F Bonnieux

P Rainelli

D Vermersch

A POLICY SCHEME TO REDUCE NITRA TE POLLUTION -THE CASE OF LIVESTOCK REARING -SUMMARY

ln many areas, livestock farming is undoubtedly the largest single source of nitrogen. A nitrate problem results whenever the nitrogen applied, of whatever kind, is net taken up by plants and reaches ground-water aquifers, or is lest in surface run-off. There are nitrogen surpluses, because prices do net reflect the damage to the environment. Governments in most countries have relied mainly on regulatory instruments in this field. At the EC level, the nitrate directive provides an example of the dominance of direct command and control instruments. Nevertheless other approaches could be chosen to improve the current situation. Economie incentives emerge as an efficient instrument to achieve a significant reduction in nitrate pollution from livestock farming.

For pig production, through a proper combination of feed ingredients and with the inclusion of industrial amine acids, it is possible to improve amine acid balance in the diet, thus enabling a reduction in protein content and nitrogen output. A subsidy put on specific components of feedstuffs (or a charge on some others) would encourage pig producers to adopt this new technology which is more demanding in terms of labour quality. The potential reduction in nitrogen output in pig waste through feeding is estimated using micro data. Similar progress is expected in the near future for other categories of livestock. A charge on minerai fertiliser would be consistent with a better animal diet. lt would increase the opportunity cost of organic fertiliser and would push farmers towards more environmental fridenly practices. Moreover a charge could help to improve the efficiency of the livestock industry and would be consistent with a policy based on education and extension services.

. .

ln all developed countries there is growing concern about the level of nitrates in drinking water because of associated human health risks. Concerns over the eutrophication of fresh waters and the consequent disruption of the ecosystem have brought attention to the excessive levels of nitrates in surface waters. lt is now becoming clear that as point source pollution has become more strictly controlled, non point source pollution has become relatively more important. Consequently we need to focus on non point sources such as horticultural crops, livestock farming and urban runoff. ln areas such as Brittany, the major contributor to nitrate pollution is the farming sector. If nitrate pollution was to be solely defined as an excessive level of nitrates in drinking water, then one option would be to do nothing about farming activity but to only treat raw water. Such a strategy would net be reasonable in the long run. To be effective any policy dealing with nitrate pollution should not only treate raw water but intervene in the agricutural sector. ln many areas, livestock farming is undoubtedly the largest single source of nitrogen pollution. The size of the livestock herd has increased rapidly in the recent past, with the expansion mainly taking place on small farms. Specialised intensive livestock production has proved to be a feasible solution to the problem of keeping farmers in business because here, land is not a limiting factor. However this process has resulted in increasing environmental problems.

A nitrate problem results whenever the nitrogen applied, of whatever kind, is not taken up by plants and either reaches ground-water aquifers or is lest in surface run-off.

There is a nitrate problem, i.e. nitrogen surpluses, because prices do not reflect the damage to the environment. ln most countries governments have relied mainly on regulatory instruments in this field. ln France, for example there are both general regulations dealing with environmental and water protection, and specific regulations for classified installations _ and intensive rearing. At the EC level, the nitrate directive aise provides an example of the dominance of direct command and control instruments. ln this paper however it is not our objective to identify the reasons why politicians have taken the regulatory approach.

Most economists agree that it appears to be impossible to value all the negative impacts of nitrate pollution ; therefore a policy based on pigouvian taxation could not be implemented. Nevertheless other approaches can be chosen to improve the current situation. Economie incentives can be used as an efficient instrument to achieve a significant reduction in the nitrate pollution resulting from livestock rearing. The cost-effectiveness of a better diet for livestock is presented in the first section.

There are aise some insights on the issue of waste treatment. A whole section is devoted to the question of fertiliser taxation. We then analyse the potential impacts of a policy which would combine an improved pig diet and a tax on minerai nitrogen.

THE CONTROL OF PIG DIET AND THE TREA TMENT OF RESIDUAL WASTES

lt is now widely recognised that an improvement in animal diet should lead to a drastic abatement of nitrogen content in animal wastes. With current knowledge it is possible to improve the amino-acid balance in the diet, which would thus enable a reduction in protein content and consequent nitrogen excretion. ln this section we consider a policy mainly based on the dietary measures which may eventually be combined with the treatment of residual wastes.

ln figure 1 we depict the equilibrium position of a representative farm and the environmental consequences of the farmer's decisions. The production function is given in the south-west section where Q is the output and N is the diet nitrogen content. The marginal profit 7t"' is given in the north-west section. Profit maximising farmer will use N 0 nitrogen and will produce Q 0 output.

The south-east section represents the transfer function i.e. the relationship between nitrogen N and the polluting emissions. Finally the north-east section gives marginal benefits 7t"' and marginal damages D,,,. lt tells us that the optimal level of emissions E.

---------'-----------~o a

Q /l Qo : Q• F------;----.....----E rrm Q V . V À .
. The former output Q 0 could be achieved with a smaller amount of nitrogen N 1 instead of N 0 •

A N* N* •••••••••••••••••••>•••••••••••••••• ............ ••••••••••••••••>••••••••••••••••• No No
Polluting emissions would be reduced from E 0 to E 1 • A further reduction in emissions from E 1 to E 2 could be achieved through a treatment of residual wastes as is shown in the southeast section. The implementation of the above policy would allow a decrease in environmental damages (the hatched area in the north-east section) but would lead to an increase in private costs as Q 0 is no longer optimal (the hatched area in the north-west section). c"' : Most economists agree that the reduction in water nitrate content presents great social and economic benefits. The most obvious of the benefits is cheaper drinking water. ln the case of eutrophication, benefits to commercial and recreational fishing activities have been considered in Sweden by [START_REF] Silvander | Farming and the countryside ; an economic analysis of external costs and benefits[END_REF]. The willingness to pay of the general population to restrict nitrate content in drinking water have been estimated for the US [START_REF] Edwards | Option prices for groundwater protection[END_REF] and the UK [START_REF] Hanley | Problems in valuing environmental improvements resulting from agricultural policy changes : the case of nitrate pollution[END_REF]. Their conclusions are difficult to adapt to the French situation.

••••••••••••••••••••••>-••••••• ... ••••••••••••••••••••••• ....
There are more relevant data on the cost side than on the demand side. Severa! research programmes are being carried out in France and in the Netherlands on pig diet.

Their main objective is to achieve a better composition of the compound feed to meet the pig changing needs :

-at the start of the fattening period the need for protein is higher than in the period preceeding slaughter. This means that the use of at least two types of compound feed would be more efficient (less waste) ;

-no overdoses of nutrients would be given ;

-the pigs would more easily assimiled nutrients if artificial amino-acids were used.

A compound feed model was constructed to take all the physiologie restrictions and economic possibilities into account. This showed that a 20 % reduction of N excretion by pigs and poultry in the Netherlands would increase the costs of compound feed by 3 % but to achieve a 27 % reduction costs would increase by 11 % [START_REF] Wijnands | Economie aspects of N flow manipulation in pig production[END_REF].

The relationship between the reduction in nitrogen and the cost of the compound feed has also been estimated at the national level for the Netherlands in three different situations (Van der Veen, 1993) :

A) the original set of protein and amino-acid requirements, B) a set with a 5 % reduction of amino-acid requirements, C) a set with a 5 % reduction of amino-acid requirements and protein requirements.

The results are displayed in figure 4. ln situation A , the total allowed quantity of nitrogen in compound feed is reduced : raw materials with a high level of (non-digestible) crude protein are used less while those with a good digestibility are used more. A charge levied on the nitrogen content of compound feeds could be a good incentive to improve feedstuffs. lt makes sense to pay farmers for the adoption of a better feed technology since they have enough political power to avoid regulation. For example, a subsidy could be paid to feed producers to enable them to use more lysine in compound feeds without any risen price.

THE CONTROL OF NITROGEN USE

The easiest policy to administer would be a tax on purchased minerai fertiliser.

