Silage of immature cereals

Technical articles - Centre National d'Agroécologie - Conserwa - Weeds

Mixed farming and livestock Mixed farming and livestock Silage weed management

Cereal immature silage worksite

Silage of immature cereals is a last resort solution when the field is infested with weeds and the crop will not be harvestable or will have too low a yield, or to prevent contamination in future years.

It is therefore mainly a prophylactic solution implemented before weed seed set (to limit replenishment of the seed bank) and allows valorisation either by methanization or as fodder.

How effective is it?

On relatively clean fields

Silage of the previous crop (year n-1) results in a significant decrease in the number of ryegrass per m², about 5 times fewer plants compared to the control treatment.

When silage is combined with plowing, there are 10 times fewer ryegrass.

Effect of various agronomic levers, alone or combined, on ryegrass emergence counted in maize following durum wheat - Arvalis trial in Crambade (31).

On infested fields

Example of a weed control strategy:

Here the impact is considered over 2 years with a non-silage control rotation. One treatment with only one silage the first year. Then silage every year. Cover crops (CC) are managed similarly with two stubble cultivations.

Technical itinerary of the three weed management treatments by immature silage.

Results

• Moderate effect on the number of emergences (-10% for one silage and -30% for two successive crops silaged)
• Large decrease in the seed bank (-41% for one silage and -86% viable grass weed seeds for two silages)

Representation of the effectiveness of treatments on ryegrass.

The number of emergences in the first years decreased slightly due to the large number of seeds already present in the soil.

Since there is no reseeding of weeds, as everything is harvested before seed set and grass weeds such as ryegrass and vulpia have a ASR (Annual Seed Decay rate) high (around 60/70%), the seed bank decreases very rapidly (-85% for two successive years of silage). The cleaning effect on weed density should be noticeable the following year.

Advantages

• Immediate and significant reduction of the grass weed seed bank (especially those with an ASR above 50% such as ryegrass and vulpia or brome).
• Reduction in the number of emergences when the strategy is planned over the long term (at least 2 years).
• Possible Economic valorisation (agricultural methanization or fodder) compared to crop shredding.

Disadvantages

• Economic losses because the crop is not harvested. Revenues from a harvested crop are much higher than those from fodder.
• Large export of dry matter (up to 10 tonnes/ha) and thus possible long-term fertility loss.
• Possible soil compaction during silage operations (depending on conditions).

Sources

This article was written by Jasmin Razongles, agronomy engineering student in work-study at the Centre National d'Agroécologie.