- Email: [email protected]
Prospects for low cyanide cassava in Nigeria
Specialfocus/Viewpoint
livestock exporters undertake their own selling. The EEC intervention facility has, however, been of particular importance to the beef industry over recent years and sales of intervention beef have become a significant feature of Irish beef exports. In 1981 however, the extent of intervention purchasing has declined, due to the scarcity of animals for slaughter and the buoyancy of the beef market generally. For the other food products, the level of direct government action has been smaller. The national export promotion board (Coras Trachtala) provides assistance towards market research and development and the promotion of export outlets for all Irish manufacturing industries, including processed food products. The two government departments most directly concerned - the Department of Agriculture and that of Industry, Commerce and Tourism - have a detailed involvement with the food industry both in production and marketing.
The great changes that have taken place in food processing in Ireland over the past decade are hardly likely to be repeated. There are, of course, still some plants which need to be modemized; others may not remain viable and will either cease to operate altogether or be absorbed into a larger operation. The development of the food industry will be concerned with further rationalization, with streamlining its operation and the creation of new outlets for new products. The breakthrough to modem technology has, however, now been largely completed and, while further will improvements in technology undoubtedly be developed, there are no entirely new processing revolutions to replace that which is now well underway. The adoption of capital intensive processing methods has created a modem food industry in Ireland with the capability of a sustained output of high quaity products. New products, new methods and new markets are now
commonplace. Research and development work is basic to the further development of the industry. The volume of raw materials will expand as the production potential of Irish agriculture is more fully exploited. The degree of domestic processing will grow. Ireland has entered the 1980s with a food industry geared to current needs and ready to meet new opportunities as they arise. E.A. Attwood, Department of Agriculture, Dublin, Ireland
‘C. Cahill, ‘Employment and value-added in the dairy manufacturing sector, 197980’, paper presented to the Agricultural Economics Association of Ireland, 1981. 21ndustrial Development Authority, Annual Reports, 1975-79, Dublin.
‘Beef Packing and Processing: A Development Study, Industrial Development Authority, Dublin, 1977.
Viewpoint Prospects for low cyanide cassava in Nigeria Sweet (low cyanide) and bitter (high cyanide) varieties of cassava are compared from the viewpoint of their production, pmcessing and consumption in Nigeria. With this information, the costs and benefits of breeding higher yielding sweet varieties are calculated. A newpmcessing method, currently in use in one region of Nigeria, is examined for its likely impact on the demand for sweet cassava.
Nigeria is a major world producer and cassava (Munihof consumer of es&en& Crantz), producing about 10.8 million tonnes per year, or about 9% of total world output. ’ There is virtually no export of the crop from Nigeria. Two types of cassava are grown: ‘bitter’ and ‘sweet’. Bitter cassava is the most common. It is high in cyanide content, while sweet cassava is low in cyanide. * Bitter cassava generally requires processing, to reduce the cyanide level, before being eaten.’ However inadequately processed bitter cassava can cause severe health problems. It FOOD POLICY August 1981
has been linked with tropical ataxic neuropathy, goitre and cretinism.4 One possible approach to reducing the health hazard and the resources used in processing would be to promote the use of sweet cassava. Currently obtainable yields of sweet cassava are generally low, but a plant breeding programme could change this. Would a higher yielding sweet cassava be accepted by growers, processors and consumers, who currently utilize the bitter type? An even more fundamental question is whether users recognize clearly the existence of the two types. If so, what factors determine their choice
between the two and how do the production and processing characteristics of the two types compare? Two aspects warrant special attention. One is the potential rodent problem. Many scientists have expressed the belief that rodent damage on sweet cassava is high. The second aspect is the potential effect of a new ‘screw press’ processing system on the acceptability of higher yielding sweet cassava. The study was launched to explore these issues and to make an overall assessment of the consequences (benefits) of breeding a high yielding sweet cassava. In the final section of the article, a comparison is made between these benefits and the costs of breeding a high yielding sweet cassava, within the context of the cassava breeding programme at the International institute of Tropical Agriculture (IITA). The methodology of the study consisted of three components: a survey to elicit information on the growing, processing and consumption of sweet and bitter cassava types; an experiment to gauge the effect of a new processing method on the likely 197
Viewpoint
acceptability of high yielding sweet cassava; and, a cost-benefit analysis of the IITA sweet cassava breeding programme. Forms of cassava production, processing and consumption depend, amongst other things upon geographic location and ethnic origin. Data were collected by administering a questionnaire to a sample of 122 farmers, selected from eight villages - two in each of Anambra, Bendel, Ogun and Kaduna States in Nigeria. Village selection was based upon accessibility to markets and upon the (high) degree of cassava production and consumption in the village. The objective was to compare the efficiency of two processing methods in terms of reduction in product cyanide levels. From a village (Aliomisi, near Agbor) where the screw press processing method was in operation, two samples of fresh sweet cassava and two samples of fresh bitter cassava were harvested and processed into gari. Two processing methods were used on each sample. The traditional processing method involves grating, fermentation for three days, while heavy rocks squeeze out moisture, and finally, frying. The other method used was the squeeze press which is similar except that a mechanical process replaces rocks in the moisture removal process. This process, and thus also the ferfrom mentation time, is shortened three or four days to one day. Finally, cyanide levels were measured in the laboratory for all of the fresh and processed samples using an enzymatic assay.5 One measurement was taken on each sample, but in the second (backup) sample, only free cyanide was measured (ie not free-plus-bound cyanide).
