Q. : What role does oilseed rape play on your farm and what sort of yield did you get in 2017?
J-H. R. : On average we plant 200 to 250 ha of OSR and this year it was 220ha. We have two types of soils on the farm – moderately deep clay-lime soils and some clay loams. On the loams, yields were good, averaging 42 dt/ha whilst on the clay-lime soil, the average was 35-36 dt/ha.
Q.: What weeds are prevalent in the OSR that you grow?
J-H. R. : The most troublesome weeds here are Cranesbill, cleavers and in recent years, milk thistle. Other broadleaf weeds are easier to control by herbicides. We also have to deal with resistant black-grass. We’ve been practising no-till for twenty-five years and that’s increased the organic matter (OM) content in the soil. But it also means that as you get over 3% OM in the soil, weeding becomes very complicated with soil-active herbicides. Therefore, in the last two years, we have re-introduced ploughing before wheat in order to redistribute the organic matter in the soil. Our goal is to plough only every 6 to 10 years.
Q.: Tell us about your weed control scheme.
J-H. R. : Pre-planting in plots with Cranesbill I use napropamide at 900 g/ha, then metazachlor, dimethenamid-P and quinmerac, either post-sowing or just after early emergence. This is followed by Ielo/Yago/Biwix at 1.5 kg/ha in December. Last year, fields were clean where OSR emerged well because the crop choked the weeds. However where OSR initially suffered and was clear, Cranesbill managed to get a foothold.
On the other plots, I adopt the same scheme without napropamide before drilling. In plots infested with field mustard, which accounts for up to 25% of my OSR fields (depending on the year), I opt for resistant Clearfield varieties. I therefore respond with a reduced dose rate of metazachlor and dimethenamid-P in post-sowing or early post-emergence and then with an imazamox herbicide on the emerged weeds, usually around the OSR 4-leaf stage.
Q.: A new post-emergence broadleaf control solution is expected to be available soon. How does that sound?
J-H. R. : Fully post-emergence weeding is of course, of great interest. It means we only need to treat once the OSR has emerged and to treat on sight after the weeds have germinated. That leads to greater flexibility when choosing the treatment date. And in the year when the crop doesn’t emerge, we don’t apply any herbicide at all.
Ideally we’re looking for a product that is effective on Cranesbill and milk thistle. It could be supplemented by Ielo/Yago/Biwix a little later during the winter or by Kerb Flo if all we have is grasses.