Farm Ireland

Monday 20 November 2017

Assess soil moisture before ploughing

PJ Phelan

PJ Phelan

Permission to plough from December 1, under the nitrate regulations, was seen as a much-needed solution to a restriction which placed Irish farmers at a severe disadvantage and which was damaging soil structure.

However, since then, nature has conspired against us and there has been no opportunity to avail of the earlier ploughing date. In 2010 and 2011 soils were frozen. This year soils are too wet. And with lengthening days and the spring workload looming for many farmers, the temptation to start ploughing is very strong.

Evidence of the damage to land by working heavy machinery in spring on soils which are too wet is widespread. Many headlands in '08, '09 and '10 were pale and yellow -- damage which no management could undo. But heavy frosts of 2010 and 2011 came to the rescue to loosen compacted areas resulting in bumper yields. It is now time to capitalise on those improvements and make sure that we do not repeat the mistakes of the past.

Heavy machinery is a fact of life. Measures such as reduced ground pressures with wider tyres, dual wheels and reducing axle loads will help, but the real key lies in delaying cultivations, particularly ploughing, until such time as soil conditions are fit. In many cases heavier, wetter soils tend to be managed better as damage is apparent immediately. Lighter and in particular medium soils are frequently subjected to greater abuse, resulting in reduced yield potential.

Assessment of conditions for ploughing is much easier in the autumn as soils get wet from the surface down. Soil wetness is immediately apparent and damage is obvious. In spring soils dry from the surface. Visual inspection of land will therefore suggest that soils are in better condition but remember that it is the subsoil that will have to bear most of the weight.

Therefore, before you plough, assess soil moisture below the plough depth. If it is wet go and find something else to do as the damage caused by working will be difficult to undo.

Heavy weights on wet soil will result in compaction. When you compact soil the larger air-filled pores in the soil are the first to suffer. Greater compaction will damage smaller pores which are critical for water supply to plant roots.

Damage to soil pores reduces natural soil drainage, leads to ponding and prevents root growth and development. Wet soils will also lead to the release of nitrous oxide, one of the most damaging greenhouse gases.

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Application of nitrogen, in the form of chemical fertiliser or animal slurry, to wet soils will also result in changes to the chemical composition of nitrogen, making it unavailable for plant growth.

Assessment of soil quality is something that we do instinctively. Maintenance of that quality is done by assessing how individual operations affect individual components of quality, as laid out in the table (above).

As I was about to finish this article, I received a phone call from a farmer who ploughed yesterday. He found the headlands looking "real sloppy" and was wondering whether to go in with a sub-soiler. This would have been a case of what Tony Fortune used to call recreational farming -- doing something when you know there is a problem but with little prospect of achieving a solution. Avoid creating problems which necessitate expensive sub-soiling.

Patrick J. Phelan is a member of the ITCA and may be contacted at

Indo Farming