Oilseed Rape Establishment
Oilseed rape seed treatment and sowing rates
Greater pressure on oilseed rape establishment means it is essential to pay close attention to seed rates and the appropriate use of seed treatments.
Oilseed rape rates will vary based on various criteria. As a starting point, it is suggested that hybrid varieties are drilled at 50 seeds/m2 and conventional varieties 100 seeds/m2. To adjust these, the following considerations need to be made. Drilling date, soil type, seed bed quality, moisture, pest pressure, and drill accuracy. These will all influence the establishment percentage and can be used to adjust rates both above and below the average given previously.
Irrespective of the cultivation system, there are a few key factors to consider during seedbed preparation. Soil that is free from compaction allows unrestricted tap root development and good seed-to-soil contact will improve germination consistency and promote early vigour. Consistent drilling depth ensures seed is planted into moisture and has sufficient soil cover to keep it safe from herbicide damage. Trash management is also important, with exact requirements dependent on the material left after the previous crop. Turning damp residues on the soil surface can dry out slug eggs and reduce later pressure. Removing weeds and volunteers growing after harvest also removes their food source. Adequate consolidation after drilling is essential in all establishment systems, improving seed-to-soil contact and physically impeding slug mobility. Cambridge rolls follow surface contours well and can be particularly useful after director strip-till drills, where as flat rolls can ride on high spots and mounds of trash, leading to uneven consolidation.
Earlier drillings established in good conditions with adequate moisture suit slower developing varieties, avoiding the over large canopies that are more prone to winter damage. Later in the drilling period, hybrids that grow away quickly are key to ensuring a robust crop that can with stand pest pressures. Set sowing rates according to seed number/m2 rather thanby weight. Target 30-40 plants/m2 after winter, working seed rates back to take into account likely in-field losses. Forhybrid varieties this equates to drilling 50 seeds/m2, which is the suggested drilling rate from most breeders. Conventional varieties will vary more due to conditions and date, although 80-110 seeds/m2 is a sensible aim. Lower seed rates are possible in good conditions, but could leave you slightly more exposed if pigeon or cabbage stem flea beetle pressure is high.
Growers must make every effort to establish crops that grow quickly through the vulnerable early stages. Drilling in dry conditions will slow emergence, and increase the risk of flea beetle damage. To reduce the chances of an early crop write-off, alleviate potential stress factors as far as possible. Foliar insecticides are available to help manage early insect pressure, including cabbage stem flea beetle, rape winter stem weevil and turnip sawfly larvae. Use full rates of the more active pyrethroids, such as lambda-cyhalothrin andzetacypermethrin, and ensure good coverage. Monitor the effectiveness of any insecticide application and avoid repeat spraying if resistance gives poorcontrol of the target pest. Results are unlikely to improve and it may have a negative effect on beneficial insect populations.
Early root development
Promoting rapid emergence and earlier growth is vital to a successful crop. Winter survival and eventual crop yield are heavily influenced by early root development. Prosper ST seed treatment has a high proportion of phosphite to stimulate early root growth, an effect enhanced by the use of water soluble phosphate fertilisers and foliar phosphite applications to the growing crop. This is never more critical than with oilseed rape. Frontier OSR seed is treated with Prosper ST along with Seed-Life™, a nutrient rich additive. Results from 20 years of trials show a yield advantage of 123kgs/ha, worth around £40/ha over single purpose dressed seed.
Crop nutrition plays a significant role in early season growth, aiding rapid emergence and establishment. This will allow the correct timing of foliar insecticide sprays but importantly, will also help to alleviate flea beetle damage. To achieve this early applications are essential, either as overall applications immediately after drilling (or even before if using shallow tillage) or placed using the drill. In terms of nutrients nitrogen is important to fuel overall growth but the inclusion of phosphate is vital to stimulate the all important root growth and development. The choice of product depends on the applicator on the drill or the technique used but options will include DAP, an NPK (e.g. Actyva S), Radistart Max micro-granules and NP clear liquids and suspensions. Applications must comply with Nmax.