CASTOR project, cover crops

The CASTOR project aims to study how plant cover can be combined with cereal crops to reduce input requirements (fertilizers and pesticides in particular) and propose more sustainable agricultural production practices. The aim of the CASTOR research programme is to conceive strategies for inserting multiservice leguminous cover crops in association with cash crops. The project also aims to work in synergy with all concerned stakeholders.

Keywords: Associated cover crops, Crop diversification, Cropping association, Innovative cropping techniques, Intercropping, Legumes, Multi-services cover crops, Regulation, Weeds

Funder: TERRA Isara

Trèfle comme couvert végétal dans le projet CASTOR

Red and white clover flowers. M. Rouge, May 2022.

Clover cover associated with cereal. M. Rouge, June 2022.

Clover cover associated with cereals after harvest. M. Rouge, June 2022.

Relay intercropped clover sowing in cereals. M. Rouge, February 2022.

Clover cover crop. M. Rouge, February 2022.

Clover associated with cereals. M. Rouge, April 2022.

Clover associated with cereals at flowering stage. ISARA, May 2009.

Our experimental approach

The project is organised in four main steps:

Innovation tracking: The aim of the tracking phase was to identify and analyze experts (innovative farmers, advisors) implementing innovative techniques. This was achieved through a survey targeting farmers throughout France.
State of the art of the scientific literature: results were compared to the latest scientific knowledge on these techniques to identify any gaps between scientific work and the references needs of farmers and advisors, and to determine relevant research area.
Experimental part with partner/farmers: Setting up of an experimental plots network of 20 plots during two years to produce recommendation and address the barriers identified in the innovation tracking. On each experimental plot, forage legumes were sown as a relay cover crop in winter cereal with three different legume species and three sowing methods. All plots were monitored during the first year of association and half of them for two years (first year of association and the following crop) to assess the behavior of the cover crops in relation to various planting and management methods, and the level of ecosystem services obtained.

Demonstration part: In the final year of the project, and on the basis of the knowledge acquired (tracking + experimentation), demonstration platforms comparing different cover crop insertion strategies developed with partner farmers were set up with volunteer farmers to showcase techniques and strategies that seem promising.

Main results

The survey work carried out allowed the identification of two major barriers to the adoption of multiservice cover crop:

Many farmers mentioned issues regarding the uncertainty of cover crops implementation, particularly in the context of climate change.
A lack of visibility on the savings in inputs and gains for the farmer associated with the services provided by the cover crop. “I know what the technique costs me, but it’s hard to know how much I get out of it”.

The project provided also answers to the following questions:

How cover crop planting strategies can be improved to maximize their chances of success of cover establishment?

Farmers whose cover crops fail to establish on fields don’t seem to take as much care in establishing them as they would do for the cash crop. Many farmers fear competition between the cover crop and the cash crop (which is generally non-existent or not strong, as the literature shows). Farmers surveyed during the innovation tracking study generally stressed the importance of careful cover crop establishment. The experiments carried out shows that the development of cover crop could be improved through planting techniques adapted to soil and climate conditions (e.g. sowing the cover crop in rows or with a direct seed drill; sowing a mixture to adapt to heterogeneous conditions).

Climatic trends in recent years mean that spring sowing is no longer a guarantee of favorable conditions for cover crop development. As a result, farmers need to think about adaptive strategies – for example, sowing earlier if conditions are favorable, or sowing in autumn, giving themselves the possibility of resowing several times during the year if the first sowing failed.

How cover crops should be managed to maximize expected services, particularly weed control?

During the innovation tracking part, some farmers stated that cover crops were unable to compete effectively with weeds. The experiments carried out showed a good link between cover crop biomass and weed control.

Is it possible to export part of the biomass of the cover crop (e.g. mowing, grazing) without losing all the benefits of the cover crops?

Some farmers asked about the possibility of exporting part of the biomass produced by cover crops without jeopardizing the expected services. This question has been addressed on a limited number of experimental plots, therefore conclusions difficult to be drawn. Nevertheless, the initial results suggest that sufficiently early export (early autumn) would ensure enough additional biomass production before winter. . Furthermore, the results show that exporting the cover crop does not jeopardize the expected services (weed control for intercropped cash crop and nitrogen supply for following crop).

