ECONOMIC ANALYSIS OF COWPEA PRESERVATION TECHNOLOGIES WITH SPECIAL FOCUS ON THE HYDROTHERMAL TREATM ENT TECHNOLOGY BY EMMANUEL DELALI KWAMLA OFORI TH IS TH ESIS IS S U B M IT T E D T O T H E U N IV E R SIT Y O F G H A N A , L E G O N , IN PA R T IA L F U L F IL M E N T O F T H E R E Q U IR E M E N T S F O R T H E D E G R E E OF M A ST E R O F P H IL O SO P H Y IN A G R IC U L T U R A L A D M IN IS T R A T IO N D EPA R T M E N T O F A G R IC U L T U R A L EC O N O M IC S AND A G R IB U SIN E SS, FA C U L T Y OF A G R IC U L T U R E , U N IV E R SIT Y O F G H A N A , LEG O N . D E C E M B E R , 2002. T * * 3 7 \2Sy S < $ , J I P S - - C 2 is . O i D E C L A R A T IO N I, Em m anuel D elali K w am la O fori, the author o f this thesis titled “E conom ic A nalysis o f C ow pea Preservation T echnologies w ith Special Focus on the H ydrotherm al T reatm ent T echnology” hereby declare that, this w ork was done entirely by m e in the D epartm ent o f A gricultural E conom ics and A gribusiness, U niversity o f G hana, Legon. The w ork has never been presented either in w hole or in part fo r any o ther degree of this U niversity or elsew here except for o ther p eop le’s w ork, w hich have been duly cited. E M M A N U EL D. K. OFORI. (STU D EN T) This thesis has been presented for exam ination with our approval as supervisors. REV. DR. S. A SU M IN G -B R EM PO N G DR. B R U C E SA R PO N G (M A JO R SU PER V ISO R ) (C O -SU PER V ISO R ). D E D IC A T IO N This w ork is w holeheartedly ded icated to m y parents Mr. G. G. K. O fori and M rs. Edith B. Ofori for their im m ense contribution to my education m ost 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 em ory o f m y late cousin M r. A m m ishadai Kwasi Agbenosi Ofori w ho died m ysteriously on Ju ly 1, 1985 at the U niversity o f Cape Coast. Brother, rest in peace. I m ust first thank Jehovah G od 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 m y sincerest appreciation to m y supervisors R ev. D r. S. A sum ing- B rem pong and Dr. B ruce Sarpong for taking tim e off their busy schedules to provide very useful contributions and suggestions for the study. I am also grateful to all other m em bers o f staff o f the D epartm ent o f A gricultural E conom ics and A gribusiness of the U niversity o f Ghana, m ost especially Dr. G eorge T-M . K w adzo , M r. F rancis Egu and Mr. R eindorf Darko. The staff o f the N utrition and F ood Science D epartm ent o f the U niversity o f Ghana, m ost especially M s. C ynthia A nku-Tsede and M r E m m anuel A fuakw a, provided me w ith the relevant data on hydrotherm al treatm ent technology. Y our contribution tow ards this study is very m uch appreciated. Mr. Isaac V anderpuye, an A gricultural Extension O fficer w ith the M inistry of Food and A griculture, G a D istrict O ffice at A m asam an in A ccra and S ister R egina, a cow pea seller at the M allam Atta m arket in Accra assisted me during the collection of data from the cow pea farm ers and consum ers, respectively. I thank you very m uch for your contribution. ACKNOWLEDGEMENT M y heartfelt gratitude goes to M essrs Benjam in H oenyenugah (m y room m ate), Francis Srofenyo, Sam uel T im po, Eric Sam pane-D onkor, G eorge H onya, N icholas D zandza, E. T. A dika, D onsananang Jatoe and M s. P eace N tum y for their contributions in diverse ways (which I cannot m ention here ind iv idually ) tow ards the com pletion o f this work. A special appreciation goes to m y dear one M s. H annah D ei for her support and patience in the course of m y study. H annah, thank you very m uch. I w ould also like to express my profound gratitude to m y course m ates m ost especially M essrs L ovelace Yanney, Siegfried A gbodza and C osm os A biw u for all their help. F inally, to all those not m entioned here but w ho contributed to this w ork in diverse ways, I thank you all very much and wish you Jehovah G od’s guidance. E m m anuel D. K. Ofori. ABSTRACT The need to increase and sustain the production of cow pea in G hana has been recognised. It is a cheaper source o f protein and thus has the potential to alleviate protein m alnutrition. S pecifically , the study determ ines the various storage and preservation technologies that are know n and/or used by cow pea farm ers, the profitability of cow pea preservation by m eans of the new ly in troduced technology called the hydrotherm al treatm ent technology and also identifies the characteristics that determ ine the purchase decision o f cow pea consum ers. T he socio-econom ic factors that influence the adoption o f preservation and storage technologies o f cow pea grain by farm ers w as also determ ined. The results show that the four storage and preservation technologies m ost w idely practised by cow pea 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 cow pea grains fo r about 10 m inutes after w hich the grain is properly dried and stored. T he profitability o f cow pea preservation using the hydrotherm al treatm ent technology w as determ ined by the use o f N et P resen t V alue 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 treatm ent technology is profitable. The estim ated values o f N PV and IRR w ere 0345,262.42 and 90% respectively. B enefits envisaged with the adoption of this technology include the reduction o f cow pea storage losses induced by insect pests thereby leading to an increase in productiv ity and subsequent increase in the incom e earning capacities o f the fanners. The three m ost im portant characteristics o f cow pea grains that are considered by consum ers in m aking the ir purchase decisions are: absence o f im purities, lack of insect em ergence holes in the grain, and cooking tim e in that order. It is recom m ended that sim ilar p rofitab ility studies should be carried out on other technologies used in the preservation and storage of cow pea grain. T he results o f such studies will form the basis for farm ers to com pare and m ake in form ed choices. vi TABLE OF CONTENTS D E C L A R A T IO N ....................................................................................................... i D E D IC A T IO N ............................................................................................................. » A C K N O W L E D G E M E N T .................................................................................... Hi A B S T R A C T ............................................................................................................. v T A B L E O F C O N T E N T S ..................................................................................... vii L IS T O F T A B L E S ................................................................................................ x L IS T O F F IG U R E S ................................................................................................ xi L IS T O F A P P E N D IC E S .................................................................................... xii A B B R E V IA T IO N S /A C R O N Y M S ................................................................. xiii C H A P T E R O N E IN T R O D U C T IO N ...................................................................................................... 