School of Agriculture, Natural Resources and Environmental Studies

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Curing reduces postharvest deterioration of biozyme® produced potatoes ( Solanum tuberosum L.)
(Global journal of Bio-science and technology, 2013) Karanja, B. K.; Isutsa, D. K.; Aguyoh, Joseph Nyamori
Potato is among food crops that are heavily relied upon for food security assurance worldwide. Potato tubers are consumed in their fresh form and therefore require proper storage to prolong their life after harvest. Being succulent, massive losses result if bruised, exposed to light and low relative humidity. The present experiment was conducted to find optimal conductions that prolong the shelf-life of potato tubers grown using the biomass and succulence enhancing Biozyme® Potatoes were grown in a split plot experiment, arranged in a randomized complete block design. The experiment was replicated three times and repeated once. Main plots were assigned to potato cultivar (Tigoni and Asante), while subplots were assigned to Biozyme® foliar feed rate (0, 125, 250, 500 and 750 ml/ha). Each subplot was planted with 28 seed potato tubers spaced at 30 cm x 70 cm in four rows. A distance of 1 m separated adjacent subplots and main plots. After harvesting, ware potato tubers, from each treatment, were divided into four groups for four postharvest handling regimes (Cured + Dark, Cured + Room, Not Cured + Dark, and Not Cured + Room Storage). Each postharvest regime had 20 tubers, replicated four times. Weight loss, shrinkage and rotting percentages increased, but firmness decreased with increase in Biozyme® rate. The deterioration was counteracted by Curing and Dark Storage of the potato tubers that reduced weight loss, shrinkage and rotting, but increased firmness. Thus, foliar-feeding potato plants with 500 ml/ha Biozyme® followed by Curing and Dark Storage of harvested tubers are recommended to ensure high potato tuber yields and effective reduction of premature postharvest deterioration of the tubers during storage. KEYWORDS : Firmness, Rotting, Shelf-life, Shrinkage, Tuber handling, Weight loss.
Economic efficiency of green maize intercropped with beans grown under Tithonia and inorganic fertilizer
(African Journal of Agricultural Research, 2015-11-20) Aguyoh, Joseph Nyamori; Opiyo, Arnold Mathew; Muturi, Esther Waithira
A field trial aimed at assessing the performance of maize and beans under intercropped systems was conducted in 2013 under three experimental components of maize, beans and maize-bean intercrop in a randomized complete block design (RCBD) with three replications. Each component was subjected to treatments that included: a control-without fertilizer (WF), mineral fertilizer (MF) at 150 kg/ha of 17:17:17, Tithonia biomass (TDB) at 8 tons/ha and integrated application of MF and TDB comprising 4 tons/ha Tithonia and 100 kg/ha mineral fertilizer (MF/TDB). The MF/TDB produced 21.7% higher green maize yields than control, while MF and TDB produced 8.96 and 7.52% higher yields, respectively than the control. The land equivalent ratios (LER) were higher than one in all the intercropping plots, thus indicating an optimum exploitation of the environmental resources. Control plots showed the highest yield advantage in terms of LER of 1.70. When maize yield was converted to bean equivalent yield (BEY), the intercropping BEY was higher than the BEY in the sole for all fertilizer types, thereby revealing an agronomic advantage. The actual yield loss (AYL) values for maize indicated a yield gain of between 11.2 and 15.05% when MF and MFTDB were used in the intercropping compared to the sole cropping. Beans recorded yield loss in all the fertilizer types except in TDB which had a yield gain of 20.45%. The economic performance of the intercropping systems, affirmed that the most advantageous fertilizer type for maize was MF/TDB with an IA of 6.566. The monetary advantage index (MAI) indicated a definite yield and economic advantage in maize-bean intercrop over their sole cropping, with integrated use of MF/TDB as nutrient sources being the most economical and advantageous fertilizer regime.
Effect of Light and Temperature through Poly Film Covers on Anthocyanin Content in Rose Cut Flowers
(International Journal of Plant & Soil Science, 2017-11-22) Abucheli, G. Oloo; Aguyoh, Joseph Nyamori; Liu, G.
