Tillage - oilseed rape an option for 'three crop' rule
The three-crop requirement under greening for farmers with 30+ ha of cereals will result in many farmers being forced to grow crops for the 2015 harvest which they have not previously grown.
Oilseed rape will suit some of those farmers. It is suitable for medium to heavy soils but will not tolerate compaction. New growers should consider growing semi dwarf varieties as growth regulation and nitrogen management will not be as critical. Ideally all rape varieties should be sown by September 10 and this is certainly true for the semi dwarfs.
Varieties are described as being either conventional or hybrids. Hybrids have greater vigour and there is a tendency with growers to rely on hybrids when sowing runs late. However the yield potential really comes down to weather conditions after sowing and plant establishment. Hybrids are considered to be less susceptible to slug and pigeon damage.
Seed is supplied with the seed count written on the bag. Use approximately 55 seeds for hybrids and 80 seeds for conventional varieties. Rates should be adjusted depending on soil conditions and sowing dates.
Oilseed rape needs a fine firm seedbed. Cultivation techniques vary from discing followed by sowing to ploughing and cultivating before sowing, with many farmers opting to use a subsoiler and seeder unit. This technique runs a greater risk of slug damage so don't forget the pellets.
A low rate of nitrogen may be beneficial on worn ground. Fertiliser nitrogen and/or phosphorus application is not likely to be of benefit and is certainly not permitted after September 15. This is the first year that seed is not dressed with an insecticide. Therefore, it is very important to inspect crops for evidence of flea beetle damage and to apply a suitable insecticide such as Karate Zeon or Decis when significant damage is observed. Flea beetles are blue black to brown in colour and up to 5mm in length. The adults chew the leaf margins of seedlings and create a shot hole effect in cotyledons/first leaves.
The adults lay eggs, September/October, near the soil surface. When they hatch the larvae bore into the petioles and later the main stem. A severe early attack can result in a total crop wipeout. Early sown crops are most at risk but delaying sowing to reduce the risk will result in reduced yield potential and perhaps failure to get the crop sown.