Compaction is a serious problem in many grassland soils, but attempting to cure it could be hazardous if the underlying drainage is failing, experts have warned.

Around 70% of UK pasture is suffering from degradation, with 10% severely compacted, leading to poor grass yields and limiting access to land following rainfall. However, farmers who are considering alleviating such compaction should check the field drains are working first, or they could be wasting their time.

According to ADAS experts who will be running the soil and nutrient advice clinic at this year’s Grassland & Muck Event, productive soils need to be both well drained and well structured; the two are closely interlinked. “I go to many sites where people have enough or even more drainage than they really need, but the soil is too compacted for water to pass through to reach the drains,” says Kirk Hill, drainage specialist at ADAS. “On the other hand, there is no point subsoiling if the drainage isn’t working; you could cause more damage than you relieve.”

The key is to identify where there may be soil or drainage problems, and then take the correct action to alleviate them. Signs of compaction or inadequate drainage can include standing water, weeds and poor yields, so farmers should dig a soil pit in these areas, says soil specialist Dr Paul Newell-Price. The pit should be at least 60cm deep, and farmers should then look at the soil structure and colour as well as root depth and presence of earth worms.

To learn more about such tell-tale signs, visitors to the Grassland & Muck Event will be able to get below ground level in the soil pit, to examine the soil profile and identify problem areas. “Half of the soil pit will have been compacted, and visitors can also see a sward lifter, aerator and drum-type loosening equipment in situ, to find out at what depth they work best,” says Dr Newell-Price.

In addition, visitors can bring a photo of their own soil profile and a soil sample to discuss with ADAS experts (stand 906), as well as recent soil and manure analysis results.

Around 6.4m ha of agricultural land in England and Wales has been drained with pipe systems in the past, but many have not been maintained and about 60% of soils would benefit from repairing or replacing the drainage, says Mr Hill. Many farmers will hold historic drainage plans, or may be able to access them through the local drainage contractor, but where they are not available the best option is to look at aerial photos, walk the field, and clear drainage ditches to look for outfalls.

“The most common problem with drainage systems is when the outfalls aren’t kept clear – so dig out your ditches and check for running water from the outfalls after rainfall,” he explains. “It may be that you only need to replace the final metre or two where the outfalls have silted up or collapsed.”

Different soils have different drainage needs – which will also depend on the average rainfall in the area, says Mr Hill. “However, changing weather patterns have put the spotlight back on drainage. We’re getting more intensive storms, leading to increased risk of soil erosion and loss of soil organic matter. Better soil management and drainage will reduce these losses and result in less soil drought, waterlogging and nutrient loss.”

The value of well drained, well-structured soils is considerable, adds Dr Newell-Price. “Healthy soils will be more resilient to adverse weather, produce higher yields, and have a longer grazing season. You’ll also have better uptake of nutrients and more timely field operations. Everything starts below ground – if you don’t get your soil right your seeds and other inputs will be wasted.”

• The soil and nutrient advice talks will take place throughout the day at ADAS stand 906. Dairy Pro points are available for attendance.
• The Grassland & Muck Event will be held at Stoneleigh from 24-25 May. Tickets are now on sale and visitors can save £4 per adult ticket by purchasing in advance. For more information visit grasslandevent.co.uk.