Quality is the most important attribute in rose cut flowers for both export and domestic market. Quality in cut flowers may be defined by many attributes however, among the most important is colour. A group of pigments commonly known as anthocyanins determine colour in plants. Anthocyanins play a significant role by ameliorate the effect of high irradiance in plants under stressful environment. They also play a key role in delaying senescence hence enhancing the cut flower vase life. Despite the advantages anthocyanins are affected by the preharvest conditions mainly light and temperature interfering with their stability. An experiment was set up to investigate the effect of light and temperature through selected coloured poly film covers on rose petal anthocyanin content. The greenhouse structure was covered by poly films of different colours that were compartmentalized i.e. UV-A clear, IR504 with yellow tint and UV-A 205/N with green tint replicated three times. Two rose cultivars Red calypso and Furiosa were established and maintained, upon maturity the flower heads were plucked and oven dried at 60°C to constant weight. 5 g of the crushed petals was used in anthocyanin extraction. The anthocyanins were extracted and quantified in comparison with commercial standards using HPLC machine. The data obtained from the chromatogram as peak areas was subjected to analysis of variance (ANOVA) using SAS statistical package (SAS Inst., Inc., Cary, NC) at P = .05. Where there were treatment differences, mean separation was done using Tukey’s procedure. Poly films significantly affected the quantity and quality of anthocyanin accumulation in rose petals. Cyanidin 3-0-glucoside was the most prevalent anthocyanin across all poly film covers and it was noted to be high under the UV-A 205/N (110.95±8.26 µg _ 5 g–1 DW) and IR504 (109.69±8.26 µg _ 5 g–1 DW) compared to UV-A clear (84.56± 8.26 µg _ 5 g–1 DW). The quantity of anthocyanins was low under the UV-A clear poly film that was characterized by high light transmission and day temperature. Combination of high irradiance and temperature affect the quality and quantity of anthocyanin in rose cut flowers.
Effect of Light and Temperature through Poly Film Covers on Anthocyanin Content in Rose Cut Flowers
(International Journal of Plant & Soil Science, 2017) G, Oloo-Abucheli; Aguyoh, Joseph Nyamori; Liu, G.
Quality is the most important attribute in rose cut flowers for both export and domestic market. Quality in cut flowers may be defined by many attributes however, among the most important is colour. A group of pigments commonly known as anthocyanins determine colour in plants. Anthocyanins play a significant role by ameliorate the effect of high irradiance in plants under stressful environment. They also play a key role in delaying senescence hence enhancing the cut flower vase life. Despite the advantages anthocyanins are affected by the preharvest conditions mainly light and temperature interfering with their stability. An experiment was set up to investigate the effect of light and temperature through selected coloured poly film covers on rose petal anthocyanin content. The greenhouse structure was covered by poly films of different colours that were compartmentalized i.e. UV-A clear, IR504 with yellow tint and UV-A 205/N with green tint replicated three times. Two rose cultivars Red calypso and Furiosa were established and maintained, upon maturity the flower heads were plucked and oven dried at 60°C to constant weight. 5 g of the crushed petals was used in anthocyanin extraction. The anthocyanins were extracted and quantified in comparison with commercial standards using HPLC machine. The data obtained from the chromatogram as peak areas was subjected to analysis of variance (ANOVA) using SAS statistical package (SAS Inst., Inc., Cary, NC) at P = .05. Where there were treatment differences, mean separation was done using Tukey’s procedure. Poly films significantly affected the quantity and quality of anthocyanin accumulation in rose petals. Cyanidin 3-0-glucoside was the most prevalent anthocyanin across all poly film covers and it was noted to be high under the UV-A 205/N (110.95±8.26 μg _ 5 g–1 DW) and IR504 (109.69±8.26 μg _ 5 g–1 DW) compared to UV-A clear (84.56± 8.26 μg _ 5 g–1 DW). The quantity of anthocyanins was low under the UV-A clear poly film that was characterized by high light transmission and day temperature. Combination of high irradiance and temperature affect the quality and quantity of anthocyanin in rose cut flowers.
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.