Results and discussion A critical result from the survey is that, without exception, farmers are aware of the two types of cassava. Farmers categorized the type(s) which they were growing and samples were taken of each type. Cyanide content of the samples was measured during the sodium picrate leaf test.6 While this test does not permit a precise quantification of cyanide, it does enable a classi-
198
-Table1.Relativeimpottanceofsweetcasszwa ------
invariousr8giansofMgerii3.
!sweetcassava state
Anarnbra Ekndel Nun Kaduna -
fication to be made into one of three high. categories - low, medium, Seventy-six per cent of the cassava categorized by farmers as sweet was, in fact, in the low or medium cyanide categories, while 81% of bitter cassava was found to be high cyanide. Farmers’ recognition of the low and high cyanide types is (surprisingly?) good. It is, of course, a prerequisite for the susbtitution by farmers of sweet cassava for bitter that they perceive differences between the two types. Cassava is an important crop in the southern states of Anambra, Bendel and Ogun States, while it is less important, but still significant in the north (Kaduna).’ No published information is available on the relative importance of the sweet and bitter types in each region. Table 1 shows that relatively small amounts of sweet cassava are grown in the south, while the cassava grown in the north is almost exclusively sweet (columns 1 and2). Although, the total amount of sweet cassava grown in the south is small, almost half of the farmers in two southern areas grow some sweet cassava (column 3). Sweet cassava is relatively more popular in areas where yams are not grown, suggesting that consumers are using the sweet cassava as a substitute for yam in their diets. Southern consumers eat processed cassava - mainly gari. Gari can be made from both bitter and sweet cassava. As the yield of bitter cassava is recognized by all farmers to be higher than that of sweet, the bitter is the preferred type. Most of the sweet cassava grown in the south is eaten unprocessed, although it may be boiled. In Kaduna State, the sweet cassava is similarly eaten unprocessed. Farmers in all regions recognize and avoid the health problems associated with eating bitter cassava in an unprocessed form. Of the twenty-six southern growers
percentaoeof fam==gmwing only 8weet cassava
0 0 3 97
e=+ bittercassava inagivenyear 0 47 45 3
who had tasted gari made from bitter and from sweet cassava, all stated that there was no taste difference. However, the survey results showed that processing time for making gari in the traditional manner cannot be shortened with sweet varieties. Thus, there seems to be no advantage or disadvantage to be gained by processors in substituting sweet cassava for bitter. No agronomic reasons were unearthed for the choice between bitter and sweet types. Farmers who grow both, use the same production techniques for each, and regard pest problems as similar. As mentioned earlier, fears had been expressed by cassava breeders that sweet cassava might be preferentially attacked by rodents, with resultant large losses. To evaluate these fears, a special survey of 108 growers was conducted, 11 of whom had experienced rodent damage and had grown both sweet and biter cassava over the previous five years. Thirtyseven per cent stated that rodent damage to bitter cassava was worse, while 26% stated that damage to sweet cassava was worse. The remaining 37% perceived no difference in damage between the two types. Assuming a binomial distribution, the 5% confidence limits of the three groups do overlap and the conclusion is drawn of no difference between rodent damage on sweet and bitter cassava.
Screw press The cyanide level of fresh roots, which had been identified by growers as sweet and bitter respectively, is shown in Table 2 (samples A, Aa, B, Ba). The growers judgement of the cyanide level is verified. Contrary to expectations, however, the screw-press processing method is no less efficient than the traditional method in reducing cyanide (compare sample C with E; D with F).
