ECONOMIC ANALYSIS OF COWPEA PRESERVATION TECHNOLOGIES WITH SPECIAL FOCUS ON THE HYDROTHERMAL TREATMENT TECHNOLOGY BY EMMANUEL DELALI KWAMLA OFORI THIS THESIS IS SUBM ITTED TO THE UNIVERSITY OF GHANA , LEGON, IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PH ILOSOPHY IN AGRICULTURAL ADM IN ISTRATION DEPARTMENT OF AGRICULTURAL ECONOM ICS AND AGRIBUSINESS, FACULTY OF AGRICULTURE , UNIVERSITY OF GHANA, LEGON. DECEMBER, 2002. T * * 3 7 \2Sy S < $ , J I P S - - C 2 is . O i DECLARATION I, Emmanuel Delali Kwam la O fori, the author o f this thesis titled “Econom ic Analysis o f Cowpea Preservation Technologies w ith Special Focus on the Hydrothermal Treatm ent T echnology” hereby declare that, this work was done entirely by me in the D epartm ent o f Agricultural E conom ics and Agribusiness, University o f Ghana, Legon. The work has never been presented either in whole or in part fo r any o ther degree of this University or elsewhere except for o ther p eop le’s work, w hich have been duly cited. EMMANUEL D. K. OFORI. (STUDENT) This thesis has been presented for exam ination with our approval as supervisors. REV. DR. S. ASUM ING-BREMPONG DR. BRUCE SARPONG (MAJOR SUPERVISOR) (CO -SUPERVISOR). DEDICATION This work is w holeheartedly ded icated to my parents Mr. G. G. K. O fori and Mrs. Edith B. Ofori for their immense contribution to my education most especially at the postgraduate level. I pray that you live long to fully enjoy the fru it o f your toil. It is also dedicated to the m emory o f my late cousin M r. Amm ishadai Kwasi Agbenosi Ofori who died mysteriously on Ju ly 1, 1985 at the University o f Cape Coast. Brother, rest in peace. I must first thank Jehovah God for his protection and gu idance that has seen me through to the com pletion of yet another level o f education. T hank you Lord. In appreciation o f the diverse assistance received from num erous individuals, I wish to acknow ledge them w ith sincere thanks. I wish to express my sincerest appreciation to my supervisors Rev. D r. S. Asum ing- B rempong and Dr. B ruce Sarpong for taking time off their busy schedules to provide very useful contributions and suggestions for the study. I am also grateful to all other members o f staff o f the D epartm ent o f Agricultural E conom ics and Agribusiness of the University o f Ghana, most especially Dr. George T-M . Kw adzo , M r. F rancis Egu and Mr. R eindorf Darko. The staff o f the Nutrition and Food Science D epartm ent o f the U niversity o f Ghana, most especially Ms. Cynthia Anku-Tsede and M r Emmanuel A fuakwa, provided me w ith the relevant data on hydrothermal treatm ent technology. Y our contribution towards this study is very much appreciated. Mr. Isaac V anderpuye, an Agricultural Extension O fficer w ith the M inistry of Food and Agriculture, Ga D istrict O ffice at Amasaman in Accra and S ister Regina, a cowpea seller at the M allam Atta market in Accra assisted me during the collection of data from the cowpea farmers and consumers, respectively. I thank you very much for your contribution. ACKNOWLEDGEMENT My heartfelt gratitude goes to Messrs Benjam in H oenyenugah (my room mate), Francis Srofenyo, Samuel T impo, Eric Sampane-Donkor, G eorge Honya, N icholas D zandza, E. T. Adika, D onsananang Jatoe and Ms. Peace N tumy for their contributions in diverse ways (which I cannot m ention here ind iv idually ) towards the completion o f this work. A special appreciation goes to my dear one Ms. Hannah Dei for her support and patience in the course of my study. Hannah, thank you very much. I would also like to express my profound gratitude to my course mates most especially M essrs Lovelace Yanney, Siegfried Agbodza and Cosm os Abiwu for all their help. F inally, to all those not m entioned here but who contributed to this w ork in diverse ways, I thank you all very much and wish you Jehovah G od’s guidance. Emmanuel D. K. Ofori. ABSTRACT The need to increase and sustain the production of cowpea in G hana has been recognised. It is a cheaper source o f protein and thus has the potential to alleviate protein m alnutrition. Specifically , the study determ ines the various storage and preservation technologies that are known and/or used by cow pea farm ers, the profitability of cowpea preservation by m eans of the new ly in troduced technology called the hydrothermal treatm ent technology and also identifies the characteristics that determ ine the purchase decision o f cowpea consumers. The socio-econom ic factors that influence the adoption o f preservation and storage technologies o f cowpea grain by farmers was also determ ined. The results show that the four storage and preservation technologies m ost w idely practised by cowpea farm ers are: preservation with ash, chem ical preservation , sealed bag storage and pod storage. The hydrotherm al treatm ent technology sim ply involves steam ing of dry cowpea grains fo r about 10 m inutes after which the grain is properly dried and stored. The profitability o f cow pea preservation using the hydrotherm al treatment technology was determ ined by the use o f Net P resen t Value and Internal Rate o f Return criteria. The estim ates o f the profitability indicators at the 38% discount rate suggest that the hydrotherm al treatment technology is profitable. The estim ated values o f NPV and IRR were 0345,262.42 and 90% respectively. Benefits envisaged with the adoption of this technology include the reduction o f cowpea storage losses induced by insect pests thereby leading to an increase in productiv ity and subsequent increase in the income earning capacities o f the fanners. The three most im portant characteristics o f cowpea grains that are considered by consumers in m aking the ir purchase decisions are: absence o f impurities, lack of insect emergence holes in the grain, and cooking time in that order. It is recommended that sim ilar p rofitab ility studies should be carried out on other technologies used in the preservation and storage of cowpea grain. The results o f such studies will form the basis for farmers to com pare and make in form ed choices. vi TABLE OF CONTENTS DECLARATION ....................................................................................................... i DED ICATION ............................................................................................................. » A CKNOW LEDG EM EN T .................................................................................... Hi ABSTRACT ............................................................................................................. v TABLE O F C O N TEN T S ..................................................................................... vii L IST O F TA B LE S ................................................................................................ x L IST O F F IG U R E S ................................................................................................ xi L IST O F A PPEN D IC E S .................................................................................... xii A B B R EV IA T IO N S /A C RO N YM S ................................................................. xiii CH A PTER ONE IN TRODU CT IO N ...................................................................................................... 1 1.1 Background and Problem S tatem en t...................................................... 1 1.2 Objectives o f the S tu dy .............................................................................. 7 1.3 Relevance o f the S tudy .............................................................................. 8 1.4 O rganisation o f the S tudy ......................................................................... 