Effects of Integration of Irrigation Water and Mineral Nutrient Management in Seed Potato (Solanum Tuberosum L.) Production on Water, Nitrogen and Phosphorus Use Efficiencies
(2014-11-27) Aguyoh, Joseph Nyamori; Isutsa, Dorcas K.; Gathungu, Geofrey
Inorganic fertilizers have become extremely important in correcting declining soil fertility in seed potato (Solanum tuberosum L.) production in Kenya. Unreliable rainfall has also limited seed production. Knowledge on water and nutrient use efficiencies in potato grown under different irrigation regimes with different nitrogen and phosphorus levels will help predict the best application rates for optimal seed potato production and yield. A study was conducted at Egerton University, Horticultural Research and Teaching Farm to determine the effect of integrated application of irrigation water, nitrogen (N) and phosphorus (P) use efficiencies of water, N and P. In a split-split plot design, the irrigation water was applied to maintain soil water at 40, 65 and 100 % field capacity in the main plots, N (0, 75, 112.5 and 150 kg N/ha) to subplots and P (0, 115, 172.5 and 230 kg P2O5/ha), which translated into 0, 50.6, 75.9, 101.2 kg P/ha) to sub-subplots, with each treatment replicated three times and the trial repeated once. The irrigation water was applied throughout the potato growth period through drip tube lines, with N supplied as urea (46 % N) in two splits, and P as triple superphosphate (46 % P2O5) at planting time. Data on seed potato yield was collected from each treatment at harvest and used to calculate water, N and P use efficiencies. High irrigation water at 100 % compared to 65 and 40 % rate resulted in relatively high N and P use efficiencies, but decreased water use efficiency. Application of intermediate to high N and P nutrient increased the water, N and P use efficiencies. It is recommended to apply low to intermediate irrigation water, intermediate to high N and P to increase their use efficiencies during seed potato production.
Improving Carrot Yield and Quality through the Use of Bio-slurry Manure
(Canadian Center of Science and Education, 2012-11-25) Aguyoh, Joseph Nyamori; Jeptoo, Agnes; Saidi, Mwanarusi
Continuous cultivation of farms has led to decline in soil fertility due to constant removal of nutrients leading to reduction of carrot (Daucus carota L.) yields. A field study was carried out at Egerton University, Horticulture Research and Teaching field in two seasons (October 2010 to January 2011 and February to May 2011) with the aim of investigating the effects of decomposed cattle bio-slurry manure on carrot growth and performance. The experimental design was a Randomized Complete Block Design (RCBD) with 3 replications. Treatments comprised four levels (0, 2.6, 5.2 and 7.8 t/ha) of decomposed bio-slurry manure. Growth, yield and quality parameters were recorded and used to discern the treatment effects. Application of bio-slurry manure generally improved growth, yield and quality of carrots. Application of 7.8 t/ha of bio-slurry increased yields by 8.8% in season 1 and 23.5% in season 2 compared to the control. Leaf numbers, plant height, dry weights of shoot and roots and root volume were also generally higher for the 7.8 t/ha treatment compared to other treatments. Total Soluble Solids of roots from plant treated with 7.8 t/ha were higher by 12.7% in season 1 and 13.2% in season 2 compared to the control. The study recommends 7.8 t/ha of bio-slurry manure for enhanced yield and quality of carrot.
Improving Seed Potato Leaf Area Index, Stomatal Conductance and Chlorophyll Accumulation Efficiency through Irrigation Water, Nitrogen and Phosphorus Nutrient Management
(Journal of Agricultural Studies, 2016) Aguyoh, Joseph Nyamori; Kingori, Gathungu Geofrey; Isutsa, Khasungu Dorcas
A study was conducted in a Rainshelter (RTrial) at Horticultural Research and Teaching Farm, Egerton University to determine the effect of integration of irrigation water, nitrogen (N) and phosphorus (P) application on seed potato leaf area index (LAI), stomatal conductance and chlorophyll content. The treatments arranged in a split-split plot layout in a completely randomised block design, consisted of three irrigation water rates (40%, 65% and 100% field capacity), four N rates (0, 75, 112.5 and 150 kg N/ha) supplied as urea (46% N), and four P rates (0, 50.6, 75.9, 101.2 kg P/ha) supplied as triple superphosphate, replicated three times and repeated once. During the growth leaf area, stomatal conductance, and chlorophyll content were measured. Data collected were subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at P≤0.05. Leaf area index was greater with high irrigation water at 100%, N at 150 kg N/ha and P at 101.2 kg P/ha, which was 2.6 and 1.3 at 51 days after planting (DAP) and 3.5 and 3.1 at 64 DAP. Furthermore, low irrigation water rate at 40% together with low N and P rates of 0 kg N/ha and 0 kg P/ha had the least LAI, which was 0.28 and 0.19 at 51 DAP and 0.28 and 0.24 at 64 DAP both in RTrials I and II, respectively. Subjecting potato to 100% compared to 40% irrigation rate increased stomatal conductance at 87 days after planting (DAP) by 32.82 and 31.99 mmolm⁻²s⁻¹, leaf chlorophyll content index by 16.2 and 16.5, 19.8 and 19.6, and 15 and 20.3, when integrated with high compared with low N and P application rates at 59, 73 and 87 DAP, in RTrials I and II respectively. Irrespective of N and P rates LAI, stomatal conductance and chlorophyll content were significantly greater with high irrigation water at 100% followed by 65% and was lowest with 40% irrigation water rate.
