BonaRes (Modul A): CATCHY – Zwischenfrüchte als agronomische Maßnahme für nachhaltige Bodenfruchtbarkeit und Ertragssicherheit, SP 1

Die Ziele der Arbeitspakete, die durch den Projektpartner HSWT bearbeitet werden, umfassen: Quantifizierung der Auswirkungen von Zwischenfrüchten und Zwischenfruchtmischungen auf die Entwicklung und Ertragsarchitektur von Hauptfrüchten (Langzeitversuch Ober 8 Erntejahre in 2 Fruchtfolgen). Bewertung des Einflusses von Zwischenfrüchten und Zwischenfruchtmischungen auf den Befall von pilzl. Erregern in Hauptfrüchten (2 Fruchtfolgen Ober 8 Erntejahre). Abschätzung der Wirkungen unterschiedlichster Zwischenfrüchte auf den Entwicklungsverlauf, die Ertragsarchitektur und den Ertrag der Hauptfrucht Mais (Kurzeitversuche Ober ein Jahr) und die Optimierung von Zwischenfruchtmischungen durch systematisch erstellte Artenmischungen auf der Basis der Ertragsleistung und Ertragsarchitektur der Folgefrucht Mais.


English Version: BonaRes (Modul A): CATCHY - Catch-cropping as an Agrarian Tool for Continuing Soil Health and Yieldincrease, SP1

Objectives summary of the consortium (Gesamtziel des Projekts)

The main objective of the project is to employ catch cropping for developing innovative farming systems as well as soil management strategies for preserving and improving soil fertility. This strategy shall have an impact towards a more sustainable land use including catch crops, and could also contribute to an enhancement of marginal locations. Therefore, the focus of CATCHY is on catch cropping considered as an essential part of an integrated concept. Our aim is not only to develop improved management regimes by applying diverse catch crop mixtures, but also to develop a better and deeper understanding of the cause-effect relationships affecting, in particular, soil fertility parameters, and biological functions and interactions in soil and rhizosphere habitats. This functional orientation is supplemented with an agronomic and economic management interaction.

In detail, CATCHY has the following objectives:

- To establish long-term field trials for testing different types crop rotations, especially including diverse catch crop mixtures
- To assess the effect of individual species of catch crops and their mixtures on crop yields, agronomic traits, and on soil parameters like the size and availability of nutrient pools, nutrient fluxes, carbon inputs into soil, soil
structure and the functions and diversity of plant and soil microbiomes
- To contribute to a better understanding of the soil microbial community and its interaction with crops
- To finally contribute improved management schemes to obtain and stabilize productive, fertile soils for yield security
- To translate these improvements in user-focused calculations of long term costs and benefits of catch crop application, by decision-support tools

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Figure 1. Network of the research consortium on catch crops as tools for sustaining soil health and yield increase.

Scientific objectives of the consortium (Wissenschaftliche Arbeitsziele des Vorhabens)

The core idea of the present proposal is to fully exploit the agronomic potential of catch crops to stabilize and improve soil health over the long term. Due to a general lack of knowledge on how catch crops are best integrated into crop rotations to yield reproducible benefits, we propose a research approach that aims at a step-by-step assessment of the proposed beneficial effects of catch crops from the perspective of soil chemistry and microbiology, plant nutrition, agronomy and socioeconomics (Figure 1). Plant production and agronomy: Our core commercial partner (SP6) acts as an agricultural enterprise in the breeding and improvement of catch crops and catch crop mixtures. SP6 further runs the research station of the Deutsche Saatveredelung AG (DSV) in Asendorf (Niedersachsen) offering it as one of the trial locations. The station provides modern and specialized field trial technologies, expertise in data acquisition (e.g. GIS trial design, GPS based sowing yield, yield structure parameters, quality parameters) and processing with specialized computer programs.

SP1 will provide a second site for field trials and analyze the effects of catch crops and some of their mixtures on agronomic traits like plant growth, phytopathological status and yield architecture in main crops as well as on soil organic matter content. Since the composition of catch crop mixtures and their effects on yield potential and pathogen infection of main crops is only poorly understood, catch crops will be examined for individual and additive effects in mixtures that promote yield of the main crop maize and/or the following crop winter wheat. This work will provide basic numbers for yield also from an economic perspective (for SP5) and determine the contribution of single species within catch crop mixtures in comparison to complex catch crop mixtures to the soil organic matter budget in two contrasting rotations.

