A great detail of attention is paid to the avoidance of soil compaction by machinery manufacturers, but just what is meant by the term and how might it effect the soil and the consequent crop yields?

One way of thinking about its effect is to compare it with a slice of bread. When dry and uncompressed the slice is open and spongy, but wet and squeezed it becomes a lump of squidgy dough with no aeration or space for roots to grow.

This is how soil may be viewed on a general basis, but this is agriculture so there are no set parameters, just indications of what effects may be observed under various conditions.

Space to breathe

What remains unarguable, however, is that a reduction in soil permeability results in a reduction of plant growth leading to poorer yields as roots need the air pockets within the soil structure to live and grow.

The weight of machinery, or livestock, bearing down on the soil is an obvious cause of reducing the porosity of the soil and it is the mitigation of this that has brought us many machinery innovations over the years.

Cows may cause compaction — Livestock can also cause soil compaction when grazing

Yet it was not the understanding of soil mechanics that kick-started the pursuit of lower ground pressure, it was simply the need to stop machinery sinking into the fields that saw the first attempts at spreading their weight, or avoid it being applied at all.

Steam ploughing

The world has a fellow by the name of John Fowler to thank for the first attempts at cultivating agricultural ground without machinery getting bogged down.

Horrified by the Irish famine of 1849. he set about designing a method of draining the ground using horse driven capstans to lay tiles after a mole, a system which eventually led to steam engines operating as a pair drawing a plough to and fro across the field.

Balance plough — The balance plough, which was reversible, was drawn between two steam engines which ran along the headlands

In doing so, he also invented the reversible plough, but the major benefit of his work was that the weight of the engines was kept to the headlands and many fields in the UK were enlarged through hedge removal around the turn of the 19th century, to increase the efficiency of the operation which also reduced overall compaction.

Prairie busting

Over in America, quite a different approach was taken in using steam engines to break the prairie. Over there they were used as tractors, pulling drag ploughs when conditions enabled them to be operated.

Soft ground was catered for with the addition of much wider wheels and then the invention of the tracklayer which allowed the boggy but fertile areas of California to be brought under cultivation.

Breaking the prairie — Ploughing the prairie with traction engine and drag plough; note the wide drive wheels to help prevent bogging down

However, the weight of the engine was still being applied to the soil as it passed over the ground causing a large area of the field to be compressed.

This was not recognised as a problem in itself, the lack of adhesion and the inability to support the machinery was seen as the greater issue with only a nod as to the damage that the weight was doing to the soil, right up until recent times.

Extra weight for traction

Even as late as the early 1980s, the standard college text book for machinery, written by Claude Culpin, suggested the most convenient way to increase traction was by ballasting the drive wheels with water.

There was little mention of any ill effect of doing so, let alone spreading the weight to avoid soil damage.

40 years on and that mindset has changed completely, for now there is a tremendous focus on reducing ground pressure and this is only likely to become more acute as our knowledge of the fauna and flora of soil increases.

County tractors compaction — In the 1970s and 1980s, traction was the creed with big wheels and big weights being two key aids

Both require air to survive, and both are deeply interconnected in a web of food chains that are only now being recognised and appreciated.

Reduce the air supply through increased soil density and life within the soil suffers.

Fungi are also a critical aspect of soil life, making up a large part of soil organic matter, and, depending on type, may form symbiotic relationships with plants that help gather nutrients to the roots, their role in the absorption of minerals is not to be ignored.

Compaction is a killer

All three help form and maintain soil structure, so by excluding their source of oxygen and carbon dioxide (an important agent within the soil biosphere), the structure is not only destroyed mechanically but the mechanism for repairing it is also damaged.

Minimising soil compression is therefore vital in maintaining soil health and so the measures we see being taken to reduce it are not to be dismissed lightly.

Farmdroid robot — Lightweight robots tending to plant rows is one answer to reducing soil compaction

Many of the emerging technologies can help with this laudable aim. Lightweight robots tending plants on an individual basis is one example, the use of drones in spot spraying is another, yet come harvest time, the crop has still to be gathered in.

This inevitably involves heavy machinery harvesting and transporting the crop which can undo all the damage saved during the growing period.

Minimising traffic

One answer to this is field traffic management which seeks to contain the running of tractors and trailers, or chaser bins, to particular tracks although a combine has to cover all the field.

Yet even here the wider the header, the less ground is run upon.

Using tracked vehicles wherever possible will also be of great help, larger harvesters of all types can be equipped with them while Claas offers the Terra Trac alternative to wheeled tractors.

Claas tractor on tracks — Claas offers one solution to reducing soil compaction with its Terra Trac conversion

If tracks are not considered viable, due to either cost or a large amount of transport work, then VF tyres are an alternative.

These can be run at very low pressures and so create a larger footprint but need to be re-inflated for road use, an operation which is slowed by the inadequate size of the standard tyre valve.

Soil compaction is a very real problem on many farms and attention to its alleviation is being helped a good deal by the machinery industry which is aware that as its products get bigger and heavier, measures will need to be taken to reduce the detrimental effect they have on the soil.

Space to breathe

Steam ploughing

Prairie busting

Extra weight for traction

Compaction is a killer

Minimising traffic

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