However its efficiency depends on the price elasticity of the demand for fertiliser. lt is currently assumed that this elasticity is low, sa the increase in price would need ta be very high ta achieve a significant reduction in consumption. For example, Dubgaard (1989) calculated that to achieve the objective of the Danish Ministry of the Environ ment, i.e. a 30 % reduction in nitrogen use, a tax rate equal to 150 % would be required.

Thus the leading argument against a tax on minerai fertiliser is that the demand is price-inelastic. The literature on this issue is large and good summaries can be found in [START_REF] Burrell | The demand for fertiliser in the United 'Kingdom[END_REF] and [START_REF] Hanley | The economics of nitrate pollution[END_REF] sa we do not intend ta review the subject again.

Nevertheless it should be emphasized that most of the produce estimates are net relevant for policy purposes because they refer ta the short-run.

The elasticities reported from linear programming studies are consistent : eg England Furthermore the elasticities relate to fixed and quasi-fixed factors. These factors are not required to be at a long-run optimum level and there is some evidence of a disequilibrium in land and family labour. For instance for arable farming in France, land was a rationed factor. ln the long-run there was a movement towards larger holdings. On the labour side, the level of available family labour gives a lower bound for the total amount of labour input.

For most farms, there is an excess of labour and farm operators do not hire wage earners.

Vermersch (1989) estimated several Hicksian-elasticities from the same random sample of French cereal farms. Assuming _ family labour and land fixed he found that the own-price elasticity of nitrogen demand is -0.25. However if the assumption of fixed family labour was to be relaxed elasticity would be -0.44 since a new equilibrium involving the utilisation of less labour would emerge. Finally if land was a variable input, elasticity would be equal to -0.63 and the farm's acreage would increase. These results are consistent with the Le Chatelier principle.

Single-equation time series models are usually based rather loosely on production theory. Sorne however specify expectations and adjustment lags in response to price changes, and they therefore provide both short-run and long-run elasticities. ln the French agricultural sector for the period 1959-84, short-run elasticity was -0.33 and long-run elasticity was -1.1 O. A full adjustment needed a little more than two years [START_REF] Bonnieux | Agricultural policy and environment in developed countries[END_REF]. For the UK during the 1956-68 period Lingard (1971) with -0.60 for short-run elasticity and -1.18 for long-run elasticity. Recently [START_REF] Tiezzi | Green taxes on nitrogen fertilisers in the Po valley : a cointegration approach in estimating fertiliser's demand[END_REF] revisited the single equation issue. She used a cointegration approach in estimating fertiliser demand for the Emilia-Romagna Region (ltaly) using annual observations for the period 1951-90. This approach allows us to establish an equilibrium relationship between fertiliser consumption and price, a long-run price elasticity is then obtained. She found that the longrun demand for nitrogen fertiliser is elastic both to its own price (-1.82) and to the output price (2.02). So the combination of a tax on fertiliser and a decrease in output price would cause a significant reduction in fertiliser demand. Given the above findings we can argue that fertiliser demand is own-price elastic.

Let us develop further arguments to support the implementation of a tax. The discussion is based on the demand for nitrogen as illustrated in figure 4, where the price of nitrogen and the use of nitrogen are denoted by W and X. Without any regulation the market equilibrium is denoted by M 0 and the use of nitrogen is equal to X 0 • ln order to achieve a decrease in the use of nitrogen from X 0 to X 1 the environmental agency implements a charge equal to w; minus w; then the market equilibrium shifts from iW 0 to M 1 •

w dW w ••••••••• .... •••••••••••• ............... . C 0 dX X X
The loss in the farmer's surplus is shown by the areas A plus B : A is net social loss due to the reduction in output involved in the taxation scheme and 8 is the revenue of the tax : farmers have to pay a higher price for their actual use of nitrogen. organizations may therefore be expected to lobby strongly against such a policy. So it is proposed to neutralize the income transfer effects from agriculture to society (area B) by reimbursing the tax revenue. This compensation would not affect the incentives to decrease nitrogen use provided that the tax revenue is paid back in the form of lump-sum payments :

there is no substitution effect since the price system is unaffected. A very simple scheme would be to reimburse the tax revenue at a fiat rate per hectare. The crucial factor here is average nitrogen use since this tax scheme would result in a redistribution of income from farmers over the average to farmers under the average, provided that administrative costs are low. The burden of the fertiliser industry is given by ar~a C. Total social loss is therefore area A plus area C. This sum has then to be compared with the social benefits resulting from a reduction in the polluting emissions.

A quota system could aise achieve the desired reduction in fertiliser use. However it is quite difficult to implement, because to obtain a cost-efficient allocation of quotas, the environmental agency must know the production technology of each farmer. There is some evidence that there are significative differences in production technologies between farmers.

For example in the case of the Swedish island of Gotland, Andréasson (1990) found large differences in own-price elasticity of fertiliser demand between a group of farmers. This may be an indication of differences in the marginal value of nitrogen and therefore show that abatement costs vary between farmers. A possible solution to this problem would be the implementation of a tradable quota scheme. If the quota market is competitive, a price equal to the tax will emerge in an equilibrium. Quotas could initially be allocated on the basis of a uniform reduction in fertliser use based on fertiliser comsumption in the previous year.

Approaches towards environmental problems differ between countries and a tradable quota scheme is not on the French policy agenda. Other types of pollution charges have been implemented in France for several decades. Up to now they have been restricted to point pollution but some suggestions have been made to extend the scheme, thereby charging agricultural inputs. Such devices exist for example in Sweden and Norway.

There is a further argument to support a tax on nitrogen. Differences in own-price elasticities are related to differences in efficiency across farmers [START_REF] Vermersch | Abatement of agricultural pollution and econometric incentives : the case of intensive livestock farming in France[END_REF].

The response to a nitrogen tax would vary according to farm operators' efficiency. The least efficient farmers can be expected to decrease their nitrogen demand more than the most efficient ones. This point has been illustrated by the elasticities obtained for several categories of intensive livestock farms. A uniform tax on minerai fertiliser would increase the

A POUGY SCHEME TO REDUCE NITRATE POLLUTION• THE CASE OF LIVESTOCK REARING • F. Bonnieux, P. Rainelli, D. Vermersch
opportunity cost of organic fertiliser thus pushing farmers towards more efficient practices at the micro level. This would involve a smaller amount of nitrogen spread thus producing both private and social benefits.

THE IMPLEMENTATION OF A POLICY SCHEME

We shall now consider a policy scheme which combines the control of animal feed and of nitrogen use. ln order to assess its potential benefits we have simulated its impacts on a sample of intensive livestock farms (mainly dairy and pig farms) located in Brittany. The sample is divided into two categories according to whether the farms have a negative impact on the environment or not. If the application rate of total nitrogen from animal or minerai origin (plus atmospheric deposition) minus the plant uptake is greater than a specific threshold, there is an excess and the farm is said to be a polluting farm. Average characteristics of both categories of farms are shown in table 1 : there are 28 non-polluting farms (category 1) and 54 polluting farms (category 2) in the sample. There is no significant difference between the categories in terms of average acreage or other structural variables such as livestock. Nevertheless there is a large difference between the amounts of nitrogen used. Moreover a number of farms does not need minerai fertilisers since organic nitrogen can be substituted for bought fertilisers. Despite a large surplus of animal wastes, the use of artificial fertilisers is great in category 2. Here minerai fertiliser constitutes an important part of nitrogen surplus. This reflects inefficient behaviour of farmers which not only involves social costs but results in higher costs of production : a profit maximizer would buy smaller amount of minerai fertilisers.

