Differentiated Weed Management Following Conversion to Organic Farming
Context
- Farmer's name: Damien SAVOYANT.
- Farm name: EARL de la Chanterie.
- Department: Vienne (86).
- UAA: 176 ha.
- UTH : 1 (+ occasional labor).
- Livestock: Herd of Beef Cows (25 mothers).
- Remarkable crops: Alfalfa, soybean.
- Irrigation: Possible on grain maize, soybean, carrots.
- Soil types: Clay-limestone on chalk sands on green clays, crusted silts.
- Soil work: Plowing, false seedbed, harrow, hoe.
- Crop rotation: Soft wheat-maize- sunflower-winter cereal-faba bean-soft wheat-alfalfa (3 years)- soft wheat-soybean.
- Farm in AAC zone (catchment feeding area) : No.
- Specifications: Organic Farming.
- Other context elements: Farm belonging to an Organic Farming group.
- Origin of the practice and farmer’s path : Conversion to Organic Farming involved rethinking rotations with their lengthening. The issue of weed management then arose. Damien therefore invested in new equipment that he uses more or less specifically depending on the cultivated species.
- Practice within the cropping system: Combine the use of different soil working tools while alternating winter and spring crops in the rotation.
- Target crop: All crops.
- Bioagressors: Weeds of winter and spring crops.
The technique
Objective
Best possible weed control to have clean fields.
Description
- Lengthening the rotation and introduction of new crops (relatively easy in Organic Farming because there is a wide choice of species).
- Investment in new equipment (in addition to the plow and the hoe, already present on the farm before conversion):spring-tooth harrow, crust breaker, thermal weeding on carrots.
NB: Differentiated use of these tools depending on the crops in place.
Start date of implementation
2014.
Farmer’s expectations
Damien seeks to limit weed competition and have clean fields by lengthening the rotation and using different tools. He must also fight against perennials (thistles).
Advantages and limits
Advantages
- Conversion to Organic Farming has eliminated the use of phytosanitary products which is a real "plus" in Damien’s eyes.
- The choice of cultivable species is greater in OF than in conventional farming and makes it easier to lengthen the rotation.
Limits
- On winter crops: later sowing which increases climatic risk (sowing conditions not always ideal).
- Weeding complicated on lentils.
- Shift in peak work periods which are stronger in spring.
Implementation and success conditions
Besides alternating spring and winter crops and lengthening the rotation to limit field weediness, it appears that plowing remains one of the bases of weeding on the farm. It is also necessary to weed early, even if it means passing several times. The spring-tooth harrow is one of the most effective tools, except on crusted soils. The hoe is well suited to spring crops. Alfalfa is introduced into the rotation to fight against thistles.
Farmer’s testimony
"By converting to Organic Farming, I sold my sprayer. I already had a plow, a cultivator with tines and one with discs, and a hoe, but I had to complete my equipment with a spring-tooth harrow. It is a relatively inexpensive tool, whose aggressiveness towards weeds can be adjusted. However, it is not suitable for silts (as soon as a crust forms, the tines no longer penetrate) and as soon as there are residues, you risk "raking" them. I then invested in a crust breaker for silts thanks to PCAE aids. But the crust breaker is not a panacea either, especially on stony soils where stones sometimes block the spoons. In fact, as soon as you have heterogeneous soils, you realize that there is no true all-purpose tool."
Farmer’s advice: "It is essential to think about the rotation. Moreover, you have to pass as early as possible to prevent early weed competition. Finally, do not hesitate to visit other farms to benefit from colleagues’ experience and to join a development group."
Planned improvements or other uses
It is difficult to keep lentil fields clean because they are low plants. It may be necessary to invest in a topper. Ideally, this investment would be made collectively. Cross passes with the crust breaker seem to give good results on wheat.
The question also arises of hoeing winter cereals, provided the spacing of the seeding elements is adjusted.
Key steps in weed management
- Delay winter crop sowing
- Alternate spring and winter crops
- Lengthen the rotation (soybean, lentil, alfalfa…)
- Work the soil differentially
Results
Result indicators
| Satisfaction level
/performance |
Farmer’s comments | |
|---|---|---|
| Weed control | 
|
Good control except in lentils (low crop) |
| Pest control | 
|
Overall satisfactory except on one particular plot |
| Disease control |
|
Satisfactory varietal choice limiting disease impact |
| IFT of the concerned crop |
|
IFT reduced to 0 |
| IFT of the cropping system |
|
IFT reduced to 0 |
| Yield |
|
Yields are satisfactory compared to the new system |
| Working time
in the field |
|
Working times are longer in spring than before. |
| Observation time |
|
Increased on weeds but almost zero on diseases |
| Mechanization costs |
|
There are more passes (mechanical weeding) |
| Semi-net margin
of the system |
|
Same as conventional on winter crops, better on spring crops |
| Risk-taking |
|
Crop diversity limits risk-taking |
Farmer’s takeaway
"I am satisfied with my conversion. It allowed me to get back to basics, that is agronomy and rotation. I have to think preventively. It is interesting to look for solutions other than chemical ones to problems I may encounter. I am more serene."
DEPHY network engineer’s opinion
Damien’s conversion went well. It required new investments in mechanical weeding equipment that were partially funded by PCAE. Introducing more spring crops into the rotation helps to control weeds but has the drawback of increasing work times during this period. Even though Damien tries to limit plowing, the plow remains an indispensable tool on the farm. The system’s profitability is slightly improved by the economic results of spring crops.
Sources and references
Ecophyto DEPHY, 2021, Remarkable practices of the DEPHY network: Differentiated weed management following conversion to Organic. Available at: https://ecophytopic.fr/sites/default/files/2021-08/PRATIQUE_16CA86GC_GCPE_NA.pdf
