February 5, 2020
Disciplined Spring Care Vital for Backward Winter Wheats
Winter wheats that have struggled through the wettest early season on record or established from very late sowing offer attractive margin-earning opportunities in a season in which supplies are set to be particularly tight. But only with well-targeted and disciplined spending this spring.
Restricted rooting and cold, wet soils make the right early nutrition critical, with timely growth regulation and effective protection of the lower leaves, in particular, more important than ever, insists Agrii regional technical adviser, David Felce.
“Well-established crops with over 200 plants/m2 should receive no more than normal yield-maximising management,” he advises. “And poorly established and weedy crops with less than 50 plants/m2 are probably best replaced with a spring crop or fallow. It’s the patchy but viable stands that fall between the two that need special care, together with any wheats sown after mid-November.
“Recognising the extent to which these crops fall short of the 260 plants/m2 wheat growth guide benchmark, our primary aim must be to do everything we can to encourage tiller production and survival. Then we need to optimise the other two components of yield – grains/ear and thousand grain weight.
“With the right help, even very late-drilled and apparently backward wheats can do us proud in margin-earning; especially so in a year in which domestic and European wheat production look like being well down. To do so they need very targeted investment, aimed carefully at where it will give the greatest return.”
EARLY NITROGEN IS ESSENTIAL
In this context, Agrii research underlines the importance of extra early nitrogen to support the greatest tillering; an additional 50kg/ha at this stage increasing ears/m2 by over 20%, yields by a good 0.7t/ha and margins by more than £60/ha in heavy land Stow Longa trials last season.
David Felce stresses this will be especially valuable with early N-Min tests showing generally low levels of soil nitrogen in the upper rooting zone following high offtakes last harvest and higher than usual losses in the very wet early winter.
For the greatest benefit, he recommends the most available nitrate nitrogen, provided as soon as conditions allow travelling without damaging the soil. As well as stimulating tiller production, this will encourage the extra root growth vital for the best tiller retention and anchorage.
“Of course, the nitrogen should be balanced with sulphur, phosphate and probably also potash given crops’ very limited root penetration and reduced nutrient availability in cold, wet soils,” he adds.
“In view of its importance for rooting and to counter particular availability issues, I strongly favour protected phosphate. Adding P-Reserve to TSP in our work under conditions known to limit phosphate availability despite a soil index of more than 2.0, for instance, has increased wheat yields by 0.54-0.74t/ha.
“Where wheat has gone into less-than-ideal seedbeds we’ve also seen highly economic responses to a specialist K fertiliser in trials, despite a healthy K Index soil. And we invariably see much more marked responses to sulphur, manganese and a range of foliar trace elements in later-sown and backward wheats.”
USING PGR’S TO DRIVE TILLERING
Alongside the right nutrition from the start this spring, Mr Felce insists there is much that the most-timely growth manipulation can do to support rooting and tillering. Physiologically, he explains, it’s about adjusting the hormonal balance between auxins and cytokinins to direct the desired plant growth.
PGRs like trinexepac and chlormequat – as well as certain biostimulants – known to favour auxin production and suppress cytokinins will really drive tillering and rooting. But only if applied ahead of stem extension before cytokinins really kick-in to fuel top growth. Otherwise, all they do is shorten the crop.
“I recommend employing a PGR able to cope with low temperatures to support thinner crops well before T0,” he suggests. “There’s a lot of rubbish talked about biostimulants. But over the years we have found two, which have given consistent results, especially with backward wheats. One of them applied very early too, with the other best applied at T0”
“Septoria certainly shouldn’t be much of an early threat to these later drilled wheats this season. But we really must protect the lower leaves that make so much more of a contribution to yield in thinner crops from powdery mildew and rusts, in particular.
“It’s all part of doing everything we can to minimise unnecessary extra stress on crops that are particularly vulnerable this season,” concludes David Felce. “Aphid control is something we need to think hard about after another mild winter and so few early spraying opportunities. And we must keep on top of weeds with the least possible effect on our crops.”
David Felce’s Top Tips for Winter Wheat Care this Spring
• Assess crop condition and grassweed pressure field-by-field
• ‘Go for Gold’ where plant populations are sufficient
• Seriously question fields where populations are very marginal;
• Given special attention to crops falling between these extremes;
• Focus resources on supporting tillering and rooting to maximise ears/m2;
• Provide extra early N in the most available form as soon as field conditions allow;
• Support this with S and ensure sufficient available P and K;
• Be sure to maintain manganese levels as the crop develops;
• Provide targeted micro nutrition in the most available form based on tissue testing;
• Direct plant physiology with early growth manipulation;
• Protect all leaves from disease, especially the lower ones; and,
• Avoid anything that stresses the crop.