Choose the right strategy for organic weed control in spring

Disclaimer: This article has been machine translated from Danish to English, so please note that there may be errors in the translation.

A large proportion of troublesome weed species can be controlled mechanically in spring. Get an overview of year-round interventions in this printable graphic.

Annual cycle for root weed control (pdf, 1 page)

Double ploughing in spring is effective against thistles

Autumn ploughing can be followed up with a spring ploughing, after which a competitive crop is sown.

Double ploughing is most effective, but if needed, colonies of thistles in the field can be controlled when the plant is most sensitive at the 6-8 leaf stage. This is followed by ploughing to bring the decomposed root weeds into the soil.

Foxglove is most vulnerable to control in spring

- When the flower buds are just about to break the soil surface and the plant is most sensitive to control, a milling operation is performed.
- This is done prior to spring ploughing.
- Then choose a competitive crop, such as oats. Pod crops to maturity should be avoided due to the low competitiveness in the latter half of the growing season.

Weaken the underground growth of grain legumes in the spring

It is in the spring that the underground growth of agri-swine milk must be interrupted. In the autumn, hogweed goes dormant, while in the spring new underground shoots are formed that are not visible above ground.

- If the soil becomes passable early in the spring, a cut is made about 3-4 weeks before ploughing. This interrupts growth and weakens the plant.
- If the soil becomes passable late, the soil should be ploughed when it is suitable. Regardless of how the control is carried out, the time of ploughing should not be postponed.
- A competitive crop, such as oats, is then selected. Pod crops to maturity should be avoided due to the low competitiveness in the last half of the growing season.

Growth starts early for vetch

The vetch plant is active as soon as the temperature is above 3-4 degrees. This means that growth often starts as early as February. After a mild winter without control, the population may have developed strongly and this requires control in the spring.

In spring, you can control chickweed by starvation or desiccation:

- Starvation of chickweed can be done by harrowing every time the chickweed has 3-4 leaves. This interrupts growth when the plant is most sensitive.
- Repeated harrowing is important to starve the plant.
- Drying out chickweed can be done by pulling the runners up to the soil surface. This requires dry weather or frost for a period of several days.
- After either starvation or desiccation, a good ploughing before sowing is recommended to bury the weakened roots deep in the bottom of the plough furrow.
- Then choose a competitive crop such as oats and avoid pulses and maize.

During control and before ploughing, it is necessary to check if there are any live chickweed roots under the harrowed layer. This can be checked by taking a spade into the field. If the ploughing is deeper than the harrowing, this may mean that fresh runners are emerging in the upper layers.

There are two options to adjust the treatment:

• Set the harrow deeper in the soil if it can pull up runners from down there, and delay ploughing

• Adjust the ploughing depth so that fresh shoots are not turned up

It is possible to control chickweed mechanically until April.

Weed brambles whenever possible

With brambles, it's all about being ahead of the game. One vine can produce 5,000-10,000 seeds per year, so you reduce seed dispersal by removing them before flowering.

In a Czech trial, the effect of weeding bittercress with a crowbar in a permanent clover-grass field was investigated. The most effective strategy was two weedings at a depth of 15 cm, which resulted in a 97% reduction.

- Weeding: remove the top 10 cm of the root as new shoots will form from here. If the plants have flowered, remove them from the field. After weeding, bare spots may appear in the field. Here it is a good idea to spread grass seed.
- Stripping: can prevent seed shedding and seed dispersal and is done before the brambles flower. Repeat the stripping when new inflorescences emerge.

Strategy for controlling broadleaf weeds in autumn