School of Agriculture, Natural Resources and Environmental Studies

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Investigations on decomposition of foliage of woody species using a perfusion method
(1992) Nyamai, Daniel
The time for half of the total oxidizable carbon to be converted into C02 and other gaseous products (t1/2) was studied for five tree species used in agroforestry. The study was conducted in a perfusion system with continuous aeration, and moisture content maintained at field capacity. This method was found to be suitable for studies of the initial stages of tree foliage decomposition. The overall rate was in the decreasing order: Leucaena > Calhandra > Gliricidia > Prosopis > Cassia. Decomposition started rapidly and then decreased rapidly for 2 to 3 weeks followed by a gradual decrease which continued for the remainder of the time. The time for 50 per cent of total oxidizable carbon to decompose was about 19 days for Leucaena, 30 days for Calhandra and Gliricidia, while Prosopis and Cassia took more than 30 days. Leucaena released the largest quantity of total N into the perfusing solution while Cassia gave the l
The status of pesticide usage in East Africa
(Research Gate, 1994) Mbakaya, Charles; Ngowi, Aiwerasia Vera
The assumption proposed by Gallo in 1984 that the cause of AIDS is infection with HIV was founded on the correlation between detection of antibodies to this virus and the onset of AIDS. This view became generally accepted, and today it is still the foundation stone of HIV-related measures for the prevention and treatment of AIDS. However, although unanimously rejected by AIDS researchers to date, Duesberg vehemently opposed this opinion, suggesting that AIDS is caused by drugs and malnutrition and that HIV is only a passenger pathogen (Duesberg, 1988; 1994; Lindermann, 1994). Earlier, it was reported that zinc deficiency was becoming a reality in the UK and the problem might be worse in developing countries, yet zinc deficiency and AIDS symptoms were similar and that micro-nutrient zinc had anti-viral, anti-bacterial and anti-cancer properties, for reasons that were only poorly understood then (Bryce-Smith, 1989).
The Impact of Human Activities on Epibenthic Bivalve Communities
(1997-10) Owuor, J. B. Okeyo; Wangila’, B.C.C.; Priscillah, N. Boera
A total of 17 bivalve species belonging to 13 families were collected and identified in Malindi and Mombasa Marine National Parks; and Kanamai from Oct.'97 to Mar.'98. Bivalve fauna showed low densities (2/m2), and low diversity. Modiolus auriculatus and Pinna muricata were the most represented. There was a significant difference in species diversity between Malindi and Mombasa reef flats at p>0.10. Shallow lagoons had very low-density and diversity as compared to sea grass and reef flat zones. This was attributed to the high deposits of shell, coral, and sand. Swimming, gogeling/scuba diving, walking/trampling and turning of rocks were identified as the main forms of human activities causing disturbance to the bivalves. Frequencies of occurrence of these activities varied in the three areas with Kanamai exhibiting the highest. Trampling had the most notable im- pact and was used to show the impact of human activities on the most vulnerable species. Results show that the distribution of bivalve fauna in the protected and unprotected areas is density independent and is not only influenced by human activities and management strategy but rather by other biological and environmental factors such as substrate type, tide range and wave activity. Human activities however affect those bivalves with fragile shells such as Pinna muri- cata, through trampling resulting in injury and/or death. Presence of man affects the routine activ- ities of the others such as Tellina flavum, Anadara antiquata, Tridacna squamosa and Codakia punctata. Therefore spreading out of human activities within the marine parks is rec- ommended to reduce their impacts. These activities should be spread out into the reserves and unprotected areas.
