9 March 2001


Trailed or self-propelled

forage harvester? Garry

Markham of Grant Thornton

costs out the options

TIMELINESS is critical for making good quality silage and owning a forage harvester means you do not need to rely on a contractor arriving on time.

But most farmers will only be able to justify owning a small trailed machine for their own acreage and the work rates are considerably less than that of a large self-propelled machine. One solution is to buy a machine in conjunction with neighbours in order to justify the costs.

In the tables we compare three different machines depending upon the acreage of silage made:

&#8226 Trailed harvester with 130 hp tractor – max capacity 1100 acres a year.

&#8226 Small self propelled machine – max capacity 2800 acres a year.

&#8226 Large self propelled machine – max capacity 3500 acres a year.

Table 1 shows the annual fixed costs for each option consisting of interest on the capital, average depreciation over its expected life and insurance. All the machines are assumed to be kept for five years.

The figures are based on a specialist dairy farm and assume the largest tractor required for all other operations on the farm to be 100hp. A proportion of the annual cost of a 100hp tractor is apportioned to the forage harvesting operation according to the acreage of silage made.

But a trailed harvester would require a 130 hp tractor and, therefore, the total cost of obtaining the extra 30hp is allocated wholly to the forage harvesting operation. A large mixed farm including an arable enterprise is likely to be able to justify the extra horsepower for arable operations and this would cut the total cost per acre for forage harvesting.

The annual operating costs vary depending on the amount of work carried out and consist of labour, fuel and, to a certain extent, repairs. The work rate and fuel consumption are taken into account for the calculation of total annual costs per acre.

Table 2 shows the total annual costs per acre, relative to the acreage of silage made, for each option including fuel, labour and repairs. The acreage of silage is the conserved area multiplied by the number of cuts taken. For example, 100 acres of conserved grass cut three times will amount to a total of 300 acres of grass silage a year.

The shaded figures are those closest to a typical contractor charge of about £20/acre. It is important to note that the contractor rate is for forage harvesting only, it does not include carting, and clamp work where the total contract charge would be in the region of £40/acre.

It should also be noted that in order to keep up with a big self-propelled harvester it requires large, fast and reliable tractors and trailers plus the associated labour. It is for this reason that many contractors insist on carrying out the whole operation including mowing, rowing, foraging, carting and clamping. They have large up-to-date machinery with high work rates and are able to cover a large acreage in a short period of time.

Based on these assumptions in order to justify the ownership, relative to a contacting charge, of a new trailed machine, you need to make a minimum of 500 acres of grass silage a year and for a new large self-propelled machine a minimum of 1750 acres of grass silage are required a year. In many instances in order for a farm to justify ownership of a new forage harvester it is necessary to share the costs with neighbours or carry out contracting work.

As always, the decision whether to buy a machine on one farm, form a syndicate or use a contractor should not be based on the annual cost alone. There are, of course, other factors to be considered such as the timeliness of starting forage harvesting, the speed of carrying out the operation, the availability of farm labour and access to a reliable contractor. &#42

Table 1: Annual fixed costs

Trailed Existing Cost of Small Large

harvester 100hp extra self self

tractor 30hp propelled propelled

Avg. workrate (acres per hour) 2.2 4.0 5.0

Hours worked a year 500 800 700 700

Acres a year 1,100 2,800 3,500

Purchase price 20,000 25,000 5,000 90,000 125,000

Selling price after 5 years 4,476 11,093 2,219 29,491 40,960

Average value 12,373 18,046 3,609 59,746 82,980

Annual costs

Interest at 8.00% 990 1,444 289 4,780 6,638

Average depreciation 3,051 2,781 556 12,102 16,808

Insurance at £15 per £1,000 186 271 54 896 1,245

Repairs 600 1,250 250 2,700 3,750

Total annual fixed costs 4,826 5,746 1,149 20,478 28,441

Operating costs per hour

Labour per hour 8.00 8.00 8.00

Fuel per hour 4.20 8.93 13.39

Total cost per acre 5.55 4.23 4.28

Repairs % of original price 3.0% 5.0% 5.0% 3.0% 3.0%

Table 2: Costs per acre (inc fuel, labour, spares and repairs)

Total acres harvested Trailed with tractor Small self-propelled Large self-propelled

100 68.56 209.01 288.69

150 48.65 140.75 193.88

200 38.69 106.62 146.48

300 28.73 72.49 99.08

400 23.75 55.43 75.38

500 20.76 45.19 61.16

750 16.78 31.53 42.20

1,000 14.79 24.71 32.72

1,250 20.61 27.03

1,500 17.88 23.24

1,750 15.93 20.53

2,000 14.47 18.50

2,500 12.42 15.65

3,000 13.76


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