Soil compaction problems could now be costing UK agriculture over £1.0Bn every year, visitors to a ProCam Prochem soils conference were told. Reductions in crop yields, costs involved in correcting soil pans and extra inputs required to boost production were combining to create significant losses, Professor Dick Godwin of Harper Adams University told delegates.

“A simple increase in soil density from 1.35t/m3 to 1.50t/m3 has been shown to reduce crop yields by 10 – 15% in addition to significantly more tillage energy and fuel being required to break the soil apart. Furthermore, air and water infiltration rates are vastly reduced and this impacts significantly on productivity of the soil, particularly with regard to the essential worms and bacteria needed for a healthy soil.”

Estimates carried out by Cranfield University in 2011 put the combined losses at £1.0Bn and with equipment getting heavier all the time and the difficult, wet years since, it is unlikely to have been reduced, he said.

“There is a lot growers can do to improve soil structure, however, and much of this revolves around understanding and using tillage equipment better. The effect of changes in geometry and speed on soil disturbance and soil-implement forces are well understood but we need to get better at choosing the right equipment for the job and setting it up correctly.”

The width, spacing and rake angles of tines can also have a dramatic effect on how soils are disrupted as well as the draught force required, he pointed out.

“Optimum rake angle is usually around 20 – 25o for most tasks with chisel tines being the best for soil loosening and mole ploughs better for drainage. Trials have also shown that winged subsoilers can double the amount of soil disturbed by a single pass compared to a conventional subsoiler whilst only increasing the draught force required by 30%. In addition, if you double the depth of your cultivations, you will quadruple the energy required so working shallower and faster is always better if you can.”

Understanding the effects of track and tyres on soil density was also important with harvest a critical area, he said.

“Subsoiling after tracked harvesters is considerably easier than after wheeled machines with a 63% reduction in force needed to pull implements through the soil being shown in some tests. All tyres also need to be used at the correction inflation pressure as there is a direct relationship between this and ground pressure  – double your inflation pressure and you double the ground pressure.”

Ultimately the less wheelings on the land, the better the soil will be and the higher the yields he concluded.

“We’ve seen controlled traffic farming systems deliver a 17% yield increase in winter wheat – 7.5t/ha to 8.77t/ha – when compared to a conventional system. The yield in the unwheeled areas was up to 1.0t/ha more than in the places where the wheels ran so it just shows the damage compaction can do. When you consider that in a random traffic system with a mouldboard plough up to 85% of a field receives at least one wheeling, the extent of the damage and cost implications of compaction in conventional farming comes into sharp focus.”