Farm Ireland

Tuesday 22 January 2019

How factors such as tractor choice, tillage systems and tyre pressure impact on agri-diesel bills


Even a modestly sized contracting outfit can very quickly run up a fuel bill of €80,000 or €90,000.
Even a modestly sized contracting outfit can very quickly run up a fuel bill of €80,000 or €90,000.
Derek Casey

Derek Casey

Agri-diesel prices are 60pc higher this spring than in 2016. This week, farmers will pay an average of €798 per thousand litres of agri diesel compared to €500 including VAT in 2016.

Farmers and particularly contractors (due to the huge amounts of fuel they use) need to be careful not to over expose themselves and run up large overdrafts just to keep pace with costs, particularly on fuel.

The key is regular cash flow; and this will be easier said than done this year given the context of a recent fodder crisis.

Silage is the big killer for diesel bills because it's such a power hungry job.

At €798 per 1000 litres including VAT, green diesel prices are up 60pc on 2016
At €798 per 1000 litres including VAT, green diesel prices are up 60pc on 2016

Even a modestly sized contracting outfit can very quickly run up a fuel bill of €80,000 or €90,000.

Contractors need to have money coming in regularly to offset what is by far and away their biggest variable input cost. Farmers can usually be encouraged to pay earlier if given the incentive of cheaper rates for upfront payment.

In general, though, farmers should expect the higher fuel prices this year to be reflected in contractor charges.

Whether you are farming or contracting, you can only improve what you can measure in the first instance.

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To this end it is worth analysing the fuel requirements for some of the more power hungry jobs like ploughing and power harrowing.

Did you know that ploughing with a four-furrow reversible plough, for example, tends to use on average 23 litres of diesel per hectare ploughed depending on the soil type?

Average fuel costs spring 2018 v 2016
Average fuel costs spring 2018 v 2016

At current prices this comes to a fuel cost per hectare ploughed of €18.40.

Equally hard on the pocket is sub-soiling, a job that many farmers do to relieve compaction caused either by poaching or machinery damage last backend.

Matching a tractor to your requirements
Matching a tractor to your requirements

Sub-soiling uses up about 18 litres of diesel per hectare worked - about €14.40 at current diesel prices.

If these figures are coming as a surprise to you (see table 1 below), turn it to your advantage by tightening up on fuel costs.

The beginning of spring is a good time to take stock of your fuel costs.

Some of the variables that have the biggest impact on fuel consumption are also the easiest to manage.

For example, tyre pressure selection is directly linked to excessive fuel consumption. Unnecessary use of counterweights is another fuel drain. And correct tractor and tillage system selection are two other ways of managing fuel use.

Tractor choice

There are significant differences in fuel consumption rates between tractors, and data from the OECD tractor tests allow valid comparisons to be made.

For these tests an individual tractor's fuel use is usually measured in something called grams per kilowatt hour (g/kWh).

Differences between tractor brands, but for tractors of similar or the same power levels can be significant, so it is worth doing your homework the next time you are on the market for a new tractor.

Obviously there are substantial cost implications for those tractors with poorer g/kWh ratings. Teagasc research has shown that, overall, the choice of tractor could easily account for fuel cost differences of up to €8/ha.


As regards the tillage system used, there are a number of different cultivation systems with various combinations of depth, tillage intensity, inversion and timing of operations.

At one extreme is the plough-based system with intensive secondary cultivation, while at the other is a direct drill system with a simple minimal disturbance disc coulter.

Minimum tillage establishment systems offer considerable scope for fuel saving because the shallower cultivation requires much less energy input per hectare.

It is estimated that min-till systems have a primary cultivation energy requirement of approximately 37pc of that required by ploughing.

In addition, the overall fuel use of a min-till establishment system is just 50pc of that of conventional systems.

This can result in a fuel saving of between €12 and €15 per hectare, with additional depreciation and repair costs accruing as well.

But there are disadvantages. Yields can be down compared to a conventional plough-based approach and weed control is more difficult.

It doesn't suit every soil type for sure, but with such attractive potential savings in fuel costs min-till will continue to grow in popularity.


Tyre selection has a huge role to play especially in tillage farming. The importance of matching the tyres on your tractor to the work that it will be carrying out cannot be overstated.

Tyres are the conduits through which mechanical power is passed to the ground.

How efficient the delivery of that power is depends on the condition and inflation pressure of the tyre.

Despite popular opinion, Michelin tests have demonstrated that tyre over-inflation can lead to more of a fuel drain in field conditions, especially in tillage applications.

Over inflation leads to the tyre leaving a deeper "footprint" in the field and more diesel is burnt in the tractor's attempt to pull out of a deeper rut than is necessary to maintain traction.

The increased fuel consumption in this case is because of a bigger rolling resistance.

On the other hand, too low a tyre pressure is also a drain on diesel because the energy required to move the tractor and its load increases above and beyond what is required for good ground flotation practice.

A balance must be reached. As a rule of thumb, modern tractor tyres should have between three or four lugs on the ground.

On the rear tyre of a typical 180hp tractor, in order to have three or four lugs on the ground at any given time the pressure should be just over 1 Bar - or 17psi in old money.

Check tyre pressure once a week at all times of the year but especially at this busy time in the fields.

If for some reason you anticipate your load will be changing significantly for a certain week (for example, if you are spreading slurry with a large tanker), then you can alter pressure as appropriate to suit the new load conditions.

Indo Farming