Maturity of Freshmarket Sweet Corn with Directseeded Plants, Transplants, Clear Plastic Mulch, and Rowcover Combinations
(1999) Aguyoh, Joseph Nyamori; Taber, Henry G.; Lawson, Vince
Impact of agro-industrial activities on the water quality of River Nyando, Lake Victoria Basin, Kenya
(2002) Raburu, P. O.; Owuor, J. B. Okeyo
The impact of agro-industrial activities on the water quality within River Nyando, Lake Victoria Basin was studied at different hierarchical levels between August 1997 and June 1999. Triplicate water samples were collected on a monthly basis from various stations ranging from the source to the mouth of the river and analyzed for selected physical and chemical water quality parameters using standard analytical methods. Statistical analysis was performed using MINITAB and STATISTICA computer packages. Agricultural land use was found to be the major factor contributing to changes in water quality. Salinity and pH varied at river basin scale, turbidity, TDS and conductivity at catchment scale, while DO, alkalinity and pH at subcatchment and river reach scale. The nutrient loads increased downstream. Anthropogenic sources contribute to high levels of nutrients within the basin. The changes recorded in water quality along the river were comparable to the modified Index of Biotic Integrity (IBI) and Nyando Habitat Evaluation Index (NHEI) derived for the river during the same period of study. Findings of this study can be used to design measures for mitigating and monitoring environmental impacts arising from agro-industrial activities within the Lake Victoria Basin. The study recommends a comprehensive Nyando River Basin Management Programme to address the multiple issues environmental within the basin.
Interference of large crabgrass (Digitaria sanguinalis) with snap beans
(Cambridge University Press on behalf of the Weed Science Society of America, 2003) Aguyoh, Joseph Nyamori; Masiunas, John B.
Field experiments were conducted to determine the effect of large crabgrass densities of 0.5 to 8 plants m-1 of row and emergence time on snap bean yield. Large crabgrass was planted either along with snap beans (early) or when the first trifoliate leaf of snap beans was opening (late). Observed yield loss ranged from 46 to 50%, and predicted yield loss ranged from 53 ? 29.3% to 63 + 18.3%. Relative leaf area was correlated to snap bean yield (r2 = 0.88 to 0.92). The relative damage coefficient (q), an indication of the competitiveness of large crabgrass with snap bean, was 1.65 ? 1.03 and 1.26 ? 0.72 for early- and late-emerging large crabgrass, respectively. Early-emerging large crabgrass reduced snap bean biomass 10 to 28% and snap bean pod numbers 44 to 60%, depending on the density. Because of intraspecies com- petition, leaf area index and number of seed for large crabgrass were reduced with increasing density. Emergence of > 2 plants m-1 of large crabgrass with snap beans should be controlled to avoid significant yield loss
Shifts in the food of Nile tilapia, Oreochromis niloticus (L.) in Lake Victoria, Kenya
(African Journal of Ecology, 2004) Njiru, M.; Owuor, J. B. Okeyo; Muchiri, M.; Cowx, I. G.
Studies of the food of introduced Nile tilapia, Oreochromis niloticus (L.) with respect to size, habitat and season were conducted between November 1998 and October 2000 in Kenyan waters of Lake Victoria. Stomach contents of 1980 specimens collected by demersal trawl and seining were analysed. Nile tilapia originally known to be herbivorous, feeding mostly on algae has diversified its diet to include insects, fish, algae and plant materials. The major diet of fish <5 cm total length was zooplankton whereas bigger fish included a wider range of food items in their diet. There was spatial variation in diet with insects and algae dominating in the gulf and open water habitats respectively. There was no seasonal variation in the food items ingested and diel feeding regime indicated that O. niloticusis a diurnal feeder. The shift in diet could be due to ecological and environmental chan- ges in Lake Victoria, which have been associated with changes in composition and diversity of fish and invertebrate fauna, emergence and dominance of different flora including water hyacinth Eichhornia crassipes (Mart.) Solms-Laub., and algae communities. The feeding habit of O. niloticus is discussed in the context of changes occurring in the lake.
Interaction of Insects and Weeds in a Snap Bean Agroecosystem
(2004) Aguyoh, Joseph Nyamori; Masiunas, John B.
Abstract.Integrated weed management strategies maintain sub-threshold levels of weeds. The remaining weeds may impact the feeding and habitation patterns of both potato leafhoppers and bean leaf beetles in a snap bean agroecosystem. The objective of our study was to determine the effect of interference between snap beans (Phaseolus vulgarisL.) and either redroot pigweed (Amaranthus retroflexusL.) or large crabgrass (Digitaria sanguinalis L.) on populations of potato leafhopper [Empoasca fabae (Harris)] and bean leaf beetle [Cerotoma trifurcata (Forster)]. Plots were seeded with redroot pigweed or large crabgrass at either the same time as snap bean planting (early) or when snap bean had one trifoliate leaf open (late). The weed density averaged two plants per meter of row. Bean leaf beetle populations, snap bean pod damage, and leaf defoliation were lower in weed-free plots compared to those with either early emerging pigweed or crabgrass. Leafhopper nymphs and adults were 31% to 34% less in plots with crabgrass emerging with snap beans compared to those in weed-free snap bean plots. Thus, the effect of sub-threshold densities of pigweed and crabgrass on insect pests in snap bean varied depending on the species and should be considered when deciding to integrate weed management approaches.