1 1.1 B ackground and Problem S tatem en t...................................................... 1 1.2 O bjectives o f the S tu d y .............................................................................. 7 1.3 Relevance o f the S tu d y .............................................................................. 8 1.4 O rganisation o f the S tu d y ......................................................................... 10 C H A PTER T W O L IT E R A T U R E R E V IE W .................................................................................. 11 2.1 Pest M anagem ent P h 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 C ontainer S to rage .............................................................................. 16 2.3.4 C o-storage w ith ash and other A biotic M ateria ls .................................. 17 2.3.5 B iological C o n 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 o d s................................................................................................ 20 2.4 R eview o f Som e Effects o f the H ydrotherm al T reatm ent o f C ow pea.................................................................................................................... 20 C H A PT E R T H R E E M E T H O D O L O G Y ................................................................................................ 24 3.1 The Study A rea ................................................................................................ 24 3.2 A nalytical 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 H ydrotherm al T reatm ent T echno logy ................................................................................... 25 3.2.2.1 N et Present V alue (N P V )....................................................................... 25 3.2.2.2 Internal R ate o f Return (IR R )................................................................ 27 3.2.2.3 C hoosing the D iscount R ate ...................................................................... 29 3.2.2.4 Sensitivity A nalysis (Treatm ent o f U ncerta in ty ).................................. 29 3.2.3 D eterm ination of C ow pea C haracteristics that Influence C onsum ers Purchase D ecisions ........................................................... 30 3.2.4 Identification of Socio-econom ic Factors that Affect Farm ers’ C hoice o f Preservation M ethods............................................. 30 3.2.4.1 The P robit M o d e l........................................................................................ 30 3.2.4.2 Specification o f the M o d e l ...................................................................... 31 3.3 D ata S o u rces ..................................................................................................... 35 3.4 M ethod o f D ata C o llec tio n ...................................................................... 36 C H A P T E R F O U R R E SU L T S A N D D IS C U S S IO N ............................................................................. 37 4.1 In troduc tion ..................................................................................................... 37 4.2 S ocio-E conom ic C haracteristics o f the R esponden ts..................... 37 4.2.1 C ow pea F a n n e rs ........................................................................................ 37 4.2.2 C ow pea C o n su m ers......................................................................................... 39 4.3 S torage P est C ontrol T echnologies U sed by C ow pea F a rm e rs ... 42 4.4 Investm ent A n aly s is .................................................................................. 46 4.5 C haracteristics o f C ow pea Grain that Influence the Purchase D ecision o f C onsum ers.............................................................................. 51 4.6 R egression R e su lts ......................................................................................... 54 C H A PT E R FIV E C O N C L U SIO N A N D R E C O M M E N D A T IO N S......................................... 57 5.1 C o n c lu s io n ..................................................................................................... 57 5.2 R ecom m endations......................................................................................... 58 R E F E R E N C E S ............................................................................................................. 60 A P P E N D IC E S ............................................................................................................. 66 LIST OF TABLES Table 1.1 A nnual Q uantities o f C ow pea Produced in G hana (1 9 8 0 -1 9 9 6 )................ 3 T able 3.1 D escrip tion of the V ariables used in the Em pirical M o d e l ...................... 32 Table 4.1 Age D istribution o f the F an n e rs ........................................................................ 38 Table 4 .2 E ducational Levels o f the F arm ers........................................................................ 39 Table 4.3 C onsum ers R esponse on w hether they cared to find out if the C ow pea grain they purchased has been T reated C h e m ic a lly ..................... 40 T able 4 .4 A ge D istribu tion o f the C onsum ers In terv iew ed......................................... 41 T able 4.5 D eterm ination o f P rofitability Indicators- N PV and IR R .......................... 