The profitability of an arable wood crop for electricity

J. agric. Engng Res. (1991) 48, 273-285

The Profitability of an Arable Wood Crop for Electricity J. E.

SELLS;

E. AUDSLEY

Information TechnologyGroup, AFRC Institute of Engineering Research, Wrest Park, Silsoe, Bedford MK45 4HS, UK. (Received

22 December

1989; accepted

in revised

form

26 August

1990)

There is a need for both alternative farm enterprisesand renewable energy sources.This paper considersthe economicsof a short rotation coppicecrop aspart of the farm from which to produce electricity, an enterprise which, if profitable, would satisfy both needs. The farmer usesIabour from the conventional side of the farm during the winter, an otherwiseslack period, to harvest the coppice. Wood chipsare produced for useasfuel for an on-farm “generating system”. This consistsof a gasifier, engine and electricity generator connectedto the National Grid. The paper usesa whole farm linear programmingmodel to calculate the profit of the farm without the new enterprise. By consideringthe additional incomesand expenditures caused by the new enterprise the profitability of the arable wood crop is assessed over a period of years using net discounted present values of the enterprise cashflows.The sensitivity of the profitability to uncertain factors, such as the generating system cost, are varied to assess which factors have the greatest impact. The resultsshow that the new enterprise can be profitable, particularly on farms with low yielding potential. However, the profit is extremely sensitiveto the most uncertain factor, the generatingsystemcost. For the enterprise to break even at the end of 20 years the generating systemcapital cost would need to be of the order of flOO-450/kW dependingupon the values of other factors such as electricity prices, crop yields, harvester cost and the future expectations. 1. Introduction

In these days of surpluses and farmers looking for alternative enterprises, growing a crop of wood is just one of many. Growing trees is not a new idea. There are various schemes encouraging woodland enterprises to be set up on the farm, including the Set-aside and Farm Woodland Schemes.’ Renewable energy sources, to produce electricity (among other things), is an important area of concern. The demand for energy is large and renewable sources are needed to replace coal and oil as these reserves are depleted. Biomass, including wood, is one source of renewable energy which could be used for electricity generation. The subject of this paper is a combination of these two ideas, that is growing short rotation coppice as an alternative crop on an arable farm to produce electricity for the National Grid. This was the subject of an RASE Conference* in 1989 which showed that a considerable amount of research had been done in this country on growing the crop, some on harvesting and relatively little on utilization for electricity production. There was, however, a lot of interest from farmers in the idea, but concern at the uncertainties. Can the farmer profit from this alternative enterprise? In what circumstances would the option be profitable in the future and what factors make it not profitable? To answer these questions, the profit to the farmer is calculated for a base scenario of the new enterprise and then the sensitivity of the profit to the uncertain factors, such as the cost of the generating system or the harvester, is assessed. Section 2 describes the 273 ODZI-8634/91/040273