Aquaculture Strategy For Restoration of Threatened Lake Victoria Fishes
(The East African Community, 2006) Maithya, Jacob
The endemic Oreochromis variabilis and L. victorianus are among Lake Victoria’s most threatened fish species whose population sizes are on the decline. This study, carried out between August 2000 and April 2001, aimed at characterizing the ‘refugia’ ecosystems of O. variabilis and its growth performance in small water bodies (SWBs), developing artificial spawning techniques and characterizing existing morphological and genetic variation of extant populations of L. victorianus in order to bring the species under aquaculture as a restoration strategy. Studies of O. variabilis were carried out by comparing its growth performance in stocked semi-intensive and modified extensive closed systems in different ecological zones within the Lake Victoria basin. Growth in O. variabilis evaluated as average growth rates, was satisfactory in both systems and eco-zones, even in areas with extreme environmental gradients. The isometric characteristics of O.variabilis estimated by formula W = aL b were better than those of wild populations in the ‘refugia’ ecosystems in each respective eco-zone. Multivariate analysis of morphological data showed that there was reasonable differentiation between L. victorianus populations from different drainages, with the southern populations being most distinct. Majority of the variation in L. victorianus was within populations (91.3%), with an overall FST of 0.08846 for all loci. For effective aquaculture and conservation, fish breeders should use local fish material for their stocking programs; yet ensure that different age classes form part of their brood-stock. L. victorianus was spawned artificially using intramuscular injection of Clarias gariepinus pituitary extracts (C.g.PE) and Human chorionic gonadotropin (HcG) to induce ovulation. Successful inducement of ovulation occurred only in trials with C.gPE. Fertilization rates in breeding experiments for L. victorianus averaged 86% and hatching percentages 70%. This study indicates the viability of the two species for culture in the basin. More hope is therefore raised for expansion on the farming practices in the basin. Such a fisheries production can provide 75% of the animal protein requirements of the poor rural households and guarantee continued survival of the species within the basin. Stocking of small water bodies for increased fish production enhances further, the integrated resource use and management of the endemic but threatened Lake Victoria fish stocks.
Effect of Harvesting on Temporal Papyrus (cyperus papyrus L.) Population among Swamps of Winam Gulf in Lake Victoria Basin, Kenya
(2008-07-29) Owuor, J. B. Okeyo; L. Osumba, J. J.; Raburu, P.O
Experiments were set to determine the effect of monthly and seasonal harvesting on temporal papyrus population density. Mean initial culm count was 21.6±2.26/m2. Initial culm counts varied across sites, but spatial differences were not significant. Mean monthly culm counts declined with successive harvests, and each sequential harvest significantly reduced culm counts. Seasonal culm counts were generally higher in unharvested than in harvested plots, and the differences were significant in Nduru (F=13.569; p<0.05). There were no culm counts differences within and among sites between initial and seasonally harvested plots. Overall, there were more culms in seasonal (32.3±3.34/m2) than in initial counts. It was found that culm counts do not depend on site, and that harvesting reduces culm counts. It is evident that seasonal harvesting does not affect culm counts. Leaving a papyrus crop stand unharvested for more than a season increases its culm count. Given that frequent harvesting reduces culm count, and considering that initial papyrus population densities were the lowest across sites, it may be concluded that Winam Gulf papyrus is harvested faster than the wetlands can replenish. This finding highlights the need for urgent conservation measures in the area. It is suggested that papyrus conservation steps be undertaken most urgently in Winam Gulf. A minimum-harvesting regime at the start is once per patch per season. However, fewer patches were studied relative to the entire swamps. A more elaborate assessment, covering larger areas and more swamps, with greater effort, should be undertaken to determine the replenishment break-even point.