FOOD POLICY August 1981
Viewpoint
The speed of the screw-press method, which reduces fermentation time to one day, was expected to result in gari with a high cyanide level, since the fermentation process was thought to be the prime reason for the low cyanide content of gari.” The main conclusion in relation to sweet cassava is that widespread adoption of the screw press is not likely to result in increased demand for sweet cassava.9 Even if sweet cassava is developed which yields the same as the bitter types, there is no apparent incentive for gari consumers or growers to switch to the sweet type. Nor are there any apparent costs - equal yielding sweet and bitter types would be preferredequally. A higher yielding sweet cassava would confer benefits on those farmers who grow, and the consumers who eat, sweet cassava. A rough est~ation of these benefits was made as follows, Total cassava production was obtained” and then the proportion of sweet cassava in each state was calculated by extrapolation from the regional figures of Table 1, Column 1. Anambra, Bendel and Ogun were assumed to represent the East Central and Western regions of the south respectively, while Kaduna was assumed to represent the whole northern region. “Middle Belt’ regions were estimated to produce equal pro~~ions of sweet and bitter cassava. On this basis, the total amount of sweet cassava grown in Nigeria was
determined to be about 35OooOtonnes. Since the base yield of sweet cassava is so low the potential improvement is higher, and a doubling of existing farm yields seems quite feasible with improved varieties. At a price of 1Ocper kilo for fresh roots, the annual gross benefit resulting from a breeding programme would be $35 million. The only Iikely cost increase is in labour for harvesting (about 7 mandays per tonne), totalling about $2 million. With consumption of cassava in Nigeria expected to rise sharply by 1990, in tine with population, ’ * no fall in the cassava price is expected to result from the increased yields of sweet cassava. success The total costs of conducting the IITA cassava and sweet potato programme has been about $lm, since it began in 1973. However, a relatively small proportion of the total has been spent on the low cyanide project. If the project is continued at current levels (about $lOOllO per year), the probability of ‘success’ (doubling of sweet variety yields) is almost 100% by the year 1986. Even allowing for the fact that it will take some years for the varieties to be accepted by farmers, the benefit-cost ratio is clearly enormous (regardless of whether all costs since 1973 are included, or only the ‘marginal’ costs of continuing the sweet cassava project from 1980-1986). The investment of re-
search resources into improving yields of sweet cassava has been, and continues to be, well worthwhile. Farmers make the choice between sweet and bitter types of cassava, not on the basis of agronomic differences, but on the basis of the end-use to be made of the cassava. Bitter cassava is grown where the end-use is gari, or some other processed product, which removes most of the cyanide. Bitter cassava is preferred, not because of an inherent taste advantage over sweet cassava, but because of its comparative yield advantage. Sweet cassava is grown where there is a taste/traditional preference for it. The breeding of a low cyanide cassava variety with yields comparable to improved bitter varieties is a feasible and practically achievable goal, at modest cost. The breeding of such varieties would have little or no impact upon and growers, processors consumers presently using bitter varieties, except in areas where processing is inadequate in reducing cyanide levels (no such areas were identified in Nigeria). Improved sweet varieties should be readily embraced by farmers currently growing sweet types. The potential benefits from the breeding of improved low cyanide cassava varieties in Nigeria are extremely high relative to the cost. Even after taking into account the pressure on cassava research resources to explore other potentially high payoff areas, continued investment in a high yielding, low cyanide cassava is warranted.
Sample Fles
Bound
Total
114.4 120.6
23.2
137.5
7.0 9.0
8.5
15.5
for f day
3.8 3.1
0.7
4.5
Sweet type after processing by screw-press methodforlday
3.0 5.8
0.8
3.8
Bitter type after prccesicg by trac.Mnal method for 3 days
12.5 11.3
0.0
12.3
Sweet type after pfccessing by tradiial method for 3 days
12.0 10.2
0.0
Il.5
Grated bier fresh root
Bittertype after pnrcessingby screw-press
FOOD POLICYAugust 1981
D.H. Oben, ENSA, Yaounde, Cameroon KM. Mew international Institute of Tfopical Ag~c~l~~e, Ibadan, Nige~a The
authors
wish
to
thank
Or
E.N.
Maduagwu for his analysis of root and product samples for cyanide, and Dr. H.C. Knipscher for comments on earlier drafts. IFAO, 1978 Production Yearbook, Rome, 1979. Some studies attribute sweetness or bitterness to sugars and other chemicals. White these may play a part, cyanide level seems to be the key factor. 3E.N. Maduagwu, ‘Cyanide content of sari’.