10 CHAPTER TWO LITERATURE REV IEW .................................................................................. 11 2.1 Pest M anagem ent Ph ilosophy ................................................................... 11 2.2 Insect In festa tion ........................................................................................... 12 2.3 Control o f S torage P e s t............................................................................... 14 2.3.1 Chem ical P reservation o f C ow pea............................................................. 14 Page 2.3.2 Edible oils and B iologic M ateria ls ........................................................... 15 2.3.3 Sealed Container S to rage .............................................................................. 16 2.3.4 Co-storage w ith ash and other Abiotic M ateria ls .................................. 17 2.3.5 B iological C on tro l.......................................................................................... 18 2.3.6 Solar and other H eat d isinfestation T echn iques.............................. 19 2.3.7 Irrad ia tion ...................................................................................................... 19 2.3.8 S torage in P od s................................................................................................ 20 2.4 Review o f Some Effects o f the Hydrothermal T reatm ent o f C ow pea.................................................................................................................... 20 CHAPTER THREE METHODOLOGY ................................................................................................ 24 3.1 The Study A rea ................................................................................................ 24 3.2 Analytical F ram ew ork ................................................................................... 24 3.2.1 Identification o f P reservation and S torage T echno log ies .................. 25 3.2.2 D eterm ination o f the P rofitability o f the Hydrothermal T reatm ent T echno logy ................................................................................... 25 3.2.2.1 Net Present Value (N PV )....................................................................... 25 3.2.2.2 Internal Rate o f Return (IRR )................................................................ 27 3.2.2.3 Choosing the D iscount R ate ...................................................................... 29 3.2.2.4 Sensitivity A nalysis (Treatment o f U ncerta in ty ).................................. 29 3.2.3 D eterm ination of Cowpea Characteristics that Influence Consumers Purchase Decisions ........................................................... 30 3.2.4 Identification of Socio-econom ic Factors that Affect Farm ers’ Choice o f Preservation M ethods............................................. 30 3.2.4.1 The P robit M ode l........................................................................................ 30 3.2.4.2 Specification o f the M o d e l ...................................................................... 31 3.3 D ata S ou rces ..................................................................................................... 35 3.4 M ethod o f D ata C o llec tion ...................................................................... 36 CHAPTER FOUR RESULTS AND D ISCUSSION ............................................................................. 37 4.1 In troduc tion ..................................................................................................... 37 4.2 Socio-Econom ic Characteristics o f the R esponden ts..................... 37 4.2.1 Cowpea F an n e rs ........................................................................................ 37 4.2.2 Cowpea C onsum ers......................................................................................... 39 4.3 S torage Pest Control Technologies U sed by Cowpea F a rm e rs ... 42 4.4 Investm ent A naly s is .................................................................................. 46 4.5 C haracteristics o f Cowpea Grain that Influence the Purchase Decision o f C onsum ers.............................................................................. 51 4.6 R egression R esu lts ......................................................................................... 54 CHAPTER FIVE CONCLUSION AND RECOMMENDATIONS......................................... 57 5.1 C o n c lu s io n ..................................................................................................... 57 5.2 R ecomm endations......................................................................................... 58 R E FE R EN C E S ............................................................................................................. 60 A PPEN D IC E S ............................................................................................................. 66 LIST OF TABLES Table 1.1 Annual Q uantities o f Cowpea Produced in G hana (1980 -1996 )................ 3 Table 3.1 D escrip tion of the Variables used in the Empirical M o d e l ...................... 32 Table 4.1 Age D istribution o f the F ann e rs ........................................................................ 38 Table 4 .2 Educational Levels o f the Farm ers........................................................................ 39 Table 4.3 Consum ers Response on whether they cared to find out if the Cowpea grain they purchased has been T reated C h em ic a lly ..................... 40 Table 4 .4 Age D istribu tion o f the Consumers In terv iew ed......................................... 41 Table 4.5 D eterm ination o f P rofitability Indicators- NPV and IR R .......................... 47 Table 4 .6 Com puted NPV and IRR values assum ing 10% fall in the Price o f T reated C ow pea ...................................................................................................... 49 Table 4 .7 Com puted NPV and IRR values assum ing 10% increase in the Cost o f Untreated Cowpea.......................................................................................... 50 Table 4.8 Consum er Ranking of Quality Characteristics o f C ow pea G ra in 52 Table 4 .9 P robit Model Results for Chem ical Pest Control by Cowpea F arm ers .............................................................................................................................. 55 Page x LIST OF FIGURES Figure 4.1 Technologies known to Farmers in Controlling Storage Pests o f C ow pea .............................................................................. 43 F igure 4.2 Technologies in Use by Farm ers in Controlling Storage Pests o f C ow pea .............................................................................. 44 Page XI Appendix I Q uestionnaire for Cowpea F arm ers............................................ 66 Appendix II Q uestionnaire for Cowpea C onsum ers................................. 70 Appendix III Q uestionnaire for Researchers W orking on the Hydrothermal T reatm ent T echno logy ................................... 73 Appendix IV Reference Notes and A ssumptions M ade Concerning the D eterm ination o f Profitability Indicators (NPV and IR R ) .............................................................................. 74 Appendix V Sensitivity A nalysis ...................................................................... 