+ 13 so3.ou/o

0

1991 The

British

Socictv

for Rescarch

in Aericultural

Eneineerine

274

WOOD

CROPS

FOR

ELECTRICITY

nature of the enterprise, or “the system”. Section 3 gives the details of the systems used in the analysis, the method of which in detailed in Section 4. The results of the profitability and sensitivity are given in Section 5. 2. The system A short rotation coppice, harvested every 3-5 years, could provide a suitable crop for the farmer to cultivate and harvest. Crops such as willow or poplar are easily established from cuttings and will produce their first full yield in 5 years. Research has been carried out on such wood crops to investigate the varieties and species, their yields and harvesting cycles, the plant spacings, weed control and disease problems.3 For example, for some species of willow the yield cannot be maximized for annual harvests at spacings wider than one square meter. Also it is important that weeds are kept completely in control for successful establishment. These experiments have clearly shown it is perfectly feasible to grow coppice wood on a short cutting cycle. However, recently there have been severe fungal attacks of many willow plots leading to the potential yield being somewhat uncertain. Harvesting coppice would take place during the winter months when the leaves have fallen. This is ideal for the arable farmer since it is well after cereal harvest and labour from the arable side of the business could be employed during this otherwise slack period. The sort of machine suitable for harvesting coppice is still under investigation. Two possible ideas are; 1. A forage type harvester (like a sugar cane harvester) which would cut and chip the coppice producing large wood chips, which would be blown into a trailer and handled in bulk.4 2. The use of two machines; one to cut and bundle the coppice stems and a second to chip the wood; the chipping technology exists and a machine to cut and bundle is being developed in Northern Ireland.5 Wood as harvested contains about 50% moisture. For combustion it should be dried to 20% or less. Air drying or leaving it in the open is best suited to the bundling system. However this imposes a delay of several months before the wood can be used. For immediate use positive drying is needed, for example using the waste heat from combustion to dry the wood chips. However, care must be taken so that this system in itself does not become expensive. Intermediate buffer storage of the wood chips could use the grain storage areas which will be becoming free during the autumn. To generate electricity the farmer would need a “generating system” consisting of a gasifier, engine and electricity generator connected to the National Grid. The size and cost of such a system is uncertain. Presently “one-off’ systems are produced, usually for the overseas market. At a capacity of 100 kW the cost of one of these systems is estimated’ to be about f6OO/kW. If they were made in bulk the price could be reduced substantially. The best time for the farmer to produce electricity is during the daytime of Monday to Friday in the winter months from November to February (during harvest). This is when the National Grid needs to be able to produce most electricity so they need production capacity which is only utilized during this peak period. This is obviously expensive and therefore they are prepared to pay considerably more for electricity generation capacity during this period. Under the privatisation of electricity supply, they also have an obligation to use non-fossil fuel sources for part of their supply. Clearly reliability and consistency are also important, but there is no reason to suppose farmers cannot achieve this as it seems less arduous than milking cows twice a day every single day.

J. E.

SELLS;

E.

275

AUDSLEY

3. System details

There are a large number of farming systems and many ways of cultivating a coppiced wood crop. To determine the difference in profitability between a conventional arable farm and a farm including a coppice wood crop (thus calculating the profitability of the wood crop) it is necessary to define the crop and the farming system. A major feature of the analysis is that much of the data is unknown or uncertain. These data are identified to determine their effect upon the profitability. Since coppicing is a long-term commitment the calculations will be carried out for an arbitrary 20-year plan. The long term interest and inflation rates are taken as 12 and 5% respectively. 3.1. The conventional

farm

The conventional farm is defined as a 250 ha farm growing winter wheat, winter and spring barley and oilseed rape. The size of the farm can be scaled up or down as necessary. However since a large capital expenditure on generating equipment and the continuity of supply are needed the new enterprise has to be shown to be profitable on large farms first. The choice of crops represents a large number of combinable crop farms in the UK. Farms with a slightly wider range of crops (e.g. oats, beans) will in general terms be little different to this farm. Table 1 shows the gross margins7** of the crops considered. The Appendix gives full details of the data used for the farm. This describes the operations to produce the crops, their work rates, the labour and machinery needed and the workable hours available in each period of the year. The workable hours on the conventional farm are those for a “light” land farm. 3.2. The electricity farm

The electricity farm is defined as a 200 ha conventional farm plus 50 ha of short rotation coppice. Thus 20% of the farm is set aside to grow coppice and qualifies for the annual set-aside payments of fl50/ha for 5 years.’ Since the wood crop is part of a farm and, in particular, the harvesting operation is carried out during an otherwise slack period, it is possible to assume that all the labour needed for the wood crop is supplied from the conventional part of the farm at zero marginal cost. Establishing the coppice and the harvesting rotation takes several years, depending upon the method. It is assumed the coppice is harvested every 3 years; thus the farmer divides the area of farm to be coppiced into three and one part is harvested each year. Then either the total area could be planted in the first year and in each of the following three years one third cut to initiate coppicing and provide the three year harvesting Table Gross

crop Winter Winter Spring Oilseed

wheat barley barley rape

margin

data

for

1 the

arable

Yield, t/ha

Price, f/l

7.4 6.3 5.1 3.2

94 92 92 230

crops

Gross

margin, f/ha 480 400 330 488

276

WOOD

The first year

Table of operations

Operation

Spread P & K Plough Cultivate (1 pass) Plant Spray Fertilize Spot Spray

CROPS

FOR

ELECTRICITY

2 to establish

coppice Workrate,

Timing

Aug. + Sep. end Aug. + Oct. Oct.+ Mar. Oct.---f Mar. end Feb. + Mar. end Feb.+ beg. Apr. Summer

h/ha

Normal Normal Normal 7.6 Normal Normal 12.0

Normal = as for conventional crops.

