Browsing by Author "Cheruiyot, Erick Kimutai"

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    The influence of soil water content and nitrogen supply on growth, yield and polyphenol content of selected tea [Camellia sinensis (l.) O. Kuntze] clones in Kenya
    (Egerton University, 2008-04) Cheruiyot, Erick Kimutai
    Tea is a major foreign exchange earner in Kenya and it accounts for about 24% of the total value of the domestic exports for the last 10 years. The sector employs 10% of Kenya’s population directly and indirectly, and contributes to infrastructural development which includes construction of schools and health facilities, rural access roads and rural industries. However, tea suffers frequent droughts with significant yield decline, often accompanied by plant deaths, a condition which seems to be worsened by fertilizer input. The objectives of this work were to determine: i) the critical minimum soil water requirements in selected tea clones and show how it varies with nitrogen (N) supply ii) the effect of N supply and progressive decline of soil water content on tea shoot growth, leaf yield and black tea quality iii) the levels of tea polyphenols and define their association with water stress in tea and their suitability as indicators for drought tolerance. Two experiments were set up in a rain-out shelter at Tea Research Foundation of Kenya (TRFK) and a field experiment conducted at three different field sites in tea growing areas. The first experiment consisted of six different tea clones which were subjected to 4 levels of soil water content (SWC) (38, 30, 22 and 14% v/v) for 12 weeks. The second experiment consisted of clone BBK 35 treated with 5 different rates of N (0, 75, 150, 225 and 300 kg/ha) using NPKS (25-5-5-5) fertilizer material, and 5 levels of SWC (38, 34, 30, 26, 22, 18% v/v). Shoot and leaf growth, dry matter partitioning, photosynthesis, stomatal conductance, transpiration, leaf anatomy and shoot polyphenol content were determined. The field experiment consisted of clone BBK 35 with five rates of N, similar to the rain-out shelter and where shoot population density and yield were determined during dry months. SWC limit for tea was shown to be about 20% v/v and that fertilizer supply increased the susceptibility of tea to drought. Contrary to earlier speculations that fertilizer raises the optimal SWC for tea, it emerged that fertilizer rates above 200 kg N ha-1 influenced assimilate partitioning to shoot and foliage, making tea more vulnerable to drought effect. Clones with high total polyphenol content and whose levels varied less with changes in SWC were more tolerant to drought. Two catechin variants, epicatechin and epigallocatechin correlated with SWC, water stress index and shoot growth in tea, which suggests they are potential indicators for drought stress in tea.
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    Leaf Gas Exchange and Root Nodulation Respond to Planting Density in Soybean [Glycine Max (L) Merrill]
    (Hindawi, 2020-01) Mwamlima, Louis Hortensius; Ouma, Josephine Pamela; Cheruiyot, Erick Kimutai
    Planting density influences structural characteristics and affects mineral nutrient acquisition, irradiance and photosynthesis amongst plants. An experiment was conducted to determine the effect of planting density on leaf gas exchange and nodulation of soybean (Glycine max (L) Merrill). e experiment was conducted as a randomized complete block design (RCBD) in a 5 by 2 factorial treatment arrangement and was replicated three times. Planting density (10, 12, 20, 40, and 80 plants m−2) and soybean varieties (EAI 3600 and DPSB 19) were first and second factors, respectively. Collected data were subjected to analysis of variance in GENSTAT. Significantly different treatment means were separated using Tukey’s honestly significant difference test at 0.05 significance level. Higher planting density significantly increased ( < 0.001) interception of photosynthetically active radiation. Increasing number of plants per unit area significantly ( < 0.001) reduced root nodulation, stomata conductance, sub-stomatal CO2 concentration, photosynthetic and transpiration rates. Total chlorophyll content was not responsive to planting density though concentration of chlorophyll “a” content was significantly ( < 0.005) higher at lower plant density than at higher plant density. Soil moisture status increased with reduction in plant density. Indeterminate variety DPSB 19 had higher rates of stomata conductance, photosynthesis and sub-stomatal CO2 concentration compared to determinate variety EAI 3600.
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    Physiological Response of Soybean [Glycine Max (L) Merrill] to Soil Moisture Stress
    (African Journal of Agricultural Research, 2019-04) Mwamlima, Louis Hortensius; Ouma, Josephine Pamela; Cheruiyot, Erick Kimutai
    This study was done to determine the effects of varying soil moisture regimes on CO2 assimilation of soybean [Glycine max (L.) Merrill] in pots under greenhouse conditions during 2017 and 2018 cropping seasons. The experiment was conducted as a Randomized Complete Block Design (RCBD) in a 4 x 6 factorial treatment arrangement and replicated 3 times. Soil moisture regimes (80, 60, 40 and 20% of field capacity) and cultivars (Gazelle, Nyala, EAI 3600, DPSB 8, Hill and DPSB 19) were first and second factors, respectively. Collected data were subjected to Analysis of Variance (ANOVA) using Linear Mixed Model in GENSTAT. Significantly different treatment means were separated using Tukey’s test at 0.05 significance level. Leaf relative water content, stomata conductance, photosynthesis rate and substomatal CO2 concentrations significantly (P < 0.001) declined with increasing soil moisture stress. Total leaf chlorophyll content increased (P < 0.001) with increased soil moisture stress. Cultivars DPSB 19 and DPSB 8 had relatively higher leaf relative water content and stomata conductance at reduced soil moisture regime at 20% moisture from field capacity indicating moisture stress tolerance potential of the cultivars. Key words: Flowering stage, podding stage, seasons, soil moisture regimes, soybean cultivars.
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