199
Viewpoint
Toxicology Letters, No 3,1979, pp 21-24. “F. Nartey, Manihot Esculenta (Cassava): Cyanogenesis, Ultfastfuctufe and Seed Gefmination, Munksgaad,Denmark, 1978. %.D. Cooke, A.K. Howlandand SK. Hahn, ‘Screening cassava for low cyanide usinn an enzymatic assay’, Experimental Agri: culture, Vol14. 1978, DD367-372. “S. Sadik, O.U. Ok&ke and S.K. Hahn, Screening fof Acyanogenesis in Cassava, Technical Bulletin No 4, IITA, lbadan, Nigeria, 1974. ‘Federal Office of Statistics, Rum/ Eco-
nomic Survey, 1977/78, ProvisionalReport on Crop Estimates, May 1979. 8Washing,drying,crushingare alsothought to reduce cyanide levels. ‘It should not automaticallyba concluded that the screw-press processingmethod is preferable to the traditional processing method. Some consumers expressed reservationsabout the taste and storability of gari made by this method. l*OP tit, Ref 7. tlWorld Bank ~nfi~nt~l Report, Nigeria Ag~cu~u~ Sector Review, Vol II, 1979.
Political pressure and the role of the economist This article is a reply to the comments of Professor van den Noort published in the May 1981 issue of Food Policy.’ Any contribution from Piet van den Noott is at all times stimulating and his recent comments were no exception. Furthermore, his comments are welcome since he examines the collation of themost jmpo~ant pillar of cogent economics policies in the Eu~pean ~rn~n~ -the CAP.
Briefly recapitulating some of the main points raised in the article, the point of departure is the question of the problems of choice as raised in economics textbooks. Logically, following this observation, van den Noort stresses that it is necessary first to know the Community’s social welfare function (SWF) if one is to make a realistic choice among the different plans put forward for the reform of the CAP. Reference is then made to the scrutinization of alternative policies by model simulation, ‘B la Tinbergen’, to arrive at ‘optimum policy determination’. At this point, reference is also made to the element of ‘intuition’ although the author does not regard this as being scientific. Moving to the world of politics, the author enters the realm of groups, coalitions and compromises. Professor van den Noort observes that at ‘least three political categories are involved, the cabinet, parliament and the bureaucracy’. He stresses the importance of this last group which, to some degree appears to be great because (though not exclusively) ‘without perfect knowledge it is not possible to calculate objective priorities and decisions’. This group, according to the author, possesses much knowledge. In his conclusions, the author stres-
ses the dangers of the consequences of an absence of a Community SWF and even goes so far as to state, ‘we can no longer accept the Tinbergen theory of economic policy as a description of reality but only as an intellectual exercise’. Finally, he examines the special case of a change in the EEC dairy policy referring to the different results gained when 68 Dutch agricultural economists were asked for their opinions - using the same model. In the present framework of the EEC, at the level of the EEC Council, the author says ‘compromises and trade-offs might be expected’, and he ultimately questions the place and pretentions of economists.
Lung cancer I shall start my reply with my colleague’s closing observation or question where he queries the position of economists. To me, the position of the economist is like that of a medical practitioner who tells a patient that he will get lung cancer if he continues to smoke 100 cigarettes a day. The patient nevertheless continues to smoke the same quantity of cigarettes and subsequently dies of lung cancer. This fact, however, does not remove the role of
the medical practitioner, but rather reinforces the joint roles of education and information. Such, I believe, is the role of the economist and the relevance of the theory of economic policy in relation to the CAP. Theory in itself is mainly a yardstick indicating optimum situations and/or targets. However, to give it rn~~urn relevance in real life it may be useful to return to the classical tradition of political economy rather than remaining in the narrower field of econometrics. However, I shall return to this consideration towards the end of my reply. Turning to the specific case of the CAP, we enter, at the same time, a world of everyday reality (since we must all eat food) and extreme technical complexity (as manifested in the fo~ulation and application of even the most simple a~cultural policies). Immediately, we also encounter political groups, as mentioned by Professor van den Noort. However, the most important group, especially in agriculture, has gone umnentioned. This group is the ‘lobby’. In the EEC, the most important lobby is the agricultural one, followed by the textile lobby and then by other manufacturing lobbies. The consumer lobby comes right at the bottom of the list and is practically unimpo~ant. The agricultural lobby has the most immediate and direct access both to the relevant ministers at the national level, as well as to the Commission and other bodies in Brussels, Luxemburg and Strasbourg. Hence, straddling the world of economic theory and reality, a ‘public preference welfare group’ has arisen with the EEC. This fact appears to be the missing link in economic theory and in my colleague’s ~ont~bution. It is this variable which should be included and given greater weight in any model. This does not remove the possibility of haggling and compromises when the Council of Ministers meet for their annual price-fixing marathons. But, it does mean that these sessions are, in advance, strongly influenced by the farmers themselves rather than by other interest groups. What should be done then to make the theory of economic policy more FOOD POLICY August 1981
livestock exporters undertake their own selling. The EEC intervention facility has, however, been of particular importance to the beef industry over recent years and sales of intervention beef have become a significant feature of Irish beef exports. In 1981 however, the extent of intervention purchasing has declined, due to the scarcity of animals for slaughter and the buoyancy of the beef market generally. For the other food products, the level of direct government action has been smaller. The national export promotion board (Coras Trachtala) provides assistance towards market research and development and the promotion of export outlets for all Irish manufacturing industries, including processed food products. The two government departments most directly concerned - the Department of Agriculture and that of Industry, Commerce and Tourism - have a detailed involvement with the food industry both in production and marketing.
