Increasingly unpredictable weather and sky-high nitrogen fertiliser prices are two significant challenges for growers in the 2022-23 cropping cycle.
To make winter wheat crops more resilient to weather extremes, particularly dry conditions in the spring, and make best use of the very expensive nutrient inputs, maximising root mass and health is paramount.
Farmers Weekly gets some industry advice on how this can be achieved through cultural, mechanical, chemical, and biological means.
1. Compaction prevention is better than cure
Good soil structure can be described as a virtuous circle. Growing healthy roots through the soil at one point – whether a cash, cover or catch crop – ensures free passage for air, water and the next crop’s root system after establishment.
These three things combined encourage biological activity within the soil profile, which drives a favourable relationship with the crop, aids nutrient cycling and uptake, and increases the chances of good yields.
However, this can be disrupted by traffic during the harvest period, says independent soils expert Philip Wright, so steps should be taken to prevent any structural damage when combines start to roll in about one month’s time.
“Growers should think about how they can minimise unnecessary traffic, keeping to confined areas in fields such as tramlines or unloading on headlands where possible,” he adds.
Further to traffic management, axle load and ground pressure of the vehicles being used are also critical, although Mr Wright says the latter is the most important in the short term.
“There is an argument that machinery has become too heavy, but that aside, if we can keep ground pressure down, we will reduce the intensity of damage.
“Then whatever is growing in it – commercial crop or otherwise – will have a much better chance of getting roots through that soil,” he adds.
He concludes that minimising the need for remedial action in the first place will significantly reduce the use of fuel – which has rocketed in price in recent months – adding a further incentive for taking a less-is-more approach.
2. Target soil loosening where compaction is identified
Where smart traffic management and biology alone can’t remediate soil structure, the appropriate targeted cultivations will help open up soil and promote rooting.
Mr Wright says the opportunities to use cover crops throughout the rotation should be taken, most likely ahead of any spring crops, as this will have a cumulative positive effect on soil structure.
However, this may not be practical ahead of autumn cereals unless growing a very early-harvested preceding crop, so steel may be the best option to ease the passage for new roots where damage has become restrictive.
He says the key thing for operators carrying out the work is avoiding working to the same depth of cultivation each year, instead defaulting to the shallowest effective depth to get the job done.
“You see it so often where soil has been worked to one depth and it creates a plain of weakness, whether ploughing, soil loosening or after shallow cultivation.
“With all the intense weather we tend to get, it destabilises the soil quite quickly. You also get fines washing down the soil too, and sediment out at one level. It’s akin to blocking a filter and it builds damaging layers that roots and water cannot penetrate,” says Mr Wright.
Dick Neale, Hutchinsons technical manager, says heavier soils seem to be tight in the upper part of the soil profile this year, even if general indicators of soil health are good.
Many growers are moving to reduced-tillage systems, with cover crops deployed to do the remedial work on structure.
But on heavier soil types he will be recommending a lifting cultivation to try to ease the surface compaction that has developed over three to four years of direct drilling.
“It will be very targeted, with the spade used to observe and ensure we are targeting the tines in the right place. I’m generally finding the issues at 10-15cm deep and where disc drills are being used.
“Each coulter is like a mini set of rolls and, if you are establishing cover crops and cash crops with them, I’m finding that soils are compacted,” says Mr Neale.
3. Consider seed treatment options
Conventional, biological and nutritional seed treatments can be used to improve establishment, protect against disease, and encourage rooting early in the crop’s development.
Mr Neale favours use of Vibrance Duo (fludioxinil + sedaxane), particularly in late-drilled wheats in blackgrass situations, where soils are typically colder and wetter.
“It just helps plants get out of the ground better, and one treatment I’m now tending to add with the Vibrance Duo is Tiros,” he adds.
Marketed in the UK by Unium Bioscience, Tiros contains endophytes that are claimed to improve germination, root mass and shoot mass, help nutrient uptake and deal with drought stress more effectively.
Mr Neale says in small plots, it’s difficult to demonstrate a big yield response to the treatment, but he is in no doubt that it increases establishment percentage of plants by about 10%.
If adding that up over a significant wheat acreage, it is likely to contribute to better output, alongside other benefits.
“You will improve your soil, as you are establishing more plants with bigger root systems on a consistent basis. In turn, that gives you a more robust plant, which gives you an edge on things such as controlling blackgrass though better crop competition.
“We have to look at several reasons why you might use it, rather than just increasing yield.”
Hutchinsons technical development director David Ellerton says it is also important to consider take-all in early-sown second and third wheats, which can significantly reduce root mass.
While other seed treatments can help improve plant health and rooting, Latitude (silthofam) is the only one to offer control of the take-all pathogen itself.
With the likelihood of more second and third wheats planted this autumn due to high grain prices, more crops could be exposed to take-all risk and require protection.
“I’d be targeting Latitude in wheats sown from September to early October. After that, the risk does decrease somewhat,” says Dr Ellerton.
The case for silthofam in these situations has been reinforced by recent trials in Germany conducted by manufacturer Certis Belchim.
Over four years between 2018 and 2021, the experiments compared second wheats treated with Latitude and a reduced nitrogen rate against untreated seed receiving a standard nitrogen rate.
The crop treated with silthofam and receiving 40kg/ha less N yielded on average 0.38t/ha more, despite less fertiliser, which the company’s Tim Eaton says is down to its proven activity on take-all.
“It’s reducing the impact of the pathogen on roots and enabling it to make more efficient use of nitrogen and other nutrients in the soil.
“When used alone or in conjunction with other seed treatments, it can make a real difference to root health,” he explains.
Other seed treatment options include micronutrients such as manganese, which can be targeted where deficiency is expected, and peptide seed treatments that have been proven to increase germination, establishment and rooting.
There are also micro-organism-based products coming to the market, such as Biolevel’s GramaxNP, which can increase availability of nitrogen, phosphorus and potassium, increasing plant uptake when applied to seed.
4. Boost rooting with foliar biostimulants
Another way to improve rooting this autumn in winter cereals is to apply foliar biostimulant products, with two types proving beneficial in independent trials.
Niab’s southern regional agronomist, Syed Shah, has tested phosphite- and amino acid-based products in trials and on farm and found that both can offer a significant yield benefit.
The benefit is most significant when lower nitrogen rates are applied, suggesting that it helps improve rooting and nitrogen use efficiency.
“If you use 200-250kg/ha N, you don’t see a big response, but in a low-input system they work well and you can justify the cost of the biostimulants,” explains Dr Shah.
He favours the use of a phosphite and endophyte seed dressing to help promote rooting early when soils are still warm and root growth rates are typically high. This also negates the need to spray when ground conditions might be deteriorating.
However, if opting for foliar applications of either phosphite or amino acid products, his work found that applying in early spring generally showed the best yield response in winter wheat, particularly with low fertiliser input.
“The issue with spraying in the autumn is that the crop is at the four- to five-leaf stage, so you are largely hitting bare ground and crop growth is starting to slow down.
“If you apply at about growth stage 25, soils will be warming up and starting to produce root mass again.”