On the policy agenda, there is a European directive which aims to limit the use of nitrogen in vulnerable areas. The first proposai is restricted to organic nitrogen. This sets up Table 2 summarizes the results of a simulation which combines an improvement in diet and a more control use of nitrogen. For fattening pigs, it was assumed that a 25 % reduction in the nitrogen content of manure was achieved. ln order to simulate the impact of a tax on minerai fertiliser different own-price elasticities wére assumed : -3.6 % for the first category and -6.8 % for the second category [START_REF] Vermersch | Abatement of agricultural pollution and econometric incentives : the case of intensive livestock farming in France[END_REF]. This policy scheme would result in a significant diminution of nitrogen surpluses : average decrease in application would be 25 kg/ha. The impact of the scheme would be greater across polluting farms (category 2) than across non-polluting farms (category 1). On average, the two policy measures would have a similar impact : -12.2 kg/ha for the control of minerai fertiliser and -13.4 kg/ha for the control of animal feed.

ln this sample, fattening pigs only account for 37 % of total organic nitrogen. lt is why the impact of a better control of diet is limited. The impact is obviously greater in pig-only farms. A better control of the diet of dairy _ cows can be imagined for the near future. There are currently several research projects dealing with this issue.

The impact of a small charge on minerai fertilisers is quite important and is higher across the least efficient farmers (category 2) than across the most efficient ones (category 1 ). After the elimination of inefficiencies the response to a tax will be similar in the two categories of farms. Nevertheless there are two reasons to keep such a charge. The first reason is to maintain the opportunity cost of organic nitrogen at a level sufficient to encourage farmers to substitute organic fertiliser for minerai fertiliser. Otherwise it is expected that a charge would make easier the adjustment of quasi-fixed factors towards their long-run optimum levels. Such a process has been shown for land in the case of arable Let us suppose now that there is a subsidy to compensate the extra costs due to the improvement in diet. The burden of the farm sector is given by area A on graph 3. lt is proportional to the own-price elasticity of fertiliser demand so the relative burden will vary across farms. The impact on farms of a 10 % charge on minerai fertiliser is given in table 3 (the price of minerai fertiliser is fixed at 4 F/kg). The net loss is very small in the first category of farms but is not negligible in the second category. The tax revenue is paid back at a fiat rate of 73 F/ha thus there is an income transfer from the less efficient farms to the most efficient farms. On average, in the first category farmers receive 33 F/ha: they are winners if they buy less than 186 kg/ha of minerai fertiliser, there are 24 winners out of 28. ln the second category farmers pay 18 F/ha but there are only 20 losers out of 54. Therefore in the whole sample there are 44 winners and 38 losers.

The 10 % charge would lead to a 6.3 % decrease in total demand for minerai fertiliser. A quota system achieving the same reduction would be more expensive for the farm sector, but as shown in table 6 the average net loss is similar in both schemes :

2.59 F/ha with the quota vs 2.45 F/ha with the charge. Main drawback of a quota system is that a similar burden is imposed on both categories of farms. lt does not take into account the disparities between farms. A uniform tax scheme would achieve an improvement that a uniform quota scheme would not. A quota scheme cannot be tailored to take into account differences across farms due to a lack of information and different policy reasons. For the first category, the quota scheme is equivalent with a 17.5 % charge i.e. 0.70F/kg of minerai fertliser. For the second category it is equivalent with a 9.3 % charge i.e. 0.37 F/kg. Therefore a uniform quota scheme would benefit the least efficient farmers.

ANNEX: THE ESTIMATION OF EXCESS N

For each farm nitrogen inputs are estimated.

-Concerning animal manure, the Farm Accountancy Data Network is used to subdivide livestock into 22 categories. For each one a technical coefficient allows us to estimate the N production. ln fact it is the nitrogen available on the spot which is estimated since volatilisation of ammonia following surface spreading is deducted.

-Concerning artificial fertilisers, N bought by farmers is given directly by the Farm Accountancy Data Network.

The nitrogen taken up by crops is a function of soil type, plant type, yield, temperature, radiation and water supply. The amount of nitrogen export is determined for the 19 types of cultivation given by the Farm Accountancy Data Network. For each crop type, the nitrogen uptake is estimated according to the average yield.

If the application rate of total nitrogen from animal or minerai origin is greater than the plant uptake there is an excess. lt is assumed that 30 kg of nitrogen per ha of Utilised Agricultural Area is the agronomie threshold below which there is no utilisation by the crops.

Nitrogen excess occurs when this threshold is passed.

A POLICY SCHEME TO REDUCE NITRATE POLLUTION -THE CASE OF LIVESTOCK REARING • F. Bonnieux, P. Rainelli, O. Vermersch

A

  POLICY SCHEME TO REDUCE NITRATE POLLUTION -THE CASE OF LIVESTOCK REARING -F. Bonnieux. P. Rainelli, D. Vermersch

  is smaller than E 0 • So the hatched area is simply the extra social costs due to the increase in output from the social optimum Q. to the private optimum Q 0 • Farmer's lasses from the reduction in output from Q 0 to Q. are shown in the north-west section. A POLICY SCHEME TO REDUCE NITRATE POLLUTION -THE CASE OF LIVESTOCK REARING -F. Bonnieux, P. Rainelli, O. Vermersch

Figure 1 .

 1 Figure 1. Mode/ of a pig farm and its environmental impact

  .......... -<•.......... . . . . . . . . . . . . . ....... .c::; ••••••• :

Figure 2

 2 Figure2shows the consequences of a combination of a better diet and a treatment of residual wastes. The use of amino-acids in the pig diet would shift the production function.

Figure

  Figure 2. lmprovement in diet and treatment of residua/ wastes

A

  POLICY SCHEME TO REDUCE NITRATE POLLUTION -THE CASE OF LIV ESTOCK REARING -F. Bonnieux, P. Rainelli, O. Vermersch

Figure 3 .

 3 Figure 3. Costs and Nitrogen reduction in situations A, B and C in comparison to costs and Nitrogen content in situation A

  compounds rise progressively the lower their content in nitrogen for the three situations. Beth situations B and C achieve the same reduction in nitrogen at a lower cost than situation A. C is more cost-efficient than B for larger reductions in nitrogen. These results are very interesting but do net take ail factors into account. ln comparison to the current situation, A, B and C require more labour and capital because they are based on several phases in feeding regimes.

(

  figures is consistent with the theory of production since the uncompensated own-price elasticity for an input cannot be less in absolute value than the compensated elasticity. The Marshallian demand is price elastic and the fixity of output is a crucial assumption.

  found similar values A POLICY SCHEME TO REDUCE NITRATE POLLUTION -THE CASE OF LIV ESTOCK REARING • F. Bonnieux, P. Rainelli, O. Vermersch

Figure 4 .

 4 Figure 4. Demand for nitrogen

  Farmer's A POLICY SCHEME TO REOUCE NITRATE POLLUTION• THE CASE OF LIVESTOCK REARING -F. Bonnieux. P. Rainelli. O. Vermersch

A

  POLICY SCHEME TO REDUCE NITRATE POLLUTION -THE CASE OF LIVESTOCK REARING -F. Bonnieux, P. Rainelli, D. Vermerschan upper limit equal to 210 kg/ha during a transitory period, falling to 170 kg/ha after. The review of the micro data in the sample shows that 49 farms comply with the most stringent standard with 62 meeting the requirements of the transitory one. The remaining twenty farms would have to reduce their nitrogen application. Of this twenty three currently apply more than 300 kg/ha.

A

  POLICY SCHEME TO REDUCE NITRATE POLLUTION -THE CASE OF LIVESTOCK REARING -F. Bonnieux, P. Rainelli, O. Vermersch farming. A tax would help a process of extensification. This tax could help to improve the efficiency of the livestock industry and is consistent with a policy based on education and extension services.

A

  POLICY SCHEME TO REDUCE NITRATE POLLUTION• THE CASE OF LIVESTOCK REARING • F. Bonnieux, P. Rainelli, D. Vermersch

  ........ ;:,, ....... .

