DESIGN, FABRICATION, TESTING AND EVALUATION OF TWO AEROPONIC SYSTEMS AS ALTERNATIVE PRODUCTION METHODS FOR SEED YAMS IN GHANA

ABSTRACT
Yam is one of the most important dietary sources of energy for households in West-Africa. Yam stores relatively longer than most root crops and this attribute have gained it recognition as a food security crop in Ghana. More effort has been put into its research and production as has been seen by numerous government interventions over the years. However, inadequate access and high cost of seed yams have prevented farmers from intensive sustainable production. New technologies to increase and make available quality seed yams to farmers can boost yam production, increase food security and improve farmers’ livelihoods. In this regard, two aeroponic systems were developed and evaluated. The two systems; power-dependent (pressurised) and power-independent (gravity-fed) were evaluated using a split-split plot design at the CSIR-Crops Research Institute. The evaluations were carried out to assess the technical and agronomic performance of the systems. The aeroponic units were the main plots, the nutrient concentrations the sub-plot, and the yam varieties the sub-sub plot. Data collected on performance of the various treatments were subjected to analysis of variance and judged significant at p < 0.05. Technical evaluation of the two aeroponic systems gave Christensen’s Coefficient for water distribution uniformity values were 97.52 % and 94.49 % for the power-dependent and power-independent systems respectively. Agronomic performance showed significant differences in number of mini-tubers harvested and weight of mini-tubers under the different aeroponic systems. Field evaluation of harvested mini-tubers also showed significant differences in final yields under the various nutrient concentrations. Economic analysis of the two systems showed a benefit-cost ratio in favour of the power-independent system. Various recommendations were made after a repeat of the experiment. The power-independent system would be disseminated to smallholder farmers for seed propagation.


CHAPTER ONE
INTRODUCTION
1.1 General Introduction
Yams (Dioscorea spp.) are among the most important staple foods in the world, especially in some parts of the tropics and subtropics (Okigbo and Ogbonnaya, 2006). It belongs to the family Dioscoreaceae (genus Dioscorea). Yams are native to tropical regions throughout the world. They are cultivated for their edible tubers, which in some species can grow up to about 2.4 m long and weigh up to 45 kg (Okigbo and Ogbonnaya, 2006). Yam is largely carbohydrate and is one of the cheaper sources of the nutrient to humans (Kochlar, 1981). Yams are major sources of nutrients (carbohydrates, phosphorus calcium) and vitamins such, iron and vitamins such as thiamine, riboflavin, and vitamins B and C (Coursey, 1967).

Yam is one of the most important dietary sources of energy produced within the tropics and plays a major role as a food and trade commodity in West-Africa. It stores relatively longer than most root crops (e.g. cassava), availing itself on the market for a considerable part of the year. This attribute has gained it recognition as a food security crop in Ghana. In Ghana, yam is produced mostly in the Guinea-Savannah and Forest-Savannah transition zones with commercial yam production areas such as Mampong, Ejura, Kintampo, Atebubu, Wenchi, Kete-Krachi, Yendi, Bole, Tamale and Wa (Twumasi, 1986). However, reasonable production occurs in almost all regions. About 80% of yam produced in Ghana is white yam, which is much preferred among the yam varieties (Tetteh and Saakwa, 1991).

Ghana is a major yam exporter in the world, exporting 20,841t in 2008 (MiDA, 2009). There are a lot of challenges with yam production in Ghana, chief among them being unavailability and high cost of seed yams. Growing yams in Ghana is labour intensive and land demanding because of its over reliance on traditional production techniques. Furthermore, farmers rely on traditional method of milking for seed generation. As a vegetatively propagated crop, all parts of the yam, with a bit of the tuber skin attached (known as setts) is expected to germinate even though most farmers prefer using the yam “head”. The size of ware yam harvested usually depends on the size of sett used in its cultivation. Farmers therefore prefer using whole setts, however big or small for planting. To generate such whole setts, farmers use a technique known as “milking”. This process involves early harvesting of ware yams to pave way for a second tuber that can be used as seed only in early maturing varieties. After “milking”, if the second tuber regrowth is not met with favourable weather conditions, the farmers cannot get enough seed to use in the next season’s planting, thus having to leave a substantial part of the ware yam as seed for planting.

