March 4, 2014
Managing the highest wheat lodging risks in recent years
Stem and root lodging pose the highest risk to winter wheat for many years, growers attending the first AgriiFocus Technology Centre agronomy day of the year near Marlborough in Wiltshire this week (Thursday February 27) were warned, putting the onus firmly on the most effective plant growth regulation from the outset this spring.
“Excellent early establishment and one of the mildest winters on record means many wheats are coming into the spring full of potential,” pointed out Agrii regional technical adviser, Tim Horton. “At the same time, though, September and October-sown crops are generally thick, lush and well-grown.
“Add to this poor anchorage support from very wet soils and the fact that almost two thirds of varieties on the Recommended List – and over 75% of Group 3 and 4 wheats – are rated
7 or less for their inherent lodging resistance and the warnings bells sound loud and clear. Especially so for crops sown in or before mid-September – when ratings can be reduced by two points – at other than low seed rates and where soil mineral nitrogen levels have been more than adequate.
“Even varieties with resistance ratings of 7 have shown as much as 90% lodging in our trial work,” he stressed. “So good PGR management will be essential in forward crops if serious stem or root lodging losses are to be avoided and canopy structures optimised.”
For such crops, Tim Horton recommends a ‘short split’ with low temperature active PGRs at both GS29/30 and GS31/32. Standard applications of Adjust, Meteor +/- Cutlass will, he explains, shorten internodes and reduce apical dominance as well as increasing root plate length and diameter, root fresh weight and stem thickness. He stresses, though, that it will be vital not to let yellow rust take hold while waiting for the right PGR timing.
While backward crops will profit from a ‘longer split’ with the first PGR application brought forward to GS21-26, Mr Horton strongly advises against this with forward crops to avoid excessive tiller retention.
“Regardless of crop condition, don’t skimp on your early PGR application as this will really improve anchorage to reduce the risk of root lodging,” he said. “Then go in with the second split to shorten the internodes and strengthen the stem base.
“A further application of Adjust + Cerone at GS37-39 will also be advisable to restrict stem elongation in particularly thick crops and varieties most susceptible to stem lodging. In all cases, our trials have shown the inclusion of Kantor improves PGR penetration and uptake to deliver valuable yield benefits.
“Alongside effective PGR management, of course, it will be vital to time nitrogen applications carefully to both crop and soil nitrogen status,” added Tim Horton. “Our early N Min results suggest available soil nitrogen levels are lower than last season. But they can vary widely from site to site so we strongly advise specific assessments for the greatest precision.
Using Agrii’s N Planner, he recommends applications targeted at achieving a Green Area Index of 6 ahead of flowering for the most productive canopies. Where less than 100 kg/ha of N is needed to achieve this, the majority should be applied around two weeks before the terminal spikelet stage at GS30. But where initial N requirements are higher two thirds of the amount required for the canopy should be applied in two early season splits followed by a third between GS32 and GS37.
“The last thing we need with thick stands is too much nitrogen too early,” he insisted. “While our trials show more early N will increase both heads/m2 and yields in thinner crops, in thicker ones this will restrict yields by creating less efficient canopies.”