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Combatting hidden threats to second wheats

Second wheats look to rise in popularity this planting season in light of the poor performance of spring crops, but growers are warned to manage the persisting challenges when it comes to growing the crop.

Second wheats look to rise in popularity this planting season in light of the poor performance of spring crops, but growers are warned to manage the persisting challenges when it comes to growing the crop.

Mr Lee Bennet, Head of Seeds at Openfield, explains that the current high wheat price may also encourage a spike in second wheat.

“Second wheats can be very profitable, however there are threats that impact on yield and quality. By implementing an integrated strategy and the appropriate management techniques growers can mitigate these,” he adds.

Robust rooting

“Many growers are moving to a late drilling strategy for wheat crops, as part of their integrated approach to managing difficult grass weed problems but also to help reduce some of the risks associated with take-all and BYDV,” explains Dr Paul Fogg, Crop Production Technical Lead at Frontier Agriculture.

“However, depending on the season and how well crops establish, later drilling dates can carry a yield penalty, especially in a second wheat situation,” he adds.

“When growing a second wheat the interval between harvesting and drilling should be extended to allow for natural decline in take-all inoculum in the soil.  In reality this means the end of September, early October at the earliest, but if grass weeds are a problem this could be mid-October.  

“However, late sown crops can struggle to develop a good root structure, particularly as soil temperatures drop and day lengths shorten.”

Dr Fogg explains that ongoing research has found that combinable crops across the UK aren’t achieving sufficient rooting at depth.

“Modern crops and establishment techniques appear to be producing less root density at depth compared to the 1970’s and 1980’s and this is potentially capping yield, irrespective of diseases or other pressures.

“Crops need 20mm of water for every tonne of biomass they produce, all of which has to come from water stored within the soil. Without deep and dense roots the plant can’t access this, which is something that has been very apparent this year.

“There could be a number of reasons for this problem, but in reality it’s likely to be a combination of factors, which includes the genetic characteristics of today’s varieties, along with modern establishment techniques and cultivation methods which don’t allow roots to penetrate deep into the soil.”

Dr Fogg explains that taking an integrated approach is key to addressing this.

“Increasing organic matter throughout the soil profile can help to hold onto moisture and maintain good structure. While cover crops can create channels, so the cereal roots can follow these down to depth,” he says.

“Bringing drilling dates forward, where possible, will extend the window of establishment and allow crops to develop more robust rooting. But, if an early drilling date is being observed then it’s important to consider the use of a seed treatment for take-all, such as Latitude (silthiofam), to help mitigate the effects of the disease,” he says. 

Mr Chris Charnock, Arable Product Manager at Certis, explains that a specialist seed treatment offers growers an insurance policy. 

“Using Latitude can help to protect roots from the take-all pathogen in the early vulnerable stages of growth by creating a zone of protection around the emerging crop’s root system.

“This is also beneficial to plant health by encouraging the crop to build robust rooting which increases the crop’s ability to take up water and nutrients, resulting in a positive effect on yield and specific weight,” he says.

Nutrition

“Nutrition is critical to encouraging crops to establish in the autumn and early spring,” explains Mr Edward Downing, National Fertiliser Manager, at Frontier.

“An application of water soluble P & K fertiliser very close to, or at drilling, will help to encourage early root growth in second wheats.

He adds that it might be worth considering a further application very early in the spring if rooting conditions haven’t been ideal. 

“Manganese deficiency can be worse in second wheat so it’s worth paying a little more attention to getting foliar applications on in the autumn, and even considering a manganese seed treatment,” he adds.

“Phosphites are also a valuable tool,” he says. “They can be applied to the foliage or in a seed treatment, and will help build early biomass, particularly the roots, by triggering the plant systems to search for phosphorous.”

However, he warns that phosphites are only effective if phosphorous is readily available in the soil profile.
“After Christmas the key is to keep the crop going, building plant and root structure and ensuring it’s more resilient in the spring to reach full yield potential.  

“Early, higher nitrogen rates can definitely help, but it’s important to address all the nutritional needs of the crop,” he says.

Soil health

“More people are going down a min-till route from a soil health perspective, which can increase the risk of take-all,” says Dr Fogg.

He explains that this not only increases slug populations but also take-all pressure.

“Trash left on the surface or incorporated into the shallow rooting zone means that take-all inoculum isn’t buried and is close to vulnerable emerging roots,” he says.

“Ensure you get a good straw chop and spread at harvest, and try to reduce large straw piles to limit the amount of trash in one area. Drill into a consolidated seed bed to ensure moisture is retained and crops can get moving as quickly as possible.”

Dr Fogg also advocates the use of catch and cover crops where the rotation allows, as they can help improve the physical and biological condition of the soil. However, it is important to choose crops carefully, as cereals species for example, can act as a green bridge to take-all.

Grass weeds

Although blackgrass still grabs the headlines, it’s becoming clear that grass weeds in general are becoming an increasing problem in “non-traditional areas”.

“Black-grass, rye grass and brome spp. can all act as a carrier for the take-all inoculum,” he says.
“Adding these weeds to your hit-list and applying the same integrated management methods as blackgrass is the best way forward.

“When it comes to stale seed beds, target the two to three leaf stage of the grass weed with a glyphosate application and go in again if you get a second flush. If there are any survivors make sure to follow up with a shallow cultivation before drilling.”

Weather

“Arguably the biggest threat against growing any crop is the weather,” explains Mr Bennett.

“You can’t predict the weather and all you can do is work against the average season to know what you’re likely to expect.

“This year, for example, has been exceptional with a cold winter, wet spring, followed by an extremely hot and dry summer which has caused extreme crop stress. 

“As we have seen here, there are a lot of factors and hidden threats affecting the production of any crop, but second wheats are up against it a bit more,” explains Mr Bennett. 

“If you’re going to plant a second cereal this year it’s vital to adopt every practice available, both culturally and chemically, to ensure yields and profits are protected.”