47 Table 4 .6 C om puted N PV and IRR values assum ing 10% fall in the Price o f T reated C ow pea ...................................................................................................... 49 Table 4 .7 C om puted N PV and IRR values assum ing 10% increase in the C ost o f U ntreated C ow pea.......................................................................................... 50 Table 4.8 C onsum er R anking of Q uality C haracteristics o f C ow pea G ra in 52 Table 4 .9 P robit M odel R esults for Chem ical Pest Control by C ow pea F arm ers .............................................................................................................................. 55 Page x LIST OF FIGURES Figure 4.1 T echnologies known to Farm ers in C ontrolling Storage Pests o f C ow pea .............................................................................. 43 F igure 4.2 T echnologies in U se by Farm ers in C ontrolling Storage Pests o f C ow pea .............................................................................. 44 Page XI A ppendix I Q uestionnaire for C ow pea F arm ers............................................ 66 A ppendix II Q uestionnaire for C ow pea C onsum ers................................. 70 A ppendix III Q uestionnaire for R esearchers W orking on the H ydrotherm al T reatm ent T echno logy ................................... 73 A ppendix IV R eference N otes and A ssum ptions M ade C oncerning the D eterm ination o f Profitability Indicators (NPV and I R R ) .............................................................................. 74 A ppendix V Sensitivity A nalysis ...................................................................... 75. LIST OF APPENDICES Page xn ABBREV IATIO NS/ ACRONYM S C R SP - C ollaborative Research Support P rogram C SIR - Council for Scientific and Industrial Research FA O - Food and A griculture O rganisation G D P - Gross D om estic Product G G D P - G hana G rain D evelopm ent P roject H a - Hectare EFPRI - International Food Policy R esearch Institute IITA - International Institute o f T ropical A griculture IRR - Internal Rate o f Return JIR C A S - Japan International R esearch C entre for A gricultural Sciences Kg - K ilogram m e M O FA - M inistry of Food and A griculture N PV - N et P resent V alue PPM E D - Policy P lanning M onitoring and E valuation D irectorate W H O - W orld H ealth O rganisation CHAPTER ONE INTRODUCTION 1.1 Background and Problem Statem ent Food item s such as cereals, root and tubers, m eat, m ilk, fish, edible oils and fats are nutritionally m ore rew arding. H ow ever, their dom estic production in certain countries have not yet caught up with the dem ands 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 betw een p lanting and harvesting of the next m ain food crops. This seasonal food shortage o r the “hungry” season is a w ell- know n phenom enon in A frican peasant agriculture. The param ount role o f im proved m ethods o f food production , preparation, processing, preservation, storage, distribution and m arketing fo r the im provem ent o f food consum ption patterns to achieve a high level o f nutrition and im proved quality of life o f the A frican people cannot be over-em phasised. A ccording to Y udelm 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 A m erica by then are to be food secure. C ow pea [Vigna unguiculata (L.) W alp] belongs to a group o f crops called grain legum es or pulses, which are generally noted for their high protein content, and has the potential o f alleviating protein m alnutrition m ost especially in developing countries. l C ow pea is an im portant legum e o f the tropics, w ith various uses, including grains in processed foods, a vegetable (fresh leaves, peas, and pods), and as fodder. C ow pea pulse processed into products such as flour o r m eal could be used to m ake sw eets, cakes and porridge for hum an consum ption. G round cow pea grain is considered a valuable feedstuff for poultry and rum inant diets. D ovlo et al. (1976) reported that cow pea 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 com plem entary to that o f cereal grains. A ccording to B arrett (1990), cow pea is am ong the top three or four leafy vegetables used in m any parts o f A frica. C ow pea in com bination or association with cereals and o ther grain legum es 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 cow pea m ake it a particularly attractive crop for the subsistence farm ers o f Sub-Saharan A frica, w here about 70% o f the w orld ’s cow pea are grown (Singh et al. 1990; Singh et al. 1997). G hana has a favourable clim atic condition for cow pea cultivation. The crop grows well in hot tropical clim ates; it requires a tem perature range o f 20 and 30 degrees Celsius, and rainfall range o f betw een 400 and 800 m illim etres per annum (M uleba and Ezum ah, 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 cow pea production in G hana betw een 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 cow pea produced declined from 17,000 tonnes in 1981 to the low est value of 11,000 tonnes in 1985 although a break in the dow nw ard trend was recorded in 1984 w hen the quantity was 14,000 tonnes. B etw 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 . T able 1.1 A nnual Q uantities o f C ow pea P roduced in G hana (1980-1996). Y ear Q uantity o f C ow pea Produced (‘000 kg). A nnual G row th in O u tput (%). 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: PPM ED , M O FA , Accra. 3 C ow pea production in G hana therefore presents a p icture o f a fluctuating but basically upw ard trend. The fluctuating output in G hana despite the useful features o f cow pea could be due to low investm ent in cow pea industry, w hich is considered risky because o f the num erous problem s in growing, harvesting and sto ring the crop (Jackai and A dalla 1997). S evere yield losses o f cow pea are caused in tropical A frica by the in terplay o f abiotic (for exam ple, drought) and biotic (for exam ple, arthropod pests, d iseases, birds, and rodents) constraints. R anked first am ong 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 cow pea from seedling em ergence to storage. It has been show n that field pest problem s during the crop’s vegetative cycle are substan tia l, and insects such as M aruca spp and A pion 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 cow pea grain is the cow pea bruchid, Callosobruchus m acula tus , also know n erroneously as the "cow pea w eevil" (Taylor, 1981). C allosobruchus m aculatus infestations start in the field and continue in storage. C ow pea on sale in m arkets often has bruchid em ergence holes. O ther im portant insect pests o f cow pea in storage include B ruchidius a tro linea tus and C allosobruchus chinensis. 