Head of Agroecology and Biometeorology at the Czech University of Life Sciences Prague, Professor Josef Soukup also runs the institute that conducts plant protection products registration trials for various companies. He has always been interested in oilseed rape (OSR) and here he outlines its importance in the Czech Republic and the how farmers manage weed control.
How important is OSR in the Czech Republic?
J.S. : Winter OSR is now one of the country’s main crops. It covers about 400,000 ha, and though less than wheat, which is 750,000 to 800,000 ha it’s more than spring barley, at 350,000 to 400,000 ha and fodder maize, at 250,000 ha. OSR surfaces depend mainly on weather conditions at sowing time and on overwintering. We usually sow between August 15th and 30th, or even early September in warm regions.
What is OSR’s potential in your country?
J.S. : The average yield has been very high for four years, 3.5 t/ha in 2013, 2015 and 2016, and almost 4 t/ha in 2016. Pol-Agro set the record with 5.25 t/ha on 170 ha in Poláky, in the north-west of the country. Domestic production amounts to 1.2-1.4 million t per year, 70% of which is processed in the Czech Republic. 400,000 to 500,000 t are exported, mainly to Germany.
What types of weeds do farmers have to deal with in their OSR?
J.S. : Cleavers and mayweed are found throughout the country, along with poppies and hedge mustard in the warmer regions, whereas cornflowers are more localised. We also see intermediates such as common field-speedwell, henbit dead-nettle, field pennycress, and shepherd’s-purse. The most frequent weedy grass in the country, the silky bent-grass is not an issue in OSR and there aren’t too many other grasses, just perennial common couch and very rare black-grass.
How do you control weeds in OSR?
J.S. : Farmers generally use metazachlor in combination with clomazone at pre-emergence or with quinmerac and dimethenamid-P at pre-emergence or early post-emergence, up to the OSR 2- to 3-leaf stage. Other post-emergence applications with herbicide containing aminopyralid, clopyralid and picloram are rare and generally restricted to areas of heavy soils and/or dry conditions. The HT technology with varieties tolerant to imazamox is not very widespread. The range of herbicides available has so far been sufficient, but now new post-emergence solutions would be welcome.
You believe that post-emergence solutions would be welcome in the Czech Republic. Why is that?
J.S. : Farmers are increasingly being faced with restrictions on their use of metazachlor in groundwater protection zones. Post-emergence can also be used for larger application window, and this provides flexibility with regard to choosing application dates. It reduces the risk of unnecessarily applying a herbicide in fields with poor emergence which might result in the need for replacement.
Post-emergence is also a better solution in soils where residual herbicides are less effective, such as dry, very sandy or very heavy soils, or plots with surface plant residues. Some weeds, such as Cranesbill, some crucifers and perennials are difficult to control with conventional pre-emergence herbicides. In post-emergence, farmers would only need to treat with one early application against broadleaf weeds followed later by treatment against volunteer cereals.