Theres more to this seasons lodging than meets the eye. Gilly Johnson gets to the root of the problem.
WEAK straw has not been the sole cause of widespread lodging this year, according to Doug Stevens of the Morley Research Centre, Norfolk. A close look shows that some plants have gone over at the base of the crop, rather than through breakage higher up the stem.
Mr Stevens says root lift – a phenomenon caused by "spongy soil", is to blame, particularly on the lighter, "tender" land. It is a result of a long period of wet weather in the spring. This ruled out rolling, which might have helped consolidate the soil. A symptom of this problem is when a partially lodged crop remains standing along the tramlines, due to the extra compaction in the wheelings.
On the lighter soils at Morley, many soaked, soggy seedbeds were unable to provide firm anchorage. So as soon as the heavy storms arrived, the root ball was pulled up under the leverage resulting from tall, leaning stems. "Heavier clay land has not had these problems to such an extent," says Mr Stevens.
The twin causes of lodging are clearly apparent in growth regulator trials at Morley, sited in weaker-strawed Reaper. The untreated plot has lodged completely, though it will still be harvestable, reckons Morleys Rachel Gaskin.
Where the straw has been shortened with Terpal, the reduction in the mechanical leverage has resulted in less root lift. But using Terpal alone, without chlormequat to help stiffen stems, there was still some lodging – even at a high rate of Terpal (2litre/ha). So lodging through stem breakage is also significant this season.
To control both elements of lodging, the best and most cost-effective option in wheat is chlormequat, followed by Terpal, according to Ms Gaskin. The complete programme is:
• 1.75litre/ha of chlormequat at tillering to stem extension (GS 25-30) applied mid March,
• second split (0.75litre/ha) at stem extension to first node (GS 30-31) at the beginning of April
• followed by 1.5litre/ha of Terpal at early flag leaf (GS37) during mid May.
The Reaper is still standing well following this application. Cost of treatment is about £36.50/ha (£14.80/acre).
It has made little difference whether the chlormequat was applied as a split or as a single treatment (2.5litre/ha at stem extension to first node (GS 30-31) this season, she adds.
Some savings could be made by cutting the Terpal dose to 1litre/ha – lodging control is still reasonable, she comments. Cost of this treatment would be about £21/ha (£8.50/acre).
Paying the extra for more costly products such as Meteor or Moddus did not appear worthwhile in this trial. The autumn root stimulant Axis has also been included.
"There is no benefit in terms of lodging control from the Axis. Yield results will tell us whether it increases yield, through greater tillering."
Where the Terpal has been replaced by Cerone in the growth regulator programme, the lodging control has not been quite as good. This is because Cerone does not shorten the upper internodes to the same extent as Terpal, she suggests. So root lift was still occurring.
This was also the case with Upgrade, which has most affect at the third node, and so did not strengthen the stem base.