Department of Plant Science

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Browsing Department of Plant Science by Author "Aguyoh, Joseph Nyamori"

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    Climate change adaptation of potato (Solanum tuberosum L.): Influence of Biozyme® rate on potato yield, quality and mineral nutrient uptake
    (2013-07) Karanja, Benard K.; Isutsa, Dorcas Khasungu; Aguyoh, Joseph Nyamori; ; ;
    Potato (Solanum tuberosum L.) is an important food crop worldwide. Growers prefer potato because of its short growing season and tolerance to poor soils. Growers are using different agrochemicals so as to improve tuber yield, quality and maturity period under erratic and unreliable rain patterns. Biozyme® foliar feed is widely used to hasten maturity and enhance yields of crops. Biozyme® is said to be a storehouse of hormones and nutrients that improve the health of a crop. It contains major hormones along with primary and secondary mineral nutrients. This study determined Biozyme® rate that is lower than the commercially recommended 500 ml/ha to curb overuse and misuse, but still enhance potato tuber yields under climate change deficit rainfall adaptation. The study was set up in split plots arranged in a randomized complete block design, replicated three times and repeated once. Main plots were assigned to two contrasting potato cultivars (Tigoni and Asante), while subplots were assigned to Biozyme® rate (0, 125, 250, 500 and 750 ml/ha). Each subplot was planted with 28 seed potato tubers spaced at 30 cm × 70 cm in four rows. A distance of 1 m separated plots. The 750 ml/ha Biozyme® significantly (P<0.05) increased total potato tuber yields by 3× to 7×, reduced unmarketable tubers by up to 3×, enhanced dry matter by 10% and starch by >2× compared to the 0 ml/ha Biozyme®. The 0 ml/ha Biozyme® produced 2-11 t/ha and 7-14 t/ha in "Tigoni' and "Asante', while the 750 ml/ha Biozyme® produced 25-33 t/ha and 39-43 t/ha in "Tigoni' and "Asante', respectively. The 750 ml/ha Biozyme® also increased leaf tissue N by >1%, P by >100 ppm and K by > 9 ppm in both seasons and cultivars. The difference in performance for 500 and 750 ml/ha Biozyme® was always not significant (P>0.05). Thus, it is not advisable to foliar-feed potato plants using Biozyme® rates e×ceeding 500 ml/ha since this will amount to overuse and misuse and e×acerbate tuber perishability. Slightly lower Biozyme® rates than 500 ml/ha may be recommended to guarantee production of "hardier" potatoes ideal for safe handling
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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.