Catchment Sensitive Farming: Practical Tips

Practical Tip: Soil damage and compaction

Soil damage and compaction from winter grazing and poaching needs to be corrected. Although this sort of damage is less visible it can cause serious losses in grass production and increase soil wash, as the compacted soil prevents water from percolating though the soil.


Source: Defra 

Source: Simon Draper

The depth of soil compaction needs to be determined by digging a hole and seeing where the compaction is - this is best done when ground conditions are wet as the boundary between seriously compacted soil and less compacted is normally seen as layer of wet over dry soil.

Source: Defra 

The dry soil indicating that water has not been able to permeate due to compaction, this also means that roots are not likely to penetrate and hence a reduction in yield is likely to occur.

If the compaction is near the surface (likely where sheep have been grazing in the winter or where stock have lightly grazed), the best option is to aerate the land using a spike. This breaks the surface compaction and allows the grass to re-colonise the poached areas whilst increasing infiltration, thus ensuring a good growth of ryegrass and not allowing the lower yielding grasses such as meadow grass to get a hold in the field. Spike machines only work in conditions when the surface is moist enough to allow the spike to penetrate yet at the same time the land is dry enough to allow a tractor to travel without causing any damage.

Where compaction is at deeper depths then decisions have to be taken on the quality of the grass in the field, where compaction is severe the sward is more likely to contain shallow rooted, low performing grasses such as annual meadow grass. Once the grass production has declined this far action needs to be taken which will either involve ploughing or subsoiling the field.

If ploughing then the field needs to be assessed, assuming that the cultivated species are more than 25%, then no environmental impact assessment will need be carried out.

Ploughing will obviously soften the land and if ploughing and re-seeding is to be done it should be done as soon as possible to allow for the land to firm up before the following autumn to allow for stock to travel freely but at the same time allowing for the land to be as permeable as possible. Stock should therefore be kept off these fields for as long as possible following re-drilling.

Subsoiling is another option, preferably this would be carried out with the Paraplow which causes minimal disruption to the grass, unfortunately this bit of equipment is no longer made.  An ordinary subsoiler working in the dry band will achieve a good reduction in the compaction. However, it will cause the soil to ‘break out’ and cause the grass to be ripped up, this needs to be rolled after subsoiling to ensure that the grass is pushed back down again, then over the winter months the grass will re-grow in these areas.

Sources: Landcare Newsletter No. 26 - April 2005 Grazing and poaching damage and Landcare Newsletter No. 45 - Soil management for grassland, Defra's Cross Compliance, Guidance for soil management, 2006 edition


 

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