4 T he financial and nutritional losses in cow pea due to storage pests in Sub-Saharan A frica are not well docum ented, but are clearly high. L ow -resource farm ers often sell their cow pea at harvest, when prices are low est in the year, partly because they anticipate storage losses. Being aw are 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 cow pea 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 dam aged 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, m ated, and laid additional eggs, counting em ergence holes to assess dam age undoubted ly represents only a part o f the problem . The next generation o f larvae, m ore num erous will generally still be developing w ithin the grain. T echnologies are now available to lim it post harvest losses due to insect pests infestation of cow pea grain. Solar disinfestation, com bined w ith subsequent storage under conditions that prevent reinfestation, enables long-term preservation of threshed grain from insect attack (M urdock et al., 1997). C ow pea varieties w ith seed resistance, pod-w all resistance, and com bined seed and pod-wall resistance have been bred through the jo in t efforts o f breeders and entom ologists (Kitch, 1992). C ow pea grain storage in airtight containers, such as m etal drum s or triple plastic bags, arrests the developm ent o f storage insect populations (Kitch and N toukam , 1991a). M ixing the grain with wood ash also stops dam age to grain by storage insect pests (W olfson et al., 1991; Kitch and N toukam , 1991b). C ow pea grain treatm ents 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 cow pea pest control, a function for w hich they rem ain unrivalled (National A cadem y o f Sciences, 1969). Currently, econom ic necessity , sensitiv ity to environm ental destruction and health considerations (chem ical residues) has rendered insecticide use socially unacceptable. The use of insecticides to protect cow pea grain in storage is probably m ore com m onplace 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 N utrition and Food Science of the U niversity o f G hana has developed a new m ethod o f cow pea preservation called h ydrotherm al treatm ent technology. This m ethod is applicable to cow pea 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 hydrotherm al treatm ent technology, which is a sim ple, 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 w hole cow pea seeds to steam follow ed by drying to acceptable storage m oisture content. P relim inary w ork by Sefa-D edeh et al. (1994) show ed that 5 to 10 m inutes steam ed cow peas w ere resistant to the weevil. Subsequent studies w ere conducted to determ ine the effect o f the steam ing process on the seeds, and som e o f the results have been presented in the chapter on literature review of this study. D espite these developm ents in technologies, the problem s of post harvest losses in cow pea are still ev ident in Ghana. It is therefore necessary to identify the constraints lim iting the cow pea industry in the country. Such studies on cow pea developm ent must lay em phasis on analysis o f constra in ts in the entire production chain, that is, from field production to consum ption and utilization, including w hat happens to the produce during storage and processing. This study basically attem pts to investigate the financial viability o f the hydrotherm al treatm ent technology for cow pea preservation . The study therefore proposes to address the follow ing questions: W hat preservation technologies do cow pea farm ers know and /o r use? O f those farm ers w ho know o f these technologies but do not use them , w hat are the factors that prevent their use? Is the hydrotherm al treatm ent technology profitab le? W hat are the characteristics o f cow pea grains that influence the purchase decisions o f consum ers? W hat are the factors that determ ine the adoption o f pest control technologies by cow pea farm ers? T hese are som e o f the issues this study has tried to address. 1.2 O bjectives o f the Study The prim ary objective o f the study is to determ ine the v iability o f the hydrotherm al treatm ent technology o f cow pea preservation. The specific objectives are: 1. To identify the various technologies used by farm ers in the preservation and storage of cowpea. 2. To determ ine the profitability o f the hydrotherm al treatm ent technology in preserving cow pea. 3. To determ ine the characteristics of cow pea that influence purchase decisions of consum ers. 4. To determ ine the factors that affects the adoption of pest control technologies by cow pea farmers. 1.3 R elevance o f the Study Protein deficiency disorders, such as kw ashiorkor and m arasm us are m ajo r nutritional problem s in m ost develop ing countries including Ghana. T he total daily protein intake o f an adult hum an being recom m ended by FAO is 55.0 g ram m es fo r norm al growth and healthy m ental developm ent (Bender, 1992). G h an a’s per cap ita protein intake according to FA O (1994) report was 46.9 gram m es falling short o f the recom m ended intake value. C ow pea, w hich 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, cow pea grain contains 23-25% protein and 50-67% starch (S ilano et al. 1981). Cow pea is also o f im portance 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 fam ilies variously derive food, anim al feed and cash, together w ith spill over benefits to their farm lands through, for exam ple, in situ decay o f root residues, use as anim al feed, and ground cover from co w p ea’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 com m unities. In fresh form , the young leaves, im m ature pods, and peas are used as vegetables, while several snacks and m ain m eal 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. B eyond its im portance for food and feed, cow pea 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. A