The great changes that have taken place in food processing in Ireland over the past decade are hardly likely to be repeated. There are, of course, still some plants which need to be modemized; others may not remain viable and will either cease to operate altogether or be absorbed into a larger operation. The development of the food industry will be concerned with further rationalization, with streamlining its operation and the creation of new outlets for new products. The breakthrough to modem technology has, however, now been largely completed and, while further will improvements in technology undoubtedly be developed, there are no entirely new processing revolutions to replace that which is now well underway. The adoption of capital intensive processing methods has created a modem food industry in Ireland with the capability of a sustained output of high quaity products. New products, new methods and new markets are now
commonplace. Research and development work is basic to the further development of the industry. The volume of raw materials will expand as the production potential of Irish agriculture is more fully exploited. The degree of domestic processing will grow. Ireland has entered the 1980s with a food industry geared to current needs and ready to meet new opportunities as they arise. E.A. Attwood, Department of Agriculture, Dublin, Ireland
‘C. Cahill, ‘Employment and value-added in the dairy manufacturing sector, 197980’, paper presented to the Agricultural Economics Association of Ireland, 1981. 21ndustrial Development Authority, Annual Reports, 1975-79, Dublin.
‘Beef Packing and Processing: A Development Study, Industrial Development Authority, Dublin, 1977.
Viewpoint Prospects for low cyanide cassava in Nigeria Sweet (low cyanide) and bitter (high cyanide) varieties of cassava are compared from the viewpoint of their production, pmcessing and consumption in Nigeria. With this information, the costs and benefits of breeding higher yielding sweet varieties are calculated. A newpmcessing method, currently in use in one region of Nigeria, is examined for its likely impact on the demand for sweet cassava.
Nigeria is a major world producer and cassava (Munihof consumer of es&en& Crantz), producing about 10.8 million tonnes per year, or about 9% of total world output. ’ There is virtually no export of the crop from Nigeria. Two types of cassava are grown: ‘bitter’ and ‘sweet’. Bitter cassava is the most common. It is high in cyanide content, while sweet cassava is low in cyanide. * Bitter cassava generally requires processing, to reduce the cyanide level, before being eaten.’ However inadequately processed bitter cassava can cause severe health problems. It FOOD POLICY August 1981
has been linked with tropical ataxic neuropathy, goitre and cretinism.4 One possible approach to reducing the health hazard and the resources used in processing would be to promote the use of sweet cassava. Currently obtainable yields of sweet cassava are generally low, but a plant breeding programme could change this. Would a higher yielding sweet cassava be accepted by growers, processors and consumers, who currently utilize the bitter type? An even more fundamental question is whether users recognize clearly the existence of the two types. If so, what factors determine their choice
between the two and how do the production and processing characteristics of the two types compare? Two aspects warrant special attention. One is the potential rodent problem. Many scientists have expressed the belief that rodent damage on sweet cassava is high. The second aspect is the potential effect of a new ‘screw press’ processing system on the acceptability of higher yielding sweet cassava. The study was launched to explore these issues and to make an overall assessment of the consequences (benefits) of breeding a high yielding sweet cassava. In the final section of the article, a comparison is made between these benefits and the costs of breeding a high yielding sweet cassava, within the context of the cassava breeding programme at the International institute of Tropical Agriculture (IITA). The methodology of the study consisted of three components: a survey to elicit information on the growing, processing and consumption of sweet and bitter cassava types; an experiment to gauge the effect of a new processing method on the likely 197
Viewpoint
acceptability of high yielding sweet cassava; and, a cost-benefit analysis of the IITA sweet cassava breeding programme. Forms of cassava production, processing and consumption depend, amongst other things upon geographic location and ethnic origin. Data were collected by administering a questionnaire to a sample of 122 farmers, selected from eight villages - two in each of Anambra, Bendel, Ogun and Kaduna States in Nigeria. Village selection was based upon accessibility to markets and upon the (high) degree of cassava production and consumption in the village. The objective was to compare the efficiency of two processing methods in terms of reduction in product cyanide levels. From a village (Aliomisi, near Agbor) where the screw press processing method was in operation, two samples of fresh sweet cassava and two samples of fresh bitter cassava were harvested and processed into gari. Two processing methods were used on each sample. The traditional processing method involves grating, fermentation for three days, while heavy rocks squeeze out moisture, and finally, frying. The other method used was the squeeze press which is similar except that a mechanical process replaces rocks in the moisture removal process. This process, and thus also the ferfrom mentation time, is shortened three or four days to one day. Finally, cyanide levels were measured in the laboratory for all of the fresh and processed samples using an enzymatic assay.5 One measurement was taken on each sample, but in the second (backup) sample, only free cyanide was measured (ie not free-plus-bound cyanide).
