Keeping Soils in the Best Condition
Compaction may create problems but growers must be aware that soils that are too loose can also be highly problematic, warned Harper Adams soil scientist, Dr Nigel Hall.
“Apart from having less soil material for roots to exploit, soils holding excessive amounts of either water or air have a very poor load-bearing capacity,” he explained. “This can lead to serious trafficking difficulties and rutting, not to mention sheet and gully erosion. So it’s important to appreciate that looser is not always better.”
Dr Hall advised everyone to use a spade to examine their ground as the basis for their cultivation decisions, stressing that if a soil looks OK to the eye it will generally have a good enough structure.
He also pointed out that soil density will invariably change over the season – from a low point after cultivation to a naturallymore dense equilibrium level, depending on soil type and levels of organic matter, amongst other factors.
“For the greatest resilience our ideal should be to maintain the best possible structural balance over the long-term as well as throughout the season,” he recommended.
“We need to encourage biopores from worms and old root runs to ensure good drainage and provide channels for new root growth. Equally we need to avoid ‘vughs’ (disconnected voids that trap water or air and give no access to roots) and voids or cracks that just run roughly parallel to the soil surface. These sort of structures tend to be produced by working the soil too wet or compaction.
“Tightening rotations and the atrocious sort of weather we’ve seen this autumn add significant risk to modern cropping systems,” insisted Dr Hall. “We’re increasingly finding that soils which are just about able to handle reasonable conditions simply can’t cope when the ‘going gets tough’. This underlines the work that must be done to improve soil structure in many cases, as well as the need for research and extension to quantify more ‘critical thresholds’ for soil condition as an aid to farm decision-making.”