or one third of the area could be planted each year, cutting the following year to initiate the coppice. In this analysis the former is assumed. Table 2 shows the operations needed in the planting year (in this case the first year). Planting and spot spraying are the only operations which differ from those used for other arable crops. Cuttings of 25 cm lengths are planted using a tractor pulling a machine like a plant setter. It is unlikely that the farmer will buy such a machine since planting is a one-off operation. It is assumed that the machine is hired’ for f42/ha and two men from the farm provide the labour. Just using the spare labour from the arable part of the farm during October to March enables a planting workrate of 7.6 h/ha, taking into account the soil workability. If planting takes longer then extra labour will be required. Potato planting* typically takes 3 h/ha. The spot spraying workrate of 12 h/ha represents one man on foot using a contact herbicide.4 It is very important to suppress weeds in the first few years when the cuttings have little ability to compete. There is no income from the coppice in the first year. The variable costs are given in Table 3. It is assumed that the farmer buys in the cuttings although he could grow his own. On the whole it will be cheaper to buy in cuttings from specialists who have the equipment to produce and handle them, as it is otherwise a labour intensive operation. Table 4 shows the operations and the variable costs for the coppice crop during its three-year rotation. The crop is sprayed and fertilized after harvest when it is possible to use the normal farm equipment. The assumed harvester is a forage type harvester which is operated from the pto of a 100 kW tractor. The machine cuts the wood, chipping it and blowing the chips into a trailer. The power requirement for this is estimated to be 10 kW per t/h throughput4 giving a workrate of 7.8 h/ha. The cost of the harvester is unknown. For the base scenario it is assumed to be f10 000. Higher costs are considered in the sensitivity analysis. Assuming the machine is replaced every 5 years and used for 130 h per annum the annual cost’ of the machine is f2107 including repairs and maintenance. rotation,

Table The variable

3

costs in the Iid

Inputs

Cuttings Spray Fertilizer Spot sprays

year Costs,

10 OOO/ha@3p each (simazine/aminotriazole) 1OON: 1OP: SOK kg/ha

f/ha

300 5 43 30

J. E. SELLS;

277

E. AUDSLEY Table The

Operation

Year

1 2 3

three-year

coppice Workrate, h/ha

Timing

Harvest Spray Fertilize Spot spray -

4

cycle of established

Nov.+Feb. end Feb.+ Mar. end Feb.+ beg. Apr. Summer

Variable COSLF, f/ha

-

7.8 Normal Normal 12.0

-

5 43 30 -

-

The yield of the coppice once established in a three-year rotation is 12 t/ha of dry matter (d.m.) per annum, thus when the crop is cut after three years growth the yield harvested is 36 t/ha of d.m. (freshweight of 78 t/ha at 54% moisture content). This is a safe estimate of the yield obtained before the fungal disease, which reduced the annual increment in yield, became a serious problem.’ It is likely that fertilized crops on fertile arable land would exceed these yields. In years 2-4, during the establishment of the three-year rotation, the yields are much lower. The assumed yields for crop cut in years 2, 3, and 4, are 1, 4, and 10 t/ha of d.m. respectively. Once the wood has been harvested it is used to generate electricity for the National Grid. The cost and size of the generating system is uncertain. This is a major cost item and in order to reduce costs it is assumed that a standard size would be manufactured in substantial quantities. For the base scenario the capital cost of the generating system is started at flOO/kW and increases are considered in the sensitivity analysis. Assuming a ten-year life and repair costs of 5% of the capital cost, gives an annual cost’ of f19*27/kW. The generating system is assumed to come in 1OOkW units with an efficiency of 80% and the generating efficiency is 25%, which reflects the system running at 95% load.” With the energy value of wood taken as 19.7 MJ/kg of d.m. the energy generated from the system is 3.9 MJ/kg of d.m. or in electricity terms l-09 kWh/kg of d.m. It is assumed that the farmer generates electricity during the winter months November to February. Table 5 gives a typical set of electricity tariffs,” from which it can be seen that it is best to generate for 12-5 h/d during weekdays over this period (i.e. rates 1 and 2). From the wood yield the number of 100 kW generating systems to provide electricity over this period can be determined. Table 6 gives the capacities for the four yields, along with the incomes and gross margins of the wood crop. 3.3. Areas of uncertainty