		/~
	No	No
	N	N

A POLICY SCHEME TO REOUCE NITRATE POLLUTION• THE CASE OF LIVESTOCK REARING • F. Bonnieux, P. Rainelli, O. Vermersch

  Publicinformation is scarce, however they exist some published data on biological processing plants. ln the Netherlands, based on 0.4 m3 slurry (11 % dry matter) per fattening pig, the gross costs (operating costs plus depreciation) are 25 Ecu/m3 i.e. 10 Ecu/pig(ten Have, 1993). ln Brittany with 1 m3 slurry (6 % dry matter) per fattening pig, the gross costs are 10 Ecu/m3 i.e. 10 Ecu/pig (Observatoire Départemental de l'Environnement, 1993). Sa the treatment cost per pig is approximately equal ta the gross margin per pig. This comparison does net take into account the sale of the end product. However it is questionable that this could be high enough to achieve a positive incarne. As was mentioned by ten Have (1993) a company called Scarabee claims much lower costs, but there is no public information. At the moment the costs of pig manure processing remain high and therefore waste treatment cannot salve the problem of nitrate pollution.

A POLICY SCHEME TO REDUCE NITRATE POLLUTION • THE CASE OF LIVESTOCK REARING • F. Bonnieux, P. Rainelli. O. Vermersch

The issue of manure processing plants has aise attracted much attention.

Table 1 . Average characteristics of polluting and non polluting farms

 1

					Nitrogen available (kg/ha)
			Average
	Category	Number	acreage (ha)	minerai	animal	total*
	1	28	25.2	101.6	117.1	228.7
	2	54	29.8	235.3	158.3	403.6
	Total	82	28.2	194.5	145.8	350.3

* lncluding atmospheric deposition.

Table 2 . A simulation of the policy scheme : impact on nitrogen use (kg/ha)

 2

		Contrai of
	Category	minerai fertiliser	animal feed	Total
	1	-3.7	-10.9	-14.6
	2	-16.0	-14.4	-30.4
	Total	-12.2	-13.4	-25.6

Table 3 . Simulation of the policy scheme : impact on farms

 3

			10 % charge		Equivalent quotas
		Net loss		Revenue of the charge	Net loss
	Category	Total (F)	F/ha	Total (F)	F/ha	Total (F)	F/ha
	1	515.43	0.73	27 604.24	39.17	1 576.29	2.24
	2	5 145.63	3.20	141 050.88	87.71	4 403.34	2.74
	Total	5 661.06	2.45	168 655.11	72.92	5 979.63	2.59

.... ..... _ _. ...... -.. ~-. ...... ••••••• ... -......... .......... ........ . -

' '. ,• • .•• •


Rivista Dl

Econoi\ua Agraria

Yves Leon

Cinquantenario del!a

pag. 9 pag. 12 pag. 14

Introduction

This contribution's subject matter is the economics of agricultural production and its developments in Europe for the last decades. De fine the scope of the subject is not an easy task in so far economics of agricultural production may embrace a great variety of matters according to the preoccupations of the scientists involved in agricultural economics. According to Bublot ( 1974).

economics of agricultural production includes a great part of agricultural economics. wi th matters as different as production economics sensu stricto at the individual or aggregate leve l, market analysis or farrn management. Given the scope assigned to the present contribution, Bublot's definition cannot be accepted and it seems preferable to follow Ritson ( 1977) and restrict the theme of this paper to the presentation of research on the producer behaviour and directly related issues examined at the unit of production and the sector level. Even with this restriction economics of agricultural production includes considerations on production, cost and profit function s, on supply analysis and o n the characteristics of inputs, as well on risk and uncertainty or technical change.

The second feature of the contribution stems from the geographical field it covers: it is limited

Lo research carried out by European scientists. Such a task is challenging because research is an activity which in its principle ignore the administrative or institutional boundaries and proceeds along interwoven avenues, the canonical example being given by the close research relationships existing between North-America and Europe. Nevertheless, it seems not unreasonable to propose an overview of what has been produced by the European profession in agricultural production economics. even on several times the influence exerted by non-European research was determining in the progress of our own work and has to be recognised.

Finally, the context of this conference and the celebration of the fiftieth anni versary of the Rivista di Economia Agraria invite to consider an historical perspective allowing for an assessment of the changes which have cccurred in the research concerns of the profession and particularly in their conceptual background in relation with the institutional context of agricultural economics in Europe.

The microeconomic basis of the research issues to address was early and largely accepted, however.

it seems important to stress the existence of other lines of thought in some countries like France for two decades and the dramatic shift given in the orientation of research in this country.

Concerning now the method used to conceive this survey, it has been essentially founded on the studying of available literature in English and French, and especially on joumals like the Europea,1

*

Economies of agricultural production in an historical and institutional context: the case of France and The United Kingdom

At the beginning of the period under study the situation of agriculture in Europe large ly influences the themes on which the profession focuses its attention. In the majority of Western European countries, there is a need for rebuilding agriculture in so far the Second W orld War has partly destroyed the potential of production and put under scrutin y the institutional structu res which organised it before and during the conflict. In some countries like France or Germany and in most of continental countries wh.ich had severely undergone the effects of the war the situation opened a new era for agriculture and agricultural production. On the contrary, the United Kingdom, while politically and military involved in the war, was Jess concerned by its consequences on the agricultural sector. at least at the level of the units of production. No doubt that the French profession of agricultural economists which was bom at the end of the war faced as a first task the dramatic problem of helping to increase the global output of agriculture and had to share this concern with the various bodies in charge of agriculture, at the first rank of them the French Ministry of agriculture and the farm unions.

Therefore, it is not surprising that the French agricultural economists turned their atten tio n to the question of farm management and develop their first research on related items. Due also to the fact that economics Departments in French universities at that time were s mall-sized and still strongly linked with law Departments the agricultural economics issues were tackled by people who do 1101 principally s pecialise in economics. Moreover, of crucial interest to agronomists were the practical answers to these questions and, therefore, the first French agricultural economists were essentially educated within the network of the faculties of agronomy.

At that time, the group of scientists who founded in 1948 the Société Française <l'Economie Rurale and Economie rurale, the first journal of agricultural economics defined the avenues where the researches of the profession could develop: economics of the farm firm and of the agricultural areas, economics of markets and prices. They complained of the lack of handbooks and appropriate methods to answer these issues and were also concerned by introducing in the researches thè met hocls and concepts of general economics (Augé-Laribé, Chombart de Lauwe. 1953 ).

A few years later, Bergmann ( 1959) went on in retlecring o n the fi elds to be CO \'Cf'Cd by the agricultural economics research. Among them he stressed the necessity of estimating factor efficiency and production fonctions. of using quantitative methods such as econometric or programming models and evaluating aggregate supply . He also pointed out the fact that the firm theory should serve ;is a basis for these programmes as well as the design of sound farm management. Actually the conce rns of Bergmann reflected the quarre! which opposed in France "ruralists" and "productivists" during the sixties . the former doctrine stressing the specificity of agricultural sector due to origi nal economic mechanisms affecting suppl y and demand , the formation of prices and production costs [START_REF] Lacombe | Les recherches sur les structures agricoles: évolution et e11seig11e111e11ts[END_REF] and the latter emphasising that the change in agriculture relied on technical change and mobility of factors and that the forces determining it had to be found outside the sec tor [START_REF] Petit | ls the re a Fren ch school of agriculr11ral Eco110111ics ?[END_REF] ).

At odds with Bergmann's view, a majority of French agricultural economists chose to develop their analyses either using a conceptual Marxist framework or stressing a « structural » approach of the sector. They gave a high priority to the understanding of the changes faced by the sector as a whole.

the farming systems and the production units [START_REF] Aubert | Systèmes de producrion et tra11!!>jon11ations de l'agriculture[END_REF]. However, at the beginning of the eighties emerged a social questioning with regard to the programmes of the national agricultural economics research and a need for redirecting them towards topics more in link with the decisionmaking issues. As a result, a dramatic shift in the research policy occurred with a new emphasis given to microeconomics, econometrics and agricultural policy issues.

In sharp contrast with this conflicting situation the agricultural economists in the UK entered the l 950's in a more straightforward way . First of all, the profession was already well-established since the first agricultural economists had been appointed more than twenty years ago in the provincial advisory centres created by the Ministry of agricufture in universities and colleges ( [START_REF] Colman | The Deve/opment, Organisation and Orienration (f Agrirnlt11rol Eco110111ics in rire United Kingdo111[END_REF]).