Results and discussion A critical result from the survey is that, without exception, farmers are aware of the two types of cassava. Farmers categorized the type(s) which they were growing and samples were taken of each type. Cyanide content of the samples was measured during the sodium picrate leaf test.6 While this test does not permit a precise quantification of cyanide, it does enable a classi-
198
-Table1.Relativeimpottanceofsweetcasszwa ------
invariousr8giansofMgerii3.
!sweetcassava state
Anarnbra Ekndel Nun Kaduna -
fication to be made into one of three high. categories - low, medium, Seventy-six per cent of the cassava categorized by farmers as sweet was, in fact, in the low or medium cyanide categories, while 81% of bitter cassava was found to be high cyanide. Farmers’ recognition of the low and high cyanide types is (surprisingly?) good. It is, of course, a prerequisite for the susbtitution by farmers of sweet cassava for bitter that they perceive differences between the two types. Cassava is an important crop in the southern states of Anambra, Bendel and Ogun States, while it is less important, but still significant in the north (Kaduna).’ No published information is available on the relative importance of the sweet and bitter types in each region. Table 1 shows that relatively small amounts of sweet cassava are grown in the south, while the cassava grown in the north is almost exclusively sweet (columns 1 and2). Although, the total amount of sweet cassava grown in the south is small, almost half of the farmers in two southern areas grow some sweet cassava (column 3). Sweet cassava is relatively more popular in areas where yams are not grown, suggesting that consumers are using the sweet cassava as a substitute for yam in their diets. Southern consumers eat processed cassava - mainly gari. Gari can be made from both bitter and sweet cassava. As the yield of bitter cassava is recognized by all farmers to be higher than that of sweet, the bitter is the preferred type. Most of the sweet cassava grown in the south is eaten unprocessed, although it may be boiled. In Kaduna State, the sweet cassava is similarly eaten unprocessed. Farmers in all regions recognize and avoid the health problems associated with eating bitter cassava in an unprocessed form. Of the twenty-six southern growers
percentaoeof fam==gmwing only 8weet cassava
0 0 3 97
e=+ bittercassava inagivenyear 0 47 45 3
who had tasted gari made from bitter and from sweet cassava, all stated that there was no taste difference. However, the survey results showed that processing time for making gari in the traditional manner cannot be shortened with sweet varieties. Thus, there seems to be no advantage or disadvantage to be gained by processors in substituting sweet cassava for bitter. No agronomic reasons were unearthed for the choice between bitter and sweet types. Farmers who grow both, use the same production techniques for each, and regard pest problems as similar. As mentioned earlier, fears had been expressed by cassava breeders that sweet cassava might be preferentially attacked by rodents, with resultant large losses. To evaluate these fears, a special survey of 108 growers was conducted, 11 of whom had experienced rodent damage and had grown both sweet and biter cassava over the previous five years. Thirtyseven per cent stated that rodent damage to bitter cassava was worse, while 26% stated that damage to sweet cassava was worse. The remaining 37% perceived no difference in damage between the two types. Assuming a binomial distribution, the 5% confidence limits of the three groups do overlap and the conclusion is drawn of no difference between rodent damage on sweet and bitter cassava.
Screw press The cyanide level of fresh roots, which had been identified by growers as sweet and bitter respectively, is shown in Table 2 (samples A, Aa, B, Ba). The growers judgement of the cyanide level is verified. Contrary to expectations, however, the screw-press processing method is no less efficient than the traditional method in reducing cyanide (compare sample C with E; D with F).
