Tips for managing drought-prone wheat soils

As the threat of drought looms for much of the UK, Farmers Weekly visits a lightland Norfolk estate where dry soils are a challenge in most years. Louise Impey reports

Sufficient soil moisture for growing combinable crops is only present in three years out of every five at Euston Farms, near Thetford in Norfolk.

Last year’s exceptionally dry conditions saw just 25mm of rainfall from the end of February to late June, meaning that average wheat yields fell to 3t/ha, with the worst affected late-drilled areas achieving just 1.5t/ha.

As the estate’s break-even yield is 6.8t/ha, the business lost money on all of its wheat in 2011, most of which is grown on Breckland sands, says estates director Andrew Blenkiron.

“Our cost of production was £240/t last year,” he says. “The rainfall total for the whole year was 300mm and we had windy conditions for much of that time. Even the best performing September sown wheat did just 5.6t/ha.”

Winter barley and oilseed rape fared better, with both reaching 4.9t/ha, he notes. “They were drilled in good conditions, earlier in the season, and the barley was on very light land. We established the oilseed rape with a subsoiler, which made a big difference.”

Cropping plans and agronomic practices have been altered to try and cope with the farm’s extreme situation. Five years ago, the decision was taken to invest in a reservoir with a capacity of 110m gallons so that one-third of the 2633ha farm could be irrigated. As a result, the business continues to produce potatoes, sugar beet and onions.

Plans are now under way for a second reservoir, says Mr Blenkiron, who points out that this year’s area of irrigated root crops has been reduced from 400ha to 336ha, due to potential water shortages.

“We’ve been granted an extension to allow water abstraction until the end of April. Even so, the reservoir is only 70% full at the moment.”

Work to improve soil structure has taken place across the farm and continues to do so, with both poultry and cattle manure used and straw chopped and incorporated.

“Our drilling plans are to get all the combinable crops in during September, wherever possible,” he says. “We have cut-off dates, for both sugar beet harvesting and cereal crop drilling, so that this target is achieved.”

But early drilling of 486ha of wheat means that it is at risk from BYDV, he admits. “Crop health can be an issue. This season, for example, we had to spray the Solstice in November for mildew.”

Early maturing Solstice and Soissons are grown on the lighter land for their premium earning potential, with the remainder being Conqueror and Invicta. “I’m not overly concerned about a variety’s maturity score, as they all ripen early here, but we do find that reasonable straw length matters.”

Fungicide use is normally just two sprays, applied at T1 and T2. “But that wasn’t the case in 2011. We got a T1 on, but there was no point in continuing after that. The crops were really struggling and most only produced one tiller.”

The main disease concern is yellow rust, rather than septoria, so susceptible varieties are avoided where possible.

“Drought tolerant types are of interest to us, but unfortunately Oakley, which has some relevant characteristics, has severe yellow rust susceptibility. So it isn’t grown here.”

Mr Blenkiron reports that the farm received 40mm of rain during March 2012. “But unfortunately the winter was so dry that there’s very little moisture at depth. The crops aren’t looking much better than they were this time last year.”

Managing drought

There are several things that growers can do to help manage drought and minimise moisture stress during the growing season, says independent agronomist Richard Palmer of Farm Vision.

“The choice of crop and variety is important,” he says. “Putting the worst land into an environmental schemes, which can earn you £400-500/ha, isn’t a bad place to start.”

Otherwise, barley’s earlier developing growth habit means that it gets through a drought better than wheat, he suggests. “Wheat varieties that develop faster, such as Gallant, Solstice and Soissons, also have a role to play. And long strawed varieties are more able to cope with stress.”

Soils should be managed to minimise moisture loss. “Direct drilling or zero tillage can be used to maintain soil moisture, but the land needs to have a bit of clay in it for this to work well. It has to be self structuring or self repairing.”

Organic matter also has a place and deserves closer attention, believes Mr Palmer. “Getting hold of it can be a problem as it has a value now. It really helps with moisture retention, as do composts.”

Early establishment of crops is also critical, he stresses. “Put the drill away by the end of October. A small rooting system comes from late drilling.”

Root growth can be promoted by good soil structure and the use of seed treatments and growth stimulants, he believes. “The phosphite-based treatments do seem to help.”

Fertiliser timings are also relevant. “On light soils, you need to apply nutrients early, while there is some moisture. And micronutrients are more limiting on these soil types.”

Nitrogen should be applied as ammonium nitrate, not urea, which is at risk from volatilisation in dry conditions and needs moisture to become available to the crop, he warns.

Once the crop is growing well, maximising green leaf area is another target, he recommends. “You need to keep any diseases under control, so that the leaf stays green.

“Fungicides have a dual role here. The physiological effects of the SDHIs and strobilurins mean that treated plants are more resilient in a drought.”

How do fungicides help?

Improved water use efficiency is just one of the effects of using strobilurins or SDHIs, explains Steve Waterhouse of BASF.

“Work done by ADAS shows that treated crops use less water to produce each tonne of grain,” he says.

Each tonne of grain produced by an untreated crop requires 453t of water per hectare, he says. “Where pyraclostrobin is used, that comes down to 314t of water, and with Xemium it is reduced to 320t of water. So there’s a big saving.”

Diseased plants also lose more water through leaf damage. “So their disease control properties are important, too. But in the absence of disease, the yield benefit of Adexar across all our trials was 0.35t/ha.”

Bill Clark, of NIAB TAG, points out that fungicides are not a golden ticket to solving moisture stress. “But we do know that they help with rooting and access to water and that treated plants have increased rates of photosynthesis.

“This means that treated plants are more robust and are better able to cope with moisture stress. As a result, they’re more likely to fulfil their yield potential.”

More on this topic

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