Influence of Irrigation Water, Nitrogen and Phosphorus Nutrient Rates on Relative Weight Loss and Sprouting Characteristics of Seed Potato Tubers After Storage
(Canadian Center of Science and Education, 2013-07-17) Aguyoh, Joseph Nyamori; Gathungu, Geofrey; Isutsa, Dorcas K.
Potato has overtime generated special importance in most parts of Kenya and the world as a means of strengthening food security and increasing revenue for farmers. However, potato productivity and industry expansion have been constrained by the poor quality seed tubers being produced in the informal seed sector due to inadequate supply of initial planting materials, improper fertilizer management practices and irregular rainfall patterns. A study was done at the Horticultural Research and Teaching Farm of Egerton University to determine the effect of integration of irrigation water, nitrogen and phosphorus rates on seed tuber relative weight loss and sprouting characteristics after storage. The three factors were tested in a split-split plot design where irrigation water supply was assigned to main plots, N to subplots and P to sub-subplots. The treatments were replicated three times and the trial repeated once. The treatments consisted of three irrigation water rates (40%, 65% and 100% field capacity), applied throughout the potato growth period through drip tube lines. Nitrogen was supplied as urea (46% N) at four equivalent rates of 0, 75, 112.5 and 150 kg N/ha, while phosphorus was supplied at planting time as triple superphosphate (46% P2O5) at four rates of 0, 115, 172.5 and 230 kg/ha P2O5, which translated into 0, 50.6, 75.9, 101.2 kg P/ha. Data collected included relative percentage weight loss, number of sprouts and sprouting percentage. Data collected was subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at p ≤ 0.05. The 100% compared to 65% and 40% irrigation water rates resulted in relatively high weight loss, sprout length and reduced the number of sprouts and sprouting percentage of seed tubers. N and P rates generally decreased the relative weight loss, improved the number of sprouts and sprouting percentage. It is recommended to apply low to intermediate irrigation water, intermediate to high N and P rates to reduce the percentage relative weight loss and sprouting characteristics.
Influence of soil moisture levels and packaging on post harvest qualities of tomato
(2015-03-11) Aguyoh, Joseph Nyamori; Imani, Caroline; Opiyo, Mathew
Preharvest factors influence postharvest quality of tomatoes. Whereas water stress improves fruit total soluble solids; and polyethylene is used for packaging of fresh horticultural produce, little is known about their combined effects on quality and shelf life of tomatoes. The objective of this study was to investigate the independent and interactive effects of deficit irrigation and packaging on postharvest quality and shelf life of tomatoes. The experiment was a split plot arranged in a Randomized Complete Block Design with three replicates. Packaging was the main treatment and water levels the sub treatments. Water treatments were 20, 40, 60, 80 and 100% of pot capacity (PC). Packaging treatments were perforated, non-perforated and non-packaged (control). Fruits harvested at breaker stage were stored at 21±2ºC. Quality parameters assessed were fruit weight loss, colour change, firmness, total soluble solids, titratable acidity and shelf life. Polyethylene bags commonly used in the market (22 x 6.37 cm of size; 0.02 mm of thickness) were used as packaging material. At 16 days storage, unpackaged fruit had lost 34.23% of initial weight compared to 9.06% in perforated and 4.43% in nonperforated packaging. At 8 days of storage, 20% PC fruits were firmer than 80% PC fruits. At 10 days storage, 20% PC fruits were firmer compared to those from 40 and 80% PC. Total Soluble Solids (TSS) increased with decrease in moisture level. At 10 DAH, the lowest TSS was recorded in fruits subjected to 100% PC and highest in 40% PC. Deficit Irrigation effectively regulates tomato fruit quality; and combining it with packaging can enhance shelf life of tomato fruits.
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.
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.
