IMPAC³ covers three land uses: arable land, grassland and woody plants. Experimental varieties or clones are cultivated in pure stands (a species A or a species B) and in mixed stands (species A and species B). Eight genotypes of species A are combined with three genotypes of species B. Combinations are arranged in blocks with four replications. The complete design is established at two sites of different conditions according to soil and microclimate.
Arable land: Vicia faba (A), Triticum aestivum (B)
Grassland: Trifolium repens (A), Lolium perenne/Cichorium intybus (B)
Forest: Populus hybrids (A), Robina pseudoaccacia (B)
Photo: Soil profile at "Reinshof", a floodplain (gleyic fluvisol).
Prof. Dr. Johannes Isselstein (Speaker)
Researcher: Sara Heshmati
Topic: Plant traits in mixed grassland stands
In this subproject we analyse the role of genetic variability of growth of clover under mixture conditions. This will give information for breeders to further improve selection for mixture components.
Prof. Dr. Wolfgang Link
Researcher: Daniel Siebrecht
Topic: Plant traits in mixed arable stands
We base on a cooperation with breeding company NPZ. Cultivars of winter faba bean were developed and are now tested for mixture ability. The group is the cornerstone for establishment and maintenance of the arable plots.
Prof. Dr. Rolf Rauber / Dr. Catharina Meinen
Researcher: Juliane Streit
Topic: Root systems in pure and mixed stands
Yet the root growth and distribution of different genotypes under mixture conditions is poorly understood. We analyse rooth growth and its interaction with above ground variables.
Prof. Dr. Klaus Dittert
Researcher: Annika Lingner
Topic: Water and nutrient uptake in pure and mixed stands
In the context of climatic changes, we have to expect more frequent and intensive drought periods during spring and summer. Stress by drought is an environmental factor with strong negative effects on plant growth and yield formation. Therefore, plant traits are especially important which are responsible for high performance in mixed cropping stands under dry conditions. In order to evaluate an improvement in productivity and water use of mixed cropping in comparison to pure stands, the development of crop stands was assessed via drone technique during multi-annual field experiments. On the basis of thermography and the normalized difference vegetation index (NDVI) it could be shown that mixed cropping with legumes increase productivity and efficiency in water use in comparison to pure stands of non-legumes. Furthermore, promising genotypes of winter faba bean and white clover are selected for detailed research on stress physiology in the greenhouse in order to reveal genotypic differences. Here it became apparent that in mixed cropping of winter faba bean and winter wheat there was a clear interaction between genotype and cropping system, indicating the need for specific breeding for mixed cropping.
Prof. Dr. Stefan Vidal
Researcher: Sandra Granzow
Topic: Multitrophic Interactions in mixtures
Beneficial plant-associated microorganisms such as bacteria or fungi are widely acknowledged as key promoter in plant growth and health. Although playing crucial roles in ecosystem functioning and in a sustainable agriculture, our knowledge on the effects of agricultural practices on the plant microbiome is still limited. The main focus of the work was to understand which factors shape microbial community composition and diversity in response to different cropping systems, namely monoculture and intercropping, in winter wheat (Triticum aestivum L.) and winter faba bean (Vicia faba L.) using Illumina (MiSeq) sequencing. For that purpose, we conducted several greenhouse experiments and also investigated under field conditions. In addition, we examined whether abiotic or biotic factors such as water deficit or the application of an entomopathogenic fungus have an influence on plant-associated microbial communities and their response to cropping systems. Fundamental knowledge of plant-associated microorganisms and their responses towards agricultural practices are important to successfully implement a sustainable agriculture
Prof. Dr. Christian Ammer
Researcher: Jessica Rebola Lichtenberg
Topic: Interactions of plants in mixed woody stands
Poplars are commonly used for production of fast growing biomass. They are preferentially used under monoculture conditions. We investigate into the chances of introducing Robinia into poplar stands to exploit mixture benefits.
