Water logging is the saturation of the soil with water to the point where roots can no longer respire.
Carbon dioxide, methane and volatile fatty acids start to accumulate during a water logging event. Plants then alter their metabolism from aerobic respiration to anaerobic fermentation, a less efficient process. As a result there is a reduction in photosynthesis and consequently growth which in cereals can result in a reduction in the number of tillers produced or ability to survive.
Should this event continue it leads to poor crop health and that in turn can result in an increased vulnerability to pests and disease resulting in yield losses.
Many crops suffer adverse effects from water logging Winter wheat is most affected during the seed germination stage whereas oilseed rape is most sensitive to water logging during seedling development and during the appearance of the floral buds.
Water logging can be reduced by improving drainage and minimising compaction.
Fields with naturally slowly permeable soils or those susceptible to high groundwater require an underground drainage system to be present and working.
However an effective ditch system is first required to capture, hold and convey the excess water from the field. Drainage pipe outlets, usually located at the lowest points in the field, should be unobstructed.
If ditches get overgrown the flows from pipes, surface water and groundwater will be restricted, so ditches regularly need to be cleared
Sub-soiling should be done when the soil is in a dry and friable state. Winged subsoilers are the machine of choice.
The subsoiler foot should be set no greater than 450 mm below ground level, with the subsoiler foot itself a constant 50 mm below the compacted layer. Sub soiling at any greater depth is unlikely to shatter the compacted layer effectively.