Farm Ireland

Monday 19 February 2018

Keep a close eye on soil structure

Best is granular, but 'loams' are typical

Deep loosening with a conventional ripper/sub soil can also help to remove compaction
Deep loosening with a conventional ripper/sub soil can also help to remove compaction

Ciaran Hickey

FOR farmers using min-till on a continuous basis, keeping a close eye on soil structure is essential. The best soil structure is granular. This is where the soil breaks up like breadcrumbs in your hands. Typical soils would be sandy loams or silty loams. Crumb structure has large pore space ideal for drainage and root growth.

At the other end of the spectrum is platy; this peels away in layers in your hands and there are very few pore spaces. Hence, water movement is very poor.

Soil particles can be made up of sand, silt, clay and organic matter, and are clumped together to form larger aggregates called peds.

A clod is not a ped, as it is formed artificially by the compression of a wet soil.

The diagrams, right, show different soil structures.


A practical test to check out the structure of the soil in a particular field is to take a section of soil approximately one foot square, the depth of your spade and then drop it on to the ground from a height of two or three feet.

If it breaks up easily and falls away it has a good structure. If it stays in a solid mass it has a poor structure that is very compacted.

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If you begin to break it up and it is in layers it has a platy structure.

You will even see grey area of anaerobic conditions highlighting the lack of air and the lack of water movement.

This is the indicator that there is a serious compaction problem and it will have to be probably loosened with a ripper.

You may find conditions as mentioned above but only in a single layer. This indicates the presence of a narrow pan within the soil profile.

In relation to tests of Teagasc's Knockbeg site, after the harvest a soil measurement will be taken using a penetrometer to measure the soil strength.

This will indicate if there is a level of compaction and then the structure will also be assessed.

It may be the case that the overall soil structure may not be the problem, but the loose spongy top layer (three or four inches) is just above a denser layer and the difference was enough to hold up water and give poor crop establishment.

It is therefore tempting after this to cultivate deeper but for experimental reasons it will all be scientifically measured to see what future practice should be adopted.

Irish Independent