Chuka University Digital Repository
Chuka University Repository is a Digital Hub for Knowledge Output From Chuka University.

Communities in DSpace
Select a community to browse its collections.
Recent Submissions
PREVALENCE AND CHARACTERIZATION OF AVOCADO FRUIT FUNGAL DISEASES IN EMBU COUNTY, KENYA AND THE EFFICACY OF Aloe secundiflora CRUDE EXTRACTS IN THEIR CONTROL
(Chuka University, 2023-10) MULEI FRANCISCA MWONGELI
Avocado production has increased exponentially worldwide due to increased demand for the fruit in the food, pharmaceutical, cosmetic, and oil industries. However, avocado production faces various constraints that include post-harvest losses due to pests and diseases, which contribute about 83% of yield losses. Fungal diseases are the most prevalent and are difficult to control using cultural methods, while continuous use of chemicals can lead to pathogen resistance and have adverse effects on humans and the environment. The main objective of this study was therefore to determine the prevalence of the fungal avocado fruit diseases in Embu County, isolate and characterize the causal pathogens and test the efficacy of Aloe secundiflora (Aloe) crude extract in the management of the fungal diseases. Aloe was selected because of its wide medicinal use and local availability. A descriptive cross-sectional survey design was carried out in six purposefully selected avocado markets in the study area to assess the prevalence of fungal diseases of avocado fruit. A structured questionnaire was administered to gather information on avocado production, marketing, and management. A total of 100 respondents were interviewed. The stores and avocado bags were randomly selected. The fruits in the bags were assessed to determine the prevalence of fungal avocado diseases. Experiments were then carried out in the laboratory to isolate and characterize the pathogens. Aloe leaves were collected in the field, and phytochemical analysis of the crude extracts was done. The efficacy of the crude extract against the pathogens was tested in the laboratory using a Complete Randomized Design (CRD). The data were subjected to an analysis of variance (ANOVA) using Scientific Analysis System version 9.4 Software. Significant means were separated using LSD at p < 0.05 significant level. Results on the demographic characteristics of the respondents showed that the majority were above 30 years of age, with more women than men, and had a primary level of education. More than 50% sourced avocado fruits from their own farms and were able to identify disease symptoms themselves. The main methods of harvesting were both handpicking and hook, and the product was mainly stored in sacks. More than 40% of the respondents used chemicals to control fruit diseases. Three fungal pathogens were isolated and characterized: Colletotrichum gloeosporioides (anthracnose), Cercospora purpurea (cercospora spot), and Sphaceloma perseae (avocado scab) and their mean percentage prevalence was 29.00%, 25.98% and 31.44%, respectively. The commonly sold varieties were Hass, Fuerte, Puebla and the local varieties, with Hass being the most preferred variety. Fuerte and Puebla were the most susceptible to these diseases. There were variations in the morphological characteristics of the pathogen isolates: C. gloeosporioides had a white to grey smooth mycelia, concentric zonation and sizes ranging from 3.0 - 5.0 μm in width and 10.3 - 18.2 μm in length. Sphaceloma perseae had a white and yellow layered mycelium with sizes ranging from 3.0 - 5.0 μm in width and 10.3 - 18.2 μm in length, while C. purpurea had a leathery grey to brown conidia of 2 - 5 μm in width and 20 -34 in length. Phytochemical analysis of the aloe-ethanol extract revealed the presence of steroids, phenolics, flavonoids, saponins, and terpenoids, but phenolics were only present in the hexane extract. The mean zone of inhibition for the ethanol and hexane extract against C. gloeosporioides was 13.50 mm and 9.36 mm, respectively, while for Cercospora purpurea was 4.72 mm and 4.32 mm, respectively, but no effect on S. perseae at any concentration. Vendors should therefore be trained on proper handling of avocado fruits to reduce post-harvest losses. Aloe secundiflora extracts can be integrated with other methods of managing avocado fungal diseases to reduce over-reliance on chemical fungicides.