Response of Males of Maruca vitrata Fabricius(Lepidoptera: Pyralidae) to Synthetic Lures in Mauritius
(University of Mauritius research journal, 2009) Unmole, L.
Maruca vitrata Fabricius (Lepidoptera: Pyralidae) is a key pest of bean in Mauritius. Their larvae feed within flowers and pods and are thus well protected from insecticidal sprays. To achieve effective control, farmers spray their bean fields on a prophylactic basis. This has consequently led to undesirable problems that threaten safe bean production, sustainability, health and the environment. Action threshold based on pheromone-baited trap catches have been developed to rationalize insecticide use against M. vitrata in cowpea fields in Benin and Ghana. The study aimed at testing the attractiveness of four promising pheromone lures to males of M. vitrata in Mauritius. The lures were formulated by Natural Resources Institute (NRI) and consisted of a major component (EE 10,12-16:Ald) alone or in combination with one or both of two minor components (EE 10,12-16:OH and E 10-16:Ald). Two of these lures are reported to be effective in Africa (one in Benin and Ghana and the other in Burkina Faso). The four lures were tested in three types of traps in treated and untreated bean plots in Mauritius. Males of M. vitrata did not respond to any of the four NRI lures but were attracted to caged virgin females. This leads to postulate that the pheromone released by virgin females were not similar to any of the synthetic lures. Results tend to indicate that the M. vitrata in Mauritius can represent another geographically distinct population from those in Benin, Ghana and Burkina Faso.
Interactive effects of packaging and storage temperatures on the shelf-life of okra
(ARPN Journal of Agricultural and Biological Science, 2009-05) Ngure, Joyce W.; Aguyoh, Joseph Nyamori; Gaoquiong, Liu
A study aimed at evaluating the potential benefits of pre-packaging and storage temperature in extending the shelf life of okra was conducted at Egerton University Horticulture Field and Biotechnology Laboratory. Okra pods were subjected to different combination of packaging and storage temperature. Three levels of packaging were used consisting of perforated (punched) polyfilm bags, non-perforated polyfilm bags (0.03mm thickness) and unpackaged to modifying the storage atmosphere. Pods weighing 100g were put in the various packages and the unpackaged pods were placed on flat cartons. Four levels of storage temperature, 4o C, 8.5o C, 13o C and room temperature storage were used for storing okra pods. The temperatures of 4o C, 8.5o C and 13o C were attained in refrigerators while room temperature was obtained by placing the pods on tables in the open. Pods stored at 4o C were unmarketable 21 days after storage as they were frozen and had the highest electrolyte leakage due to high chilling injury. All unpackaged okra pods stored at all temperatures were also not marketable by day 21 of storage as they were dry and shriveled. These pods had the greatest weight loss (79%) at 13o C compared to weight loss of less than 30% observed in the pods stored at the same temperature (13o C) but kept in perforated packages. The best marketable pods that were not frozen and had the least off odour were those kept at 13o C storage temperature treatment in non perforated and perforated packaging. Blackening was inhibited under these storage conditions resulting in the best visual appearance of okra pods. It is possible that pod discoloration was controlled by atmosphere modification provided by packaging thus resulting in enhanced quality and marketability of the pods for 21 days.
Effect of organic and inorganic phosphorus sources on maize yields in an acid soil in western Kenya
(Research Gate, 2009-06-20) Kisinyo, Peter; Opala, P. A.; Okalebo, Æ J. R.; Othieno, Caleb
Maize production in western Kenya is commonly limited by P deficiencies and aluminum phytotoxicity. Due to high costs of imported fertilizers and lime, focus is now shifting to solutions that utilize local resources. We tested the effect of three inorganic P sources i.e., triple superphosphate (TSP), Minjingu phosphate rock (MPR) and Busumbu phosphate rock (BPR), each applied in combination with two organic materials (OMs) i.e., farmyard manure (FYM) and Tithonia diversifolia green manure (tithonia), or with urea on soil chemical properties related to soil acidity, P availability and maize yields for three consecutive seasons in western Kenya. The OMs and inorganic P sources were applied to provide 20 and 40 kg P ha-1 respectively in their combination. Where urea was used, the inorganic P sources were applied at 60 kg P ha-1. Maize did not respond to application of TSP, MPR or BPR with urea in the first two seasons. However, after three seasons, maize significantly responded to application of MPR with urea. FYM was more effective than tithonia in increasing the labile inorganic P pools but it gave lower maize yields than tithonia which was more effective in reducing the exchangeable Al. It appears that the ability of an OM to lower the exchangeable Al is more important inincreasing maize yields than its ability to increase P availability. The effectiveness of the inorganic P sources in increasing maize yields followed the order of their effectiveness in increasing available P, i.e., TSP[MPR [BPR, once Al phytotoxicity was reduced by application of tithonia but the difference between TSP and MPR was not significant. The extra maize yield obtained by the additional 40 kg P ha-1 from the inorganic P sources was, however, in most cases not substantial enough to justify their use. Economic considerations may therefore favour the use of tithonia or FYM when applied alone at 20 kg P ha-1 than when combined with any of the inorganic P sources used in this study at a total P rate of 60 kg ha-1.