1.2 Problem Statement
Yam is an intensively cultivated root/tuber crop in Africa, only following cassava in terms of production volumes (Mignouna et al., 1998) with mean yields of about 10 t/ha. It is a food security crop in most of sub-Saharan Africa (Delebo, 2008). In 2007, yam production worldwide was almost 52 million tonnes with 96 % of this coming from Africa (IITA, 2006). There is a high labour requirement in yam production. Challenges also persist in the availability of high quality yam seeds, mechanization and staking especially in the forest areas, weed control and harvesting, which account for over 40 % of the total yam production cost (Nweke et al. In: Okoro, 2008).

Yams are predominantly grown by small scale farmers in Ghana. Most of these farmers propagate their seed yams using traditional methods such as “milking” or harvesting the ware yams early and the use of “yam heads” or parts of the yam that can easily sprout. The setback with these methods is that they do not produce enough and/or good quality seed yams (MiDA, 2008). Also, if the second plant propagation (after “milking”) is not met with favourable weather conditions, farmers could lose most or all of their seed yams and end up with nothing to plant the next season. This can result in the farmer spending more money than initially intended, in the acquisition of seed yams for the next season’s planting. This arrangement is even subjected to the availability and affordability of seed yams on the market, which is not the case in most cases.

1.3 Project Justification
Research has produced methods that results in a higher propagation ratios for yams. These include the minisett technology with a multiplication ratio of 1:30, in-vitro tissue culture multiplication with a ratio of 1:200 and in-vivo yam vine multiplication with a ratio of 1:240 (CSIR-CRI, 2012) which has not been fully disseminated. Unfortunately, adoption of these technologies is low, and to a high degree, not attained the needed impact despite its numerous advantages.

The minisett technology developed and promoted by International Institute for Tropical Agriculture (IITA, 2006) and CSIR-Crops Research Institute (CSIR-CRI, 1991) in Ghana is still striving to attain high adoption by farmers. Minisett is based on a principle targeted at increasing the number of setts derived from one tuber. In this technique, one tuber can be sliced, with tuber skin attached, into about 40 pieces ranging in weight from 50-100 g each. The cut pieces are dipped in a solution containing pesticides to disinfect the setts before planting (MiDA, 2010).

Despite the high propagation rate and low disease infestation of the minisett technology, many farmers still rely on the age old method of using tubers of ware yam or milked yam for planting.

Plants require light, water, nutrients, oxygen and carbon dioxide for photosynthesis. Soil can be a supplier of nutrients, but is not necessary in and of itself - hence the effectiveness of hydroponic and aeroponics. Water is also becoming more and more scarce as a commodity and as global population increases, the concern over water and soil quality also continues to grow.

New technologies for growing foods that are not overly dependent on soils and water are becoming not only a distinct advantage, but a necessity. The aeroponics and hydroponics technologies have been demonstrated in several ways to be a significantly more water- and energy-efficient means for food production. Hence, the hydroponics and aeroponics technology is being adapted for use in this research to propagate seed yam.

In aeroponics, plants are grown in an air or mist environment without engaging soils or any soil aggregate or soil medium (Arunkumar and Manikand, 2011). Aeroponics gives room for easy access to plant roots since it is not planted in any aggregate media (Pagliarulo and Hayden, 2002). The growth chamber and fertigation system employed in aeroponics also give room for complete regulation of the root zone setting, including temperature, humidity, pH, nutrient concentration, mist application frequency and duration. Plants grown using aeroponics often show signs of accelerated growth and early maturity (Mirza et al., 1998). These abilities have made the technology a popular research tool for studying root growth and nutrient uptake (Barak et al., 1998). Aeroponically generated seed yams can improve the seed multiplication ratio of yams and thus make available more seed yams on the market. It can also reduce disease incidence of seed yams which results in yield losses.

