1.1 Backgrounds of the Study
Pulses are annual leguminous crops yielding grains or seeds used for food, feed and sowing purposes. Pulses are crops yielding from one to twelve seeds of variable size, shape, and colour within a pod. In addition to their values as food and feed stuffs, pulses are also important in cropping systems for their ability to produce nitrogen and thus increase the fertility of the soil (FAO, 2011). Included in the pulses are groundnut and cowpea.Groundnut (Arachis hypogaea L.) also known as peanut,is a member of the family papilionaceae, the largest and most important of the three divisions of leguminasae (Alonge and Adegbulugbe, 2005).The groundnut seed composed of approximately equal weight of fatty and none fatty oil; the relative amount of each depends upon its variety and maturity (Young, and Ahmed, 1982). It is one of the world‟s most popular crops cultivated throughout the tropical and sub-tropical areas where annual precipitation is between 1000 – 1200mm for optimum growth of the crop.Groundnut is the 13th most important food crop of the world (John, 2010). It is the world‟s 4th most important source of edible oil and 3rd most important source of vegetable protein (Taru et al., 2008). The crop is native to South America, Mexico, and Central America. It was first cultivated in a valley in Peru. The leading world producers of the crop are China, India, Nigeria, USA, and Senegal. Nigeria ranks third among the major producers (Abubakar and Abdulkadir, 2012). In Nigeria,agriculture was the dominant sector of the economy before independence;with groundnut cultivation as one of the vital areas of its economic built up (Ani et al, 2013). Emergence of petroleum products, poor government sustenance, and inadequate viable as well as qualitative farm machinery are some of the factors contributing toNigeria‟s declining economic buoyancy (Yusuf, 2011). The total world output of the groundnut crop in 2008 was 34.8 million metric tons out of which Nigeria accounted for 3.8million metric tons (FOA, 2008). In Nigeria, the processing of groundnut into various products is mostly done by women either for home consumption or for commercial purposes (Ibrahim et al., 2010). The most common commercial products of groundnut are; groundnut oil, groundnut cake and fried groundnut which are sold at market places or hawked on the streets. The processing of groundnut is both the source of income and employment to a large proportion of rural women in northern Nigeria(Ibrahim et al., 2010).
In developed countries groundnut processing is highly mechanized but in most developing countries, manual processing is still the norm despite the drudgery and time wastage involved (Maduako et al., 2006). The manual shelling method is achieved by applying pressure to crack the shell. In some cases, the groundnuts are first moistened with water and parked in a small sack whereby pressure is applied by beating the bag on a stone or any hard surface. Groundnut shelling machine is used to remove the shell of groundnut so as to obtain the groundnut seeds. Harvesting and shelling of groundnut are the most important and labour intensive operations in groundnut cultivation(Akcali and Onur, 1990). According to the authors, the present practice of these manual processes consumes huge amount of labor to the magnitude of 84 man-h ha-1 . During peak seasons delay in harvesting and threshing resulted in heavy loss due to non-availability of labor at peak period of harvesting. One of the solution for increasing the profit and productivity is to mechanize the operations in groundnut cultivation. For mechanizing threshing operations, power operated groundnut machinery such as; harvesters, strippers, and sheller have been developed. The adoption level is very low due to varying constraints(Akcali and Onur, 1990).
Cowpea is one of the most economically and nutritionally important indigenous African grain legumes produced throughout the tropical and subtropical areas of the world (GATE, 2008).In Africa, despite the values of cowpea, the methods involved in its production, harvesting and shelling are mostly manual. For instance, shelling is done by pounding in a mortar with a pestle or spreading the dried crop on the floor where it is beaten with a stick (Dauda, 2001). Production of cowpea on a large scale is likely to continue to increase with the adoption of improved production technology and availability of wider market. This would mean a higher demand on labour for all farming operations particularly harvesting, threshing, cleaning and grading (Irtwange, 2009). Most of the imported shelling machineries are very costly and hence beyond the reach of Nigerian small-scale farmers. Some have been found unsuitable for shelling the local varieties (Adewumi et al., 2007). If there has to be increased production of cowpea, farmers have to be provided with the means by which their products can be processed with minimum drudgery, cost and achieving good quality products.
1.2 Statement of the Problem
Abubakar and Abdulkadir (2012) reported that, traditional method of shelling groundnut has proved to be inefficient, time consuming, laborious, and low output. Due to the lack of an efficient motorized machine to shell groundnut, small scale farmers generally depend upon manual shelling. These are time consuming operations and do not match the shelling requirements within a limited period of time. Manual processing is still the norm in Nigeria despite the drudgery and time wastage involved. The search for more efficient and cost effective way of shelling raised the demand for the modification of IAR groundnut shelling machine.IAR groundnut sheller was developed in 1985 and the design was based on the properties of the then variety known as Ex-Dakar. The performance of the sheller was satisfactorily optimum withthroughput capacity of 200 kg/h as reported by IAR (1987). New varieties were later developed whose acceptability in practice override, this has conspicuously affects the performance of the IAR groundnut shelling machine which is not yet modified for the new varieties. A preliminary test of the sheller was carried out using groundnut variety; SAMNUT 23, and its performance was evaluated. The results (Appendix E1) indicated a very low output capacity of 76.50 kg/h, which was determined at a combination of 160rpm and 3kg/min cylinder speed and feed rate, respectively. This could be attributed to the effects of some factors such as varietal difference, inappropriate sieve type required among others.
Cowpea cultivation is also very essential in Nigeria;it plays a key role in the agriculture and food supply of the country. Nigeria is the largest producer and consumer of cowpeas, accounting for about 45 percent of the world‟s cowpea production (GATE, 2008). However, most ofthe farmers grow it as inter crop (Rowland, 1993), though its post-harvest operations are mostly done manually due to lack of precise machinery for such operations and this curtailed its effective productivity.
Groundnut and cowpea are of great economic benefit to mankind. Therefore, developing the pulse sheller will help to bridge the overtime disparity in its performance improvements and subsequent modifications. It will provide an avenue for improving groundnut and cowpea productivity, reduction of drudgery on such processes, and subsidize the cost of procuring groundnut and cowpea shelling machinery by the farmers. It will also help to increase the number of viable machines available for shelling of groundnut, cowpea and other related crops. Drudgery is generally conceived as physical and mental strain, fatigue, monotony and hardships experienced while doing a job(Renuka, 2007). It is certain that, if appropriate drudgery reducing machineries are made available to the rural farmers, it would contribute to more drudgery reduction in labour productivity, increased capability, and consequently red uction in greater workload thereby improving labour efficiency. According to Chima (2013),manufactured goods in agriculture are one of the preferred sectors of an economy and therefore the bedrock of economic and technological advancement. Chima (2013) further stated that, one important strategy used by China, India, Indonesia, Pakistan and Brazil, the nations with large populations in their quest for industrial and economic development was strong internal demand/consumption of their manufactured goods. Therefore, producing high quality products like pulse sheller will contribute meaningfully to the country‟s GDP and enhances its global competitiveness. It will also contribute in disabling the importation opportunities in the country.
1.4 Objectives of the Study
The aim of the study is to modify the existing IAR groundnut shelling machine for selected varieties of groundnut and cowpea crops. The objectives of the study are:-
(i) to determine the related physical and mechanical properties of the selected varieties of groundnut and cowpea
(ii) to carry out the design analysis for the modified pulse shelling machine
(iii) to construct and test the modified pulse shelling machine
(iv) to evaluate and compare the performance of the modified and existing machines.