- There is a drought, and it will be even worse. Rapeseed volunteers are becoming even more dangerous, because the fields will be dried out to a great extent.
- The preparation of the site for cereals and the initial conditions for their development will be much worse where volunteer rapeseed remains for longer.
As a catch crop, a medium solution
Rapeseed volunteers are sometimes treated as catch crops. But their fertilizing value, or generally as catch crops, is also low. The same applies to phytosanitary properties. In principle, in a crop rotation with a large share of rapeseed, rapeseed volunteers should absolutely not even be considered in this context, as catch crops. We mentioned this a few days ago – in fact, few farms in Poland can afford to leave rapeseed volunteers for longer after harvest. Generally, they can be treated as catch crops only if rapeseed appears in a given location once every four to five years. However, with such a large area of rapeseed, it appears much more often on many farms, even every other season. In such a case, leaving rapeseed volunteers unattended is a direct path to the development of diseases, greater numbers of pests, and even "inviting" clubroot to the plantation.
Here, let us note that in previous years we often complained that catch crops were drying out the soil, and people asked for the possibility of giving up sowing them in the context of drought. Such conditions prevail now, the drought is severe locally and will be even greater. We have the possibility of eliminating self-seeding and in this drought context they must be eradicated as soon as possible.
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Prices of agricultural services autumn 2024: How much for traditional and no-till sowing?
Cultivation for cereals will be difficult
At the moment, the situation is changing even more. Let's pay attention to the meteorological situation. In many regions of the country, forecasts indicate a lack of rainfall even until the second half of September. In addition, we have high temperatures. The scenario is therefore similar to last year's. Already, very strong volunteer rapeseed plants are "pulling" huge amounts of water from the soil. Some plants have several leaves and a high biomass, even exceeding 25 cm. At the same time, volunteer rapeseed plants are densely distributed on the plantation – they do not produce a good, strongly developed root system, but it is sufficient to deplete the soil of water. Additionally, with such a high density on the plantation, these plants will compete with each other for access to water and light, which will make their upward growth even more dynamic. In a week, such volunteer rapeseed plants may be several centimeters higher. This means that their destruction, "all-in-one" plowing, may be extremely difficult.
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Silage Corn: High Cut or Low Cut?
Another thing is that such strong self-seeding of rapeseed will make it impossible to prepare the site well for sowing cereals. It is dry anyway, and the difficult moisture situation will deepen. The soils where these plants remain will be a real rock. In addition, with such a high biomass, it will be difficult to perform good cultivation. In the case of ploughing, whole leaves will be thrown into the furrow, which will create a kind of coating, an impermeable mulch. In addition, they will be a source of diseases. In turn, standard cultivation with a disc harrow (or even a no-tillage unit) will not bring the expected effect in most cases, because it will be difficult to destroy such large plants in one pass. No matter what we try to prepare the site with, with the predicted lack of rainfall, and at the same time high temperatures currently and the placement of self-seeding rapeseed for the next few weeks, the soil will be even more dry and it will be difficult to "drive" anything into the ground.
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Flea beetles have been attacking rapeseed since its inception. How to combat them?
The decision to eliminate self-seeding must be made now, although it is already late
We have two options. Either precise mechanical destruction of rapeseed volunteers now or application of a total herbicide. In the latter case, 2.5 l/ha of a preparation containing 360 g of glyphosate is enough for small rapeseed volunteers. However, if the weeds, because in this context we are considering rapeseed, are very large, the dose necessary for application may oscillate around 3 l/ha. At the same time, acidification of the working environment (appropriate water pH, glyphosate does not like an alkaline environment) and concentration (smaller amount of water than in standard treatments, e.g. 150 l/ha) are very important for the effectiveness of the treatment.