Effects of combining organic materials with inorganic phosphorus sources on maize yield and financial benefits in western Kenya
(Cambridge University Press, 2009-10-09) Opala, P. A.; Othieno, Caleb; Kisinyo, Peter
Effects of cowpea leaf harvesting initiation time on yields and profitability of a dual purpose sole cowpea and cowpea maize intercrop
(2010) Aguyoh, Joseph Nyamori; Saidi, Mwanarusi; Itulya, Francis M.; Mshenga, Patience. M.; Owour, George
Harvesting of cowpea leaves for use as leaf vegetable has gained prominence in many parts of Africa and Asia. Little is known on effects of leaf harvesting on leaf and grain yields and profitability of cowpea-based cropping systems. This study sought to determine yields and profitability sole cowpea or cowpea-maize intercrop under different cowpea leaf harvesting initiation times. The study was conducted at Kenya National Dry land Research Center – Machakos using a Randomized Complete Block Design with cowpea grown as a monocrop or intercropped with maize. Leaf harvesting was initiated at 2, 3 or 4 weeks after cowpea emergence (WAE) and a control where no leaf harvesting was done. Initiating leaf harvesting at 3 and 4 WAE resulted in highest leaf and grain yields, respectively among leaf harvested cowpea. Overall, cowpea grain yields were highest in control treatment. Leaf vegetable and grain yields were lower in intercrop than in monocrop treatments. Maize yields in intercrop treatments were improved following harvesting of leaves of the companion cowpea. Initiating leaf harvesting at 3 and 4 WAE yielded highest returns in cowpea-maize intercrop and sole cowpea, respectively. Intercropping was on overall more profitable than sole cropping.
Antibacterial activity of Moringa oleifera and Moringa stenopetala methanol and n-hexane seed extracts on bacteria implicated in water borne diseases
(African Journal of Microbiology Research, 2010-11) Arama, Peter; Atieno, Walter; Wagai, Samuel; Ogur, Joseph
The anti-bacterial activity of methanol and n-hexane extracts of Moringa oleifera and Moringa stenopetala seeds was conducted on 3 bacterial species (Salmonella typhii, Vibrio cholerae and Escherichia coli) which normally cause water borne diseases. The paper disc diffusion method was used with treatments arranged in a completely randomized design and replicated four times. The highest inhibitions were observed at dilutions of 20, 5 and 40% for M. oleifera and M. stenopetala methanol extracts on E. coli, S. typhi and V. cholerae respectively. The n-hexane extract of both M. oleifera and M. stenopetala had a higher inhibition on S. typhii than V. cholerae and E. coli. The results of this study showed that M. oleifera and M. stenopetala had a degree of antibacterial properties especially in low doses.