75. LIST OF APPENDICES Page xn ABBREVIATIONS/ ACRONYMS CRSP - Collaborative Research Support P rogram CSIR - Council for Scientific and Industrial Research FAO - Food and Agriculture O rganisation GDP - Gross Domestic Product GGDP - Ghana G rain D evelopm ent P roject H a - Hectare EFPRI - International Food Policy Research Institute IITA - International Institute o f T ropical A griculture IRR - Internal Rate o f Return JIRCAS - Japan International Research C entre for Agricultural Sciences Kg - K ilogramme MOFA - M inistry of Food and Agriculture NPV - Net P resent Value PPMED - Policy P lanning M onitoring and Evaluation D irectorate WHO - W orld Health O rganisation CHAPTER ONE INTRODUCTION 1.1 Background and Problem Statem ent Food items such as cereals, root and tubers, m eat, m ilk, fish, edible oils and fats are nutritionally more rewarding. However, their dom estic production in certain countries have not yet caught up with the demands o f the rap id ly expanding and urbanising population. Local food supplies from the farm s are essen tially seasonal; availability is highest soon after harvest and lowest in the interval between p lanting and harvesting of the next main food crops. This seasonal food shortage o r the “hungry” season is a well- known phenom enon in A frican peasant agriculture. The paramount role o f improved methods o f food production , preparation, processing, preservation, storage, distribution and m arketing fo r the im provem ent o f food consumption patterns to achieve a high level o f nutrition and improved quality of life o f the A frican people cannot be over-emphasised. A ccording to Yudelm an (1998), the supply of food - especially grains in developing countries will have to rise by around 70 percent by the year 2020 if the 6.5 billion people w ho are expected to be living in Africa, A sia and Latin America by then are to be food secure. Cowpea [Vigna unguiculata (L.) Walp] belongs to a group o f crops called grain legumes or pulses, which are generally noted for their high protein content, and has the potential o f alleviating protein malnutrition most especially in developing countries. l Cowpea is an important legume o f the tropics, w ith various uses, including grains in processed foods, a vegetable (fresh leaves, peas, and pods), and as fodder. Cowpea pulse processed into products such as flour o r meal could be used to m ake sweets, cakes and porridge for human consumption. G round cowpea grain is considered a valuable feedstuff for poultry and rum inant diets. Dovlo et al. (1976) reported that cowpea is chosen in an extrusion cooking as a source o f nutrient because o f its relatively high protein content and its am ino acid profile which are both superior to and complem entary to that o f cereal grains. A ccording to Barrett (1990), cowpea is among the top three or four leafy vegetables used in m any parts o f A frica. Cowpea in combination or association with cereals and o ther grain legumes contributes to the sustainability o f cropping system s in m arginal lands o f the sem iarid areas, w ith its fixation o f nitrogen, ground cover, and the soil im provem ent it provides from plant residues. These features o f cowpea make it a particularly attractive crop for the subsistence farm ers o f Sub-Saharan A frica, where about 70% o f the w orld ’s cowpea are grown (Singh et al. 1990; Singh et al. 1997). Ghana has a favourable clim atic condition for cowpea cultivation. The crop grows well in hot tropical clim ates; it requires a temperature range o f 20 and 30 degrees Celsius, and rainfall range o f between 400 and 800 m illim etres per annum (M uleba and Ezumah, 1985; S ingh, 1985). D espite the prevailing favourable clim atic conditions and the high nutritional value o f the crop, production figures continue to fluctuate in Ghana. An indication o f the perform ance o f cowpea production in G hana between 1980 and 1996 is given in Table 1.1, which contains data on the quantity produced and annual growth in output. The quantity o f cowpea produced declined from 17,000 tonnes in 1981 to the lowest value of 11,000 tonnes in 1985 although a break in the downward trend was recorded in 1984 when the quantity was 14,000 tonnes. Betw een 1986 and 1996, there was a steady increase in the quantity produced w ith 85,244 tonnes at the end o f the period. The average production estim ates over the period under consideration (1980— 1996) is 38,909 tonnes per annum . Table 1.1 Annual Quantities o f Cowpea Produced in Ghana (1980-1996). Year Quantity o f Cowpea Produced (‘000 kg). A nnual G rowth in Output (%). 1980 16,100 - 1981 17,000 5.6 1982 14,100 -17.1 1983 11,700 -17.0 1984 14,000 19.7 1985 11,000 -21.4 1986 19,500 77.3 1987 23,500 20.5 1988 35,000 48.9 1989 51,000 45.7 1990 48,000 -5.9 1991 52,000 8.3 1992 56,316 8.3 1993 60,990 8.3 1994 71,535 17.3 1995 74,472 4.1 1996 85,244 14.5 Source: PPMED, MOFA, Accra. 3 Cowpea production in G hana therefore presents a p icture o f a fluctuating but basically upward trend. The fluctuating output in Ghana despite the useful features o f cowpea could be due to low investm ent in cowpea industry, which is considered risky because o f the num erous problem s in growing, harvesting and sto ring the crop (Jackai and A dalla 1997). Severe yield losses o f cowpea are caused in tropical A frica by the in terplay o f abiotic (for example, drought) and biotic (for example, arthropod pests, d iseases, birds, and rodents) constraints. R anked first among the latter group, a w ide array o f insect pests can cause total yield failure in cases o f severe attack (Jackai and D aoust, 1986). Insect pests dam age cowpea from seedling em ergence to storage. It has been shown that field pest problem s during the crop’s vegetative cycle are substan tia l, and insects such as Maruca spp and Apion are highly im plicated in production losses. Insect infestation both in the field and during storage reduces m arkedly both y ield and quality o f the grain. The principal storage pest o f cowpea grain is the cowpea bruchid, Callosobruchus macula tus , also known erroneously as the "cowpea weevil" (Taylor, 1981). Callosobruchus maculatus infestations start in the field and continue in storage. Cowpea on sale in markets often has bruchid em ergence holes. O ther important insect pests o f cowpea in storage include Bruchidius a tro linea tus and Callosobruchus chinensis. 4 The financial and nutritional losses in cowpea due to storage pests in Sub-Saharan A frica are not well docum ented, but are clearly high. Low -resource farmers often sell their cowpea at harvest, when prices are lowest in the year, partly because they anticipate storage losses. Being aware of the storage problem , they are interested in better techniques for preserving their grain after harvest (M urdock et al. 1997). Caswell (1984) has docum ented the loss o f cowpea grain during trad itional post harvest storage in N igeria. He found out that pods stored for 8 m onths had 50% o f the grain damaged by bruchids, but when stored as grain, 82% of the grain had one or m ore holes. Since em ergence holes represent insects that have developed and left the seed, mated, and laid additional eggs, counting emergence holes to assess dam age undoubted ly represents only a part o f the problem . The next generation o f larvae, more num erous will generally still be developing w ithin the grain. Technologies are now available to lim it post harvest losses due to insect pests infestation of cowpea grain. Solar disinfestation, com bined w ith subsequent storage under conditions that prevent reinfestation, enables long-term preservation of threshed grain from insect attack (Murdock et al., 1997). Cowpea varieties w ith seed resistance, pod-wall resistance, and combined seed and pod-wall resistance have been bred through the jo in t efforts o f breeders and entomologists (Kitch, 1992). Cowpea grain storage in airtight containers, such