nother im portant 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. A ccording to K ay (1979) a vigorous grow ing food legum e such as the cow pea can add as m uch 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 am m onium sulphate. In addition, cow pea is drought hardy, and it is able to m aintain som e 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 ro p ’s ability to grow and yield under the sem i desert conditions of the A frican Sahel. T he off-take o f cow pea fodder m akes an im portant contribu tion to feed supplies for large and sm all rum inants. The spill over benefits are that traction anim als m aintain reasonable health status during the dry season, enabling tim ely land preparation when the w et season begins. A lso, return of anim al m anure to the land by cartage from kraals o r in situ grazing contributes to soil fertility. W ith the developm ent o f irrigation schem es in som e areas o f W est and C entral Africa, and the general increased use of w etlands, cow pea 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 som ew hat sim ilar to the production of cow pea in rice-based cropping system s. T his 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 cow pea, there is the need to undertake this study to establish the profitability o f the hydrotherm al treatm ent technique. R ecom m endations based on the findings w ould be useful in sustaining the 9 cow pea industry through reduction o f post harvest losses and enhancing the quality o f available grain for consum ption. 1.4 O rganisation o f the Study The study is organised into five chapters. The background and problem statem ent, 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 recom m endations o f the study. 10 CHAPTER TWO LITERATURE REVIEW This chapter presents a review o f the relevant literature on cow pea preservation m ethods. The review entails general as well as literature specific to the G hanaian situation. 2.1 Pest M anagem ent Philosophy Insects are considered pests because o f the socio-econom ic and m edical th reat they pose to m an and his property. B iologically , an insect is a pest when its population density and/or dam age 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 low est population or dam age level capable of causing econom ic im pact (Poston, et al 1983). If the population of an organism exceeds the econom ic injury level, the organism becom es 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 environm ental stress factors such as predation, com petition, and other natural m ortality factors, constituting the environm ental 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 som e 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. U sually, the dam age or population density o f the pest is not allow ed to reach levels that w ould 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 m ust therefore be in troduced, augm ented, or applied to the system (H orn, 1986; M etcalf and Luckm ann, 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 cow pea 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 tim e. Farm ers are well aware of the losses they suffer in storage and in m any cases estim ate that everything will be eventually lost if no contro l m easures are taken (W olfson et al. 1990; G oldm an 1991). C ow peas 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 cow peas. A m egatse (1995) reports that 66.7% of respondents in a survey in G hana indicated that insect (w eevil) infestation was the m ajor prob lem associated with cow pea storage. A bout 80 insect species have been identified as pests o f stored cow peas in G hana including C allosobruchus m aculatus, which is one o f the nine m ajor pests, identified (A gen-Sam pong, 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 m onths. T he FA O (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. V arious estim ates o f the m agnitude o f the post harvest losses (due to insect attack) have been made. T he values are generally very high, an estim ated 30% o f stored rice is lost to insects in S ierra Leone w hilst, 25-45% o f sto red m aize is lost to insect pests in G hana (Hill and W aller, 1988). C om parable levels o f losses have been reported in E ast and Southern A frica and other parts o f the tropical w orld (Boxall, 1989). In the Sahelian areas of N igeria, w eevil infestation o f cow pea grain m ay reach 40% in m arkets by the early w et season, w hich is June/July (C asw ell, 1981). T he loss o f food m aterial as a direct result o f insect attack occurs through two main m eans. Insect activity either through boring into the seeds and/or surface feed ing results in the rem oval o f food m aterial, usually from the portions o f h ighest nutritional value. There is also the respiring activity of the insects, w hich results in high m oisture developm ent in the stored grain encouraging the growth o f m icro organism s with their ow n associated problem s. A rela tively insignificant w eight loss in a grain sam ple m ay have far reach ing effects. This is especially im portant if it leads to either a total rejection o f the w hole batch by the consum er or to a drastic price reduction. A ccording to S ingh and Jackai (1985), up to 30% loss in w eight may occur after six (6) m onths with 70% o f seeds being infested and grain being alm ost unfit for consum ption. Insect infestation leads not only to econom ic losses but also results in nutritional losses in cases w here 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; L ow enberg-deB oer, 1995). 