approach:
The project’s dissemination activities will target farmers, advisors, scientific community as well as the agricultural support industries and policy makers. The main innovative strategy of the project is the adaption of conservation agriculture approaches to organic farming drawing on existing field experiments across Europe.
Interim results: At the kick-off meeting in Frick all partners defined their activities in the six work packages on data collection from field trials (WP1), crop yields and quality (WP2), soil fertility (WP3), weed management (WP4), nutrient dynamics (WP5), and farm prototyping (WP6). All partners met again at the interim meeting at the occasion of the Organic Producers Conference in Birmingham in January 2013.
Most of the TILMAN-ORG research activities are based on replicated field trials that were classified into long-term (older than seven years), mid-term (three to seven years) and short-term (younger than two years or starting). Field trial data from the past and data from literature were collected in WP1 and used for a meta-analysis on the crop and soil effects of reduced soil tillage under organic farming conditions in WP2. Likewise, it was planned to do the same for green manures, but the available data appeared too small under organic conditions. Analyses of multi-year field data and literature conducted to date confirm that reduced tillage increases soil carbon content and produces lower yield as compared to the plough system. Yield gaps varied strongly between different studies, indicating that local farming practices, crop type, and site conditions (soil, climate) had a strong influence on system performance. More than 150 farmers across Europe were interviewed and expressed their views and experiences with reduced soil tillage and green manures in WP2. Results from seven field trials, the literature and 150 farmer interviews were also used in WP6 for farm prototyping.
Soil analyses and soil emissions of greenhouse gasses are focus of WP3. Here soils from treatments of seven field trials were analyzed for a previously defined minimum data set, which is part of the Handbook of Methods, produced at the beginning of the project. Soil strata were sampled according to the respective soil tillage depths in each field trial down to the layer below the plough pan. Soils were analyzed for organic, microbial, and dissolved organic carbon and nitrogen in 2012. Carbon stocks were influenced by the form of tillage management at all sites, as expected, but they were additionally driven by the time of tillage management and the form of fertilization. Based on the results it was decided to focus on soils from Thil (FR), Scheyern (DE) and Frick (CH) for in depth soil analysis in the year 2013. These in depth analyses comprise methods based on DNA and phospholipid fatty acids as molecular markers to describe microbial community structure and functions as well as soil microbial activities (soil respiration, soil enzymes). Greenhouse gas emissions are measured at the three sites Frick (CH), Scheyern (DE) and Fischbach (LU).
Weed control may be the most challenging work for organic farmers, who want to implement reduced soil tillage. Without herbicides and without ploughing weed management is becoming a problem for farmers. Based on 13 field trials across Europe the outcome of WP4 was that despite elevated weed density, biomass, and diversity in reduced tillage treatments as compared to ploughing, crop yield was rarely reduced in the examined TILMAN-ORG field sites (one year study). Some field trials, where green manure types were tested across the tillage treatments, showed that certain green manure species are more suitable to suppress weeds than others.
Nutrient dynamics were modelled with NDICEA (Nitrogen Dynamics In Crop rotations in Ecological Agriculture) based on data sets from five field trials. The output of the modelling is not yet satisfying as measured data were only consistent with the modelled ones in one field trial. The model may need to be calibrated with suitable complete data sets from TILMAN-ORG field trials to work properly. Four new field trials with reduced tillage and green manures as factors have been set up.
TILMAN-ORG was disseminated actively to the public (website, print media, videos), to the farmers (articles, presentations, field days), and the scientific community (conferences, peer reviewed articles). All partners participated in disseminating TILMAN-ORG wherever possible.
For partner details: www.tilman-org.net/tilman-org-partners.html