The areas of uncertainty from the defined base scenario are as follows. 1. The establishment costs, i.e. the plant density, cuttings’ price and planting hire charge. Table Electricity Period 00.30-07.30 07.30-20.00

GMT

GMT Mon.-Fri.-Nov., Feb. Dec., Jan. All other times

5 tariffs Tariff

p/kWh

Rates

1.64

4

4.25 7.25 266

2

1 3

machine

278

WOOD

Table Yearly

Year

1 2 3 4 5+

Yield t/ha of d.m. harvested

Variable cosu, f/ha

26.5 93~6 218.2 732.9 Table

Variation

Crop prices Electricity prices Wood yield All crop and wood yields Cost of cuttings Density of plants* Planting cost Harvester cost Generating cost

378.0 26.0 26.0 26.0 26.0

Gross

margin f/ha

I

-378.0 0.5 67.6 192.2 706.9

7

of data for sensitivity

Data

ELECTRICITY

of coppice

Income, f/ha

100 100 200 600

1 4 10 36

FOR

6

gross margins Generator capacity, kW

-

CROPS

aoalysis Variation

f20% f20% f20% f20% 5p;7p 5OOO/ha;20OOO/ha halved ;doubled f2oooo;f3oooo increasing from f NO-2OO/kW

* Unchanged yield

2. The harvesting machine, i.e. the cost. 3. The generating system, i.e. the cost. 4. The electricity prices, crop prices, wood and arable crop yields. By varying these factors in the analysis their effect on the profitability can be assessed. Table 7 lists the data varied for this sensitivity analysis and by how much. It is also interesting to look at future scenarios. A reasonable projection is constant or falling arable farm profits and rising electricity (energy) prices. A set of 10 such scenarios is considered which depicts constant farm profits or those falling by 5% p.a. in real terms and electricity prices rising by 0, 50, 100, 150 or 200% in real terms over 20 years. 4. Method of analysis

The profit due to the coppice crop is the difference between the profits of the electricity and conventional farms for each year over the twenty-year plan. This is the same as calculating the profit from the coppice crop (including any fixed costs associated with the crop) and subtracting what the farmer could have made from the land if he were still growing arable crops. The annual profit for the conventional farm is calculated using the Arable Farm Model’* (AFM) which uses linear programming to maximize the long-run farm profit. This profit is the sum of the crop gross margins minus the labour, machinery, timeliness and crop rotation costs. The annual profits of the electricity farm are calculated by adding the income to and subtracting the variable and fixed costs due to the coppice crop from the profit for 200 ha of arable crops.

J. E. SELLS;

279

E. AUDSLEY

To assess whether investing in the wood crop is a worthwhile option the net discounted present value of the yearly profits’ is calculated. If positive this indicates that the crop would be worthwhile over the 20 years. It is also interesting to calculate the year in which the initial investments of the enterprise have been recovered (the break even year). To accomplish this the yearly “bank balance” due to the coppice crop is calculated. Each year the balance is updated by adding the year’s actual profit and any interest earned or owed. The internal rates of return are calculated for each different scenario in order to compare them with the base scenario and thus determine the effect of the change upon the profitability. The internal rate of return (IRR) is “that rate of interest or return which would render the discounted present value of its expected future marginal yields exactly equal to the investment cost of the project”.13 In other words the IRR is the maximum rate of interest the farmer can afford to pay on his bank balance, given his future coppice profits, to break even at the end of the 20 years. The higher the IRR value the better the investment. For some of the scenarios the largest generating system cost is also calculated, where the analysis is carried out for different costs until the IRR of the scenario is 12%. At 12% the farmer will break even at the end of 20 years since the long-term interest rate is assumed to be 12%. For the future scenarios the rate of increase of electricity prices is varied for either a fixed arable farm profit (i.e. decreasing at 5% in real terms) or arable farm profits increasing at the rate of inflation (i.e. remaining constant in real terms) over the twenty-year period. l-log(l+$O)+log(I+&)-) 1%(1+AI =@ _ 1)