Prof. Dr. Andrea Polle
Researcher: Dr. Dejuan Euring
Topic: Nutrient uptake in short rotation coppice
Poplars are well recognized as an excellent bioenergy feedstock for short rotation coppice plantations. However, available poplar cultivars require relatively high water and nitrogen supply for optimal growth. For ecologically sustainable farming systems, it is of great interest to know whether the yield of poplars can be increased by mixed cropping with nitrogen-fixing tree species. In this project, the fast growing nitrogen-fixing tree species, Robinia pseudoaccacia has been selected for mixing with Populus sp. In order to investigate whether the productivity in the mixture of poplar and Robinia has changed, the growth of the poplars is determined several times a year and selected plants are harvested. Based on biomass and nitrogen content, the nitrogen use efficiency can be determined. Photosynthesis and transpiration measurements as well as foliar biomass together with δ13C measurements enable the evaluation of short- and long-term water use. Wood anatomy and wood density are important properties for further utilization of wood. These traits will be determined after harvest. In order to gain insight into the molecular genetic basis of growth changes, transcriptome analyzes are carried out in the wood and the roots of poplars. It is expected that potential marker genes for positive traits in mixed cropping practice can be identified.
Prof. Dr. Oliver Gailing
Researcher: Dr. Oleksandra Kuchma
Topic: Plant traits in mixed woody stands
IThe need for biomass production leads to an intensification of land use systems and lower diversity. Populus hybrids (poplar) are widely used for bioenergy in monoculture systems due to their rapid high biomass production. Robinia pseudoacacia L. (black locust) is a lesser known species for energy production, but is known to have the ability to fix nitrogen. The hypothesis of the project IMPAC3 states that mixing an economic important tree species with a nitrogen fixing tree species may improve ecological functions and enhance crop systems stability. In 2006 the genome of Populus trichocarpa, was fully sequenced by the Joint Genome Institute, United States Department of Energy, USA. This genome assembly can be used as a reference genome sequence for further genetic analysis of poplar species with ecological and economical importance. Transcriptome analysis allows a detailed look into gene expression of tree species at different developmental stages for a better understanding of gene functions. To identify differences in gene expression levels in leafs, gene expressions in different growing and site conditions will be analyzed by RNA sequencing.
Biology and Ecology
Prof. Dr. Stefan Scheu
Researcher: Paul Götsch
Topic: Multitrophic interactions in mixed stands (soil aspects)
Soil organisms including microflora and soil fauna, form an essential component of the biodiversity in agroecosystems. In particular in the rhizosphere of plants they sensitively respond to the identity and diversity of plants. Thereby, plants modify both the structure and functioning of soil communities with potential important feedbacks to plant performance, biomass production and crop yield. It is increasingly recognized that biota in the rhizosphere of plants not only affect plant growth but also the susceptibility of plants for being attacked by pathogens and herbivores. In the framework of IMPAC3 we investigate the response of belowground biota to variations in plant genotype identity and mixture of plant genotypes with other plant species of arable, grassland and forest systems. Further, we will explore the response of different plant genotypes and genotype mixtures with other plant species to variations in rhizosphere biota. The structure of belowground microbial communities will be analyzed using substrate induced respiration and phospholipid fatty acid analysis and that of soil animal communities using heat extraction. Certain microorganisms and soil animals significantly responding to variations in plant genotypes and mixtures of plant genotypes with other plant species will be used for evaluating soil feedbacks of these to plant performance.
Socio economics and modelling
Prof. Dr. Achim Spiller
Researcher: Dominic Lemken
Topic: Attitudes towards mixed cropping
New technologies could be seen as chance, but often farmers see the barriers and do not adopt advfanced farming systems such as mixed cropping. We aim to identify drivers and barriers for mixed cropping which might help to improve further research and extension.
Prof. Dr. Oliver Mußhoff
Bearbeitung: Vanessa Bonke
Thema: Risk economics of mixed cropping
Often it is assumed that a diversified production portfolio has a risk-reducing effect on the total gross margin of the whole farm. In this subproject we therefore assess intercropping from an economic perspective. Based on the experimental results for yield and associated variables, gross margins for the different cultivation methods will be calculated. Using stochastic simulation techniques, risk profiles for different production activities shall be derived. Building on these calculations, an integrative whole-farm optimization model will be developed. In addition, the influence of farmer’s subjective risk attitude on the decision to adopt mixed cropping is going to be evaluated.
Prof. Dr. Reimund Rötter / Dr. Munir Hoffmann
Researcher: William Nelson
Topic: Modelling of mixed stands
We use APSIM crop model for simulating various crops and growth conditions. In the IMPAC³ project we calibrate the model for better forcasting plant growth under mixture conditions.