Cultivation tips to avoid compaction Ditch the discs and turn to tines for oilseed rape establishment if wet soil conditions continue this season, advises Philip Wright of Wright Resolutions. Speaking at the recent Syngenta Driving Up UK Oilseed Rape Yields initiative meeting, he warned that even with scalloped and angled discs, there is a real risk of causing smearing and compaction in wet soils, making tines that can lift and fissure the soil structure a more appropriate option. Shallow discs may still have a role to bury crop residues, if the surface dries out, he added.
Tines that will lift and fissure soil will be more appropriate than discs in this season’s wet soil conditions.
“Compaction is the real killer for oilseed rape; it’s the cause of most structure issues for the crop. With the wet soils this year, there is a real risk that problems will be created for the establishing crop, and that could take years to resolve,” he warned. Mr Wright highlighted that there is a straight line relationship between oilseed rape root growth and crop yield; deeper rooting equals higher yields as a combination of better water and nutrient uptake, along with greater standing power. However, the correlation between compaction and root depth indicates just a little bit of compaction, has a serious reduction in root growth, leading to a significant yield loss.
Even low levels of compaction will impact severely on oilseed rape root development and ultimately yield, warns Philip Wright.
He reported that, globally, 25% of oilseed rape yield potential is estimated as being lost to compaction, but in the UK it could well be even higher. Whilst tyre, track and machine technology have all made a huge improvement in lowering ground pressure, at the same time axle loadings have increased. Penetrometer testing has shown an 18 tonne trailer can be causing deep seated compaction at over 550mm – and can be further exacerbated by wet soil conditions this harvest. Wherever possible, he urged growers to avoid working soils when they are in a plastic state, which makes it impossible to achieve the desired lifting and loosening of the soil; generally working in these conditions will make the situation worse, he advised. “Tine cultivations will be better suited to wetter soil conditions we are likely to face this season,” he said. “But it remains important to set-up the rake angle and operating depth.” Whilst a flatter rake angle will lift the soil, if it is too steep, it could result in pushing and smearing. Similarly, if the tine is operating too deep it can cause smearing below the surface that roots cannot penetrate, without any real benefit in creating a surface tilth; too much lift can bring large clods to the surface that small oilseed rape seeds will struggle to emerge in.
Take care with set-up to optimise seed placement depth and avoid large clods where oilseed rape will struggle to emerge.
Mr Wright also advised growers to watch out for wear, since the angle of lift on points will change as the metal is eroded. This can make a significant difference on draft and effective operating depth. He advocated carbide tipping on wearing parts can extend their life, but more importantly, retain the original shape to give consistent lift, even if uncoated edges continue to wear. Sharp edges and points reduce the risk of smearing. Mr Wright told growers that 75% of the compaction damage typically occurs in the first pass, so focussing traffic in restricted areas will limit the overall impact. “And if you know where the compaction is, you can do something to alleviate the effects more cost effectively with targeted cultivations.” Getting the conditions right for the oilseed rape crop will create big root structures that generate beneficial deep fissures through the profile and put back essential organic matter. That will not only enhance the yield potential of the oilseed rape, but also creates better soil conditions for the following crop, and the opportunity to minimise future cultivations, he added.
Seedbed creation sets seedling emergence Accurate seed placement is a critical factor in achieving high emergence rates and even establishment of oilseed rape crops, advises independent cultivation and machinery design consultant, Philip Wright. Speaking at the recent Syngenta Driving Up UK Oilseed Rape Yields initiative meeting, he reported that, at a consistent sowing depth of four to five cm in a decent seedbed, with good soil-to-seed contact, growers could reliably achieve over 90% emergence; where a seed rate of 220,000 seeds per hectare would produce a desired 20 plants per m2.
Maintaining a consistent sowing depth is essential to achieve even oilseed rape germination and establishment.
However, at a sowing depth of 10cm, trials have shown the emergence could be anything from 40 to 80%. If the seed rate is adjusted up to 330,000 seed per hectare - aiming to give 20 plants per m2 at the mid-point 60% emergence - that could produce anywhere from less than 13 to over 26 plants per m2. In practice, many growers would err on the side of caution, sow 500,000 seeds and potentially end up with a stand of over 40 plants per m2. “Such a variability in plant population makes subsequent management more difficult and, inevitably, less precise, which will impact on yields and profitability,” he warned. “The move to lower plant populations makes precision sowing and the reliability of emergence even more important, since there is less room for error with plant losses.” Cultivations and establishment technique clearly plays a crucial role in consistent seed placement. With the rough surface left by sub-soiling or deep cultivations, he strongly advocates using a press or double press to consolidate the cultivated surface before sowing – ideally with the press mounted in a tillage-train design, or as a separate pass if necessary. Adequate consolidation – not compaction – is an essential factor of good germination, he added. It is also an important element in managing water movement through the soil. “Smaller surface aggregate size is generally beneficial to higher germination and faster establishment of oilseed rape. However, the fine particles will hold tightly onto soil moisture and prevent downwards movement if there are disproportionally larger aggregate particle
below; pressing can help to minimise layers of differences in particle size and break up any barrier to capillary movement,” he advised. In the dry conditions establishing oilseed rape in 2011, Lincolnshire grower, Andrew Ward, saw significant benefits from a post-sowing pass with a DD-press, even after rolling on the cultivator drill. Although it required an additional pass, it was a relatively quick and low cost operation and could be timed when soil conditions were optimal, he added. With this approach, Mr Ward reported germination and establishment had been over 95% from seed rates as low as 20 seeds per m2. The success has seen him develop a new 6m one-pass integrated cultivator, packer and seeding system, which will be out into practice this season.
Adequate consolidation to ensure good seed-to-soil contact can achieve very high establishment rates from low seed rates, reports Andrew Ward.
Read the Power Farming report on Andrew Ward’s oilseed rape drill here. Philip Wright believes too high a sowing rate was the primary cause for the levels of crop lodging being seen this year, coupled with the influence of variety and the application of autumn Nitrogen. “The situation has been more marked this season, where crops at up to 100 plants per m2 have typically gone flat, whilst those at 20 plants have been standing strongly,” he added.
Achieving the right plant population has been crucial in maintaining standing crops and harvesting the full potential yield.
For more information or to contact Philip Wright visit the website: http://www.wrightresolutions.co.uk/