2.3 C ontrol 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. T he choice o f the m ethod is affected by m any considerations including the availability and costs o f inputs, labour requirem ent, tim e fram e 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 (M urdock, et al., 1997). A m egatse (1995) found that m ajority (56.2% ) of cow pea farm ers interview ed in the G a D istric t o f the G reater A ccra R egion, G hana, em ployed interm ittent drying o f bagged cow peas w hilst 27% used chem ical pesticides or airtight containers. P reservation w ith palm kernel oil, sm oke, w ood ash and kerosene were other traditional o r ind igenous m ethods used. 2.3.1 C hem ical Preservation o f C ow pea Synthetic chem icals continue to be im portant 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 harm ful side effects (Yudelm an 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, w hich could exceed the recom m ended safety levels. For instance, applying 100 gram m es o f actellic super dust per 90-100 kilogram m e bag of grain produces residues of 3.3 m illigram m es perm ethrin and 17.7 m illigram m es pirim iphos methyl per kilogram m e grain. T his is m ore than the 14 FAOAVHO recom m ended residual levels o f 2 m illigram m es and 10 m illigram m es per kilogram m e, respectively (Golob, 1988; U ronu, 1988). In A frica, m ost subsistence farm ers do not keep their produce in storage for long periods. T hus 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 cow pea farm ers 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 E d ib le oils and B iologic M aterials M ixing 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 em bryo. It also deters ov iposition and causes death o f adult insect pests. V arieties o f oils are suitable, for exam ple palm kernel oil, cotton seed oil and groundnut oil. A ccording to studies undertaken by Singh et al., (1979) and P ereira (1983), groundnut oil was found to be the m ost effective of the edible oils, providing com plete protection for up to 25 w eeks 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 m ethyl. The am ount o f oil needed for an effective preservation is usually very small, 5 m illilitres per kilogram m e of grain (Singh et al., 1979). T here are, how ever, some difficulties associated with this treatm ent. 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 exam ple 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 m aterials. O funya (1986) noted that onion scales and dried chilli pepper conferred som e degree o f protection against C allosobruchus m aculatus. 2.3.3 Sealed C ontainer Storage In this m ethod, the m oisture present results in germ ination o f som e grains. The resulting respiration elim inates oxygen in the enclosure thus suppressing insect infestation. Sealed containers m ay be large, underground silos or sim ple m etal drum s (M urdock et al., 1997). A practical drum storage technique has been developed in Senegal under the B ean/C ow pea C ollaborative R esearch Support Program (CRSP). T he beans are first sun dried and then the drum is filled w ith the dry beans. It has been recom m ended that the drum be sealed for a m inim um period o f 2 m onths before opening. It is also im portant that the drum be airtight. Its advantages include the relatively low initial cost and repeated use o f the drum s. H ow ever, the period within w hich the drum m ust remain sealed for the treatm ent to be effective is quite long. There is also the problem of weight of large drum s but this is usually overcom e by using racks. 16 Storage using triple plastic bagging is another sim ple and inexpensive m ethod also developed by the C R SP in Cam eroon. T he technique m akes use o f clear plastic bags, w hich are w idely available. T he grains are put in a bag (40-50 k ilogram m es) and tightly sealed with tw ine. This is then p laced com pletely into a second and then a third bag and sealed sim ilarly. T ests in various C am eroonian villages have show n that the m ethod is effective and readily accepted by sm all-scale farm ers. D ue to the transparent nature, the farm er can observe the grains periodically . H ow ever, 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 G hana has investigated the potential o f storing cow peas 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 farm ers in storing their ou tput (O sei, 1993). 2.3.4 C o-storage w ith A sh and other A biotic M aterials W olfson et al., (1989) found that the m ost com m on traditional post harvest storage m ethod in N orthern C am eroon was the use of ash. This has also been noted in other Sub-Saharan A frican countries including G hana (M urdock et al., 1997). The ash used com es 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 m ore effective if the ratio is three or m ore parts ash to four parts grain. A lthough the ash stops the developm ent of the bruchid population in the grain stored, it does not kill them . It is therefore im portant to mix the ash im m ediately after threshing. 17 2.3.5 B iological Control H uffer 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, m ore 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-docum ented exam ples o f classical biological control is the successful in troduction o f the solitary endoparasito id E pid inocasis lopezi (De Santis) (H ym enoptera E ncyrtidae) to control the cassava m ealy bug Phenacoccus m anihoti M at. -Ferr. (H em inoptera, Pseudococcidae) in A frica (H erren and N euenschw ander, 1991). The term “biological con tro l” concerning pest control in cow pea has usually been used to ind icate the naturally occurring interactions betw een pests and their antagonists (Singh et al., 1990; Ezueh, 1991). R ecom m endations fo r biological control were therefore m erely aim ed at preserving the available natural enem ies (Ezueh, 1991). M urdock et al., (1997) gave an exam ple of biological contro l m ethod involving the use o f resis tan t seeds or pods or a com bination of resistant seeds and pods. They observed that seed resistance is a valuable tool but it m ust be carefully contro lled to avoid the rapid developm ent o f a virulent bruchid biotype. Som e observations in C am eroon have suggested that the developm ent 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 S olar and other H eat D isinfestation T echniques (a) S uscep tib ility o f Insects to T herm al D estruction: 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 im m obile canno t escape from a hot environm ent and therefore are excellent targets for post harvest m anagem ent using elevated tem peratures. Sub-Saharan A frican farm ers w ho d isin fest cow pea have used this for a long tim e by heating on iron plates over fire. T hough this technique works, it is d ifficu lt to control the cow pea from overheating and burn ing (M urdock et al., 1997). (b) C R SP P lastic S olar H eater: 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. T he grains are spread out on the sheet and the tw o 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. T he 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 N orth Cam eroon (M urdock et al., 1997). 