Performing false sowing during the intercrop period
This cultural control method aims to [[:Category:Objective|exhaust the seed bank of weeds], by stimulating their emergence through repeated shallow tillage during the intercrop period, then destroying them shortly after germination.
Presentation
Characterization of the technique
Description of the technique:
The principle:
This cultural control method aims to [[:Category:Objective|exhaust the seed bank of weeds], by stimulating their emergence through repeated shallow tillage during the intercrop period, then destroying them shortly after germination. It concerns open-field crops (arable crops, vegetables) or market gardening, including under cover. False sowings should be performed about 1 to 2 months before the planned sowing date of the crop. Each new pass allows the destruction of emerged weeds and soil preparation for a new false sowing.
This technique is effective on annual weeds with low dormancy (ryegrass, brome, blackgrass…) and crop regrowth (oilseed rape, cereals). However, it is not effective if the dormancy of weed seeds is not broken. For more information on the ability of weeds to emerge depending on the false sowing period. It is also moderately effective during the first false sowing (the deepest) against perennials by using a tine tool to bring rhizomes to the surface and dry them out. Do not use disc tools, which tend to cut and multiply them. In this respect, false sowing represents an alternative to the use of glyphosate during the intercrop period.
Conditions for success:
The shallow soil work performed must be fine and superficial, like for sowing, at a maximum depth of 10 cm, as it is about establishing good seed-soil contact favoring weed emergence. Rolling can therefore be decisive in dry conditions. Late summer thunderstorms can be a favorable factor for emergence. It is advisable to perform several passes, spaced 15-20 days apart, depending on the length of the intercrop period and environmental conditions, with increasingly superficial passes to avoid bringing seeds from deeper layers that are dormant due to lack of light. Warning: combined sowing can cause additional emergence compared to conventional sowing.
Equipment:
Different tools can be used working at various depths and showing differences in effectiveness for preparing false sowing and destroying weeds.
Source: ARVALIS-Institut du Végétal, ITAB
Details on the technique:
Trials in Finistère showed that from the first false sowing, a reduction of 30 to 50% in weed emergence can be observed. The reduction rises to 50-60% when two false sowings are performed successively and 65 to 80% after three false sowings. Intervention dates should be considered according to the emergence period of the field flora and the following crop:
- Before winter crops, false sowings are useful to reduce heavy infestations of grasses (except wild oats) in the absence of ploughing. If the flora mainly consists of autumn-emerging weeds, more passes should be made in September and October. If emergence is mainly summer, passes should be made in July and August with still one pass in September-October. However, soil refinement can increase drying time and delay sowing date, thus harming crop establishment quality. In this case, simply postponing the sowing date is possible.
- Before summer crops, false sowings are fully justified as they strongly reduce weeds in the crop if performed at decreasing depth or superficially.
Implementation period
During the intercrop period
Spatial scale of implementation
Plot
Application of the technique to...
All crops:
Easily generalizable
The intercrop period must be long enough (15-20 days between each pass) as it must take into account weed emergence and destruction and be during a favorable climatic period.
Performing false sowings depends on the presence and, if applicable, the duration of a possible catch crop. Depending on the previous and following crops, the intercrop period is sometimes shortened, limiting false sowing possibilities (wheat after beet, oilseed rape after a winter cereal). Performing false sowings before summer crops such as buckwheat, sorghum, or soybean is possible.
All soil types:
Easily generalizable
In clay soils, it is better to start shallow preparations early to make false sowing effective.
In some soils, especially loamy ones, false sowing can be tricky: refinement and absence of clods can indeed favor crusting.
All climatic contexts:
Generalization sometimes tricky
Climatic conditions must be favorable to allow weed emergence and the passage of shallow soil tillage tools; false sowing may not always be feasible.
False sowings before spring crops do not favor the emergence of spring weeds (temperatures too cold).
Regulations
The obligation to establish cover crops during the intercrop period in sensitive areas reduces the possibilities of performing false sowings (Nitrate Directive). However, establishing a competitive and fast-growing intercrop cover (grasses, crucifers) also limits weed development.
The acquisition of weed control equipment (harrow tine, rotary hoe, rotary harrow, hoe) for row crops is subject to a CEPP fact sheet (action no. 30: Weed row crops using mechanical weed control tools).