as metal drum s or triple plastic bags, arrests the development o f storage insect populations (Kitch and N toukam , 1991a). M ixing the grain with wood ash also stops damage to grain by storage insect pests (W olfson et al., 1991; Kitch and N toukam , 1991b). Cowpea grain treatments with num erous plant-derived oils, such as that from groundnut, are also effective (Schoonhoven, 1978; Singh et al., 1979). In addition, insecticides are the fire-fighting analogue in cowpea pest control, a function for which they rem ain unrivalled (National A cademy o f Sciences, 1969). Currently, econom ic necessity , sensitiv ity to environmental destruction and health considerations (chem ical residues) has rendered insecticide use socially unacceptable. The use of insecticides to protect cowpea grain in storage is probably more commonplace and controversial than their use on the field crop, because chem ical residues are feared to persist in the bean after cooking. The D epartm ent o f Nutrition and Food Science of the U niversity o f G hana has developed a new m ethod o f cowpea preservation called hydrotherm al treatment technology. This m ethod is applicable to cowpea both on the fa rm er’s field and at the m arket place in response to the need to address the high level o f post harvest losses in cowpea. The hydrothermal treatm ent technology, which is a simple, inexpensive and safe physical m odification process, is chem ical free, and does not require the use of sophisticated equipm ent o r trained personnel. As a result it could alleviate the fear associated with insecticide use. It involves the exposure o f whole cowpea seeds to steam followed by drying to acceptable storage moisture content. P relim inary work by Sefa-Dedeh et al. (1994) showed that 5 to 10 m inutes steam ed cowpeas were resistant to the weevil. Subsequent studies were conducted to determ ine the effect o f the steam ing process on the seeds, and some o f the results have been presented in the chapter on literature review of this study. Despite these developm ents in technologies, the problem s of post harvest losses in cowpea are still ev ident in Ghana. It is therefore necessary to identify the constraints lim iting the cowpea industry in the country. Such studies on cowpea developm ent must lay emphasis on analysis o f constra in ts in the entire production chain, that is, from field production to consumption and utilization, including what happens to the produce during storage and processing. This study basically attempts to investigate the financial viability o f the hydrotherm al treatm ent technology for cowpea preservation . The study therefore proposes to address the follow ing questions: W hat preservation technologies do cowpea farmers know and /o r use? O f those farmers who know o f these technologies but do not use them , what are the factors that prevent their use? Is the hydrothermal treatment technology profitab le? W hat are the characteristics o f cow pea grains that influence the purchase decisions o f consumers? What are the factors that determ ine the adoption o f pest control technologies by cowpea farm ers? These are som e o f the issues this study has tried to address. 1.2 Objectives o f the Study The prim ary objective o f the study is to determ ine the v iability o f the hydrothermal treatment technology o f cowpea preservation. The specific objectives are: 1. To identify the various technologies used by farmers in the preservation and storage of cowpea. 2. To determ ine the profitability o f the hydrothermal treatm ent technology in preserving cowpea. 3. To determ ine the characteristics of cowpea that influence purchase decisions of consumers. 4. To determ ine the factors that affects the adoption of pest control technologies by cowpea farmers. 1.3 R elevance o f the Study Protein deficiency disorders, such as kwashiorkor and m arasm us are m ajo r nutritional problem s in most develop ing countries including Ghana. T he total daily protein intake o f an adult human being recommended by FAO is 55.0 g ramm es fo r norm al growth and healthy mental developm ent (Bender, 1992). G hana’s per cap ita protein intake according to FAO (1994) report was 46.9 grammes falling short o f the recommended intake value. Cowpea, which can easily be in tegrated into the farm ing system , is high in protein and can serve as a relatively cheap source o f vegetable protein. On average, cowpea grain contains 23-25% protein and 50-67% starch (S ilano et al. 1981). Cowpea is also o f importance to the livelihoods of m illions o f rela tively poor people in less developed countries o f the tropics. From the production o f this crop, rural families variously derive food, animal feed and cash, together w ith spill over benefits to their farm lands through, for example, in situ decay o f root residues, use as anim al feed, and ground cover from cow pea’s spreading and low grow th habit. In addition , because the grain is w idely traded in production areas, it provides a cheap and nutritious food for relatively poor urban communities. In fresh form , the young leaves, imm ature pods, and peas are used as vegetables, while several snacks and m ain meal dishes are prepared from the m atured dry grain. All the plant parts that are used as food are nutritious, p roviding protein, v itam ins, and minerals. Beyond its im portance for food and feed, cowpea can equally serve as the fulcrum of sustainable farm ing in sem iarid lands. It provides ground cover thus providing some protection against soil erosion. Another important feature o f cow pea as a food legume in the cropping system is its ability to produce nitrogen and so increase the overall fertility o f the soil, thus partially replacing the use o f expensive n itrogenous fertilizers. According to K ay (1979) a vigorous grow ing food legume such as the cow pea can add as much as 45 kg/ha o f nitrogen to the soil, which is equ ivalen t to 112 kg/ha o f urea, or 225 kg/ha o f ammonium sulphate. In addition, cowpea is drought hardy, and it is able to m aintain some grow th or at least survive under dry soil conditions. This trait is in part exp lained by the deep rooting habit o f som e varieties, and it accounts for the c rop ’s ability to grow and yield under the semi desert conditions of the A frican Sahel. The off-take o f cowpea fodder makes an important contribu tion to feed supplies for large and small rum inants. The spill over benefits are that traction anim als maintain reasonable health status during the dry season, enabling tim ely land preparation when the wet season begins. A lso, return of animal manure to the land by cartage from kraals o r in situ grazing contributes to soil fertility. W ith the developm ent o f irrigation schemes in some areas o f W est and Central Africa, and the general increased use of wetlands, cowpea has found a n iche in dry-season cropping. This is based m ainly on the use of residual soil m oisture, and it is somewhat sim ilar to the production of cowpea in rice-based cropping system s. This relatively new production system is popular and expanding. As with rain fed production , both grain and fodder are p roduced (Quin, 1997). C onsidering the above uses and potential advantages o f cowpea, there is the need to undertake this study to establish the profitability o f the hydrotherm al treatment technique. Recommendations based on the findings would be useful in sustaining the 9 cowpea industry through reduction o f post harvest losses and enhancing the quality o f available grain for consumption. 