How to cut back on your fuel costs this spring
It is worthwhile having an idea about the fuel requirements for some of the more power-hungry spring planting jobs such as ploughing and power harrowing that are now taking place.
As of this week, you will pay around €780 per thousand litres of agri diesel, including VAT. Whether you are a big contractor or a part-time farmer, you should have an idea of which spring planting jobs use the most fuel.
Ploughing, for example, uses on average 21 litres of diesel per hectare ploughed, depending on the soil type. At current fuel prices, this comes to a fuel cost per hectare ploughed of €16.40. Equally hard on the pocket is subsoiling, which uses up about 15 litres of diesel per hectare worked, so about €11.70 at current diesel prices.
Spring is always a good time to take stock of what your real fuel costs are and to plan to reduce unnecessary fuel use (see table on opposite page). Some of the variables that have the most considerable effect 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 additional ways of managing fuel use.
Let's start with the choice of tractor. 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, except 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 as the shallower cultivation system 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. Yields will be lower, but margin is often still higher.
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 both the making of that footprint and 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 one bar - or 17psi in old money.
Contractors and farmers should 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.
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