Basic Principles of OSR Establishment
24 Aug 2017
Time and again, establishment is recognised as the number one challenge when it comes to growing winter OSR. However, as soil and cultivation expert Philip Wright explains, if crops can be established quickly, they are better able to withstand pest, weed and disease pressures and far more likely to reach their full yield potential.
Key to achieving this and getting the crop off to the best possible start, is getting the soil structure right.
Philip Wright, independent advisor on soils and cultivations at Wright Resolutions Limited said, “Growers often have difficulty achieving quick, consistent establishment because soil conditions are often challenging at this time of year but it pays to be patient. Soil conditions should dictate the time of drilling, not the calendar date – although this is, of course, important. Cultivating in the wrong conditions can do more harm than good.”
Mr Wright outlines the steps to take to ensure your oilseed rape crop establishes successfully, which can also be seen here:
Principles of establishment
There are many options available for establishing oilseed rape, all of which now tend to follow the blueprint of precise drilling into a loosened, structured seedbed.
The basic principles of oilseed rape establishment involve growers focussing on:
- precision of the seedbed
- placement of the seed
By getting this correct, growers will create optimum conditions for root growth, general growth and herbicide efficacy.
Precision of the seedbed
Size of aggregates
Aim to create a seedbed with a fine tilth. The rule of thumb is the smaller the seed, the smaller the aggregate that is needed around it, if only just in the area where the seed is. This gives that good seed to soil contact, which allows moisture to move through the seed coat effectively and give good germination.
Effects of compaction
Worldwide research sponsored by Unilever in 2002, looked at the effect of compaction on oilseed rape yield and showed an average yield loss of 25%.
However, the weather pattern plays a huge part in the size of yield reduction: a wet year (or a prolonged, very wet period) can result in total crop failure, as oilseed rape does not like to have waterlogged roots; in drier seasons, you might get away with growing a crop in a poorly structured soil.
The effect on yield depends entirely on the season’s weather pattern. This is one of the reasons why farmers find the yields of oilseed rape so variable.
If the soil structure is in good nick, then go out and drill it. However, in many cases soils sometimes need a bit of help. Less well-structured soil will inhibit oilseed rape root growth, meaning less access to moisture and nutrients. Therefore, if the season turns dry, the crop can desiccate early.
If you restructure the soil for oilseed rape, then this has further benefits for future crops. The oilseed rape will power down through that loosened structure and stabilise it and so hopefully give you the opportunity to do less in future seasons, saving money.
Looking at soil structure
- Start with the previous crop or just after harvest. Dig down and look at the soil profile to see if, or confirm exactly where, there is a compacted layer. Root structure of the previous crop is a good indicator too.
- Get the timing of restructuring right. Take a small lump of soil from the depth you will be working at and roll it between the palms of your hands. If it can be rolled out to form a solid “worm”, then the soil is too wet to cultivate. If when rolling, the soil just breaks apart, then it is in the perfect condition for cultivating. Loosening is also effective when drier than this, provided clod strength is not too great for the soil to shatter – where it can then raise excessively large clods.
- Set the machine to cultivate to an appropriate depth to deal with the problem.
- Dig down afterwards to make sure the machine has done the job.
Placement of the seed
Consistency of sowing depth
Sowing depth is all about consistency, which is more important than what the actual depth is; this will depend on the season and the conditions. Lack of consistency can result in areas where some plants grow straight away whilst others are delayed, or fail to emerge. This not only has an effect on the growth but also causes management issues throughout the season.
Resist the temptation to increase seed rates to compensate for inconsistent emergence, otherwise this can lead to excessively high plant numbers in areas where structure is better.
Soil looseners with seed distribution are widely used. Where seed placement is then inconsistent, consider upgrading to a set of openers fitted behind the loosener roller to precisely place seed at the same time.
Finally, consolidation ensures good seed to soil contact enabling seeds to take up adequate moisture for germination. Consolidation is also needed to assist slug control.
Oilseed rape can be a high risk, high input crop but returns are also appropriate, provided the crop can reach its potential by getting a good start. Attention to detail pays here – and that starts with the combine. Residue management is key, both to make cultivations efficient and to minimise unnecessary passes which can lose moisture. Residue levels should be consistent and well chopped across the field to ensure pest issues are minimal, and for the best seed to soil contact. The use of locally placed nutrients (especially N and P) can assist here, particularly where residue levels are high.
Where farm policy is influenced by the need to manage grass weeds, oilseed rape provides a valuable break for the rotation. This assists natural structuring whilst maintaining weed seed bank levels appropriately – so best use can be made of all controls available to the farmer.