Aeroponics, if successfully used in the propagation of seed yams, can significantly increase the incomes of farmers, improve access to quality seed yams all year round (by making it more accessible and affordable to commercial growers and small scale farmers) and reduce the production costs of yams. This would improve farmers’ livelihood and also enhance food security in the country.

1.4 Objectives of the Study
The overall objective of this research was to determine the feasibility of generating seed yams from aeroponic systems.

1.4.1 Specific Objectives
To achieve the main objective of this work, the following sub-objectives were developed:

Design, set up and test two types of aeroponic systems (power-dependent and power-independent) for propagating seed yams

Evaluate the two aeroponic systems for their ability to agronomically propagate mini-tubers successfully

Assess the ability of the resulting mini-tubers to be used for propagating seed yams and

Determine the economics of using either of the two aeroponic systems to commercially produce seed yams.

1.5 Research Questions
The following questions were formulated to guide the study:

Are there differences in the fabrication and operation of the two designed aeroponic systems?


Are there differences in growth and yield of seed yams from the two aeroponic designs?

Can the mini-tubers generated from either of the systems be used to propagate seed yams?

What are the cost implications of using either of the two systems to propagate seed yams?

1.6 Research Hypotheses
The following research hypothesis guided the studies:

The alternative and null hypothesis for objective one

The Null hypothesis (HO): System performance of the power-dependent set up is same as the power-independent set-up.

The alternate hypothesis (HA): System performance of the power-dependent set up is not the same as power-independent set-up.

The alternative and null hypothesis for objective two

The null hypothesis (HO): Agronomic performance of vine cuttings grown using the power-dependent system is same as that of the power-independent system

The alternate hypothesis (HA): Agronomic performance of vine cuttings grown using the power-dependent system is not the same as that of the power-independent system

The null and alternative hypothesis for objective three

The null hypothesis (HO): Agronomic performances of resulting mini-tubers from both the power-dependent and power-independent aeroponic systems are same

The alternative hypothesis (HA): Agronomic performances of the resulting mini-tubers from the power-dependent and power-independent systems are not the same.

The null and alternative hypothesis for objective four

The null hypothesis (HO): There are no economic differences in the design, fabrication and operation of the two aeroponic systems.

The alternative hypothesis (HA): There are economic differences in the design, fabrication and operation of the two aeroponic systems.

1.7 Limitations of the Research
The following are the limitations of this research:

The initial set-up of the two aeroponic systems was capital intensive.

One of the systems evaluated was power-dependent and vulnerable to power outages (a more common event in Ghana as it faces an energy crisis). Prolonged power interruptions could have led to irreversible damages to the plants, thus additional costs were incurred in providing for a standby generator.

The aeroponic technology involves a lot of expertise and also requires constant attention and maintenance.

1.8 Organization of the Research
This thesis is organised into six (6) chapters. The first chapter constitutes the general introduction to the research, detailing the background, justification, objectives, research questions and hypothesis and the limitations of the study.

Chapter Two reviews literature on yams and its production in Ghana defines and explains aeroponics, its advantages and uses in research as well as its limitations. Also a general overview is given on the types of aeroponic systems based on their components, accessories and operation.

Chapter Three details the designs, fabrication and setting up of the two aeroponic systems and also reports on the materials and methods used in the technical evaluation of the two aeroponic systems as well as results from the evaluation. It gives detailed description of the aeroponic designs, its setting up and operational characteristics as well as the experimental designs used in their evaluation.

Chapter Four reports on the materials and methods used in the agronomic evaluation of vines planted on the aeroponic systems as well as evaluation of the resulting mini-tubers from the aeroponic propagation. The methods explain the type of research designs adopted for the agronomic evaluations of the systems. It also includes various data collection methods and analysis.

Chapter Five presents the data, calculations/derivations and results of analysis from the various agronomic experiments. It further interprets and discusses results obtained from the study.

Chapter Six presents a summary of the major outcomes of the research, the conclusion made from the analysis and proposes areas for further research as well as recommendations for policy makers.

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Item Type: Ghanaian Postgraduate Material  |  Attribute: 229 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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