1.4 O rganisation o f the Study The study is organised into five chapters. The background and problem statement, objectives o f the study, the relevance o f the study and the organisation o f the study, which constitutes the in troduction , are presented in chapter 1. The literature review is presented in chapter 2. The m ethodology em ployed to achieve the ob jectives of the study are outlined in chap ter 3. T he results o f the study and discussion are presen ted in chapter 4. The final chapter presents the conclusion and recommendations o f the study. 10 CHAPTER TWO LITERATURE REVIEW This chapter presents a review o f the relevant literature on cowpea preservation methods. The review entails general as well as literature specific to the Ghanaian situation. 2.1 Pest M anagem ent Philosophy Insects are considered pests because o f the socio-econom ic and medical th reat they pose to man and his property. B iologically , an insect is a pest when its population density and/or damage level exceeds a p re-estab lished or conceptualised threshold (the econom ic injury level) below which the insect does not constitu te an econom ic threat (Horn, 1986). This is defined as the lowest population or dam age level capable of causing econom ic impact (Poston, et al 1983). If the population of an organism exceeds the econom ic injury level, the organism becomes a pest. W hen an insect is introduced into a favourable environm ent, its population density tends to increase to the carrying capacity o f the resource. This is not usually exceeded because of the balance in environmental stress factors such as predation, competition, and other natural mortality factors, constituting the environmental resistance. The econom ic injury level is usually below the carrying capacity o f the resource. M aintaining a pest population below this level may require some m anipulation using one or more of the in terventions such as resistant cultivars, beneficial organism s and insecticides at the disposal o f growers. Usually, the damage or population density o f the pest is not allowed to reach levels that would result in econom ic loss before action is 11 taken. The resource dam age level, o r pest population density p rio r to the econom ic injury level is the econom ic or action threshold (Stem et al, 1959), o r dam age boundary (Pedigo et al., 1986). Control m easures must therefore be in troduced, augm ented, or applied to the system (Horn, 1986; M etcalf and Luckmann, 1994). A lterations in crop- pest dynam ics, for instance by m any o f m an’s agricultural activ ities, dictate how pest m anagem ent proceeds and the tools that can be used. 2.2 Insect Infestation Storage is one o f the very im portant operations in cowpea production. Essentially , it prolongs the she lf life o f the harvest, m aking it available on the m arket for a much longer period o f time. Farmers are well aware of the losses they suffer in storage and in many cases estim ate that everything will be eventually lost if no contro l m easures are taken (W olfson et al. 1990; Goldman 1991). Cowpeas are seasonal and there is therefore the need to store the surplus for use during the lean season. D uring storage, various pests including rodents, m oulds and insects attack cowpeas. Amegatse (1995) reports that 66.7% of respondents in a survey in G hana indicated that insect (weevil) infestation was the m ajor prob lem associated with cowpea storage. About 80 insect species have been identified as pests o f stored cowpeas in G hana including Callosobruchus maculatus, which is one o f the nine m ajor pests, identified (Agen-Sampong, 1977). The infestation usually occurs on the field and som etim es during storage by cross contam ination. The fem ales reproduce rapidly and therefore the population can grow exponentially within a few months. The FAO (1989) estim ates that post-harvest food losses o f grains in developing countries through m ishandling, spoilage and pest infestation average 25% o f the total food grain production. Various estim ates o f the m agnitude o f the post harvest losses (due to insect attack) have been made. The values are generally very high, an estim ated 30% o f stored rice is lost to insects in S ierra Leone whilst, 25-45% o f sto red maize is lost to insect pests in G hana (Hill and W aller, 1988). Com parable levels o f losses have been reported in East and Southern A frica and other parts o f the tropical world (Boxall, 1989). In the Sahelian areas of N igeria, weevil infestation o f cow pea grain may reach 40% in markets by the early wet season, which is June/July (Caswell, 1981). The loss o f food material as a direct result o f insect attack occurs through two main means. Insect activity either through boring into the seeds and/or surface feed ing results in the removal o f food material, usually from the portions o f h ighest nutritional value. There is also the respiring activity of the insects, which results in high moisture developm ent in the stored grain encouraging the growth o f m icro organism s with their own associated problem s. A rela tively insignificant weight loss in a grain sample may have far reach ing effects. This is especially im portant if it leads to either a total rejection o f the whole batch by the consum er or to a drastic price reduction. According to S ingh and Jackai (1985), up to 30% loss in weight may occur after six (6) months with 70% o f seeds being infested and grain being almost unfit for consumption. Insect infestation leads not only to econom ic losses but also results in nutritional losses in cases where the attack is substantial. The nutritional losses occur from decrease in essential am ino acids and vitam ins, and also from contam ination with uric acid, a m etabolite o f insects (Bressani, 13 1985; U zogara and O funya, 1992). Seed viability can also be affected (W olfson, 1989; Lowenberg-deBoer, 1995). 2.3 Control o f Storage Pests Pest m anagem ent techniques are varied and involve m ethods that integrate either cultural practice, b iological, chem ical o r physical factors. The choice o f the method is affected by many considerations including the availability and costs o f inputs, labour requirem ent, tim e frame for application o f the technique, the level o f know how for using the technology, the econom ic status o f the person, cultural considerations and am ount o f grain to be stored (Murdock, et al., 1997). Am egatse (1995) found that m ajority (56.2% ) of cowpea farmers interviewed in the G a D istric t o f the G reater Accra R egion, Ghana, em ployed interm ittent drying o f bagged cowpeas whilst 27% used chem ical pesticides or airtight containers. P reservation w ith palm kernel oil, smoke, wood ash and kerosene were other traditional o r ind igenous m ethods used. 2.3.1 Chem ical Preservation o f Cowpea Synthetic chem icals continue to be important agents in the contro l o f insect pests of stored grains, especially in developing countries, in spite o f the continu ing controversy surrounding their harmful side effects (Yudelman et al., 1998). Even though these chem icals are generally targeted at insect pests, som e o f them are broad-spectrum biocides that have profound effects on non-target species in the agricultural ecosystem . There is also a problem of chem ical residues after application, which could exceed the recommended safety levels. For instance, applying 100 grammes o f actellic super dust per 90-100 kilogramme bag of grain produces residues of 3.3 m illigramm es permethrin and 17.7 m illigrammes pirim iphos methyl per kilogramme grain. This is more than the 14 FAOAVHO recommended residual levels o f 2 m illigrammes and 10 m illigrammes per kilogramme, respectively (Golob, 1988; U ronu, 1988). In A frica, most subsistence farmers do not keep their produce in storage for long periods. Thus there is the danger o f consum ing or selling grains w ith high chem ical residues. In Tanzania, it has been reported that 1000 deaths per year could be attributed to various pesticide po isoning (A k ’habuhaya and Lodenius, 1988). A lthough cowpea farmers have long recognised the usefulness of insecticides, factors such as availability, inform ation and cost have kept the technology beyond their reach (Jackai et al., 1985). 