Driving Yield to Cut Cost
By David Leaper, Agrii
Always the first key to arable profitability, driving yield is more important than ever at current winter OSR values.
Commercial crop margin calculations for the coming harvest from our consultancy services show that every 0.5 t/ha increase in winter rape yield is likely to drive down production costs by £10/tonne – considerably more if the improvements are achieved without extra inputs.
First and foremost, much can be done to raise average farm yields at little or no cost simply by being more selective about where rape is grown. Most growers know from bitter experience which fields don’t really suit the crop. So, they ought to be thinking seriously about how frequently they put it into these fields, in particular.
Growing winter barley rather than wheat ahead of oilseed rape will help too. In addition to being a far less favourable bridge for slugs, barley provides valuable extra time for August establishment; something that’s especially critical where flea beetles are problematic.
With a difference of 0.65t/ha between the treated yields of the 26 varieties on the current East & West Recommended List, variety choice clearly has a major part to play in improving OSR performance. However, I have no doubt that the greatest gains in variety selection will come from looking well beyond yield – or even gross output – to several key yield-preserving and enhancing characteristics.
Most important in my view are establishment ability, speed of early crop development and foliar disease resistance; especially in matching varieties carefully to individual farm and field circumstances.
Establishment is everything in getting the most out of winter rape. Not only does it determine whether there’s a worthwhile crop to manage, it sets the plant population for the rest of the season. And we know excessive populations can be just as damaging to performance as inadequate ones. So, more than anything else, varieties need to be selected to match establishment conditions.
Hybrids certainly seem to have the edge in the vigour of their establishment in the large-scale variety trials we run across the country. But our measurements of leaf emergence and Green Area Index show different hybrids varying as widely as pure lines in their speed of development. This can make all the difference to their performance, depending primarily on soil type, seedbed conditions and sowing date.
For the best results with demanding soils, in less-than-ideal conditions or from late sowing choose a fast or medium-fast developing variety which has sufficient get-up-and-go to grow away from these challenges. This will allow sowing at relatively low seed rates with confidence to achieve the 20-30 plants/m2 in the spring giving the most productive canopies.
Where the ground is fertile, the seedbed quality good and sowing early, however, a less rapidly developing variety is needed so it doesn’t put on too much lush, thick growth ahead of the winter, leaving a canopy that’s both difficult and costly to manage.
I’d also advise everyone to prioritise high levels of resistance to both phoma and light leaf spot in their variety choice given the yield losses these diseases can so easily cause without the most timely and costly spraying. As early drilling puts far more light leaf spot pressure on crops, the most robust resistance as especially crucial for this drilling slot.
Regardless of variety, there’s now overwhelming evidence of the value of placing nitrogen or DAP in the seedbed. Our research also shows extra returns from a root-boosting seed dressing like Take-Off and/or Nutri-Phite PGA in the autumn or spring spray programme. And while we still see too much spring nitrogen going onto large canopies, most crops could almost certainly profit from more potash at this stage.
Towards the end of the season, particular care will pay dividends in OSR desiccation. Each day of seed-filling lost is known to reduce yields by 1-2%. So, going in a week too early with glyphosate could leave typical crops half a tonne or more worse off.
It is important to appreciate that, at the traditional spray timing for traditional high plant population crops bearing most of their yield on the main raceme, more than a third of the pods in well-structured, modern hybrid OSR canopies may be immature.
To capture the greatest yield, desiccation needs to be delayed until the bulk of these pods are sufficiently ripe. This can be 7-10 days later than those on the main raceme. Patience, coupled with genetic resistance to pod shatter to minimise seed losses from the more mature upper main raceme pods, will clearly be valuable virtues here.