Second, the separation of these centres from the universities after the second World war induced the agricultural economists to seek for closer links with academic economic departments. Third. given the historical orientation of economics in Great Britain, agricultural economists founded the ir work on the neoclassical paradigm. Last but not least, it may be assumed that the miner place of agriculture in the free-trade oriented economy of the UK gave the scientists more room for developing academic work.

On the other band, Colman States that it is only after the war that the theoretical and mathematical background of British agricultural economists began to develop substantially and he analyses this change as a result of the training of British graduates in American universities in the fifties and sixties. This evolution induced a crucial shift in the contents of the research work: the economics of agricultural production was firmly established on microeconomic theory and econometrics, white research in welfare as well as international tracte became to develop.

Progressively, farm management and agricultura] economics split into diverging directi o ns with the creation of a Farm management association and the journal "Farm Management".

The analysis of the producer and sector response to prices

The main topic of concern for agricultural production economists is a series of questions on the way the producer takes its decisions and the agricultural output is obtained at the level of individual farm and at the aggregate one . regiona] or national. Thus, he has to answer such themes as the combination of the products, the level of output and the combination of inputs ( Colman. Young. 1992). Actually, his ana]ysis can be conducted with two purposes: the first can be defined as normative and the aims at helping the farmer or the policy-maker in its decision-making. T he second can be called descriptive and is more concerned by forecasting. The scope of this section is to foc us on the latter considering that farm management has become an autonomous field which can no longer be included in such a reflection stressing agricultural production issues, while problems of agricultural policy are beyond the scope of this contribution (Bublot, 1974: Ritson. 1977 ).

Even restricted in such a manner, the field covered remains vast because it deals with questions as various as the suppl y of products and the derived input demand, the special isation or the diversification of farms, the role of supply control instruments, the economies of scale. the rh ythm and nature of technical change, or the intensity of production, ... [START_REF] Bonnieux | Quelques orientations de recherche en économie de la production[END_REF].

Relying on microeconomic theory a number of research have progressively brought sorrie light on these issues, the point of view for treating them having varied over the period under study according to progress in theory, methodology, data collection and also according to the concerns of the rea] life, i.e., the economic events which have marked European agriculture.

In the first decades after the second World War the focus is on indiviélual and aggregate supply, what seems logical for a period of economic reconstruction. Yet it appears an early concern on the economies of scale in agriculture and the implications of this issue on agricu ltural po licy.

Highly correlated with the evaluation of supply is how the former deals with risk and uncertainty in its decision-making. First concerned by the production hazards due to climate and biological events. th::

issue develops nowadays in the direction of economic risk and specifically the risk linked with changes in prices. During the period of steady growth encountered by European agriculture until the 80's, some question were progressively questioned such as a more balanced appraisal of the benefits of both the intensification process or the specialisation of farms, while the economic rationale of the continuously growing support for agricultural output has been put under scrutiny with the emergence of agricultural surpluses. The presence of rationing and the emergence of a supply management policy creating production rights have produced research developments on equity and efficiency questions [START_REF] Guyomard | La 11ouvelle instrumenlation de la poliriq11e agricole co1111J11111e[END_REF][START_REF] Piot | Ejfïcacité techniqu e et ga in., potentiels d e p roductivité des explo itarions céréalières.fiw,çaises[END_REF]).

Obviously. these developments have heavily relied o n the use of new theorie:; and methods.

ln 1947, the discovery of methods for solving complex mathe matical problems gave a g reat momentum to the programming tec hniques. During two decadcs. they werc favourecl by :.1gric ultural economists both for farm management purposes and analyse the behaviour of the farmers [START_REF] Chambers | Applied Prod11crio11 Anolysis. A Duo/ Approaclr. C.1mbridgè[END_REF]). From this period on, non parametric methods have developed following the pioneering work of [START_REF] Farrell | The measure111enr of productive ejficimc_y[END_REF]. However, the more ancient econome tric methods early usecl in agri c ultural economics [START_REF] Heady | Agricultura/ Production Functions[END_REF] have known a renewal of interest due to both the introduc tion o f flexible functional forms and the use of duality theory. Lastly, the exten sion of the individual data collection due to the creation and consolidation of the European Farm Accountancy Data Network has also boosted the empirical applications of production theory [START_REF] Hallam | The European Community's FAON/RICA Data Set as a Vehicle for Econometric Suppl y Anal y sis[END_REF] ).

Programming in agricultural production

Directly derived from operational research the programming methods have been extensively

used by agricultural production economists with at least two main objectives : the first concerns farm management and the second issues related to economic planning and forecasting. As previousl y mentioned, farm management is beyond the scope of this contribution which will be focused on the other field in which the programming methods developed during the last decades . It is maybe necessary to firstly remind their specific features. This class of models allow for a representation o f the technology used at the farm level without any a priori assumption on the analytic form of the underlying production fonction. The technology is described by the means of an objective function to be maximised under constraints on the availability of inputs. It exi sts obviously a cl ose relationship between such methods and the econometric-based models, but mathematical programming and particularly linear programming is a tool which permits an easie r treatment o f many varia bles. In a linear programming mode! it is assumed that the productio n of each output can be linearly specified and that these linear production fonctions are additive. The limits o n resource avai lability is also linear. The objective function to be maximised is usually a profit fonction. although it can be re placcd by a cost function to be minimised. On these premise, a numerous cohort of scientists have developed research applying linear programming to aggregate supply and sector modelling while at the samc time was explored its extensions possibilities towards risk or dynamic contexts.

Concerning the first objective, the sector models based on linear programming have been developed in Europe during the sixties and the seventies at the regional and national leve ls. A first generation of models is built for difforent countries under an assumption of fixed demand (Weinschenk et al., 1973 for Germany;Folkesson, 1968, for Sweden), while others are priceendogenous and developed at the French regional level (Tire!, 1971 ), for the European Community [START_REF] Weindlmaier | Trade and Welfare eftects (f various nwrker po/icies and developments in the European Comm11niry[END_REF] or the United Kingdom [START_REF] Thomson | A Microeco110111ic ogriculr11ral s11pply nwdel[END_REF]. Ali these models are designed to study the farm level adjustments to changes in technology and econoniic condi tio ns and the regional and national consequences of these adjustments. As a resu lt of changes in the Common agricultural policy and, lastly, of its reform in May 1992. more recent work:-in the sarne ve in adclress the implication of supply con trol on productions such as cereals . o il seed~ and cat tlc at the regional and national levels. To be noted is the attempt of comparison between France and United Kingdom conducted by [START_REF] Hofstteter | An application of linear programming to mode ! the impacts on agricultural s upply and incarne of the new CAP reforms[END_REF], which provides information o n suppl y response for single products at the level of homogenous agricultural regions.

Ali these models are based on the approach of the representati ve farm set out by S harples ( 1969), which cons ists in an aggregation of s uppl y fonctions representative of groups o f homogenous farms. Among the difficulties encountered when using this method there are bias w hich corne from aggregation. As regards this issue, Boussard ( 1970) reviewed the possibilities of reclucing them , while [START_REF] Thomson | A Microeco110111ic ogriculr11ral s11pply nwdel[END_REF] concluded that they could not be totally eliminated.

