Harrowing as a weed control method in cereals
Harrowing is one of the oldest weed control methods and remains widely used as an alternative to herbicides in organic farming. Various types of harrows, including spring tine harrows and rotary harrows, can be employed in cereal fields. The effectiveness of this method depends on several key factors, including weed species, weed development stage, soil conditions, and weather.
Harrowing is particularly effective against annual dicotyledonous weeds, which are most susceptible to mechanical disturbance. The development stage of the weeds is critical for success. The best results are achieved when weeds are in their early growth stages, from the white-thread stage (germinated but not yet fully emerged) to the cotyledon stage. However, since weeds do not germinate uniformly, repeated harrowing may be necessary to achieve adequate control. Each treatment may involve multiple passes across the field to increase intensity.
The depth and speed of harrowing are important parameters that influence weed control efficacy. While more aggressive harrowing can improve weed suppression, it also increases the risk of crop damage. Therefore, it is essential to optimize these parameters based on the crop species, growth stage, and variety, as some crops are more tolerant to mechanical stress than others.
Soil type significantly affects the outcome of harrowing. In soils that form clumps, small weeds can survive inside the clods if they are not adequately dispersed during treatment. Additionally, weather conditions play a crucial role. Harrowing is most effective when performed on dry soil, with dry weather conditions continuing for some time afterward to reduce weed recovery.
Despite its advantages, harrowing has drawbacks: it causes shallow soil disturbance, which may increase erosion and disrupt ground-nesting birds and fauna. Farmers may also worry about its lower efficacy on grass and perennial weeds and its slow operation speed on large farms.
Additional information
Although harrowing is a traditional practice, farmers unfamiliar with it or seeking to optimize its use can benefit from demonstrations, consultations, and knowledge exchange. Choosing the right equipment and adjusting techniques to specific farm conditions are crucial for maximizing the effectiveness of this mechanical weed control method.
Jevgenija Ņečajeva, LBTU, Latvia University of Life Sciences and Technologies
European Thematic Network for unlocking the full potential of Operational Groups on alternative weed Control
Completed | 2022-2025
- Main funding source
- Horizon Europe (EU Research and Innovation Programme)
- Geographical location
- Greece, Italy, Spain, Latvia, France, Sweden, United Kingdom