AB INITIO STUDY OF STRUCTURAL AND PIEZOELECTRIC PROPERTIES OF HAFNIUM DOPED BISMUTH SODIUM POTASSIUM TITANATE
(Chuka University, 2023-10) MWANZIA BONFACE MUTUKU
Piezoelectric materials have gained increased attention in the recent times due to their
significant technological applications. These materials are widely used to make
ultrasound transducers, sensors, actuators and others are used for energy harvesting.
Due to its brilliant piezoelectric properties, Lead Zirconate Titanate (PZT) is mostly
used with a piezoelectric constant of 𝑑33 = 374 𝑝𝐶/𝑁 from experimental reports and
306 − 314 𝑝𝐶/𝑁 from theoretical studies. However, due to the toxic nature of lead
oxide which is formed when PZT is being manufactured, there is increased effort in
development of lead-free materials. Several classes of materials have recently been
studied and are now being considered as potential alternatives to PZT. Lead free
perovskite systems such as Bismuth Sodium Potassium Titanate (BNKT) have been
developed, with a piezoelectric constant 𝑑33 = 157 𝑝𝐶/𝑁 . However, the main
drawback of this system is that it is highly corrosive and has a low piezoelectric constant
compared to PZT. In the quest to provide suitable alternatives, dopants such as
zirconium have been used, which improved the piezoelectric constant of BNKT up
to203 𝑝𝐶/𝑁. Hf which possesses similar physico-chemical properties as zirconium has
led to an improvement in the piezo electric constant of other piezoelectric systems such
as in hafnium doped Barium Titanate (BT). It has an added advantage of being
extremely resistant to corrosion, which is expected to mitigate the corrosive nature of
BNKT. In this study, hafnium has been incorporated in BNKT so as to engineer an
alternative material suitable for piezoelectric applications. Density Functional Theory
(DFT) method was used to predict the structural and piezoelectric properties of hafnium
doped BNKT, starting with those of Bismuth Sodium Titanate (BNT) and BNKT. The
exchange and correlation was taken as the Generalized Gradient Approximation
(GGA). The optimal lattice parameters for BNT were found to be 𝑎 = 5.57 Å and 𝑐/𝑎
ratio of 2.50 for the conventional cell, having space group R3c space group number
161. Piezoelectric constant for this system was found to be 97.67 pC/N. This structure
was adopted for doping and further calculations. Potassium doped bismuth sodium
titanate was modelled using VESTA software and its optimized lattice parameter was
found to be 𝑎 = 5.60 Å. Piezoelectric constant for this system was found to be 147.42
pC/N. Hafnium doped BNKT had an improved piezoelectric constant of 205.52 pC/N
for 3% hafnium doping, which decreased to 163.22 pC/N at the level of 6% doping.
The results shows that small amounts of hafnium improved the piezoelectric constant
of BNKT from 147.42 pC/N to 205.52 pC/N. Elastic and elastic compliance full tensors
for these systems was also generated with elastic constants of C33 = 286.48 Gpa, 282.13
Gpa, 257.193 Gpa and 276.43 Gpa for BNT, BNKT, 3% Hf doped BNKT and 6% Hf
doped BNKT respectively. This study concludes that doping BNKT with hafnium
indeed improves the piezoelectric properties of BNKT. This makes this material more
useful in energy generation since high piezoelectric constant leads to efficient
mechanical – electrical energy conversion in the piezoelectric materials.