Sowing a clover cover as a relay crop: what to expect from nitrogen fixation?

Nitrogen fixation from the cover crop and recycling making it available to a following cash crop appears to be higher than often estimated by farmers and advisors. Thus, despite biomass production often limited by climatic conditions during the two years of experimentation, the quantities of nitrogen potentially returned by the cover crops we were able to measure are highly variable, but generally well above the 30 kg N/ha generally estimated. On average, we observed restitution potentials of around 60 kgN/ha, and up to 120 kg N/ha in certain situations.

What is the impact of cover crop on the associated cash crop?

The presence of a cover crop generally had no effect, either positive or negative, on the yield of the associated crop. On the other hand, a slight negative effect was observed in certain situations where the cover crop grew strongly before the harvest of cereal cash crop. Inversely, the crop following the cover crop clearly benefits from nitrogen input. This has been estimated as a gain of 3-4 tonnes of grain in organic maize production, in a previous study. In conventional farming systems, these biomass gains could not be shown, as farmers were already supplying the amount of nitrogen needed by the crop. It is therefore likely that the benefit of extra nitrogen provided by the cover crop is not valorised.

Project team

Florian Celette, Edouard Sory, Camille Pierre and Mathieu Rouge.

Partners

INRAE (UMR Agronomy and SAS)

Publications

Amossé, Camille et al., 2013. Relay-intercropped forage legumes help to control weeds in organic grain production. European Journal of Agronomy. Vol. 49, pp. 158–167. DOI 10.1016/j.eja.2013.04.002.

Amossé, Camille, Jeuffroy, Marie Hélène and David, Christophe, 2013. Relay intercropping of legume cover crops in organic winter wheat: Effects on performance and resource availability. Field Crops Research. Vol. 145, pp. 78–87. DOI 10.1016/j.fcr.2013.02.010.

Vrignon-Brenas, Sylvain, Celette, Florian, Amossé, Camille, et al., 2016. Effect of spring fertilization on ecosystem services of organic wheat and clover relay intercrops. European Journal of Agronomy. Vol. 73, pp. 73–82. DOI 10.1016/j.eja.2015.10.011.

Vrignon-Brenas, Sylvain, Celette, Florian, Piquet-Pissaloux, Agnès, Jeuffroy, Marie Hélène, et al., 2016. Early assessment of ecological services provided by forage legumes in relay intercropping. European Journal of Agronomy. Vol. 75, pp. 89–98. DOI 10.1016/j.eja.2016.01.011.

Vrignon-Brenas, Sylvain, Celette, Florian, Piquet-Pissaloux, Agnès and David, Christophe, 2016. Biotic and abiotic factors impacting establishment and growth of relay intercropped forage legumes. European Journal of Agronomy. Vol. 81, no. October, pp. 169–177. DOI 10.1016/j.eja.2016.09.018.

Vrignon-Brenas, Sylvain et al., 2018. Intercropping strategies of white clover with organic wheat to improve the trade-off between wheat yield, protein content and the provision of ecological services by white clover. Field Crops Research. Vol. 224, no. May, pp. 160–169. DOI 10.1016/j.fcr.2018.05.009.

Duchene, O., Vian, J.-F., Celette, F., 2017. Intercropping with legume for agroecological cropping systems: Complementarity and facilitation processes and the importance of soil microorganisms. A review. Agriculture, Ecosystems and Environment 240, 148–161. https://doi.org/10.1016/j.agee.2017.02.019

Gardarin, A., Celette, F., Naudin, C., Piva, G., Valantin-Morison, M., Vrignon-Brenas, S., Verret, V., Médiène, S., 2022. Intercropping with service crops provides multiple services in temperate arable systems: a review. Agronomy for Sustainable Development 42, 39. https://doi.org/10.1007/s13593-022-00771-x

Valantin-Morison, M., Verret, V., Médiène, S., Lorin, M., Pelzer, E., Celette, F., Naudin, C., 2019. ALLIANCE : Amélioration des performances écologiques et économiques par association de plantes de services Légumineuses dans des systèmes de grandes cultures. Innovations Agronomiques 71, 349–365.

CASTOR – Cover crops to foster agroecological transition and input reduction

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Our experimental approach

Main results

Project team

Partners

Publications