2.3.2 Ed ib le oils and B iologic M aterials Mixing dry cow pea seeds thoroughly with small am ounts o f vegetable oils has proved to be an effective protection against insect pests (Schoonhoven, 1978; Singh et al., 1979). The oil covers the testa and plugs the egg m icropyle (acting as an ovicide) and therefore prevents oxygen supply to the embryo. It also deters ov iposition and causes death o f adult insect pests. Varieties o f oils are suitable, for exam ple palm kernel oil, cotton seed oil and groundnut oil. According to studies undertaken by Singh et al., (1979) and Pereira (1983), groundnut oil was found to be the most effective of the edible oils, providing complete protection for up to 25 weeks after treatm ent. Cockfield (1992), studying the effectiveness o f groundnut oil as a contro l m easure, found that using the oil afforded a protection sim ilar to that of p irim iphos methyl. The amount o f oil needed for an effective preservation is usually very small, 5 m illilitres per kilogramme of grain (Singh et al., 1979). There are, however, some difficulties associated with this treatment. Thorough m ixing o f oil and grain becomes 15 tedious when the quantity o f grain is large. There is also the problem o f rancidity or other inherent negative properties, fo r example neem oil stains the hands and has an unpleasant ‘garlic’ odour (M urdock et al., 1997). It is also easy to pick up dust and debris. A nother m ethod involves the use o f p lant parts such as leaves o f various m ints or pungent sm elling plant materials. O funya (1986) noted that onion scales and dried chilli pepper conferred some degree o f protection against Callosobruchus maculatus. 2.3.3 Sealed Container Storage In this m ethod, the moisture present results in germ ination o f some grains. The resulting respiration elim inates oxygen in the enclosure thus suppressing insect infestation. Sealed containers may be large, underground silos or sim ple m etal drum s (Murdock et al., 1997). A practical drum storage technique has been developed in Senegal under the Bean/Cowpea Collaborative Research Support Program (CRSP). T he beans are first sun dried and then the drum is filled w ith the dry beans. It has been recommended that the drum be sealed for a m inimum period o f 2 months before opening. It is also important that the drum be airtight. Its advantages include the relatively low initial cost and repeated use o f the drums. However, the period within which the drum must remain sealed for the treatm ent to be effective is quite long. There is also the problem of weight of large drums but this is usually overcom e by using racks. 16 Storage using triple plastic bagging is another simple and inexpensive m ethod also developed by the CRSP in Cameroon. The technique makes use o f clear plastic bags, which are w idely available. The grains are put in a bag (40-50 k ilogrammes) and tightly sealed with tw ine. This is then p laced completely into a second and then a third bag and sealed sim ilarly. Tests in various Cameroonian villages have shown that the method is effective and readily accepted by sm all-scale farmers. Due to the transparent nature, the farm er can observe the grains periodically . However, the bags can be easily destroyed through im proper handling and they are also vulnerable to rodent attack (M urdock et al., 1997). The G rains D evelopm ent Project in Ghana has investigated the potential o f storing cowpeas in Sealed K ilner ja rs and found the m ethod to be effective but d id not look at the acceptability o f the m ethod to farmers in storing their ou tput (Osei, 1993). 2.3.4 Co-storage w ith Ash and other Abiotic M aterials Wolfson et al., (1989) found that the most common traditional post harvest storage method in Northern Cameroon was the use of ash. This has also been noted in other Sub-Saharan A frican countries including Ghana (M urdock et al., 1997). The ash used comes from the cooking fire and results vary with d ifferences in m ode of application as well as the ash to grain ratio used. The latter factor is usually more effective if the ratio is three or more parts ash to four parts grain. A lthough the ash stops the development of the bruchid population in the grain stored, it does not kill them . It is therefore important to mix the ash immediately after threshing. 17 2.3.5 B iological Control Huffer and Sm ith (1980) defined biological control as both the undisturbed activity of an tagon ists naturally present in a given ecosystem (naturally occurring biological con tro l), and the m anipulation of natural enem ies in o rder to achieve better control levels (applied biological control). G enerally, biological contro l as an in tervention tactic refers to the latter form and, more specifically , to “classical b io logical con tro l” as the in troduction o f exotic antagonists against exotic pests. O ne o f the best-documented exam ples o f classical biological control is the successful in troduction o f the solitary endoparasito id Epid inocasis lopezi (De Santis) (H ym enoptera E ncyrtidae) to control the cassava m ealy bug Phenacoccus m anihoti Mat. -Ferr. (H em inoptera, Pseudococcidae) in A frica (Herren and Neuenschwander, 1991). The term “biological con tro l” concerning pest control in cow pea has usually been used to ind icate the naturally occurring interactions between pests and their antagonists (Singh et al., 1990; Ezueh, 1991). R ecommendations fo r biological control were therefore m erely aimed at preserving the available natural enem ies (Ezueh, 1991). M urdock et al., (1997) gave an example of biological contro l m ethod involving the use o f resis tan t seeds or pods or a combination of resistant seeds and pods. They observed that seed resistance is a valuable tool but it must be carefully contro lled to avoid the rapid developm ent o f a virulent bruchid biotype. Some observations in Cameroon have suggested that the development o f varieties with com bined resistance to bruchid both in pods and seeds could result in an effective approach to ach iev ing a durable and high level of bruchid resistance. 2.3 .6 Solar and other Heat D isinfestation Techniques (a) Suscep tib ility o f Insects to Thermal Destruction: High tem peratures can be used to kill insects due to their lim ited physiological capability o f therm oregulation . As a result, bruchid eggs, larvae and pupae that are imm obile canno t escape from a hot environm ent and therefore are excellent targets for post harvest m anagem ent using elevated temperatures. Sub-Saharan A frican farmers who d isin fest cowpea have used this for a long tim e by heating on iron plates over fire. Though this technique works, it is d ifficu lt to control the cowpea from overheating and burn ing (M urdock et al., 1997). (b) CRSP P lastic Solar Heater: This also exploits the therm al susceptib ility o f the storage pest. A sim ple solar heater was developed from a sheet o f b lack polythene p laced on the ground. The grains are spread out on the sheet and the two edges folded and secured w ith objects like stones thus enveloping the grains. W hen exposed to the sunrays fo r 2 hours, all stages of the insects were killed. The m ethod did not change the cooking tim e, rate o f germ ination or the vigour o f the seedlings. The solar heater has been field tested and introduced in North Cameroon (M urdock et al., 1997). 