2.3.7 Irradiation R adiation sterilisation using gam m a rays helps to reduce the fertility o f the fem ale C allosobruchus m aculatus (Ahm ed et al., 1979). A com bination o f irradiation with o ther m easures such as tem perature has been suggested as a viable m eans of controlling insect infestation o f stored food. However, irradiation has not been fully accepted by m ost consum ers on food safety basis (W olf, 1992). T here is also the problem of the high initial capital requirem ent, especially for A frican processors who are m ostly sm all- scale industrialists. 19 2.3.8 Storage in Pods C ow peas are som etim es stored in the pods by farm ers. K itch et al., (1991) conducted studies to determ ine w hether storage in pod form w ere effective in lim iting C allosobruchus m aculatus 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 C allosobruchus m acula tus em ergence by as m uch as fifty percent. In addition, som e varieties also possess pod-w all resistance factors that are believed to account for an additional 20-30% m ortality 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 Som e E ffects o f the H ydrotherm al T reatm ent o f C ow pea Seeds The hydrotherm al treatm ent is a sim ple, inexpensive and safe physical m odification process, w hich does not require the use of sophisticated equipm ent o r trained personnel. It involves the exposure o f the w hole cow pea seeds to acceptable storage m oisture content. Sefa-D edeh et al., (1994) reported that 5 tolO m inutes steam ed cow peas were resistant to the weevil. A detailed study was subsequently undertaken to com pare the effect o f steam and solar heat on som e aspects o f the developm ental biology (oviposition, developm ental period, sex ratio, and food preference) and control of C allosobruchus m aculatus under am bient laboratory conditions (Sefa-D edeh et al., 1998). It was concluded that even though the num ber of eggs laid was not affected by the treatm ent, there was no em ergence of adult insects in the steam ed cow peas. This 20 was the sam e even after 6 m onths storage w hilst the seeds o f the untreated and solar dried sam ples were com pletely destroyed w ithin the period. Egyir-Y aw son (1999) obtained sim ilar results. A ccording to his report, m icroscopic exam ination show ed that all hatched eggs had initiated feeding but som ehow were unable to com plete 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 m olecules after steam ing. The study also revealed significant differences in the resistance show n in steam ed sam ples dried either in the solar d ryer as com pared to those dried in an air oven. The latter sam ples w ere 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- D edeh and Saalia, 1997). R esults have show n that up to 10 w eeks o f storage, steam ed seeds w ere still clean with no signs o f insect infestation. A fter this period, the 5 m inutes steam ed seeds show ed som e signs o f infestation, how ever, the rate o f dam age was m uch low er com pared with the control. T he 10 m inutes steam ed seeds rem ained uninfected for the entire experim ental period o f 24 weeks. A nother observation m ade was that infestation was stopped when infested sam ples were steam ed and then stored. Seed viability was, how ever, com pletely lost follow ing steam ing and seeds could thus not be used for cropping. 21 Sefa-D edeh and D em uyakor (1994) investigated the effects o f steam ing and storage on som e physicochem ical properties o f cow pea seeds and flour. T hey reported that whilst the steam ing resulted in an increase in w ater absorption o f the flour sam ples, the steam ed seeds show ed reduced w ater absorption capacities. S to rage further reduced the w ater absorption capacity for both seeds and flour. S team ing also increased the fat absorption capacity o f the flour w hilst the foam ing property decreased w ith steam ing and storage for the seeds and also the flour. O beng (1996) investigating the effect o f steam treatm ent on processing and chem ical characteristics o f cow pea seeds and flour recorded reduced seed viability w ith steam ing. T he effect o f the steam treatm ent was m ore pronounced in the “A m an tin” variety com pared to “A sontem ” . A general reduction in both tannic and phytic acid concentration w ith increasing steam ing tim e was also recorded. It w as also found out that cooked seed hardness was affected significantly by cow pea variety , cooking tim e and steam ing tim e. Both variety and cooking tim e but not steam ing tim e also significantly affected acceptability o f the cooked bean. Sefa-D edeh and S aalia (1996) have also conducted consum er evaluation studies on the steam ed seeds. T w o procedures were used- adm inistering questionnaires and focus group discussion. S team ing reduced the acceptability o f the cow pea based on the appearance, an attribute deem ed im portant in consum er selection o f product. A m ajority o f the respondents (84% ) reported that unsteam ed seeds had h igher sw elling capacity than the steam ed seeds. H ow ever, the steam ed seeds soaked w ere relatively softer to touch as com pared to the unsteam ed. No conclusive in form ation was ob ta ined on the tim e required to cook the beans to the desired softness. The reported ‘n o rm al’ cooking 22 tim e ranged betw een 45 to 120 m inutes possibly due to d ifferences in heating system s. S team ing affected neither the flavour nor the taste of the cow pea m eals prepared using the sam ples. 23 CHAPTER THREE M ETHODOLOGY 3 .1 T he Study A rea The study was carried out in the G reater A ccra Region. The region has been producing som e am ount o f cow pea and is a m ajo r cow pea-consum ing centre with a high m arketing potential. “M alla ta” m arket in A ccra w as se lected for the study; cow pea consum ers were interview ed w ith the assistance o f cow pea traders. A village called M aanpehyia in the Ga D istrict o f the G reater A ccra R egion was also selected w here cow pea producers w ere interview ed. The choice o f these locations is based prim arily on the fact that B ean/C ow pea C R SP o f w hich this study is a part undertook som e prelim inary studies at these locations. Som e o f these farm ers 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 A gricultural E xtension O fficer is currently w orking with. This was very useful in identifying the respondents. 