The major improvements of linear programming models came fro m the introduct ion of ri sk parameters and the dynamic dimension of the decision process. Each of these problems have deserved specific attention from European scientists over the period under study. The behavio ur of the farmer.

as every economic agent, may be completely altered in the presence of risk and uncertainty . T hus. the si mplifying assumption made concerning the profit -maximising behaviour of the farmer. w hich underlines the building of any linear programming mode! is no longer relevant when risk is taken into account (Norton, Schiefer, 1980). In that case, the results obtained by the optimisation procedure are likely to lead to an overestimation of supply responsiveness. This question has been studied by the means of models introducing a risk dimension based either on the portfolio selection mode! of [START_REF] Markowitz | Portfolio Select io n: Efficient Diversijïcation of l11 vesr111ents[END_REF] or on a safety-first criterion mode!. In Europe, there are few examples of application of these techniques to be reported. They were almost developed during the sevent ies.

while Jess attention seems to have been paid to the risk constraints in the last decades. Accorcl ing to Boussard ( 1970), who compares the interest of the different criteria stemming from these two c lasses of model s, it seems more important to explicit the parameters expressing risk aversion than se lecting the best decision criteria. From that point of view, the maximin approach developed by Mc lnerney ( 1967) couic! be criticised. [START_REF] Hanf | Linear risk progra111ming i11 supply response wwlysis[END_REF] provide empirical evidence about the reduction of certainty bias in supply estimates using a MOT AD approach. They empirically show that estimatecl levels of suppl y are significantly reduced if allowance for risk is made.

In the aforementioned models, time does not play any particular role. although it is an essential dimension governing the producer's behaviour. Thus, including dynamics in the decision problem appears to be of crucial importance. Recursive and dynamic programming developed in the sixties have allowed for dealing with the issue of intertemporal decisions. This class of models and particularly the recursive ones have been developed in Europe for analysing production decision at the sector or regional levels, as in the works of Heidhues(l 966) or Andersen and Stryg ( 1976). As pointed out by Norton and Schiefer ( 1980) these models are well-adapted to the analyse problems uf structural changes, but generally neglect the investment issue.

The eco110111erric approach

In an excellent review, [START_REF]A Re1•ie11• of rire Arts <f Supply Response r'wolysis. Rc,•ie,• or[END_REF] provides a detailed analysis of the state of the art in agricultural su pply response. Our subsequent analysis will therefore rely partly on Colman's work. In face, Colman has well shown the variety of methods that have been used to estirnate the agricultural s upply response emphasising their advantages and drawbacks. A part from its exhaustive p resentation of both programming and econometric approaches usable in production economics. a remarkable feature of Colman's review consists in the well-documented analysis of the methods based on duality theory. lt is noticeable chat until the mid-eighties the great majority of European research ignored the benefits that could be drawn of from the use of the dual approach. although its developments in Northern America. Therefore, this survey is a convenient landmark for our present work.

The econometric researches on production functions, output supply and input demand rely on the assumptions of the microeconomic theory, i.e., that the individual farmer either minimises the cost of variable inputs at a given level of production or maximises its profit. Under these assumptions the output supply and input demand can be estimated through classical econometric methods.

Early in the sixties, the study of agricultural supply response was based on the direct estimation of suppl y functions from time series. The extent to which such studies rely on the theory is limited because it is assumed that the aggregate "national farm" adopts a behaviour analogous with the individual producer's one. They are generally of a single-commodity type, what is a major restriction in a multiple-output sector such as agriculture. It is worth mentioning the work by [START_REF] Rayner | The demand for inp llls a nd the aggrega1e s11pply f 11nc 1io11 for agrirnlr11rc[END_REF].

which provides a n indirect estimation of the aggregate supply fonction for British agriculture. The author concludes on the interest to first estimate an input demand fonction and then derive the aggregate supply function.

Historically, a great number of studies have followed a primai approach using a Cobh-Douglas production fonction as reviewed by Martin ( 1977Martin ( -1986)), but only a few in the European context. In France the works conducted by [START_REF] Brangeon | L'allocation du temps des agriculteurs et des ag ricultrices[END_REF] and Faudry ( 1969) giving estimates derived from aggregate time series or individual cross section data can be quoted.

As a counterpart of its simplicity the Cobb-Douglas function is constraining as far as the s ubstitution elasticities are concerned. Therefore, there have been the developme nt of less constraining or more flexible production fonctions. In a first stage, the Constant Elasticity of Substitution (CES) fonction has allowed for non-unitary substitution elasticities, while progressively flexible functional forms such as the translog , the quadratic or the generalised Leontief have become in favour among production economists. The use of such fonctions provides a more realis tic representation of the technology, although the restricted approximation of the true fonction the y authorise [START_REF] Bonnieux | Quelques orientations de recherche en économie de la production[END_REF].

For the French agriculture. [START_REF] Mahé | Une représentario1111wcroéco110111ique de /'agric11l111re fra nçaise: MAALT (Projections 1990 et variantes)[END_REF] have estimatcd a four-input tran. ,log runction the results give some details on input complementarity and substitutability at the ~ector k\'cl. U'.--ing regional translog production functions [START_REF] Bonnieux | Spécialisatio11 régionale et efficacité de l'agriculrure[END_REF] '.shows the existence or ,ub,titutahility between inputs with the exception of land and capital which are complements.

Among the more recent works on production technology using flexible function in a primai approach, we can quote the study conducted by Thijssen ( 1992). Its interest stems from the comparison of the results of primai and dual approach in the case of a translog production function applied to Dutch farms. According to this study, the results provided by both the prim ai and dual approaches would not be substantially different.

Due to the fact that the primai approach does not allow fo r a proper esti mat ion in the mul tioutput case and because of some estimation difficulties, the use of the duality way has progressively been adopted by an increasing number of European agricultural economists.

The introduction of the dual approach A major step in agricultural production economics is made with the introduction of the dual approach. Rigorously described in 1953 by Shephard, the duali ty relationships between the production function, the profit and cost functions and the transformation function are extensively used since the beginning of the seventies. This expansion is especially due to the work of McFadden and his associates which made possible the application of Shephard intuitions [START_REF] Chambers | Applied Prod11crio11 Anolysis. A Duo/ Approaclr. C.1mbridgè[END_REF]. Firstly considered as a simpler way of treating issues previously addressed through a primai approach.

duality reveals itself progressively as a powerful tool to tackle problems not solvable by the forme r one. as for instance the multi-output case (Paris, Caputo, 1995).

European agricultural economists have taken part in the application of duality theory to agricultural production economics since the mid-eighties. A survey of the studies conducted using dual ity by [START_REF] Guyomard | Applying duality theory in agricultural production economics as a basis of policy decision making[END_REF] gives a comprehensive view of the research concerns addressed with this method. By and large, they are close to those treated by primai approach. a majority of them aims at analysing the economic behaviour of the former. deriving aggregate suppl y and input demand.

or modelling the agricultural sector. Founded on the estimation of cost and profi t functi ons. it is assumed that the associated unknown function is approximated by a flexible functional form which is generally a translog or a quadratic function.

Following Guyomard et al. it is possible to detail some characteristics of the dual models used in the European literature for the last ten years. The first consideration concerns the behavioural assumptions to choose. It depends on the economic situation in which the farm operates (supply management programme for example), the objective of the work and the data availability. In that respect, although a cost-minimising behavior could be considered as appropriate in the context of production quotas, those colleagues who studied the European dairy sector after 1984 have more often chosen a profit fonction (Tiffin. 1991: Thijssen. 1992a and b: El horst. 1993) than a cost one [START_REF] Stefanou | D,-,1w11ic S1rucr11re of Production under a quota: The cas of milk in the Federal rep11hlic of" Cernw11y[END_REF]. Second, among the main purposes generally defined is the i-.-.uc or pricc-.

elasticities and s ubstitutability of inputs and outputs. In the multioutput-multiinput ca"c thcre 1" 110 straightforward answer on the degree of complementarity or substitutability of inputs. given the conditions in which the conditions of [START_REF] Sakai | Sustitution and expansion effects i11 p roduction 1heo1~Y: 1he case ofj oinr producrion[END_REF] apply. In general, it appears that the demand for labour is often inelastic (own-price elasticity of demand less than o ne ) as reported by [START_REF] Boyle | The generation of output suppl_v and i11put demand elosricities fo r a Johansen -type mode! of the Irish ag riculrural secror[END_REF], Tiffin (199 1) or Higgins ( l 986) in con trast with feed and fertiliser which seem 10 be more elastic (own-price elasticity near to or g reater than one) in the reponed studies. Concerning input substitutability , the general case is that inputs substitute for each other with the exception of labour and feed which are complements.

