Oilseed rape (OSR) growers for 2017 will once again begin the process of working out how best to prepare for and establish their crop of rape. OSR seedlings are weak and susceptible to poor seedbed conditions, weather and a number of pests.
Assessing soil conditions in July can be a good place to start when preparations begin. Oilseed rape requires soils free from compaction to allow a substantial tap root to grow; this in turn will aid the crop in fulfilling its potential. Any compaction found needs to be corrected before drilling.
Weather conditions, not date, should be your main driver with regards to drilling dates. Early sowing may ease autumn workflow but increase pesticide costs, however this could reduce your autumn nitrogen requirement. That said, sowing date trials have shown that high yields can be achieved when drilling anytime between mid-August and mid-September. Drilling after these dates can have a negative impact on plant establishment, so it may be necessary to increase seed rates.
There are many techniques used to establish oilseed rape ranging from ploughing systems to broadcasting into stubbles. The most suitable method for a given site depends on soil type, soil conditions, prevailing weather and likely pressure from weeds, and pests. In dry conditions you may look to sow seed as soon as possible after light cultivations to minimise soil moisture loss. Consolidation rolling (twice if possible) is generally recommended in the majority of situations to retain moisture and minimise slug damage. These consolidations will also allow optimal performance of soil applied herbicides.
Recommended seed rates at drilling vary depending on varietal choice (hybrid or conventional). In general, most will look to drill conventional varieties at 80-100 seeds/m2; however the latter figure would be drilling on the thick side and would recommend 70-80 seeds/m2 while hybrid varieties can be reduced to 50 seeds/m2. Rule of thumb, an optimal plant population count of 25-35 plants/m2 (both hybrid and conventional) is ideal when heading into spring.
Effective weed control is another vital element in allowing the oilseed rape crop to achieve its full potential. and move away from any pests quickly at what is a vulnerable time for the young plant. Prior to drilling, stubbles should be allowed to green over and any emerging weeds sprayed off with a non-selective herbicide. Herbicide trials work carried out in 2016 near Chichester, West Sussex, showed that both pre and post emergence herbicides certainly have a place in establishing oilseed rape, however growers should be wary of the effect certain actives can have on young OSR plants. Clomazone can be used pre-emergence only on oilseed rape and is a useful active for controlling difficult weeds such as cleavers and hedge mustard, however it can check the young plant at a vital growth stage and also bleach the leaves.
In short, OSR establishment needs planning and attention to detail at what is a very busy time of year. Drilling into a moist, clod free seedbed with as little trash as possible will give you every chance of establishing a profitable break crop.