What lies beneath?

Soil is agriculture's most valuable asset and a healthy soil leads to healthy profits. But are farmers looking after it as well as they could be?

Soil hasn’t, until relatively recently, commanded much attention in the UK. On most traditional farms, the soil was more than able to keep up with the modest demands made of it by a traditional low output outfit.

Over the past few decades, however, the adoption of more intensive arable rotations, particularly across large swathes of the eastern and southern counties, has seen the quality of this precious asset decline.

Organic matter levels have fallen sharply, in the most serious cases leaving structureless, anaerobic, poorly drained soil. Many fields are unable to provide the optimum growing conditions that today’s potentially high-yielding crops need. Soil is also prone to further damage from heavy machinery that is often operated in less than ideal conditions.

"The signs of poor soil are easy to spot: compaction, poor drainage – leading to water run-o and erosion – and substandard crops,” says Tom Brunt of Savills Agribusiness.

He believes the problem is on the rise across the country. “Although some soils are more prone, all are at risk,” he stresses.

"The main problem is lack of organic matter and its affect on soil structure and fertility. is, together with bigger machinery and changing weather patterns is becoming a major problem.”

Tom is convinced that poor soil is one of the key causes of the yield plateau that has been seen in recent years. “Without action, soil productivity will decline. ere is a need to return to good agricultural practice,” he says.

Correcting organic matter is a long-term process, which can take five to 15 years depending on the current state of a farm’s soil. "That’s no excuse not to take action, as a gradual improvement in soil quality will be noticed from relatively early on,” he adds.

"Testing for organic matter every few years allows growers to measure the problem and start managing it. We all test for nutrients but I would wager very few do so for organic matter."

Compaction zones and anaerobic areas that cannot support healthy root growth can be identified by simply digging holes with a spade, says Tom. This will help target correction measures such as subsoiling and improved drainage.

"Applying farmyard manure (FYM) will start restoring organic matter. Alternatively, processed sludge, digestate from anaerobic digesters and some composts can make good substitutes," he adds.

Longer-term management is then vital to produce and maintain a healthy, aerated, well-drained soil. Reduced cultivations or even zero-till can improve timeliness of operations and encourage worm numbers to rebuild.

Cover crops are becoming an integral part of the process on more and more farms. These crops provide valuable humus, condition soil from the surface to deep down and can prevent erosion. "Simple mixes using a couple of species need not be expensive," Tom says.

Overbury Farms, part of the Overbury Estate, near Tewkesbury, Gloucestershire is recognised as a pioneer in soil management. Cover crops integrated with direct drilling of cash crops are key components of farm manager Jake Freestone’s strategy on the 2,350 acre arable farm.

Jake is passionate about soil. He is a Nueld Scholar who, in 2013, examined the techniques used by growers around the world to increase yields, with special emphasis on improved soil management.

It was an inspirational few months, he recalls. “I started out on my scholarship looking at the possibility of increasing wheat yields to eight tonnes per acre in 20 years. I thought the answer would be in plant breeding, but soon discovered that our current varieties already have the genetic potential. It was just poor soil health and soil management that were holding them back,” he says.

Once back from his travels he continued his research. The more he learned, the more he realised that all fields on Overbury Farm suffered from soil problems of some description. Gravel and sands had depleted organic matter levels, Cotswold brash soils were suffering from low levels of erosion and heavy Evesham clay soils were compacted to varying degrees.

"The key to improving soil health is to get more organic matter into the soil to boost not only its physical properties, but its biological properties too. We need to increase levels of beneficial bugs and fungi that are crucial for plant growth as well as more obvious soil health indicators such as earthworms,” says Jake.

Specific mixtures of overwintered cover crops, followed by a spring crop, are now grown to combat these problems. Mixtures of shallow-rooting species such as rye, oats, phacelia and small radishes hold the soil, tackle surface compaction and capture nutrients.

Stubble turnips are also gown to provide bulk and as fodder for sheep – Jake has introduced a small flock specifically to improve the soil, and he intends to increase this to 1,500 ewes in the future.

"Oil radishes put down roots of 80cm or more in just a few months, helping to alleviate compaction more efficiently than conventional subsoiling,” says Jake.

In addition, a fast-growing mix of linseed, phacelia, buckwheat and millet is sandwiched between oilseed rape, cut in late July, and winter wheat, planted eight to 10 weeks later. This builds valuable organic matter quickly and prevents erosion from summer storms.

Some of these cover crop mixtures are not cheap, Jake admits. "We need to reduce the cost of some we use. Farmers should not be put o by that – if they grow oats, linseed, peas or beans, or can get hold of some, then it won’t cost a lot to put a 40kg/acre mix together, especially at current commodity prices. It’s a pretty cheap investment for what could be a substantial gain."

Overall about one-third of the cropped land at Overbury Farms is now cover cropped every year. The farm’s investment in a direct drill has been integral to the scheme. This "no till" drill can cope with large amounts of cover crop residue, allowing the following cash crops to be drilled soon after the cover has been sprayed off or even beforehand to minimise the risk of rain delays.

After just three years, the benets are starting to show. Water inltration has improved and the soil is becoming more friable and full of earthworms, improving aeration and drainage further.

The financial position is improving too. The farm’s horsepower requirement for the arable area has dropped from 680hp to 370hp as the direct drilling means less soil preparation, and operational costs have dropped by £24 per acre, or nearly £50,000. While the drill was a significant investment, it will pay for itself in three and a half years, Jake calculates.

Fertiliser bills are reducing and the farm is benefiting from better timeliness of operations.Yields in some fields are already rising – the farm’s best oilseed rape crop last year was in its third year of zero tillage – and Jake foresees a bright future at Overbury.

"We are three years down the line and are already seeing signicant improvements. We’ll consolidate what we are doing and will keep trying new ideas, to ensure the soil we currently farm is fit to meet the demands of future crops and future generations that will grow them."



Key contacts

Philip Gready

Philip Gready

Executive Director
Rural, Energy & Projects Division

Savills Margaret Street

+44 (0) 20 3107 5470

+44 (0) 20 3107 5470


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