Plant Nutrition:

SP2 will use individual plant traits as “read-outs” for soil health, to determine the effect of individual catch crops on yield and nutritional traits of the subsequent main crop maize. The main crop maize will be grown after single catch crop species or a mixture thereof and assessed by three approaches:

i) The nutriome of maize will be determined to build a signature of the nutritional status throughout plant development. Transcriptomics will be undertaken to reveal the nutritional and plant health status. In addition, the nutritional content of the catch crop will be measured to determine the contribution of individual catch crop species to nutrient mobilization in the soil.

ii) The second approach assesses root growth throughout the crop rotation by analyzing root system depth and root density by modern measures of quantitative PCR. It will be assessed if catch crop root systems
occupy different niches within the soil profile that correlate with soil chemical or physical properties (with SP3) or microbial profiles (with SP4) and zones of greater root exploitation by the main crop.

iii) Soil solutions will be extracted by suction probes (with SP1) from catch crop niches for a metabolite analysis to search for molecular components that affect the root growth of the subsequent crop and to identify a link between metabolite signatures in soil solutions and microbial profiles. Based on results from the initial 3 years, the project will be expanded to rotations that include legumes, to effects on another main crop species (barley), and to the examination of newly designed catch crop mixtures.

Soil chemistry and soil microbiology:

SP3 addresses the nutrient- and resource economy in the soilmycorrhizal-plant system in the context of catch crops in order to assess process-oriented management options. The approach of SP3 hereby lies in connecting soil carbon and nutrient monitoring with stable isotope tracing of carbon and nutrient (exemplarly nitrogen and potassium) turnover kinetics (e.g. 1, 2) and biological triggering of biogeochemical fluxes (3, 4) in conjunction with molecular approaches in monitoring biodiversity and functional trait identification of the soil microorganisms of SP4 (5, 6). This allows for the identification of processes of nutrient and energy transfer and the direct relation of these processes to below- and above-ground community shifts in biodiversity depending on catch crop management, thus triggering resource partitioning and stand amelioration.
As soil bacteria and fungi often defy cultivation approaches, culture-independent population studies are required to assess their diversity and functions (SP4). The microbial nitrogen cycle and other beneficial functions of the microbiome in soil and rhizosphere will be analyzed by SP4 to identify processes and markers. Superior over mere 16S rRNA surveys is the retrieval of structural genes encoding key enzymes (functional marker genes, e.g. for the microbial N cycle) to assess the microbial functional diversity or activity (7). Particularly the analysis of gene expression (mRNA) reflects gene induction and thus actual activities and processes (8). Thus SP4 will apply mRNA and DNA-based methods which they have recently developed to quantify key genes of the microbial Ncycle by quantitative (RT-)PCR. Innovative next-generation sequencing (NGS) methods will be additionally applied to assess the functional diversity of the underlying populations, and also to evaluate changes in the overall functions of the microbiome by transcriptome studies, now allowing a previously unprecedented depth of analysis of the microbiome, its capacities, and changes therein caused by catch crops. In later phases of the project, localization of specific microbes at high spatial resolution with a link to the nutrient flow (Nano-SIMS, jointly with SP3) may be considered.

Economics of catch crops and socio-economic impact:

SP5 will model and program crop rotations, including catch crops, while focusing on economic viability. Including catch crops in more diverse rotations is a challenge because it requires a dynamic analysis of short and long term costs and benefits that are prerequisites for farmers’ acceptance. In particular different rotations have to be evaluated for long run benefits, and values put at specific elements such as the investigated catch crops. Our research will master the challenge by using the new concept of a transition matrix and its dynamic programming (9, 10). The focus is on costs and benefits of (i) (i) dynamics in cropping patterns, (ii) benefits of catch crops as a long term fertility instrument, (iii) soil organic enrichment as a fertility strategy, and (iv) weed, pest and pathogen control. We aim to show how natural capital aspects which can be built up by the integration of catch crops can be visualized by pricing. Crop rotations are considered tools to promote eco-system services provided through resources which are then modeled; in detail SP5 will provide a cost-benefit analysis of long term and discounted net benefits of catch crops in rotations. This question is addressed by a joint programming of farming and ecosystems, i.e. how a potential drop in natural fertility can be avoided by better economic planning of crops, space and rotation. The interesting issue for agronomists is how planning deficits result in unsustainable resource use and how to get better actions based on knowledge of long term costs and benefits of rotations. In conceptualizing eco-system services by catch crops with regard to improved soil properties, the knowledge gained in the natural science and agronomy SPs are translated in economic variables.