Soils may not be able to cope with the increasingly heavy demands likely to be put on them in the next couple of decades unless the right science is available, a new report suggests. Robert Harris reports

Drainage, erosion and structural problems are some of the key areas that need to be tackled urgently if Britain’s soils are to remain fit for purpose.

Rapid population growth and food security issues will put even greater demands on soils that are already being pushed to their limit in some areas, warns Dick Godwin, professor of agricultural engineering at Cranfield University and lead author of a recently-released Royal Agricultural Society of England report on soil management.

“Farmers are facing a challenge to increase yields, reduce inputs and maintain and improve soil health while enhancing the environment,” Prof Godwin told Farmers Weekly. “Then we have to ask what effect climate change and increased summer rainfall will have. Can we continue to cope?”

Obvious areas where soils were suffering included the west country, where maize was widely grown on fragile soils, said Prof Godwin. But key arable and field vegetable areas, including parts of East Anglia, were suffering mechnical damage, too.

“We expect much of our soils,” he said. “We want then to sustain crop growth, support large loads to enable mechanisation, while permitting infliltration and storage of water. There is a major conflict – and challenge – here.”

Much has been done to spread the footprint of heavy machinery but more work is needed, says Dick Godwin.

Good soil condition was key in preventing flooding and soil run-off, said Prof Godwin. Without protection, areas such as the south-west could suffer soil loss of 3-5t/ha a year, while soil regeneration amounted to only 1t/ha.

But the UK had little history of conservation structure or measures to control water erosion, he said. Good soil conservation meaures that fitted in with efficient machinery operations was needed to avoid run-off and soil loss.

Drainage installation had fallen from about 150,000ha a year in the 1980s to just 5000ha a year today as falling farm incomes prevented anything but urgent investment. “We are relying on the effectiveness of drainage installed 30 years ago,” said Prof Godwin. That not only put crop yields at risk, but also raised concerns about a possible impact on peak flood flows and subsequent widespread flooding.

Soil structure also needed urgent attention, he said. “Reduction in crop yields due to poor and weak soil structure are widespread in wet years.”

Rising labour costs and falling profitability had driven up the size and weight of machinery, with large, fully-loaded combines weighing in at 30t and sugar beet harvesters at about 50t. Although much research had taken place to keep ground pressures low, using larger-section tyres or rubber tracks, more was needed, especially in the area of reduced traffic systems, he added.

Work by Cranfield University and TAG comparing three establishment systems showed a normal traffic plot yielded 10.84t/ha, while one using controlled traffic farming techniques, where machinery is matched to cut down wheelings to about 20% of a field, yielded 12.14t/ha, nearly as much as where no traffic was used.

“This also improved the effectiveness of shallow or no-till sytems and reduced the need for deeper soil-loosening to improve root penetration and water infiltration,” Prof Godwin noted. That, in turn, reduced the size of tractors needed and labour requirements.

Irrigation water management also needed to be improved, he said. “Although irrigated agriculture accounts for only 1% of total UK water abstraction and 4% of the crop area, it accounts for 20% of the crop value.”

But increased competition for water, rising environmental concerns and climate change all threatened the sustainability of businesses relying on irrigated supplies. “It is essential that irrigation water management receives priority support,” said Prof Godwin.

More focus was likely on Less Favoured Areas. Increased output might be needed in such areas, which accounted for 45% of the UK’s agricultural land, to provide additional food and fuel. But, as well as inherently fragile soils, these marginal regions also contributed 70% of the UK’s water supply, which would need to be protected.