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
Maturity of Freshmarket Sweet Corn with Directseeded Plants, Transplants, Clear Plastic Mulch, and Rowcover Combinations
(1999) Aguyoh, Joseph Nyamori; Taber, Henry G.; Lawson, Vince
Optimization of Seed Potato Specific Density, Starch and Dry Matter Contents and Tuberization Capacity of Resultant Plants Through Integrated Irrigation, Nitrogen and Phosphorus Management
(Journal of Plant Sciences, 2015-07-30) Aguyoh, Joseph Nyamori; Gathungu, Geofrey; Isutsa, Dorcas Khasungu
A study was conducted in a Rainshelter (RTrial) at the Horticultural Research and Teaching Farm of Egerton University to determine the effect of integrated application of irrigation water, nitrogen (N) and phosphorus (P) on seed potato physiological quality and performance of plants resulting from them. The treatments arranged in a split-split plot in a completely randomized block design, consisted of three irrigation water rates (40%, 65% and 100% field capacity), four N rates (0, 75, 112.5 and 150 kg N/ha) supplied as urea (46% N), and four P rates (0, 50.6, 75.9, 101.2 kg P/ha) supplied as triple superphosphate with experiment replicated three times and repeated once. After harvest seed specific density, starch and dry matter contents were determined after which 15 seed tubers per treatment were stored for 90 days under diffuselight sprouting conditions for postharvest (PTrial) evaluation. Later, three potato tubers were selected per treatment and planted to study growth vigour and tuberization capacity of resultant potato plants both in PTrials I and II. Data collected were subjected to analysis of variance and significantly different means were separated using Tukey’s Studentized Range Test at P=0.05. Specific density, starch and dry matter contents increased from 40% to 65% irrigation water. Application of irrigation water beyond 65% reduced the specific density, starch and dry matter contents by 0.03, 2.6%, 3.7% and 0.04, 3.7%, 5.2% in RTrials I and II, respectively. The 100% compared to 65% irrigation rate reduced post-treatment evaluation stem number, density and height at 57 DAP by 1.3 and 1.1, 15.1 and 12.6, and 13.4 cm and 10.3 cm, and tuberization capacity in resultant plants by 5 and 8.7 tubers, in PTrials I and II, respectively. Application of N and P significantly increased seed potato specific density, starch and dry matter contents but application of N and P beyond 112.5 kg N/ha and 75.9 kg P/ha respectively reduced the same both in RTrials I and II, respectively. In postharvest evaluation integration of N at 0 to 112.5 kg N/ha with 65% irrigation rate increased the number of tubers produced by the resultant plants by 3.4 and 5.4, while high P rate at 75.9 kg P/ha increased tuberization by 8.4 and 10.7, in RTrials I and II, respectively. Integration of 65% irrigation rate, 112.5 kg N/ha and 75.9 kg P/ha rates optimized potato growth, and vigour of resulting potato plants.
Seed Potato Growth, Harvest Index and Net Economic Benefit Improvement through Irrigation Water, Nitrogen and Phosphorus Management
(Columbia International Publishing American Journal of Agricultural Science and Technology, 2016) Gathungu, Geofrey; Aguyoh, Joseph Nyamori; Isutsa, Dorcas Khasungu
A study was conducted in a Rainshelter (RTrial) at Egerton University to determine the correlation between irrigation water, nitrogen (N) and phosphorus (P) application on seed potato growth, harvest index (HI) and net economic benefit (NEB). The Rainshelter was to separate the effects of rainfall from those of irrigation water treatments. The treatments arranged in a split-split plot layout in a completely randomized block design, consisted of irrigation water (40%, 65% and 100% field capacity), N (0, 75, 112.5 and 150 kg N/ha) and P (0, 50.6, 75.9, 101.2 kg P/ha), replicated three times and repeated once. During growth plant height, days to 50% flowering and physiological maturity were determined and at harvest seed potato tuber yield and total biomass were determined to estimate HI and NEB. Data collected were subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at P≤0.05. 100% irrigation water yielded plant heights of 98.3 and 103.3 cm for RTrials (Rainshelter Trials) I and II compared to 76.2 and 80.4cm for the 40% treatment, while days to 50% flowering were 53.5 and 54.7 days compared to 68.3 and 69.8 days, and delayed days to physiological maturity were 109.8 and 108.7 days compared to 89.6 and 88.3 days. High N and P application significantly increased plant height and delayed days to 50% flowering and physiological maturity. 100% compared to 65% irrigation rate reduced HI by 5.3% and 4.9%, seed potato NEB by 2,852 US $ (Ksh. 288,991) and 2712 US $ (Ksh 274,792) in RTrials I and II, respectively. The N and P rates improved potato growth and development, HI and NEB. Combined application of N and P at 112.5 kg N/ha and 75.9 kg P/ha, compared to 0 kg N/ha and 0 kg P/ha increased seed potato HI by 8.5%, and NEB by 4,837 and 6,115 US $, in RTrials I and II, respectively. Integration of 65% irrigation rate reduced HI by 5.3% and 4.9%, seed potato NEB by 2,852 US $ (Ksh. 288,991) and 2712 US $ (Ksh 274,792) in RTrials I and II, respectively. The N and P rates improved potato growth and development, HI and NEB. Combined application of N and P at 112.5 kg N/ha and 75.9 kg P/ha, compared to 0 kg N/ha and 0 kg P/ha increased seed potato HI by 8.5%, and NEB by 4,837 and 6,115 US $, in RTrials I and II, respectively. Integration of 65% irrigation rate, 112.5 kg N/ha and 75.9 kg P/ha rates optimized potato growth characteristics, and net economic benefit.
