Shredding cover crops between crops
Shredding is an easy-to-implement technique consisting of cutting the cover crop into pieces, thus reducing its volume: it is especially recommended when there is a large biomass (> 2 tDM/ha).
Presentation
Characterization of the technique
Description of the technique:
Since the shredder does not touch the soil, only the bearing capacity of the soil needs to be considered to avoid compaction. Another particularity of this technique is to leave 100% of the residues on the surface for good soil protection. However, shredding is not recommended on grass cover crops since they are capable of regrowing after cutting.
Different models of shredders exist (width, shredding mechanisms), shredding tools with horizontal axis are often preferred because they avoid the phenomenon of windrowing (local accumulation of residues which may hinder subsequent operations).
Thus, shredding promotes:
- the decomposition of plant biomass due to chopping.,
- the mechanical destruction of potential pests, larvae sheltering in the cover crops,
- the breakdown of cover crops to avoid mechanical interference if incorporated into the soil with tine tools (risk of clogging) and also for the establishment of the following crop.
However, without soil tillage, some cover crop species (grasses, crucifers), or weeds present under the cover crop, may "resume" their growth. To achieve total destruction, shredding may sometimes need to be complemented by a second technique.
Details on the technique:
Shredder axes can be horizontal or vertical: in the first case, fine shredding facilitates residue decomposition, and in the second case, the shredder has a higher work rate.
Application of the technique to...
Implementation period During the intercrop period
Spatial scale of implementation Field
All crops: Easily generalizable
All soil types: Generalization sometimes delicate. Shredding of cover crops must be carried out on bearing or drained soils to avoid any soil compaction during tractor passage. On soils sensitive to waterlogging (loamy soils, very clay soils), it will be necessary to wait for drained or frost periods, when the soil becomes bearing again, to perform shredding.
All climatic contexts: Easily generalizable
Regulations
In vulnerable zone, the regional Nitrates Directive order may authorize shredding of the cover crop before the imposed destruction date if the cover crop is at flowering stage and risks "seed setting". Residues must be left on the surface (no soil tillage) until the destruction date imposed by the regulation. Refer to the regulations in force in your region.
No regulation concerns the "destruction by shredding of cover crops". However, in vulnerable zones for water quality, subject to the Nitrates Directive, this technique is essential if the regulation requires non-chemical destruction.
Effects on the sustainability of the cropping system
"Environmental" criteria
Effect on air quality: Decreasing
Phytosanitary emissions: DECREASE
GHG emissions: INCREASE
Effect on water quality: Increasing
N.P.: DECREASE
Pesticides: DECREASE
Effect on fossil resource consumption: Increasing
Fossil energy consumption: INCREASE
Phosphorus consumption: DECREASE
The work rate is low (3 ha/h versus 10 ha/h for chemical treatment). Soil tillage may be necessary to finalize cover crop destruction.
"Agronomic" criteria
Productivity: Variable, if soil structure is degraded: risk of yield loss in the following spring crop (about 5%).
Soil fertility: Increasing, better residue breakdown and assimilation by soil organisms, fight against soil erosion.
Water stress: Decreasing, mulch effect on surface slightly reduces soil evapotranspiration.
Functional Biodiversity: Increasing, better residue breakdown and assimilation by soil organisms.
"Economic" criteria
Operational costs: Decreasing, no phytosanitary products used.
Mechanization costs: Increasing, high work costs because working time is significant: €20 to 30/ha (for 4 m and 130 hp tractor) + soil tillage to finalize cover crop destruction. Maintenance costs: €2 to 3/ha. This technique is longer and more expensive than chemical destruction.
Margin: Decreasing in the short term, in the long term, "beneficial effect" of residue return by shredding: better assimilation, development of soil microorganisms, .....
"Social" criteria
Working time: Increasing, increased mechanical working time (compared to chemical treatment)
Peak period: Increasing, choice of intervention date?
Favored or disadvantaged organisms
Disfavored bioagressors
| Organism | Impact of the technique | Type | Details |
|---|---|---|---|
| Perennial grasses | LOW | weeds | Capable of regrowing after cutting |
| Mustards | HIGH | weeds | Shredding is also effective on Faba bean, Buckwheat and Phacelia |
| Vetches | MEDIUM | weeds | Shredding is also moderately effective on Peas, Lentils |
| vole | LOW | pest, predator or parasite | Accessible to predators (fox, buzzards) |
| annual grasses | LOW | weeds | Capable of regrowing after cutting |
| wood mouse | LOW | pest, predator or parasite | Accessible to predators (fox, buzzards) |
| Italian ryegrass | LOW | weeds | |
| wild sunflower | HIGH | weeds | |
| clovers | LOW | weeds |
For further information
- Cover crops during intercrop period - S. Boulet, S. Piaud, B. Savalle, L. Van Cranenbroeck, S. Philippe, Chamber of Agriculture of the Ile-de-France Region, Technical brochure, 2018 Link to the technical brochure.
- Catch crops (Technical sheet no. 2) - ECOPHYTOPIC, Technical brochure, 2009, Link to the technical brochure.
- Catch crops during long intercrop period - F. Leon, M. Chereau, L. Temen, F. Guerin, C. Le Gall, H. Francois, Chamber of Agriculture of Pays de la Loire, Technical brochure, 2014 Link to the technical brochure
- Destroying cover crops: a technical and economic challenge - C. Suchel (CA 01) Du Lien !, Professional report, 2017, Link to the Bio & Water program newsletter no. 34
- Guide on mechanical destruction of cover crops - CUMA Béarn - Landes - Basque Country, Technical brochure, Link to the technical brochure
- The guide to cover crops during intercrop period - Chamber of Agriculture of Isère, Technical brochure, 2017, Link to the technical brochure.
- Cover crop destruction equipment - N. Figeac (CUMA Charentes), Chamber of Agriculture of Charente-Maritime, Multimedia, 2017. Link to the video.
- Choosing the most appropriate cover crop destruction technique - D. Brun, J. Labreuche, ARVALIS, Website, 2018. Link to the article.
Appendices
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