(1)

where i = average annual rate of increase of electricity prices, % k = increase of electricity prices in real terms over n years, % i = inflation rate, % (=5%) Eqn 1 is used to calculate the average annual rate of increase of electricity prices given the increase in the prices in real terms over 20 years. For example, if in year 20 the electricity prices are 50% larger, then they would have been at the normal rate of inflation (5%) then the average annual rate of increase is 7.3%. 5. Results The conventional farm’s annual profit is fi2 391. The areas of winter wheat, winter and spring barley and oilseed rape are 113.1, 33.1, 41.3 and 62.5 ha respectively. Table 8 shows the profit of the electricity farm each year and that due to the coppice. Table ‘Ibe

profit

8

of tbe electricity famm and coppice each year, f

Year

Electricity farm profit, f

Profit due to coppice, f

1 2 3 4 5 6+

28 125 44511 47 867 52 169 70 198 62 698

-24 266 -7880 -4 624 -222 17807 10 307

for

280

WOOD

CROPS

FOR

ELECTRICITY

5P Cuttings

cost 7P

5,OOOlha Plant

density 20.0001

ha

halved Planting

cost doubled I 10

0

Internal

rate -

Fig. 1. Differences

I 30

I 20

in internal

Base

of

I 40

return

0

(a/.)

scenario

rate of return for varying

establishment

costs

There is an annual loss of profit due to the coppice until the fifth year. These initial investments are recovered by year 9 (i.e. with interest at 12% the bank balance due to coppice breaks even in year 9). The net discounted present value of the coppice crop over 20 years is f49 195 (with inflation at 5%). Therefore based on the initial data the coppice crop increases the farm profit over 20 years. Fig. 1 shows the effect of varying the establishment costs. It is quite clear that changes

Crop

prices

Elec.

prices

Wood

yields

All

yields I 10

L 0

I 20 Internal

0

Fig. 2. Differences

-I 20”/.

in internal

k%#

I 30 rate

of return

-2O”/.

-Base

I 40 (01.1 scenario

rate of return for varying prices and yields

I 0

J. E.

SELLS;

E.

281

AUDSLEY

Table

9

‘Ibe internaI rate of return (IRR) for increasing generating system capitpl costs

cost, f /kW

IRR, %

loo 150 180

23.8 11.9 -2.1

Generating

capital

system

in the establishment costs have very little effect on the overall investment. For example, doubling the plant density decreases the IRR from 23.8 to 18.5%. The reason is that only the first year’s profits are affected out of the 20 years of the investment. Fig. 2 shows that changes in the prices and yields have much more effect on IRR. For example, a 20% decrease in crop prices produces an IRR double that of the original scenario. This is also true of a 20% decrease in yields of all the crops including coppice. Thus on a farm with a low yielding potential, coppicing for electricity could be a favourable investment as a greater proportion of the costs are linked to the yield. Table 9 shows that the IRR is extremely sensitive to generating system cost and a 50% increase in price reduces it to 12%. Therefore, at present, a capital cost of only flSO/kW could be justified, which is considerably lower than the f6OO/kW quoted present system. Even with 20% higher wood yields the justified generating system capital cost is only f173lkW. Table 10 shows how doubling and tripling the harvester capital cost effects the IRR. At f30000 the IRR is only just greater than the 12% needed to break even in year 20. To break even in year 20 at that cost, the generating system capital cost needs to be flOS/kW. Table 11 shows the largest generating system capital cost for which coppicing to produce electricity would be profitable for a future of constant or falling arable farm Table The

internal increasing

10

rate of return (IRR) harvester capital costs

Harvester capital costs, f

IRR, %

10000 20000 30000

23.8 18.6 13.2 Table

for

11

Generating system costs, f/kW, allowable electricity prices and constant or faIIing

for various changes arable farm profit

Percentage increase of electricity in real terms in year 20 0 50 100 150 None Decreasing

at 5%

150 184

225 260

290 324

351 385

prices 200 410 444

in

282

WOOD

CROPS

FOR

ELECTRICITY

profits and rising electricity (energy) prices. For example, if electricity prices double in real terms by year 20 then, with the arable farm profit remaining constant in real terms, electricity generation from coppiced wood will be profitable with a generating system cost of up to f29O/kW. However if arable profits fall meanwhile, then an investment of $324/kW can be justified. 6. Conclusions A procedure for calculating the profitability of an arable wood crop to produce electricity for the National Grid shows that, as an alternative enterprise on a 250 ha arable farm, it is only profitable if the generating system cost is less than f 150/kW. At a cost of flOO/kW, the initial investments are recovered by year 9, the net discounted present value is f49 195 and the internal rate of return is 24% after 20 years. Varying the uncertain factors which determine the profitability shows that:

1. The profitability of the enterprise is insensitive to changes in establishment costs such as the price of the cuttings, plant density and planting costs. 2. Changes to prices or yields affect the profitability substantially. A 20% decrease in conventional crop prices or the overall yield potential of the farm doubles the internal rate of return. 3. Tripling the harvester cost halves the internal rate of return. 4. The profitability of the enterprise is very much determined by the generating system capital cost (the most uncertain factor). At a harvester cost of UO 000 the enterprise is only profitable with a generating system cost less than flOS/kW. If electricity prices double and farm profits remain constant in real terms over 20 years the generating system capital cost must be less than f290/kW. References ’ ADAS; The Royal Bank of Scotland; NFU Woodland grants for farmers, pp 20 * National Agricultural Conference “Arable wood crops for electricity-a new market opportunity”, Country LandownersAssociation and Royal Agricultural Society of England, NAC, March 1989 ’ Pearce, M. L. Coppiced trees as energy crops, Report EUR 9988EN, 1985 4 Durand, L.; Becker, J. J. La Production D’une Suspensionde Charbon Vegetal/Eau: Interet Economiqueet Perspectives,CEMAGREF, Antony Ott, 1987, pp 57 5 McElroy, G. H.; Dawson, M.; Stott, K. G.; Par&t, R. I. Willow biomassas a source of fuel, AFRC Institute of Arable Crops Research,Long Ashton ResearchStation, Bristol, 1982,pp 10 ’ Bridgewater, A. V. Market and technical assessment of biomassgasification in the UK, Project summary ’ Nix, J. Farm Management Pocketbook, Wye College, 1987 * Agro Busioess Consultants, The Agricultural Budgeting and Costing Book N”. 25, November 1987pp 250 ’ Audsley, E.; Wheeler, J. A. The annual cost of machinery using actual cash flow. Journal of Agricultural Engineering Research1978, 23: 189-201 lo Bodria, L.; Fiia, M. Resultsof testswith different gasifiersfor farm use, Proceedingsof the 3rd E.C. Conference “Energy from biomass”, London: Elsevier Applied Science Publishers, 869-873, pp. 869-873 ” Yorkshire Electricity Board Tariffs applicable to private generatorsor suppliers, 1987. l2 Audsley, E. An arable farm model to evaluate the commercial viability of a new machine or technique. Journal of Agricultural Engineering Research1981,26: 135-149 ” Baumol, W. J. Economic Theory and Operations Analysis (4th edn), London: Prentice/Hall International, 1977,p. 604

J. E. SELLS;

283

E. AUdSLEY

Appendii The arable farm data used in the analysis Table 12 The sequence of operations of the crops

Ooeration

Timeliness

Start End (see A)

penalty (see D1

Crop: winter wheat S read P & K PPough

2:

Liz

Power harrow

s3

D5

Seedbed cults.

s3

D5

Plant

s3

D5 H5 I?!

Ei: Fertilize Spray Combine Burn straw

K A4 A4

E

Crop: winter barley S read P & K Prough

ii

E

Power harrow

s3

D5

Seedbed cults.

s3

D5

Plant

ii: H5 I?2

Fertilize Roll

Spray

Combine Bale straw Crop: spring barley Plough Base fertilize Seedbed cults. Plant Spray Combine Bale straw Crop: oilseed rape Heavy cults. Seedbed cults. Plant

Spray

Fertilize Fertilize Combine Burn straw

H4 T::

::

E

:1 A4 A4

El

Y4

01

A2

01

Y4

or

or or or

or

s2 F2

E

or

G

SS

6: J4

or

2

D5

Spray Spray

or

or or

z 01 ii: H5 t;’

or or

3+1/2+L 1+4+L 2+4+L 1+5+L 2+5+L l+L 2+L 6+l+L 7+l+L l+L 2+L 8+1+L 7+l+L 9+2*(1/2)+3*L L+l/2

0.59 2.38 1.42 1.69 1.01 1.19 0.71 034 0.41 0.41 0.24 0.41 0.41 0.74 l-06

3+ 1/2+L 1+4+L 2+4+ 1 1+5+L 2+5+L l+L 2+L 6+l+L 7+l+L 7+l+L 8+l+L l+L 2+L 7-kL 9+2*(1/2)+3*L 10+3*(1/2)+3*L