DELOCALIZED PRINCIPALS’ TRANSFORMATIONAL LEADERSHIP, PERSONAL CHARACTERISTICS AND INSTITUTIONAL PERFORMANCE OF PUBLIC SECONDARY SCHOOLS IN LOWER EASTERN REGION, KENYA
(Chuka University, 2023-10) MUTUNGA STANLEY MAWIRA
In Kenya, Principal’s leadership greatly predicts institutional performance. They are responsible for the overall management of their institutions. A majority of schools continue to report management challenges resulting in poor performance. The teachers’ employer, the Teachers Service Commission introduced the policy of delocalization of school Principals with the aim of improving institutional management and ultimately performance. However, data that could help illustrate the extents to which implementation of the policy has contributed to improved institutional management and ultimately performance remained limited. This study therefore sought to contribute in bridging the existing research gap by establishing the relationship between delocalized principals’ transformational leadership, personal characteristics and institutional performance among public secondary schools in lower Eastern region of Kenya. The study adopted transformational leadership theory, path-goal theory and contingency theories. A descriptive survey and correlational research designs were utilized. Multistage sampling was used to select 144 principals, 144 senior teachers and 6 educational officials from 1086 subjects comprising of 540 delocalized principals, 540 senior teachers, 3 County Quality Assurance and Standards Officers and 3 Kenya Secondary Schools Heads Association Chairpersons. Questionnaires and interview schedules were used to collect data. The instruments were pre-tested in Embu County and results obtained used to estimate reliability using Cronbach’s Alpha and Exploratory Factor Analysis, where a coefficient of 0.785 and a KMO of 0.778 were taken and deemed acceptable. Validity of the instruments was ascertained through face, content and construct validity techniques. Qualitative data was analyzed thematically while quantitative data was cleaned coded and analyzed descriptively and inferentially with the aid of the Statistical Packages for Social Sciences program version 26.0 computer software. Frequency and percentages were used to describe the existing relationship between the variables while hypothesis were tested using simple and multiple regression analysis at 0.05 level of significance. The study established that there is a positive and significant relationship between transformational leadership and institutional performance. Findings also established that principal’s experience partially mediates while type of school moderates the relationship between transformational leadership and institutional performance. It is therefore recommended that TSC should formulate and implement best practices of delocalization to enable education stakeholders reap its inherent benefits. Ministry of Education should organize training workshops for principals on best practices for implementation of transformational leadership.
EFFECTS OF CLIMATE VARIABILITY, ADAPTATION AND PRICE CHANGES ON YIELD AND GREEN GRAM PRODUCTION TECHNICAL EFFICIENCY IN THARAKA SOUTH SUB COUNTY, THARAKA NITHI COUNTY, KENYA
(Chuka University, 2023-10) MATHENGE BEATRICE MUGURE
Globally, green gram is a significant pulse, particularly in Arid and Semiarid Lands (ASALs), as a source of food, livelihood, soil management and integrates easily into different cropping systems. Green gram availability in Tharaka South Sub County is equivalent to household income and food security. Despite this importance, green gram yield in Tharaka South Sub County is still low at 0.56 mt/ha far below the crop’s estimated national potential of 1.5 mt/ha and compares unfavorably with the global and national averages of 0.73 mt/ha and 0.67 mt/ha, respectively. Green gram yield is mainly constrained by climate variability, fluctuating producer prices and inefficiencies in production. Given that production of green gram is predominantly rain-fed, climate fluctuation affects the ideal conditions needed for the crop growth. Further, rational producers may only improve yield and technical efficiency in response to anticipated price increase. This study aimed at analysing the effect of climate variability, adaptation and price changes on yield and green gram production technical efficiency in Tharaka South Sub County. The research employed descriptive research design and utilize both primary and secondary data. Primary data was obtained from 385 smallscale farmers selected randomly and five Key Informants’ Interviews (KII) who were purposively selected. Further, secondary data on seasonal rainfall, temperature, yield and farm gate prices was obtained from the Meteorological Services and County department of Agriculture, respectively. The analysis on the effect of rainfall, temperature variability and price, on green gram yield was analyzed using the pearson correlation coefficient, simple and multiple regression methods. Cobb-Douglas stochastic frontier method was used to determine technical efficiency of the various adaptation strategies used by green gram farmers. The findings of the study showed that rainfall variability explained 30.4% of the variables affecting green