8 December 1995

Time for a drill change

Most farmers will, at some stage, have considered replacing their current drilling system with a power harrow/drill combination. Gary Markham and Robert Jones, farm business advisers at Grant Thorntons Bedford office, compare the cost of a combination system with the cost of carrying out the operations separately

AN arable farm with 200 hectares (500 acres) of combinable crops is considering changing its drilling system from separate passes with power harrow and drill to a single-pass combination outfit. So what are the implications – financial and otherwise?

The annual cost of replacing the current system (see table below) will partly depend upon whether the farm already has a 150hp tractor.

Therefore the annual cost of the current system needs comparing with the annual cost of a power harrow/drill combination in two different situations:

(1) The farm already has a 150hp tractor.

This currently works about 400 hours/year, and the purchase of the combination drill would increase that work load to about 600 hours/year.

(2) The farm does not have a 150hp tractor.

The purchase of the combination drill would include replacing the current 120hp tractor with one supplying an extra 30hp.

If the farm already has a 150hp tractor, it may currently be used for ploughing.

Therefore it is important to consider its availability for drilling to ensure operation timing does not clash.

The costing method incorporates initial capital cost, estimated selling price, interest, depreciation and spares and repairs.

This results in total fixed costs to which the operating costs of labour and fuel must be added. The overall result is the total annual cost.

In each case, the annual cost of the tractor is apportioned to the operation according to the amount of time required for that job. However, where the farm does not have sufficient horsepower for the power harrow/drill combination it is necessary to allocate the whole cost of obtaining the additional 30hp to the drilling operation (see table above).


If the farm already has a 150hp tractor the difference in cost between the current system and the combination system is minimal. However, if it is necessary to invest in additional horse power in order to change system the difference in cost is more significant; in this case, on a 500-acre farm, there is an additional cost of £3255/year.

So changing to a power harrow/drill combination may increase the cost per/acre of drilling and in many cases it will not improve timeliness (unless you are a one man band).

However, it may be possible to reduce the total labour costs of the business or utilise man hours more efficiently. One-man-bands should seriously consider changing to a power harrow/drill combination in order to improve timeliness and also reduce the requirement for casual labour.

As with any machinery purchase decision it is important to consider your own circumstances and the effect the proposed purchase may have on total labour/machinery costs and crop performance. &#42

Current systemTractor usedWorkrate

4m power harrow120hp tractor4 acres/hour

4m drill90hp tractor6 acres/hour

Both tractors work a total of 800 hours per annum.

Proposed new systemTractor usedWorkrate

4m p/harrow/drill combination150hp tractor3.5 acres/hour

NB. actual workrates will vary according to soil conditions.

Other factors


The total time to power harrow and sow 500 acres is 143 hours for combination outfit, compared to 208 hours if the operations are carried out separately. In a one-man-band situation this will improve the timeliness of the operation and hence the eventual performance of the crop.

Labour costs

The use of a combination system frees one man and may mean reductions in casual labour or overtime costs are possible.

Tractor numbers

In some cases the purchase of a power harrow/drill combination may make it feasible to reduce the total number of tractors on the farm.


The flexibility of the system is critical, hence it is important to consider the ease with which the individual components of a combination system can be used separately. In some cases it may be more practical to own an additional power harrow to avoid the need to split the combination system at a busy time of year. This gives rise to an additional cost for the business which would need to be taken into account.

Cost/Acre of each operation (£/Acre)

Combination system:

CurrentUse existingPurchase

system150hp tractor150hp tractor

Power harrow8.22–

Drill7.53 —




Powerharrow/drill combinations – are they the most cost effective system for arable farmers or is it better to perform individual operations?