2.3.7 Irradiation Radiation sterilisation using gamma rays helps to reduce the fertility o f the female Callosobruchus maculatus (Ahmed et al., 1979). A com bination o f irradiation with o ther m easures such as temperature has been suggested as a viable means of controlling insect infestation o f stored food. However, irradiation has not been fully accepted by most consum ers on food safety basis (Wolf, 1992). There is also the problem of the high initial capital requirem ent, especially for A frican processors who are mostly small- scale industrialists. 19 2.3.8 Storage in Pods Cowpeas are sometim es stored in the pods by farmers. K itch et al., (1991) conducted studies to determ ine w hether storage in pod form were effective in lim iting Callosobruchus maculatus dam age. T heir findings ind icated that pods, which resist breakage and are non-dehiscent, form a physical barrier to the developing larvae, and can reduce Callosobruchus m acula tus em ergence by as much as fifty percent. In addition, some varieties also possess pod-wall resistance factors that are believed to account for an additional 20-30% mortality above that due to the physical barrier effect alone. S ince bruchid larvae have to penetrate both the pod wall as well as the testa of the underlying seed, pod-seed in teractions which involve specific seed characteristics such as seed coat texture and pod characteristics such as pod strength or thickness also play an im portant role in resistance. 2.4 R eview o f Some E ffects o f the Hydrothermal T reatm ent o f C owpea Seeds The hydrothermal treatm ent is a simple, inexpensive and safe physical modification process, which does not require the use of sophisticated equipm ent o r trained personnel. It involves the exposure o f the whole cowpea seeds to acceptable storage moisture content. Sefa-Dedeh et al., (1994) reported that 5 tolO m inutes steam ed cowpeas were resistant to the weevil. A detailed study was subsequently undertaken to compare the effect o f steam and solar heat on some aspects o f the developmental biology (oviposition, developmental period, sex ratio, and food preference) and control of Callosobruchus maculatus under ambient laboratory conditions (Sefa-Dedeh et al., 1998). It was concluded that even though the number of eggs laid was not affected by the treatment, there was no em ergence of adult insects in the steam ed cowpeas. This 20 was the same even after 6 months storage whilst the seeds o f the untreated and solar dried samples were completely destroyed w ithin the period. Egyir-Yawson (1999) obtained sim ilar results. A ccording to his report, m icroscopic exam ination showed that all hatched eggs had initiated feeding but som ehow were unable to complete developm ent in the steam ed seeds and had died at an early instar. It is suggested that death could have resulted from an inability to utilise the nutrients possibly, due to structural changes in the protein and starch molecules after steam ing. The study also revealed significant differences in the resistance shown in steamed samples dried either in the solar d ryer as com pared to those dried in an air oven. The latter samples were not resistant to the attack, that is, there was em ergence o f adult insects. Prelim inary field studies have been conducted both at the farm and m arket levels (Sefa- Dedeh and Saalia, 1997). Results have shown that up to 10 weeks o f storage, steamed seeds were still clean with no signs o f insect infestation. A fter this period, the 5 m inutes steam ed seeds showed some signs o f infestation, however, the rate o f damage was much lower compared with the control. The 10 m inutes steam ed seeds remained uninfected for the entire experim ental period o f 24 weeks. Another observation made was that infestation was stopped when infested samples were steam ed and then stored. Seed viability was, however, completely lost follow ing steam ing and seeds could thus not be used for cropping. 21 Sefa-Dedeh and D em uyakor (1994) investigated the effects o f steam ing and storage on some physicochem ical properties o f cowpea seeds and flour. T hey reported that whilst the steam ing resulted in an increase in water absorption o f the flour samples, the steam ed seeds showed reduced w ater absorption capacities. S to rage further reduced the water absorption capacity for both seeds and flour. S team ing also increased the fat absorption capacity o f the flour whilst the foam ing property decreased w ith steam ing and storage for the seeds and also the flour. Obeng (1996) investigating the effect o f steam treatm ent on processing and chem ical characteristics o f cowpea seeds and flour recorded reduced seed viability w ith steam ing. The effect o f the steam treatm ent was more pronounced in the “Am an tin” variety com pared to “A sontem ” . A general reduction in both tannic and phytic acid concentration w ith increasing steam ing time was also recorded. It was also found out that cooked seed hardness was affected significantly by cow pea variety , cooking time and steam ing time. Both variety and cooking tim e but not steam ing time also significantly affected acceptability o f the cooked bean. Sefa-Dedeh and Saalia (1996) have also conducted consum er evaluation studies on the steam ed seeds. Two procedures were used- adm inistering questionnaires and focus group discussion. S team ing reduced the acceptability o f the cowpea based on the appearance, an attribute deemed important in consumer selection o f product. A majority o f the respondents (84% ) reported that unsteamed seeds had h igher sw elling capacity than the steam ed seeds. However, the steamed seeds soaked were relatively softer to touch as com pared to the unsteamed. No conclusive in form ation was ob ta ined on the time required to cook the beans to the desired softness. The reported ‘no rm al’ cooking 22 time ranged between 45 to 120 m inutes possibly due to d ifferences in heating systems. S team ing affected neither the flavour nor the taste of the cow pea m eals prepared using the samples. 23 CHAPTER THREE METHODOLOGY 3 .1 The Study Area The study was carried out in the G reater A ccra Region. The region has been producing some amount o f cowpea and is a m ajo r cowpea-consum ing centre with a high marketing potential. “M alla ta” m arket in A ccra was se lected for the study; cowpea consumers were interview ed w ith the assistance o f cowpea traders. A village called M aanpehyia in the Ga D istrict o f the G reater A ccra Region was also selected where cowpea producers were interviewed. The choice o f these locations is based prim arily on the fact that Bean/Cowpea CRSP o f which this study is a part undertook some prelim inary studies at these locations. Some o f these farmers and traders have been introduced to the hydrotherm al treatm ent m ethod o f preserving cowpea. A lso, a farm ers group exists in M aanpehyia and an Agricultural Extension O fficer is currently w orking with. This was very useful in identifying the respondents. 3.2 Analytical Framework Information gathered from both prim ary and secondary sources were analysed to achieve the objectives of the study. 24 3.2.1 Identification o f Preservation and S torage Technologies The first objective o f this study is to identify the various cowpea preservation technologies used by farmers in the study area in preserving cowpea grain. This objective was achieved by asking the respondents to indicate the technologies that they know o f and use in preserving cow pea through the use o f questionnaire. The inform ation was analysed using graphs and descriptive statistics, m ainly frequencies and percentages. In addition, o ther docum ented technologies including traditional ones were reviewed through literature search. 