3.2 A nalytical Fram ew ork Inform ation gathered from both prim ary and secondary sources were analysed to achieve the objectives of the study. 24 3.2.1 Identification o f P reservation and S torage T echnologies The first objective o f this study is to identify the various cow pea preservation technologies used by farm ers in the study area in preserving cow pea 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 review ed through literature search. 3.2.2 D eterm ination o f the P rofitab ility o f the H ydrotherm al T reatm ent T echnology The second objective o f this study is to determ ine the profitability o f the hydrotherm al treatm ent technology in preserving cow pea. T he m ethod of analysis used to achieve this objective was to com pute the N et Present V alue (NPV) and the In ternal R ate o f Return (ERR) o f investing in the technology to determ ine its financial viability. 3.2.2.1 N et Present V alue (NPV) T he N et Present Value is the m ost straightforw ard discounted cash flow m easure of project worth. It is sim ply the present worth of the increm ental net benefits or increm ental cash flow stream and may be in terpreted as the present value of the incom e stream generated by an investm ent (G ittinger, 1982). The m ethod consists o f discounting all future cash flows to the present value by means of an appropriate rate o f interest. NPV w orks on a sim ple but fundam ental principle that, an investm ent 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). D yson (1994) asserts that N PV is considered a highly acceptable m ethod o f investm ent appraisal because it takes into account the tim ing of the net cash flow s, project profitability and the return o f the original investm ent. The N PV will be com puted for investing in the steam er used in the hydrotherm al treatm ent technology of preserving cow pea 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 , N PV is com puted as fo llo w s: N P V = - C , ) / ( l + 0 ' ] ...............................................(1) 1=0 W here: 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 T he decision criterion is to accept all independent investm ents/pro jects w ith N PV of zero or greater when discounted at the appropriate cost o f capital. 3 .2 .2 .2 Internal R ate o f R eturn (IRR) A nother w ay of using increm ental net benefit stream or cash flow for m easuring the worth o f an investm ent is to find the discount rate that m akes N P V o f the increm ental 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 w ords, IRR is the m axim um 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 w hile it is invested in a project. M athem atically , IRR is expressed as the d iscount rate, R such that: W here: B(, C,, n and t are as earlier defined ‘R ’ is the IRR in equation 2. 27 The IRR was com puted by iteration, w hich m eans using trial and erro r m ethod. The com putation involves choosing an arbitrary discount rate to com pute the NPV. If the N PV is found to be greater than zero, a higher discount rate is used; and a low er d iscount rate used if com puted N PV is found to be less than zero. T he process is repeated until a d iscount rate that equates N PV to zero is discovered. This d iscount rate is the ERR. To determ ine w here the real IRR lies betw een the low er 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 show n 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 \ W here, L d = L ow er d iscount rate; U D = H igher discount rate; N P V l = N et present value at the low er discount; N PVu = N et present value at the higher discount. /N P V |j/+ /N P V h/ = Sum o f the absolute net present values at the tw o discount rates (signs ignored). The decision criterion for IRR as a m easure 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 C hoosing the D iscount Rate T o be able to use the discounted m easures o f project worth, there was the need to m ake a decision on the discount rate to use to calculate N PV or the rate below w hich 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. T his is often the lending rate or the rate at w hich the enterprise is able to borrow m oney. T he lending rate quoted by the B ank o f G hana during the period of the study (January to June, 2001) was used. 3.2.2.4 Sensitivity A nalysis (T reatm ent o f U ncertainty) One o f the real advantages o f a careful investm ent analysis is that, it m ay be used to test w hat happens to the earning capacity o f the project if events d iffer from guesses m ade about them during planning. F or exam ple, how sensitive is a p ro jec t’s N PV at financial prices o r its financial rate o f return? R ew orking to see w hat 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. C alculating sw itching value involves determ ining how m uch an elem ent w ould have to change in unfavourable direction before the project w ould no longer m eet the m inim um 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 axim um benefit delay before the NPV of an investm ent will fall below zero for the investm ent to be rejected. 29 3.2 .3 D eterm ination o f C ow pea C haracteristics that In fluence C onsum ers Purchase D ecisions T he third objective o f the study is to determ ine the characteristics o f treated and un treated cow pea that in fluence consum ers 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 cow pea that in fluence purchase decisions of consum ers. T he 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’ C hoice o f Preservation M ethods T he 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 cow pea farm ers. T he chem ical pest control m ethod as a technology was used for the analysis. This w as determ ined using the Probit regression m odel. 3.2.4.1 The Probit M odel The P robit regression m odel was used to determ ine objective four. Farm ers face outcom es from the adoption of storage technologies that are uncertain. In this m odel, cow pea farm ers are assum ed to make adoption decisions based upon an objective of utility m axim isation. 30 T h e P ro b it m o d e l is g iv e n as: f 1 nlf _ ' 2 l I . V2H 2\ / W here: t is a random variable distributed as a standard norm al deviate (3 is a vector o f unknow n coefficients X, is a vector o f characteristics o f the individual