gram yield. The findings of the model further showed that a 1% increase in rainfall during March-April- May (MAM) season increased green gram yield by 49.3% with no effect during OND (October-November-December) season. Temperature variability explained 28.5% of the variables affecting green gram yield. Further, the model findings revealed that a 1% increase in temperature during OND season decreased yield of green gram by 48.5% with no effect during OND season. A combination of rainfall and temperature variability resulted to the highet effect, and explained 34.2% of the variables affecting green gram yield. The assessment on the technical efficiency levels of the climate adaptation strategies utilized by small holder green gram farmers showed that use of minimum tillage was the most efficient strategy with a technical efficiency of 75.58%. Use of crop rotation, maximum soil cover, early maturing green gram varieties showed a technical efficiency of 75.55%, 74.86% and 73.09% respectively. Crop insurance as a climate adaptation strategy was the least efficient strategy at 51.67%. Price changes on the other hand explained 25.3% of the variables affecting green gram yield. The findings of the regression analysis showed that there existed an inverse relationship between output price and green gram yield. A 1% increase in price was associated with 0.47% decrease in yield probably due to reuse of the grains as seed. The study concluded that climate variability and output price had an effect on green gram yield. Based on the findings there was a positive effect between rainfall and green gram yield while temperature variability and price changes had a negative effect on yield. Futher, adaptation to climate change is an important factor explaining efficiency differentials among smallscale green gram farmers. The study recommends that green gram farmers in ASALs need to adopt and intensify use of minimum tillage. A functional agricultural commodity market should be set for structured marketing of green gram. Further research institutions and department of agriculture need to ensure access to certified seed for the farmers to reduce chances of seed recycling or reuse.
A CRITICAL DISCOURSE ANALYSIS OF KENYA’S BUILDING BRIDGES INITIATIVE SPEECHES
(Chuka University, 2023-10) GITONGA EURIDISE NKATHA
Language is vital in communication between people. People understand each other through shared knowledge between the speaker and the hearer. It is a major mechanism within the process of social construction, seen as an instrument for consolidating, manipulating concepts, seek attention, create relationships in the area of power, and use it as tool to control the society. Anchored in Critical Discourse Analysis theoretically, this study shed light on the crucial use of language in the society. The study sought to explain specific linguistic ways in which language is used to represent an instrument of control and manifest symbolic power in the Kenya’s Building Bridges initiative speeches. The study developed and proposed various strategies of (de) legitimization employed by political leaders in Kenya to justify their course of action regarding the Building Bridges initiative. The study was guided by two objectives; to analyze how political actors (de) legitimize the Building Bridges Initiative in Kenya and to analyze how political actors, use language to create a Kenyan identity through the Building Bridges Initiative discourse. Qualitative research methodology was used in this study, of which the descriptive survey method was employed for the analysis of data. YouTube videos of speeches made by specific political actors regarding the Building Bridges Initiative since November 2019 to 2021 were purposively sampled, transcribed and analyzed in their written form. De(legitimization) strategies were identified until saturation point was reached where no new strategies were being generated without resulting to redundancy. These were then categorized into thematic areas in accordance to the objectives of the study. The study established that strategies used by politicians in (de)legitimizing BBI were; authorization, rationalization, moral evaluation, and mythopoeic. It also established that majority of the speakers used language to attract attention, and advance ideologies that created a Kenyan identity. The study found that Kenya’s identity was to a large extent shaped negatively in the BBI discourse with only two out of the six having a positive orientation. These included: Kenya as a nation in need of national conversation, Kenya as a country struggling with tribalism and corruption and Kenya as a peaceful country with fairness and inclusivity. The information gathered in this study is useful to linguists since it provides them with ways to understand the language of politicians world over. Politicians may use language with hidden meaning that needs unravelling. Therefore, this study offers some of the ways of understanding and disambiguating what the politicians really say in their speeches. From the findings of this research, the researcher suggests the following areas for interested scholars: A study on creation of identity using other theories for example politeness theory, speech acts theory, or conceptual metaphor theory.