Browsing by Author "Gathara, Mary"

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    Can Climate-Driven Change Influence Silicon Assimilation by Cereals and Hence the Distribution of Lepidopteran Stem Borers in East Africa?
    (Elsevier, 2016) Calatayud, P. A.; Njuguna, E.; Mwalusepo, Sizah; Gathara, Mary; Okuku, G.; Kibe, A.; Musyoka, B.; Williamson, David; Ong’amo, Georges; Gerald, Juma; Johansson, Tino; Subramanian, Sevgan; Gatebe, E.; Le Ru, Bruno P.
    In East Africa, lepidopteran stemborers such as Chilo partellus and Busseola fusca are major constraints to production of maize, which is the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Using altitudinal ranges in the East African highlands as ecological surrogates for inferring climate change, it was shown that Si concentrations in soil and maize decreased with altitude. This was attributed, in part, to low temperatures at high altitudes, which negatively affected Si assimilation by maize. Experiments showed that B. fusca was more susceptible to Si than C. partellus. Hence the predominance of B. fusca in the highlands and of C. partellus in the lowlands could be partly explained by altitudinal differences in Si concentrations in maize plants. Therefore, a rise in temperature due to climate change should enhance the plants’ Si assimilation and as a result C. partellus might move into the higher altitudes and increasingly displace B. fusca.
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    Characteristics of Soils in Selected Maize Growing Sites along Altitudinal Gradients in East African Highlands
    (2015) Ong’amo, George; Njuguna, Elijah; Gathara, Mary; Nadir, Stanley; Mwalusepo, Sizah; Juma, Gerald; Kimani, Jackson; Landmann, Tobias; Williamson, David
    Maize is the main staple crop in the East African Mountains. Understanding how the edaphic characteristics change along altitudinal gradients is important for maximizing maize production in East African Highlands, which are the key maize production areas in the region. This study evaluated and compared the levels of some macro and micro-elements (Al, Ca, Fe, K, Mg, Mn, Na and P) and other soil parameters (pH, organic carbon content, soil texture [i.e. % Sand, % Clay and % Silt], cation exchange capacity [CEC], electric conductivity [EC], and water holding capacity [HC]). Soil samples were taken from maize plots along three altitudinal gradients in East African highlands (namely Machakos Hills, Taita Hills and Mount Kilimanjaro) characterized by graded changes in climatic conditions. For all transects, pH, Ca, K and Mg decreased with the increase in altitude. In contrast, % Silt, organic carbon content, Al and water holding capacity (HC) increased with increasing altitude. The research provides information on the status of the physical-chemical characteristics of soils along three altitudinal ranges of East African Highlands and includes data available for further research.
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    Variation of Soil Nutrients in Maize Growing Areas along the Altitudinal Gradient of Taita Hills Transect in Kenya
    (2015) Njuguna, Elijah; Le Ru, Bruno P.; Okuku, G.; Gathara, Mary; Mwalusepo, Sizah; Juma, Gerald; Sambai, K.; Johansson, Tino; Ong’amo, Georges; Gatebe, E.; Calatayud, P. A.
    Maize is the main staple food crop in Kenya but its yield is being affected by biotic and abiotic factors which reduce maize yield while soil nutrient elements increase the yield. Most plants grow by absorbing nutrients from the soil depending on the nature of the soil. Soil texture affects how well nutrients and water are retained in the soil. Clays and organic soils hold nutrients and water much better than sandy soils. As water drains from sandy soils, it often carries nutrients along with it through leaching. When nutrients leach into the soil, they are not available for plants to use thus affecting the plant health. This study evaluated several physical and chemical properties of soil along the altitudinal gradients of Taita hills which is characterized by graded changes in climatic conditions. Both nitrogen and carbon increased with increase in altitude while Potassium, phosphorus and pH deceased with increase in altitude. Moisture and temperature appear to be important drivers in soil parameter and therefore biological patterning along the transect.