2. Services provided by the technique
see +
Weed regulation and management
Shallow soil tillage destroys already emerged weeds and promotes germination of other weeds that will be destroyed during the next pass. The technique is therefore effective on weeds whose preferred emergence period is before the crop sowing date and that have low dormancy. Effect level: MEDIUM if used alone, to be combined Confidence index: HIGH
COMPLEMENTARY TECHNIQUE(S)
Late sowing / transplanting
Perform shallow soil tillage after harvest
INCOMPATIBLE TECHNIQUE(S)
see +
Pest management
Shallow soil tillage is very unfavorable to slugs as it destroys eggs and adults directly or by drying. Effect level: MEDIUM if used alone, to be combined Confidence index: HIGH
COMPLEMENTARY TECHNIQUE(S)
Late sowing / transplanting
Perform shallow soil tillage after harvest
INCOMPATIBLE TECHNIQUE(S)
3. Effects on the sustainability of the cropping system
"Environmental" criteria
Effect on air quality:
Increasing
By reducing the seed bank and destroying emerged weeds, false sowing helps reduce the use of herbicides and their transfer to the air.
Effect on water quality:
Increasing
By reducing the seed bank and destroying emerged weeds, false sowing helps reduce herbicide use and their transfer to water.
Effect on fossil resource consumption:
Increasing
The use of false sowing consisting of successive passes of soil tillage increases fossil resource consumption and related GHG emissions. However, these additional passes require less energy than deep soil tillage passes (ploughing).
"Agronomic" criteria
Productivity:
Variable
This technique presents a risk of:
- Drying out the seedbed, especially for surface sowings (seeds < 1 mm), which may require irrigation for crop emergence;
- Yield degradation if destruction of emerged weeds during false sowings is not complete.
Soil fertility:
Variable
With bare soil, there is a risk of erosion. However, infiltration is better than on a crusted surface.
Also, if performed in too wet conditions, passes may cause crusting (especially for loamy soils) and soil compaction.
Water stress:
Increasing
There is a risk of drying out the seedbed, which can hinder surface sowing emergence.
Functional biodiversity:
No knowledge on impact
Mechanical tool passes may disturb surface fauna (macro/micro).
"Economic" criteria
Operational costs:
Variable
The increased number of passes leads to higher fuel consumption, which can be offset by the absence of herbicide treatment (glyphosate for example).
Mechanization costs:
Variable
Due to purchase (if necessary) and maintenance of soil tillage and mechanical weeding equipment.
Margin:
Variable
Slight reduction due to soil tillage passes, possible savings on herbicide passes. The cost of weed control must be evaluated globally. For example (see page 1, Shallow soil tillage during intercrop, AgroTransfert), three false sowings cost less than a stubble cultivation followed by glyphosate or a stubble cultivation followed by ploughing.
"Social" criteria
Working time:
Increasing
False sowings require time (about 30 minutes per hectare per pass) which increases working time during intercrop periods. However, implementing this technique can save time on other weed control operations.
Example: in organic carrot production, a farmer reduced manual hoeing by 140 hours/ha by performing 3 false sowings (testimony Vianney Estorgues, CA29). Poor equipment adjustment (too deep work) slows forward speed.
4. Favored or disadvantaged organisms
Favored bioagressors
Disadvantaged bioagressors
Favored auxiliaries
Disadvantaged auxiliaries
Favored climatic and physiological accidents
Disadvantaged climatic and physiological accidents
5. For more information
- Weed management: false sowing
- -Estorgues V., Perennec S., Buffard J. Aujourd'hui & Demain, n°111, Press article, 2012
- Tropical Guide - False sowing fact sheet no. 5
- -Bruchon et al. Technical brochure, 2015
- Practical guide for designing vegetable cropping systems saving phytopharmaceutical products - Fact sheet T18
- -Launais M., Bzdrenga L., Estorgues V., Faloya V., Jeannequin B., Lheureux S., Nivet L., Scherrer B., Sinoir N., Szilvasi S., Taussig C., Terrentroy A., Trottin-Caudal Y., Villeneuve F. Ministry of Agriculture, French Agency for Biodiversity, GIS PIClég, Book, 2014
- Overview of alternative techniques: False sowing and weed management
- -Pierre S.-P., Pérus M., Villeneuve F. CTIFL, Technical brochure, 2012
- Shallow soil tillage during intercrop
- -Pierre Mischler Agro-Transfert resources and Territories, Technical brochure, 2011
- Practicing false sowings to reduce the seed bank of fields
- -Bonin L., Gautellier Vizioz L., Metais P. ARVALIS-Institut du Végétal, Multimedia, 2018
- Alternative weed control in market gardening - Preventive measures
- -Ferrier J-D. Chamber of Agriculture of Ain, Technical brochure, 2016 See page 17
6. Keywords
Bioagressor control method:
Physical control
Mode of action:
Action on the initial stock
Type of strategy regarding pesticide use:
Substitution
Annexes
Est complémentaire des leviers
- Practice mechanical weeding in the open - Harrow tine
- Perform shallow soil tillage after harvest
- Collect small straw during harvest
- Late sowing / transplanting
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