3.2.2 Determ ination o f the Profitab ility o f the Hydrothermal Treatm ent Technology The second objective o f this study is to determ ine the profitability o f the hydrothermal treatm ent technology in preserving cowpea. The method of analysis used to achieve this objective was to compute the N et Present Value (NPV) and the In ternal Rate o f Return (ERR) o f investing in the technology to determ ine its financial viability. 3.2.2.1 N et Present Value (NPV) The Net Present Value is the most straightforward discounted cash flow measure of project worth. It is sim ply the present worth of the increm ental net benefits or incremental cash flow stream and may be in terpreted as the present value of the income stream generated by an investm ent (G ittinger, 1982). The method consists o f discounting all future cash flows to the present value by means of an appropriate rate o f interest. NPV works on a simple but fundamental principle that, an investment is worth pursuing if, and only if, the present value o f the cash 25 inflow s is at least equal to, o r greater than, the present value o f the cash ou tflow s arising from an investm ent (Selvavinayagam , 1991). Dyson (1994) asserts that NPV is considered a highly acceptable m ethod o f investment appraisal because it takes into account the tim ing of the net cash flows, project profitability and the return o f the original investment. The NPV will be com puted for investing in the steam er used in the hydrothermal treatm ent technology of preserving cowpea grain. The quantita tive data required to calculate NPV are: • the in itial investm ent cost • the value o f future cash flow (inflow and outflow ) in each period • the econom ic life o f investm ent inputs • the d iscount rate representing cost o f capital (Selvavinayagam , 1991). M athem atically , NPV is com puted as fo llow s: NPV = - C , ) / ( l + 0 ' ] ...............................................(1) 1=0 Where: B, is the benefit in year 0 , l ,2 , .. .n C t is the cost in year 0 ,1 ,2 ,...n ‘n ’ is the expected econom ic life span of the investm ent ‘t ’ takes values of 0 ,1 ,2 ,....n ‘i ’ is the discount rate. 26 The decision criterion is to accept all independent investm ents/pro jects w ith NPV of zero or greater when discounted at the appropriate cost o f capital. 3 .2 .2 .2 Internal Rate o f Return (IRR) Another way of using incremental net benefit stream or cash flow for m easuring the worth o f an investm ent is to find the discount rate that makes N PV o f the incremental net benefit stream equal to zero. This discount rate is called the in ternal rate o f return. It m easures the average earning capacity o f an investm ent year afte r year throughout its useful life. In other words, IRR is the m aximum interest that a pro ject cou ld pay on average for the resources used if the project is to ju s t recover its investm ent and operating costs (G ittinger, 1982). M errett and Sykes (1973) assert that IRR is the rate o f return on cap ita l ou tstanding per period while it is invested in a project. M athem atically , IRR is expressed as the d iscount rate, R such that: Where: B(, C,, n and t are as earlier defined ‘R ’ is the IRR in equation 2. 27 The IRR was computed by iteration, which means using trial and erro r method. The computation involves choosing an arbitrary discount rate to com pute the NPV. If the NPV is found to be greater than zero, a higher discount rate is used; and a lower d iscount rate used if com puted NPV is found to be less than zero. The process is repeated until a d iscount rate that equates NPV to zero is discovered. This d iscount rate is the ERR. To determ ine where the real IRR lies between the lower discount rate that gives a negative NPV and the h igher in terest rate o f return that gives a positive NPV, linear interpolation technique was em ployed as shown in equation 3. IRR = L d + (U D - L d ) 7 T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 ) D v D d j \n p v u \ + \n p v l \ Where, Ld = L ow er d iscount rate; UD = H igher discount rate; NPV l = Net present value at the lower discount; NPVu = Net present value at the higher discount. /N PV |j/+ /N PV h/ = Sum o f the absolute net present values at the two discount rates (signs ignored). The decision criterion for IRR as a measure for financial analysis is to accept all independent projects or investm ents having an IRR equal to or greater than the cost of capital or cost o f loan. 28 3 .2 .2 .3 Choosing the D iscount Rate To be able to use the discounted measures o f project worth, there was the need to make a decision on the discount rate to use to calculate NPV or the rate below which it will be unacceptable for the IRR to fall (the cu t-off rate). A ccording to G ittinger (1982), the discount rate for financial analysis is the m arginal cost o f m oney to the firm for which the analysis is being done. This is often the lending rate or the rate at which the enterprise is able to borrow money. The lending rate quoted by the Bank o f Ghana during the period of the study (January to June, 2001) was used. 3.2.2.4 Sensitivity Analysis (Treatm ent o f Uncertainty) One o f the real advantages o f a careful investm ent analysis is that, it may be used to test what happens to the earning capacity o f the project if events d iffer from guesses made about them during planning. For example, how sensitive is a p ro jec t’s NPV at financial prices o r its financial rate o f return? Reworking to see what happens under these changed circum stances is ca lled sensitiv ity analysis (G ittinger, 1982). A variation of sensitivity analysis is the sw itching value. Calculating sw itching value involves determ ining how much an element would have to change in unfavourable direction before the project would no longer meet the m inimum level o f acceptability as indicated by one o f the m easures o f project worth. One sw itching value test is to determ ine the m aximum benefit delay before the NPV of an investm ent will fall below zero for the investment to be rejected. 29 3.2 .3 Determ ination o f Cowpea Characteristics that In fluence Consum ers Purchase Decisions The third objective o f the study is to determ ine the characteristics o f treated and un treated cowpea that in fluence consumers purchase decisions. This ob jective was achieved through the use o f structured questionnaire and/or personal interview s to co llect data on the factors and/or characteristics o f cowpea that in fluence purchase decisions of consum ers. The inform ation collected was analysed using descriptive statistics, m ainly frequencies, percentages and ranking. 3.2.4 Identification o f Socio-econom ic Factors that A ffect F arm ers’ Choice o f Preservation M ethods The fourth objective o f the study is to determ ine the socio-econom ic factors that affect the adoption o f pest control technologies by cowpea farmers. T he chem ical pest control m ethod as a technology was used for the analysis. This was determ ined using the Probit regression model. 3.2.4.1 The Probit Model The P robit regression model was used to determ ine objective four. Farm ers face outcom es from the adoption of storage technologies that are uncertain. In this model, cowpea farmers are assumed to make adoption decisions based upon an objective of utility maxim isation. 30 T h e P ro b it m ode l is g iv e n as: f 1 nlf _ ' 2 l I . V2H 2\ / Where: t is a random variable distributed as a standard normal deviate (3 is a vector o f unknown coefficients X, is a vector o f characteristics o f the individual