Browsing by Author "Gathungu, Geofrey Kingori"

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    Improving seed potato leaf area index, stomatal conductance and chlorophyll accumulation efficiency through irrigation water, nitrogen and phosphorus nutrient management.
    (Macrothink Institute, 2016-01) Gathungu, Geofrey Kingori; Aguyoh, Joseph Nyamori; Isutsa, Dorcas Khasungu; ; ;
    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.
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    Optimization of seed potato specific density, starch and dry matter contents and tuberization capacity of resultant plants through integrated irrigation, nitrogen and phosphorus management.
    (Science Publishing Group, 2015-08-01) Gathungu, Geofrey Kingori; Nyamori, Aguyoh Joseph; 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 diffuse-light 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.