Destroying Cover Crops Without Tillage or Glyphosate
Debates on glyphosate have accelerated questions regarding the dependence of no-till or reduced-till systems on this molecule. However, several farmers practicing conservation agriculture have sought to reduce their consumption related to the destruction of their cover crops.
These alternative techniques to shredding and/or tillage all share the characteristic of being a means of destruction with an efficiency that can be only partial. Indeed, although they have different performances, most farmers interviewed (except those in organic farming) continue to use glyphosate some years or in certain cases. Farmers often distinguish two steps in the destruction of their cover crops: destruction of the aerial parts and destruction of regrowth of cereals or weeds, the crown or tillering plateau.
Destroying the aerial parts of cover crops while valorizing them
Destruction of the aerial parts of the cover crop without tillage or glyphosate generally poses few problems. Nevertheless, shredding, the most commonly used technique to destroy developed cover crops, is a barrier for some farmers who see it as an additional intervention that can be long and costly. During this search for innovations, farmers with innovative practices allowing both valorization and destruction of aerial parts were met.
Harvesting the cover crop allows control and valorization of the aerial parts. To illustrate these practices, two types of cover crop valorization are developed: one for the feeding of their beef cows and ewes, the other for methanization. The latter harvested the covers in a rather original way since he did not use a forage harvester but a shredder-windrower followed by a self-loading wagon.
Harvesting the cover crop is a way to valorize it, but exporting the aerial parts can influence the ecosystem services provided by the cover due to the export of organic matter and the mineral elements it contains.
Among the identified farmers, four valorized their cover crops by a method that does not export the aerial parts but transforms them: grazing. Two are sheep farmers and grazed their cover crops and the other two have no livestock but planted their cover crops to be grazed by ewes from a neighboring farmer. According to these two farmers, this partnership is win-win since the action of the sheep is like "a shredder in front and a spreader behind". One farmer also thinks that "the remains of cover crops trampled by the sheep form a mulch that reduces weed emergence during winter". In exchange for the provision of the plot, the livestock farmer supplies cover crop seeds. According to the livestock farmer met, less disturbed soil and a greater presence of straw on the surface help limit lameness problems. For him, putting his ewes to fight in the cover crops improves their prolificacy. The benefits for the animals have recently been well documented (high nutritional value, very low parasite pressure):
Destroying regrowth, tillering plateaus and crowns
Destruction of roots, crowns and tillering plateaus of cover crop plants and weeds present in the cover often poses problems if there is neither tillage nor glyphosate because the risk of regrowth is high. A first lever is to choose species with determinate growth (White mustard, faba bean, sunflower, nyjer, Abyssinian mustard etc.) which, once stem elongation has started, hardly produce new stems. Even if species choice limits the risk of regrowth, regrowth of cereals and weeds is generally poorly destroyed during shredding/harvesting or even mechanical destruction.
Some farmers nevertheless manage to limit the risk of regrowth or regrowth of vegetation even if the result remains uneven depending on the years or plots.
Two scenarios were extracted from the interviews conducted: farmers who succeed have innovated either on the use of their equipment or on the equipment they use.
Innovation in equipment use
Innovation in equipment use was carried out mostly with disc cultivators with independent discs:
| Case | Soil type | Department | Decision rules | Quotes |
|---|---|---|---|---|
| 1st case | Champagne chalk | Aube | Intervene on frost in January
or February (at night if necessary) |
“You have to be patient and wait for the frost” |
| 2nd case | “Glyphosate is not systematic”
“1 plot out of 2, if there are grasses” | |||
| 3rd case | “If the plant starts to thaw it no longer works”
“If there are grasses in spring before sowing, I apply glyphosate” | |||
| 4th case | Clay-loam | “Refining before sowing finishes the destruction
of the few remaining regrowth” “Don’t hesitate to go at night” | ||
| 5th case | Intervene in November | “I only treat dirty plots with glyphosate
before spring sowing” |
Decision rules and farmers’ feelings regarding mechanical intervention on frost
Farmers interviewed chose to adhere to a decision rule for stubble cultivation intervention on the covered plot. They choose either intervention on dry soil or on frozen soil. Even if it is agreed that this technique is not new, their feedback provides information on the relevance of the technique depending on the years. Moreover, coupling with a study of frost frequency allows placing these farms in the regional context and reflecting on their deployment in other geographical contexts.
Innovation in equipment choice
Innovation in equipment choice concerns three farmers surveyed. Two of them use cultivators equipped with goosefoot shares with high overlap. The first uses a Kockerling trio cultivator equipped with shares co-designed and manufactured with a manufacturer to perform a scalping work at 5 cm depth aiming to manage cover crops and weeds between crops:
- destroy cover crops without excessive soil disturbance,
- avoid possible clogging with a toothed tool,
- not use a disc cultivator to avoid multiplying perennials,
- not shred.
| Equipment | Soil type | Department | Decision rules | Quotes |
|---|---|---|---|---|
| Kockerling trio –
special shares |
Loess and | Aisne | Intervene on the 2nd day of frost and
stop before plants start to thaw (9–10 am) |
“I use glyphosate case by case in spring,
sometimes only on grass patches in the plot” |
| Chisel and Morris
weeding bar |
Heavy clay | Aube | Intervene on dry soil:
first without the weeding bar to avoid clogging and a second time with the weeding bar a few days later |
“Plant residues must be well shattered
or friable” |
| Dyna drive | Loams | Ille-et-Vilaine | Do not intervene on too wet soil,
intervention is possible in a large volume of vegetation |
“In wet conditions there is a risk of clogging
in the roller” |
Source
Agro‑Transfert Ressources et Territoires (n.d.). INNOVATIVE PRACTICE SHEET: Destroying cover crops without tillage or glyphosate.
Available at: https://cultivons-les-couverts.agro-transfert-rt.org/glyphosate/index.html