The question of economies of scale is also addressed in some of the studies under review. in so far it is crucial to answer it for policy purposes. In fac t, economies of scale are difficult to measure in the case of multiouptut producing firms, i.e. , in the case of most farms.

The structural approach in economics of production: two examples

While the previous section has been focusing on what may be considered as the "core" of agricultural production econo•mics, it is clear that this research field cannot be reduced to the themes we have just treated. Indeed, as already mentioned in the introduction, a larger definition of the scope of our contribution may be contemplated and it is now necessary to present an other approach of the question unde r study. This approach e mphasi ses w hat may be called "farm economics" and conce ntrate more on the characteristics of the production units and the farming systems. the organisation of the industry and the g lobal c hanges faced by the agricultural sector. These preoccupations are obviously in close link and in comple me ntarity with those described in the previo us section. However, they have often been tackled by more inductive methods and someti mes using the Marxist conceptual framework and, therefore, deserve a specific exposition.

Historically, these issues have been particularly in favour in France [START_REF] Blanc | Quarante ans d 'économie rurale en Fran ce[END_REF] and ltaly [START_REF] Lechi | Réflexions sur l'évol11rio12 de la pensée éco110111iq11e ag ricole en l rolie[END_REF], a nd Jess developed in Germany [START_REF] Schmitt | Etat actuel et évolution de la recherche en économie rnrale dans la R épuhlique fédéra le allemande[END_REF] and in the United Kingdom (Colman , 1989). The institutional reasons why French scientists devoted a sig nificant part of thei r work to that kind of research for two decades ( 1970-1 980) have been previously exposed and may be reminded as follows [START_REF] Petit | ls the re a Fren ch school of agriculr11ral Eco110111ics ?[END_REF]. In the late sixties, there was in France a widespread question in g on the neo-classical paradigm and the answers it provided when analysing the changes occurri ng in the French agriculture: were the farmers actually profit-maximisers'? How could the heterogene ity of farmers' situations and objectives be taken into account? Was not the Marxist approach more efficient in analysing the changes in the sector, .... ? These questions led a majority of French agricultural economists to develop work of inductive inspiration, which among others emphasised the specificities of agriculture as compared to other industries. Although the debate was not exac tly developed along the same premise in ltaly, there was also a stream of research questioning the appropriateness of the neo-classical paradigm to agriculture. It may be said that in other European countries. some economists also agreed with the idea that the standard microeconomic theory was not able to answer all the issues raised by the observation of the sector or the farms changes. without fundamental ly question it (Colman, 1989;[START_REF] Schmitt | Etat actuel et évolution de la recherche en économie rnrale dans la R épuhlique fédéra le allemande[END_REF]). Because it is not possible in this con tribution to consider a review of ail the fields related to production economics on which research has been conducted

following this Stream, we will concentrate on two signifi cant examples regarding the nature of the farm firms in Europe and the consequences of this situation on some aspects of the production process.

One of the issues investigated at most concerns the agricultural structures and the way farms was accepted in France by other authors for building their own analyses, no factual evidence of its validity was brought [START_REF] Bartoli | Sur le.fonctionnement de la référe11ce marxiste[END_REF][START_REF] Cavailhès | Bilan de quinze ans de leadership marxiste[END_REF]. Taking part in the debate on the size distribution of farms, the arguments of [START_REF] Boussard | la notion d 'économie d'échelle dans 1111 secteur mufti produits et !'al'enir de l'agriculture[END_REF] were of a completely different nature.

Having based its demonstration on the production theory, he showed that the quasi-absence of scale economies in agriculture did not provide any possibi lity of "industrialisation" of the sector, the observed discrepancies in size depending on the differences in profitabil ity. As a conscquenoe. ,,•hen economies of scale emerge in a specific agricultural production process through L echnical change. thi, process is taken over by an other industry. what hampers the farms operating this specitïc prooes, to increase the ir size. In a more recent paper. Schmitt ( 1991) While some agricultural economists concentrated the ir a tte ntio n upon the specific organisation of the industry in small and medium-sized production units, other tackled a correlated issue often neglected by the neo-classical approach, i.e ., the relations existing between the holding a nd the household operating it. Instead of considering the produce r as a standard profit-maximiser agent. this line of research e mphasises the analysis of the farm house hold as a factor suppl ie r and the consequences o f this situation on the produc tion decision-making at the farm level. ln an ex tcnsi,•e review, [START_REF] Gasson | Tire Fam, os o Family Business: a Review[END_REF] points out the great numbe r o f issues raised by the interacti on of a household and a unit production within the individual farm. Among these issues. it seems ,,•onh stressing those re lating to the labour and capital supply to the farm by the household.

As far as the family labo ur supply is concerned, the quasi-fixed nature of this factor leads 10 a series of considerations on the way the farm household can combine it with the othcr factors of production according to the horizon envisaged. Faced with a factor desequ ilibrium charactérised by a labour surplus, the ho usehold can e ither try to increase the size of the ho lding ( Upto n. Ha\\'orth.

1987) or seek for its a llocation between on-farm and off-farm employment. ln the case o f a labour deficit, both hiring labour or inc reasing the quantity of labour supplied by the fam ily can be en,•isagcd ( Brangeon. Jegouzo. 1990) although it ha been shown chat these two kind of labour are not pcrfectly substitutable (Ye rmersch, 1989). How fami ly labour is d istributed betwee n on -farm and off-farrn employme nt and the related question of farm household pluriactivity was early on the research agenda in Europe to examine in w hic h direction part-time farming would evo lve (Brun et a l. . 1976).

Although largely analysed, the issue is far from being definitely solved in so far family farms reveal the mselves as being extreme ly flexible in adjusting their labour force to economic necessities ( Bryden e t a l., 1992). On the other hand, Gasson et al. underline in their review the fact that the d ifficulty in explaining the way family la bo ur is allocated in family farms may corne from a n insufficie nt attention paid to the farm househ old as compared with the holding. This statement seems to be of far-reachin g e ffect, obviously because the emphasis has been centrally put o n the produce r dec ision-making .

while it was clcar that it could not be independent of the household decision-making. Thi~ a11i1udc.

re levant when the s urvi val of the fann household depends heavily or exclusively on the income clr;mn from 1he farm activity and. in fact. it has been shown the capital supply to 1he fo.rm was gi\cn a higher priority by the ho usehold than the family needs.

Concluding remarks

The period under revie w has been characterised by an impressive development of researc h in agricultural production economics which a llows for a better appraisal of the way European agriculture reacts to changes in its economic e nvironment. From our point of view. the progress made are due to:

first, the importance now g iven to solid theoretical bases in the education o f European agricultural economists, what was not always the case a few decades ago: second. the develo pme nt of the 1heory of the firm and, conseque ntly, an enlarged range of actual cases that can be treated in an analytica l way inc luding risky s ituations, production quotas or interactions between ho useholds a nd farms:

third, the availability of analytical tools and relevant data for applying them: fou nh. the gcneral agreeme nt among the community of agricultural economi sts o n the prob le ms to put on the research agenda, with the conseque nces of the CAP reform o n agricultural s upply and the environme nt al issues.

While the three first ite ms have been develope d in the core of the paper. it is wonh e mphasising how the CAP reform has induced some new researc h avenues in production economics.

Concerning the supply issue, it seems clear that European agriculture has now e ntered a ne w e ra characterised by multiple bounds constraining its future. The implications for research are impo rtant.

A growing proportion of policy instrume nts used in the ne w CAP apply to quantities . instead of a iming to c hange the price relationships. This generalised rationing syste m leads to ri gidities and allocative inefficiencies. which need to be studied. On the other hand. the sel of producing right~.

combined with the eut in prices, give significant incentives to reduce technical incftïciency. and. then.

L o increase the intensity of production. whi lc its decrease is looked for as a major goal of the CAP.

The signais provided by the European agricultural policy appear to be confusing. From the analytic point of view, they introduce a more complex set of situations than in the past and invite agricu ltural production econornists to largely renew their approaches.

