Elimination of Perennials in Intercropping without Glyphosate

Case studies - Occitanie Chamber of Agriculture - Aglae - Joël Coureau (2010) - Weed management

Field crops Weed control in field crops Weed control

Tarn-et-Garonne (department)

145

1

Clay-limestone hillsides (40% clay)

Arable crops

Conventional agriculture

Occasional plowing

ETA

Experience feedback from Joël Coureau, as part of the Aglae project. He presents his technique for controlling perennials in intercrop without glyphosate.

Motivations

I committed to a territorial AEM (Agri-Environmental Measure) "progressive reduction of pesticide use" a few years ago, and the reduction of herbicides has been extensively worked on in my farm. Managing intercrops without glyphosate is also an objective of the AEM, so I implemented mechanical weeding techniques (false seedbed, harrow and hoe) on most of my crops, especially to fight against thistle.

The farm

Location: Le Causé (82)
UAA: 145 ha
Field crops: 50% of the area in wheat, Chickpea 10 ha, Oilseed rape seeds 10 ha, Alfalfa seed production 6 ha, Sunflower 46.5 ha
AWU: 1
Soil: Clay-limestone hillsides (40% clay)
Soil work: Occasional plowing
Specifications: Conventional
ETA activity in parallel

Implementation

Started in 2010.

My cropping system

145 ha, 8-year rotation.

Only practices related to mechanical weeding are presented here.

Intercrop without glyphosate, a 100% mechanical elimination of perennials in intercrop: my method

This sequence of mechanical interventions is carried out in plots under high pressure from perennials (especially thistle) before spring crops.

August

Disc cultivator: I start by working after harvest with a disc cultivator to bring to the surface the couch grass present. Be careful, a first pass too deep creates clods in which couch grass rhizomes can survive and regrow.

September

Chisel, Vibroflex: Then I make successive passes with toothed tools: a pass with a chisel at 18-20 cm then a cross pass with vibroflex to stir the entire soil structure. I obtained a coarse structure but without excess, with clods up to 15 cm diameter.

Chisel equipped with duckfoot shares: Mid-September, I do another pass with a chisel equipped with duckfoot shares at a depth of 20-25 cm to rework the entire horizon.

October

Winged share subsoiler: One month later I make a pass with a subsoiler equipped with winged shares to thoroughly crack the soil and prevent any new couch grass regrowth. This sequence allowed me to clean a plot infested with couch grass at a cost lower than a solution involving glyphosate and plowing (see table).

To eliminate thistle patches

I rely on the same principle, intervening deeper at each pass to cut the thistle taproots, namely: disc stubble cultivation to trigger emergence, chisel with duckfoot shares at 10-15 cm, chisel at 25 cm when the thistles reappear, then subsoiler at 35 cm. These operations are carried out from early August until autumn. I get good results, but it is work to be repeated over several seasons.

Exception in wet years

I do not forbid myself, in case of too wet conditions before spring sowing, to use glyphosate, but at low dose and low volume (50L spray mixture/ha).

Against cereal regrowth: 240 g of glyphosate + 0.3 kg of ammonium sulfate.

Against perennials: 480 g of glyphosate + 0.3 kg ammonium sulfate.

In low volume, conditions must be optimal: high humidity and zero wind.

Mechanical strategy


	Working time (min/ha)	Cost (€ / ha)
Chisel (3.5 m)	40	26
Cultivator (4.5 m)	20	14.5
Chisel (3.5 m)	20	15
Subsoiler (2.5 m)	65	34
Total	145	89.5

Strategy with glyphosate

	Working time (min/ha)	Cost (€ / ha)
Glyphosate (5L/ha)	10	54
Plowing (5 furrows)	75	50.5
Total	85	104.5

Important: The costs of the mechanical strategy and the glyphosate strategy were calculated specifically for my farm, taking into account that I do ETA work, which allows me to amortize my equipment over large areas. These costs can vary greatly from one farm to another, and must therefore be evaluated case by case. Regarding associated costs, these are costs excluding equipment depreciation.

Other levers I use

Shifting sowing date.
Combination of chemical weeding and mechanical.

My analysis of the combination of levers I use

Benefits

Reduction of inputs costs.
Good results.
Low IFT.

Points of caution

Increased working time per hectare.
More observation time.
Fuel consumption.
Risk of Erosion.
Practice incompatible with cover crop establishment.

My advice for success

Always intervene at early stages. Do not wait for weeds to develop to avoid having to use too heavy tools.
Adapt according to weather.

My perspectives

This technique has been in use on the farm for 10 years and I do not intend to change it.
The ban on glyphosate does not bother me much. It is a bit unfortunate because we will have one less solution available, but it is not a problem for me.