1.1 Introduction
Cowpea is an erect to sub-erect, or prostate, climbing, glabrous, annual herb. The stems are somewhat square and ripped, often with violent nodes (Ton and Koop, 2008). Cowpea can be used at all stages of growth as a vegetable crop. The tender green leaves are an important food source in Africa and are prepared as herb, like spinach. Immature snapped pods are used in the same way as snap beans, often being mixed with other foods. Green cowpea seeds are boiled as a fresh vegetable, or may be canned or frozen. Dry mature seeds are also suitable for boiling and canning (Davis et al., 1991).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Cowpea is a heat-loving, drought tolerant crop with high protein content and lower soil fertility requirements than many other crops (Coetzee, 1995). The seed coat can be smooth or wrinkled and of various colours including white, cream, green, buff, red, brown and black. Seed may also be speckled, mottled or blotchy. Many are also referred to as “eyed” (black-eye, pink-eye, purple hull, etc.) where the white coloured hilum is surrounded by another colour (Davis et al., 1991). It is widely grown in Africa (with Nigeria and Niger Republic predominating), Brazil, West Indies, India, United States, Burma, Sri Lanka, Yugoslavia and Australia. The history of cowpea dates to ancient West African cereal farming, five to six thousand years ago, where it was closely associated with the cultivation of sorghum and pearl millet(Ton and Koop, 2008).
Cowpea can be used at all stages of growth as a vegetable crop. The tender green leaves are an important food source in Africa and are prepared as herb, like spinach. Immature snapped pods are used in the same way as snap beans, often being mixed with other foods. Green cowpea seeds are boiled as a fresh vegetable, or may be canned or frozen. Dry mature seeds are also suitable for boiling and canning (Davis et al., 1991).
Cowpea has been identified as an ideal summer cover crop for many areas which can both produce abundant biomass and fix substantial quantities of atmospheric nitrogen (Creamer and Baldwin, 2000). It was observed by (Singn and Rai, 1988) that less time was required for germination initiation of medium seeds and small seeds than big seeds of cowpea. However, germination percentage has a distinct advantage of larger over smaller seeds. Larger seeds showed early vigorous seedling growth as compared to smaller seeds) (Singn and Rai, 1988). Small seeds were reported to germinate earlier as well as higher germination index than large seeds in Turkish cultivars of chickpea (Cicer arietinum L.) under interactive study of seed size and NaCl (Kaya et al., 2008). In many cases one observes small or tiny seeds of cowpea which were sorted and thrown away germinated and produced fruits. It is therefore the objective of this study to investigate the effects of seed size and sowing depth on the germination and seedling development of some local cowpea varieties in Akwa Ibom, Nigeria.
1.3 Statement of Problems
Investigation reveals the problems of the research work which entails the documentation limitation on the effect of seed size and depth of sowing on cowpea vigour, germination, establishment, growth and yield. This makes it a challenge to predict the best outcomes possible when propagating the seeds of cowpea (Vigna unguiculata L., (Walp.)), hence making it difficult to achieve maximum yield and production.
1.4 Aim and Objectives of Study
The aim of the study is to scrutinize the Effects of Seed Size and Sowing Depth on the Germination of Cowpea (Vigna Unguiculata L. Walp). In achieving this aim, the following specific objectives were laid out as follows to:
- Investigate the effect of seed sizes on the growth performance of cowpea (Vigna unguiculata),
- Identify the physicochemical properties of the experimental soil,
- Determine the effect of sowing depths on the growth performance of Vigna unguiculata, and
- Evaluate the optimum seed size and sowing depth for higher productivity and yield of Vigna unguiculata.
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- What are the effects of seed sizes on the growth performance of cowpea (Vigna unguiculata)?
- What are the physicochemical properties of the experimental soil?
- What are the effects of sowing depths on the growth performance of Vigna unguiculata?
- What are the optimum seed size and sowing depth for higher productivity and yield of Vigna unguiculata?
1.6 Significance of Study
The effect of seed size and sowing depth on germination of cowpea would yield very vital data which is useful and helps to provide agricultural extension delivery to farmers for increased crop productivity and poverty alleviation. If the right combination of seed size and sowing depth are known, it becomes possible to achieve greater yield which is beneficial for both subsistence and commercial Agriculture.
This study will be of immense benefit to other researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.7 Scope of Study
The study focuses on the Effects of Seed Size and Sowing Depth on the Germination of Cowpea (Vigna Unguiculata L. Walp) in Nigeria.
1.8 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
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