- Rapeseed self-seeds intensively deepen their roots, thereby drawing water from deeper layers of the soil.
- It may turn out that before we start preparing the field for the next sowing, the soil will already be very dry.
Rapeseed volunteers dry out the soil significantly
Rapeseed volunteers take up significant amounts of water by the very fact that they develop their roots quite intensively. This is not as extensive a root system as in the case of cultivated rape plantations (if only because of the high density of rapeseed volunteers), although despite the poorer development, the tap root itself can penetrate the soil quite deeply. And in this way it draws water from layers that cereals cannot even reach in autumn.
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Spraying for weeds in rapeseed. What affects the effectiveness of herbicides?
Let's note that the rapeseed volunteers left until now have already developed quite a large biomass. They are developing more leaves, sometimes they are already in such advanced stages that they have 3-4 leaves. And if they are left in the field, they will produce more in a moment.
The development of each successive leaf means that the root sinks into the soil by another 4-5 cm. It may therefore turn out that even soil with a fairly good water supply will be dry before grain sowing. On the other hand, if rapeseed volunteers are to be eradicated as a so-called "one-time operation", i.e. after post-harvest cultivation, sowing will soon take place, then one must count on rainfall. Otherwise, ploughing will not be an easy task, because volunteers – despite the fact that they constitute, in a sense, cover and protect against erosion – at the same time draw water from the soil.
Of course, there are some advantages, because they produce roots that are deeper than cereals, so they also penetrate the soil. However, it must be remembered that this task was basically fulfilled by the previous crop itself, i.e. the main crop, which was rapeseed. Leaving volunteer rapeseed for "longer" in a crop rotation where rapeseed has a large share is not the best choice. It may turn out that the rapeseed itself, together with volunteers, remains in the field for up to 13 months.
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How long do seed dressings protect rapeseed?
Plate or glyphosate
What are our solutions? In order to destroy weeds, such as rapeseed volunteers, glyphosate can be used. The dose should be adjusted to the volume of the plants. Generally, in most cases, it is enough to apply 900 g of glyphosate (which is 2.5 l of a preparation containing 360 g of active substance per liter). If the controlled volunteers are smaller, even 720 g of glyphosate will be enough. In the case when rapeseed volunteers are exceptionally grown, and in addition there are other weeds, 1080 g of the substance can be applied (i.e. 3 l/ha of the same product). At the same time, the effectiveness of the treatment will be better if we add an adjuvant or ammonium sulphate.
Of course, you can also make another pass with a disc harrow. Considering the costs themselves, the outlay will be similar (with a disc harrow, of course, the main cost will be fuel, while in the case of a chemical solution, the plant protection product itself).
