Weed control in organic cropping systems
Currently two major weed problems put severe constraints on organic crop production in Denmark:
- Perennial weeds, most notably Elymus repens (L.) Gould, Cirsium arvense L. Scop, Rumex crispus L. and Tussilago farfara L., causing problems in various crops and crop rotations
- Annual intra-row weeds entailing laborious hand-weeding, especially in vegetable rows.
Perennials are traditionally controlled by repeated and prolonged stubble cultivation in late summer and autumn but this strategy conflicts with the objective in organic farming to retain nutrients in the upper soil layer by keeping the soil plant-covered during autumn and winter.
In a DARCOF II project just finished, effective control of C. arvense was obtained without disturbing the plant cover but treatment intensity was high and not immediately acceptable for organic growers. It was concluded that further research should focus on strategies involving fewer and timelier treatments based on a better understanding of the carbohydrate source/sink dynamics in regenerative roots in response to growth disturbances.
In this proposal we will seek to gain a better understanding of the source/sink allocation pattern to optimize tillage and cutting regimes. The work will include both C. arvense and T. farfara and also provide other essential information, currently missing to plan proper management strategies:
- vulnerability to intensity and timing of root/rhizome fragmentation, desiccation and subsequent burial
- the effect of treatments on the fragmentation and distribution of roots/rhizomes in the soil and proliferation potential.
The research will be undertaken under controlled conditions in growth chambers and glasshouses and subsequently validated and further modified under semifield and field conditions to identify the most prospective strategies to control the two species.
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The work on perennials also includes E. repens and R. crispus L. but with an entirely different approach. Owing to the rather superficial placement of rhizomes and rootstocks, research will concentrate on the development of novel technology for effective uprooting, exposing and destroying of rhizomes and rootstocks within a short time span. Such technology will meet the key objective of quick and cost-effective E. repens and R. crispus control, while having the soil plant covered over most of the year. The work includes an iterative development of appropriate tools followed by field validation of functionality and biological effects. Finally, a prototype implement will be used for validation of the new technology in a wider organic cropping system context.
Methods for controlling intra-row weeds have been studied in previous DARCOF-funded projects. However, finding a solution for effective and selective intra-row weed management, which confidently reduces the need for hand-weeding, remains a challenge in organic farming. Several research institutes have studied different advanced technologies for intra-row weeding, some of which have potential for integration into an intelligent system for arable intra-row weed control.
In this project, research will be directed towards an integration of knowledge on the biological environment, cultivation tactics, implements, perception, robotic technology and seeding technology into a system capable of unmanned and selective weeding under field conditions in a given growing system. Technical progress will be evaluated iteratively during the project, in terms of weeding effectiveness and reliability under field conditions.
To gain a better understanding of the perspectives for weed management in organic cropping, the results obtained in the project will be included in an ongoing modelling effort to describe the long-term weed population dynamics in organic and conventional crop rotations. Modelling will be used in the project as a tool to integrate knowledge from literature in combination with new results, as they are generated in the project. The model will serve to organize the work packages into a coherent whole, ensuring a common standard that will make results applicable across the project and also be for the benefit of the end-users by providing an analytical tool to formulate integrated weed management strategies.
Project title
Effective control of perennial weeds and intra-row weeds in organic cropping through novel technology and new management strategies (WEEDS)
Project leader
Bo Melander, Senior scientist, Institute of Integrated Pest Management, Faculty of Agricultural Sciences, University of Aarhus, Research Centre Flakkebjerg, Forsøgsvej 1, DK-4200 Slagelse, Denmark. Phone: (+45) 8999 3593; Fax: (+45) 8999 3501. E-mail: bo.melander@agrsci.dk
Project participants
Niels Holst, Ilse A. Rasmussen, Svend Christensen, Henning Tangen Søgaard, Erik Fløjgård Kristensen, Michael Nørremark, Rasmus N. Jørgensen, Claus G. Sørensen, Kristian Kristensen (Faculty of Agricultural Sciences, University of Aarhus), Jens Carl Streibig, Jesper Rasmussen, Hans-Werner Griepentrog (Faculty of Life Sciences, University of Copenhagen), Inger Bertelsen (Danish Agricultural Advisory Service)
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