Harvesting surface rainwater – purification using Moringa oleifera seed extracts and aluminum sulfate
(Journal of Agricultural Extension and Rural Development, 2011) Wagai, Samuel; Arama, Peter; Ogur, Joseph Acholl; Otieno, Walter Atieno; Ochieng, Owido Seth
Ground water harvesting is a method of collecting surface runoff from a catchment’s area and storing it in surface reservoirs. The water harvested is usually contaminated and turbid. Methods used to purify water include filtration, sedimentation, boiling and chlorination. This project was carried out in Nyatike district, Western Kenya where water is scarce and water-borne diseases such as cholera, typhoid and dysentery are prevalent. The main objectives of the research were to disseminate water harvesting technology using hand-dug water pans and to evaluate the effect of Moringa oleifera seed extract as water purifier. Sites were identified for construction of demonstration water pans. Moringa seeds were milled after which methanol was used to extract water soluble components.. Representative water samples from Victoria Lake, Kuja River and Otho pond were collected and subjected to purification studies using M. oleifera seed extract and aluminum sulfate. M. oleifera was also tested for antibacterial activity against Escherichia coli (ATCC 25922) Salmonella typhii and Vibrio cholerae (ref. Romel Cary Blair Lot. 452610). A total of 452 farmers were trained in water harvesting and purification technologies. Studies on water purification indicated that Alum lowered the water pH from 7.4 to 4.4 while samples treated with Moringa extract did not affect water pH. Alum was the better water purifier whereby application of 0.25 g/L decreased water turbidity from 310.7 to 1.1 NTU while M. oleifera decreased turbidity to 45.6 NTU. M. oleifera extract showed antibacterial activity. S. typhii was the most sensitive while V. cholera was the least sensitive.
Antibacterial activity of Moringa oleifera and Moringa stenopetala methanol and n-hexane seed extracts on bacteria implicated in water borne diseases
(African Journal of Microbiology Research, 2011) Peter, Arama; Walter, Atieno; Wagai, Samuel; Joseph, Ogur
The anti-bacterial activity of methanol and n-hexane extracts of Moringa oleifera and Moringa stenopetala seeds was conducted on 3 bacterial species (Salmonella typhii, Vibrio cholerae and Escherichia coli) which normally cause water borne diseases. The paper disc diffusion method was used with treatments arranged in a completely randomized design and replicated four times. The highest inhibitions were observed at dilutions of 20, 5 and 40% for M. oleifera and M. stenopetala methanol extracts on E. coli, S. typhi and V. cholerae respectively. The n-hexane extract of both M. oleifera and M. stenopetala had a higher inhibition on S. typhii than V. cholerae and E. coli. The results of this study showed that M. oleifera and M. stenopetala had a degree of antibacterial properties especially in low doses.
Screening of maize single cross hybrids for tolerance to low phosphorus
(2011) Ouma, Evans Ochieng; Gudu, Samuel; Agalo, Joyce; Matonyei, Thomas; Ligeyo, Dickson
Harvesting surface rainwater – purification using Moringa oleifera seed extracts and aluminum sulfate
(Journal of Agricultural Extension and Rural Development, 2011) Arama, Peter; Otieno, Wagai Samuel; Acholla, Ogur Joseph; Otieno, Walter Atieno; Ochieng, Owido Seth; Mukisira, Mahagayu Clerkson
Ground water harvesting is a method of collecting surface runoff from a catchment’s area and storing it in surface reservoirs. The water harvested is usually contaminated and turbid. Methods used to purify water include filtration, sedimentation, boiling and chlorination. This project was carried out in Nyatike district, Western Kenya where water is scarce and water-borne diseases such as cholera, typhoid and dysentery are prevalent. The main objectives of the research were to disseminate water harvesting technology using hand-dug water pans and to evaluate the effect of Moringa oleifera seed extract as water purifier. Sites were identified for construction of demonstration water pans. Moringa seeds were milled after which methanol was used to extract water soluble components.. Representative water samples from Victoria Lake, Kuja River and Otho pond were collected and subjected to purification studies using M. oleifera seed extract and aluminum sulfate. M. oleifera was also tested for antibacterial activity against Escherichia coli (ATCC 25922) Salmonella typhii and Vibrio cholerae (ref. Romel Cary Blair Lot. 452610). A total of 452 farmers were trained in water harvesting and purification technologies. Studies on water purification indicated that Alum lowered the water pH from 7.4 to 4.4 while samples treated with Moringa extract did not affect water pH. Alum was the better water purifier whereby application of 0.25 g/L decreased water turbidity from 310.7 to 1.1 NTU while M. oleifera decreased turbidity to 45.6 NTU. M. oleifera extract showed antibacterial activity. S. typhii was the most sensitive while V. cholera was the least sensitive.

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