With a supplementary degree of complexity and in direct relation with these question!s. there is the entering of environmental problems in agricultural production econornics. The concerns on some negative consequences of intensive agriculture in Europe are ancient. However. the reality of the damages was not frequently taken into account until recently in most Europe an cou ntries ( Mahé. Rainelli, 1987). For a while, agricultural economists also neglected these aspects which are now of general concern among the profession. lt becomes clear that agricultural production has 10 be analysed including this environmental dimension, in considering pollution as an undesirable output and environment as an endowment to be preserved given the social cost of its destruction. even at the expense of a decline in the intensity of production. In that respect, there is a room for an en large ment of the work including in the analysis of the sector response the existence of externalitie!s generated hy agriculture as well as the instruments to take them into account.

  of agricultural production in an historical and institutional context: the case of France and The United Kingdom 3. The analysis of the producer and sector response to prices 3.1 Programming in agricultural production3.2 The econometric approach 4. The structural approach in economics of production :

  Nevertheless. Stefanou et a l. (1992) andThijssen (1992 a) have tried to test the nature of scale re turns in the case of respectively German and Dutch dairy farms: in both cases the hypothesis of constant returns is rejected. On the contrary, increasing returns are found. This conclu sion is inconsistent with the assumed context of perfectly competitive firms, but supports an other result established by Ye rmersc h ( 1990). who demonstrate the existence of local economies of scale in cereal farms and obviously contradicts the hypothesis of an absence of scale economies in agriculture.

  change in the long run. The origin of this concern was founded on the tremendous process of adj ustment faced by the European agriculture since the last World W ar. Could a change in the organisation of the agricultural sector and a decline in the share of family farms be forecast'? Did an optimal size of farms exist? Which farming system would best fit the changes ... . ? ln the late sixties these themes were rendered even more topica! by the release of the well-known Mansholt report. the conclusions of which designed a dramatic change in the picture of the European agriculture of the next twenty years and pied for a vigourous European structural policy. Such a position on a crucial matter renewed the debate on the existence of scale economies in agriculture and the compared advantages of small and large farms. In the seventies this debate was boosted on theoretical bases both by Marxist and neo-classical economists. Rather surprisingly, when the Marx's prophecy on the future of agriculture in industrialised countries is borne in mind, a prominent Marxist scientist.[START_REF] Servolin | Aspects économiques de l'absorption de l 'agriculture dans le mode de production capitaliste[END_REF], argued that the organisation of European agriculture on the basis of a spec ific production mode ,the "S mall Merchant Production" had hampered capitalism to enter the sector and woul d continue to do so in the future. Due to fundamental obstacles such as the individual ownership of land by the farmers and the complexity of a non completely mastered biological process. family farming was due to remain the dominant kind of organisation of agriculture in Europe. Although thi s thesi~

  adds an argument in the debate introducing the family dimension of most farms. He stresses the persistence of medium-sized farms in European agriculture as a consequence o f their efficiency in combining agricultural and household p roduction. According to him, this situation cornes from a number of considerations: first the internai organisation of the farms allows for lower tran saction costs than in hired labour farms. second. labour-saving technologies have increased the labour capacity of farm househo ld favouring a more efficient mixing o f on-farm and off-farm labour a nd increasing the income of family farms relative ly to other farms.Finally. Schmitt argues that these comparati ve advantages o f the family farms should persist in the future and allow for their survival at least in the medium term.

  Researc h o n the savings behaviour confirmed in the seventies the high rate of saving achieved by the agricultural household for business purposes and the limits which were o fte n imposed to the family consumption (Harrison. I 989: Léon. Rai ne lli. 1976). Research o n both the capital and the labour supply o f the farm household know a current re newal with the household modelling approach ins pired by the works of Singh et al.. 1986: and Nakajima ( 1986). B ased on the theory of the firm this vein of literature fo llows from the afore mentio ned e xistence of the production and consumptio n decis ions to be jointly taken by the agricultural household. A number of studies question the hypothesis of recursivity assumed in the early agric ultural mode ls as regards labour supply and demand o n the farm and conclude o n the influence of the production decisions o n consumptio n decisions and vice ve rsa (Ca illavet e t al.. 1994 ). A s a conseque nce, non-recursive models sho uld better fit the ac tuai behav iour o f the household tha n recursive ones . The interaction of investment a nd consumption dec isio ns can be studie d using an analogous conceptual framework, what allows for a re newed apprai sal o f issues such as savings and financing in relation with production decisio ns ( Phimiste r. 1995).

  Due to that. our contribution presents Ob\'ious limit:-and must be considered only as a first attempt in reviewing the European literature 111 agricultural production economics and a first work. which colleagues are invited to improve.The present contribution is organised as follows. In the second section. the historical and institutional context of the development of agricultural economics is presented comparing France and the United Kingdom. The third is devoted to the progress made in analysing the producer•s behaviour u sing microeconomic theory. Then, some examples of research based on a « s truc tural » approach are discussed. Finally, some concluding comments and research avenues are proposed.

Institut National de la Recherche Agronomique. Département d'Economie et Sociologie Rurales Rennes. Franoe Review of Agricultura/ Economies. the Jo11mal ofAgric11/t11rol Eco110111ics. Eco110111ie R//rnle ,111d the Cahiers d'Eco110111ie et Sociologie Rurales.


Philippe Label

Marie-Anne Lelu

come

Germination and plantlet frequencies of hybrid larch somatic embryos in relation with their endogenous ABA levels

Among the conifers, the hybrid between European and Japanese larches has a great potential for reforestation programmes due to its fast growth and good wood quality. Somatic embryogenesis allows the production of illimited number of genetically identical propagules which represents the best production tool for hybrid larch. Maturation, leading to the development of cotyledonary somatic embryos, has been improved by the use of exogenous abscisic acid (ABA) in the culture medium. Using an enzyme-linked immunosorbent assay (ELISA), we measured the changes of ABA content in larch somatic embryos during the maturation process. Endogenous ABA level of somatic embryos cultured in presence of exogenous ABA (60µM) dramatically increased during maturation reaching its maximum at the end of the culture (week 5). The highest germination and plantlet frequencies (90% and 70% respectively) were obtained with somatic embryos matured for 3 weeks. Extension of the maturation duration from 3 to 4 and 5 weeks resulted in a significant decrease in both germination and plantlet frequencies. Our results show a clear correlation between endogenous ABA levels in somatic embryos and their latter germination and plantlet formation abilities. In consequence, we hypothesize that endogenous ABA levels of somatic embryos were responsible for these inhibitions. Further works are on progress to test this hypothesis. This the first report dealing with hormonal analyses during somatic embryo maturation and evidence of correlation between endogenous ABA content and further growth abilities of larch somatic embryos.

  http://www.inra.fr/prodinra Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript GERMINATION AND PLANTLET FREQUENCIES OF HYBRID LARCH SOMATIC EMBRYOS IN RELATION WITH THEIR ENDOGENOUS ABA LEVELS. P. LABEL & M-A. LELU Institut National de la Recherche Agronomique, Station d'Amélioration des Arbres Forestiers, Avenue de la Pomme de Pin, F-45160, Ardon, FRANCE.


J L Barry

Christine Hoebler

F Kozlowski

Stéphane Guéneau

Cell wall polysaccharides determination : comparison of detergent method and direct monomeric analysis

teaching and research institutions in France or abroad, or from public or private research centers.


est destinée au dépôt

  The role of cell-wall polysaccharides and alpha-galactosides in the flatus induced by the comsumption of a legume seed (lupin) in the rat Martine Champ, J.L. Barry, C. Bonnet, Serge Bérot, J. Delort-Laval To cite this version: Martine Champ, J.L. Barry, C. Bonnet, Serge Bérot, J. Delort-Laval. The role of cell-wall polysaccharides and alpha-galactosides in the flatus induced by the comsumption of a legume seed (lupin) in the rat. 6. Journees d'Etudes Sciences des Aliments, Association Francaise de Nutrition, May 1989, Nantes, France. hal-02849012