Soil Incorporated Plant Residues and Nemacur affected Weed Population and Soil Nitrogen Dynamics in Asclepia Field
(International Journal of Agricultural and Food Research, 2013) Aguyoh, Joseph Nyamori; Kagai, Kenneth; Tunya, Geoffrey
Field trials were conducted for two seasons in 2006 and 2007 to test the effect of Tagetes patula, Lantana camara, Tephrosia vogelii, Azadirachta indica and Nemacur on the growth of asclepiad, soil pH, and soil nitrogen as well as weed population dynamics. The experiment was replicated three times under complete randomized block design. Chopped plant materials were applied singly or in combination with nemacur. T. patula was applied at 300 g/m2 , A. indica at 150 g/m2 , L. camara at 10% w/w, and T. vogelii at 10% w/w. Organic plant materials were applied at half rate in combination with nemacur at 20 g/m2 . Nemacur treatment alone was applied at a full rate of 40 g/m2 . Tagetes patula with nemacur reduced weed biomass between 33.6% and 36.6% while L. camara alone decreased the population density of Oxalis cornulata weed between 14% and 17% compared to the untreated control. The improvement of nutrient status of the soil and the control of weeds could have led to an improvement of yield characteristic of asclepias. A combination of L. camara with nemacur may be used instead of synthetic nematicides alone to control weeds and improve soil nutrient levels.
Soil moisture levels affect growth, flower production and yield of cucumber
(2022) Aguyoh, Joseph Nyamori; Odhiambo, Judith Achieng
Field trial to determine the optimum soil moisture level for enhanced performance of cucumber was conducted in polyethylene covered rain shelter for two seasons in 2017 and repeated in 2018. The research was conducted at Rongo University Research and Teaching field. Three seeds of cucumber ‘Ashley’ were sown directly in 3.5 litre plastic pots containing 8 kg of sterilised air‑dried growth medium made up of sand and top soil in the ratio of 1:2. The treatments were four levels of water applied at 100% (control), 80%, 60% and 40% pot capacity. The experimental design was completely randomised block design replicated three times. Data on the plant growth, flower production and yield were subjected to Analysis of Variance (ANOVA) and mean separation tests at p ≤ 0.05 level of significance. There were significant differences on the vine growth, internodes length and diameter as a result of Water Stress (WS) levels. The treatments also significantly affected the Relative Leaf Water Content (RLWC) and Relative Leaf Expansion Rate (RLER) but did not affect the number of leaves per vine. Fruit firmness was also affected by water stress. To optimise the productivity of cucumber, the soil moisture level should be maintained to at least 80% of the field capacity throughout its productive phase.
Tithonia Manure improves carrot yield and quality
(Global Institute for Research & Education, 2013-12) A. Jeptoo,; Aguyoh, Joseph Nyamori; M. Saidi,
A study on the effect of decomposed tithonia manure on growth, yield and quality of Carrot (Daucus carota L.) was undertaken in the Horticulture, Research and Teaching field, Egerton University for two seasons. The field experiment was laid out in a Randomized Complete Block design (RCBD), with 3 replications. The treatments consisted of four levels of decomposed tithonia manure (0, 1.5, 3.0 and 4.5 t/ha). Data was subjected to Analysis of Variance (ANOVA) and significant treatment means separated using the Turkey’s Honestly Significant Difference Test at P ≤ 0.05. Application of Tithonia diversifolia manure resulted in increase in total fresh root weight, dry root and shoots biomass and root volume compared to the control. Total yield of carrots subjected to 3.0 t/ha increased by 33% and 18% in season 1 and 2 respectively compared to control. The sweetness of carrot was influenced at the highest level of tithonia. Key words: Nutrient, Carrot yield, quality, brix content, biomass.

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