0.59 2.38 1.42 I .69 1.Ol 1.19 0.71

1+4+L 2+4+L 3+ 1/2+L l+L 2+L 6+1+L 7+l+L 9+2*(1/2)+3*L 10+3*(1/2)+3*L

2.38 1.42 0.59 1.19 0.71

l+L 2+L l+L 2+L 6+l+L 7+1+L 8+l+L S+l+L 9+ 1/2+2*L L+ l/2

1.19 0.71 1.19 0.71 0.84 0.41 0.41 0.41 I.53 l-06

a a

b

X:Z 0.41 0.41 0.41 0.24 0.41 0.70 0.80

8:: 060 0.50 100 100 El 80 1: 100 :“o

WOOD

284

Month Month

Table 13 codes and weeks

ELECTRICITY

Code

4 4 5 4 4 5 4 4 5 4 4 5

Table

FOR

per month

No. of weeks

January February March April May June July August September October November December

CROPS

J F H P M IJ Y A : N D

14

Machinery

Number

1 2 3 4 5 6 7 8 9 10 L

Machine

Capital

Tractor 60 kW Tractor 100 kW Trailed fertilizer spreader Plough Power harrow Drill Sprayer Mounted fertilizer spreader Combine Baler Labour

Table

Week.9

Jl-J3 J4-F2 F3-Hl H2-H3 H4-H5 Pl-P2 P3-P4 Ml-M4 Ul-Y3 Y4-Al A2-A3 A4-S2 s3-!+I s5-01 02-03 04-N2 N3-Dl D2-D5

Cost,

f

15 093 23 165 3oGu

10

7500 1500 67 333 5200 8500

10 10 5 5 10 5 5 (annual cost)

15

Workable

hours

Available

hours

Replacement interval, years

for ploughing

18.6 56.5 94.3 83.9 loo.7 117.6 134.4 268.8 537.6 133.8 130.6 189.3 121.8 118.3 99.3 119.6 84.3 58.4

5

5

f. E. SELLS;

285

E. AUDSLEY Table Timeliness

1611 and b penalties, f/ha

a: Planting and spraying timeliness penalties Weeks

Planting W. Barley S. Barley

W. Wheat

A2-A3 A&S2 s3-s4 s5-01 02-03 04-N2 N3-Dl D2-D5 Jl-J3 J4-F2 M-H1 H2-H3 H4-H5 PI-P2

OS. Rape

Spraying W. Wheat W. Barley

58.9 7.36 15.1 0.0 37.7 60.4 75.5 98.1

6.2 12.4 55.8 93.0 111.6 111.6

58.9

10.6 0.0 15.9 47.7 79.5 111.3

7.55 15.1 30.2 31.0 37.2

37.7 45.3

6.2 12.4 24.8

b: Combining and baling timeliness penalties Weeks

Combining W. Barley S. Barley

W. Wheat

Y4-Al A2-A3 A4-S2 s3-s4 s5-01

0.0 12.4

22.1

0.0 37.7

Table

17

costs,

E/ha and areas

Previous

W. Wheat

* 83 31 32 0

I

W. Wheat l

136 37 32 0

W. Wheat 0.0 0.0

16.0

0.0 26.5

Rotational

W. Wheat I W. Wheat W. Barley S. Barley OS. Rape

Baling OS. Rape 0.0

W. Barley

0.0 0.0 20.0

crop

W. Barley

30 * 68 58 0

S. Barley

30 I 68 58 0

OS. Rape

0 * 0 0 *

Max area, 70 of farm area

25

A = The “start” and “end” times of each operation indicate the period over which the operation can be done. The letter indicates the month and the number indicates the week of the month. Table 13 gives the month codes and the number of weeks per month. Example: A4 means the fourth week of August. B = The “machinery” are the machine numbers from Table 14; l-10 and L for labour. Where more than one particular machine is needed this is indicated as m *n which means m of machine n. Example: 9 + 2 *(l/2) + 3 * L means one combine, two tractors (either 60 kW or 100 kW) and three labourers. C = The “hours” are expressed as percentage of the available hours for ploughing given in Table 15. D = “a” and ‘lb” represent Tables 16a and 16b which give the “timeliness penalties” for the appropriate operations.