FOOD POLICY August 1981
Viewpoint
The speed of the screw-press method, which reduces fermentation time to one day, was expected to result in gari with a high cyanide level, since the fermentation process was thought to be the prime reason for the low cyanide content of gari.” The main conclusion in relation to sweet cassava is that widespread adoption of the screw press is not likely to result in increased demand for sweet cassava.9 Even if sweet cassava is developed which yields the same as the bitter types, there is no apparent incentive for gari consumers or growers to switch to the sweet type. Nor are there any apparent costs - equal yielding sweet and bitter types would be preferredequally. A higher yielding sweet cassava would confer benefits on those farmers who grow, and the consumers who eat, sweet cassava. A rough est~ation of these benefits was made as follows, Total cassava production was obtained” and then the proportion of sweet cassava in each state was calculated by extrapolation from the regional figures of Table 1, Column 1. Anambra, Bendel and Ogun were assumed to represent the East Central and Western regions of the south respectively, while Kaduna was assumed to represent the whole northern region. “Middle Belt’ regions were estimated to produce equal pro~~ions of sweet and bitter cassava. On this basis, the total amount of sweet cassava grown in Nigeria was
determined to be about 35OooOtonnes. Since the base yield of sweet cassava is so low the potential improvement is higher, and a doubling of existing farm yields seems quite feasible with improved varieties. At a price of 1Ocper kilo for fresh roots, the annual gross benefit resulting from a breeding programme would be $35 million. The only Iikely cost increase is in labour for harvesting (about 7 mandays per tonne), totalling about $2 million. With consumption of cassava in Nigeria expected to rise sharply by 1990, in tine with population, ’ * no fall in the cassava price is expected to result from the increased yields of sweet cassava. success The total costs of conducting the IITA cassava and sweet potato programme has been about $lm, since it began in 1973. However, a relatively small proportion of the total has been spent on the low cyanide project. If the project is continued at current levels (about $lOOllO per year), the probability of ‘success’ (doubling of sweet variety yields) is almost 100% by the year 1986. Even allowing for the fact that it will take some years for the varieties to be accepted by farmers, the benefit-cost ratio is clearly enormous (regardless of whether all costs since 1973 are included, or only the ‘marginal’ costs of continuing the sweet cassava project from 1980-1986). The investment of re-
search resources into improving yields of sweet cassava has been, and continues to be, well worthwhile. Farmers make the choice between sweet and bitter types of cassava, not on the basis of agronomic differences, but on the basis of the end-use to be made of the cassava. Bitter cassava is grown where the end-use is gari, or some other processed product, which removes most of the cyanide. Bitter cassava is preferred, not because of an inherent taste advantage over sweet cassava, but because of its comparative yield advantage. Sweet cassava is grown where there is a taste/traditional preference for it. The breeding of a low cyanide cassava variety with yields comparable to improved bitter varieties is a feasible and practically achievable goal, at modest cost. The breeding of such varieties would have little or no impact upon and growers, processors consumers presently using bitter varieties, except in areas where processing is inadequate in reducing cyanide levels (no such areas were identified in Nigeria). Improved sweet varieties should be readily embraced by farmers currently growing sweet types. The potential benefits from the breeding of improved low cyanide cassava varieties in Nigeria are extremely high relative to the cost. Even after taking into account the pressure on cassava research resources to explore other potentially high payoff areas, continued investment in a high yielding, low cyanide cassava is warranted.
Sample Fles
Bound
Total
114.4 120.6
23.2
137.5
7.0 9.0
8.5
15.5
for f day
3.8 3.1
0.7
4.5
Sweet type after processing by screw-press methodforlday
3.0 5.8
0.8
3.8
Bitter type after prccesicg by trac.Mnal method for 3 days
12.5 11.3
0.0
12.3
Sweet type after pfccessing by tradiial method for 3 days
12.0 10.2
0.0
Il.5
Grated bier fresh root
Bittertype after pnrcessingby screw-press
FOOD POLICYAugust 1981
D.H. Oben, ENSA, Yaounde, Cameroon KM. Mew international Institute of Tfopical Ag~c~l~~e, Ibadan, Nige~a The
authors
wish
to
thank
Or
E.N.
Maduagwu for his analysis of root and product samples for cyanide, and Dr. H.C. Knipscher for comments on earlier drafts. IFAO, 1978 Production Yearbook, Rome, 1979. Some studies attribute sweetness or bitterness to sugars and other chemicals. White these may play a part, cyanide level seems to be the key factor. 3E.N. Maduagwu, ‘Cyanide content of sari’.
199
Viewpoint
Toxicology Letters, No 3,1979, pp 21-24. “F. Nartey, Manihot Esculenta (Cassava): Cyanogenesis, Ultfastfuctufe and Seed Gefmination, Munksgaad,Denmark, 1978. %.D. Cooke, A.K. Howlandand SK. Hahn, ‘Screening cassava for low cyanide usinn an enzymatic assay’, Experimental Agri: culture, Vol14. 1978, DD367-372. “S. Sadik, O.U. Ok&ke and S.K. Hahn, Screening fof Acyanogenesis in Cassava, Technical Bulletin No 4, IITA, lbadan, Nigeria, 1974. ‘Federal Office of Statistics, Rum/ Eco-
nomic Survey, 1977/78, ProvisionalReport on Crop Estimates, May 1979. 8Washing,drying,crushingare alsothought to reduce cyanide levels. ‘It should not automaticallyba concluded that the screw-press processingmethod is preferable to the traditional processing method. Some consumers expressed reservationsabout the taste and storability of gari made by this method. l*OP tit, Ref 7. tlWorld Bank ~nfi~nt~l Report, Nigeria Ag~cu~u~ Sector Review, Vol II, 1979.
Political pressure and the role of the economist This article is a reply to the comments of Professor van den Noort published in the May 1981 issue of Food Policy.’ Any contribution from Piet van den Noott is at all times stimulating and his recent comments were no exception. Furthermore, his comments are welcome since he examines the collation of themost jmpo~ant pillar of cogent economics policies in the Eu~pean ~rn~n~ -the CAP.
Briefly recapitulating some of the main points raised in the article, the point of departure is the question of the problems of choice as raised in economics textbooks. Logically, following this observation, van den Noort stresses that it is necessary first to know the Community’s social welfare function (SWF) if one is to make a realistic choice among the different plans put forward for the reform of the CAP. Reference is then made to the scrutinization of alternative policies by model simulation, ‘B la Tinbergen’, to arrive at ‘optimum policy determination’. At this point, reference is also made to the element of ‘intuition’ although the author does not regard this as being scientific. Moving to the world of politics, the author enters the realm of groups, coalitions and compromises. Professor van den Noort observes that at ‘least three political categories are involved, the cabinet, parliament and the bureaucracy’. He stresses the importance of this last group which, to some degree appears to be great because (though not exclusively) ‘without perfect knowledge it is not possible to calculate objective priorities and decisions’. This group, according to the author, possesses much knowledge. In his conclusions, the author stres-
ses the dangers of the consequences of an absence of a Community SWF and even goes so far as to state, ‘we can no longer accept the Tinbergen theory of economic policy as a description of reality but only as an intellectual exercise’. Finally, he examines the special case of a change in the EEC dairy policy referring to the different results gained when 68 Dutch agricultural economists were asked for their opinions - using the same model. In the present framework of the EEC, at the level of the EEC Council, the author says ‘compromises and trade-offs might be expected’, and he ultimately questions the place and pretentions of economists.
Lung cancer I shall start my reply with my colleague’s closing observation or question where he queries the position of economists. To me, the position of the economist is like that of a medical practitioner who tells a patient that he will get lung cancer if he continues to smoke 100 cigarettes a day. The patient nevertheless continues to smoke the same quantity of cigarettes and subsequently dies of lung cancer. This fact, however, does not remove the role of
the medical practitioner, but rather reinforces the joint roles of education and information. Such, I believe, is the role of the economist and the relevance of the theory of economic policy in relation to the CAP. Theory in itself is mainly a yardstick indicating optimum situations and/or targets. However, to give it rn~~urn relevance in real life it may be useful to return to the classical tradition of political economy rather than remaining in the narrower field of econometrics. However, I shall return to this consideration towards the end of my reply. Turning to the specific case of the CAP, we enter, at the same time, a world of everyday reality (since we must all eat food) and extreme technical complexity (as manifested in the fo~ulation and application of even the most simple a~cultural policies). Immediately, we also encounter political groups, as mentioned by Professor van den Noort. However, the most important group, especially in agriculture, has gone umnentioned. This group is the ‘lobby’. In the EEC, the most important lobby is the agricultural one, followed by the textile lobby and then by other manufacturing lobbies. The consumer lobby comes right at the bottom of the list and is practically unimpo~ant. The agricultural lobby has the most immediate and direct access both to the relevant ministers at the national level, as well as to the Commission and other bodies in Brussels, Luxemburg and Strasbourg. Hence, straddling the world of economic theory and reality, a ‘public preference welfare group’ has arisen with the EEC. This fact appears to be the missing link in economic theory and in my colleague’s ~ont~bution. It is this variable which should be included and given greater weight in any model. This does not remove the possibility of haggling and compromises when the Council of Ministers meet for their annual price-fixing marathons. But, it does mean that these sessions are, in advance, strongly influenced by the farmers themselves rather than by other interest groups. What should be done then to make the theory of economic policy more FOOD POLICY August 1981