Browsing by Author "Narla Rama"

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    Effect of Lablab Green Manure on Population of Soil Microorganisms and Establishment of Common Bean (Phaseolus vulgaris L.)
    (American Journal of Agricultural Science, 2018-11-05) Okumu Oliver Otieno; Muthomi James; Ojiem John; Narla Rama; Nderitu John
    Green manures improve soil health and fertility but application of undecomposed lablab residues lead to low crop establishment. The study was carried out to determine the effect of green manure on microbial population and establishment of bean crop. Bean varieties were planted on plots each treated with lablab green manure at one ton ha-1 over whole plots and in rows, DAP fertilizer was applied at 75 kg/ha. Data was collected on microbial population, crop emergence, root rot incidence and severity, and yield. Green manure incorporation increased soil organic carbon, nitrogen, phosphorus and potassium but reduced germination percentage by about 35% and increased incidences of root rot by 30% compared to plots without green manure. The population of root rot pathogens was significantly higher in plots treated with green manure two weeks after emergence while the population of saprophytic fungi was low. Plots treated with lablab green manure reduced grain and biomass yields by 25%. Green manure increases soil nutrients directly and improves crop establishment after decomposition. Results of the study revealed a considerable increase in the population of root rot pathogens with corresponding decrease in the population of antagonistic fungi thus the poor emergence and crop establishment can be associated with increase in population of root rot pathogens and stress experienced by seeds during decomposition.
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    Effect of Legume Extracts on Germination, Seedling Health of Beans (Phaseolus vulgaris L.) and Soil Microorganisms
    (International Journal of Plant & Soil Science, 2019-05-10) Okumu Oliver Otieno; Muthomi James Wanjohi; Ojiem John; Narla Rama; Nderitu John Huria
    Application of undecomposed green manure has been reported to cause poor emergence and establishment of common beans in the field. Therefore, to understand the mechanisms’ contributing to the poor crop establishment, the effect of extracts from fresh and decomposed legume green manures on bean seed germination, fungal mycelial growth, spore germination and germ tube elongation were evaluated. The extracts were prepared in either ethanol or distilled water. Data was collected on percentage seed germination, seedling length, mycelial radial growth, spore germination and germ tube elongation. Ethanol extracts from fresh lablab inhibited bean germination by 56%, increased mean germination time to 8 days, and decreased germination index while ethanol extracts of groundnut and beans caused highest inhibition in bean shoot length and reduced biomass. Ethanol extracts from fresh green manures significantly inhibited fungal mycelia growth while the aqueous extracts from beans, groundnuts and soybean had significant level of antifungal activity while aqueous lablab extracts stimulated mycelial. Aqueous extract of lablab and soybean enhanced spore germination by over 70% with more pronounced effect on germ tube length and number of germ tubes by 8.0% and 13% respectively. The study comparatively reveals that the extract of lablab was inhibitory to common bean germination compared to other legume extracts and also stimulated the growth of root rot pathogens that may have resulted in poor establishment of beans.
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    Effect of Time after Incorporation of Lablab Green Manure on Root Rot Pathogens and Establishment of Common Bean (Phaseolus vulgaris L.)
    (World Journal of Agricultural Research, 2018) Okumu Oliver; Muthomi James; Ojiem John; Narla Rama; Nderitu John
    Green manure incorporation is important for restoration of soil quality, particularly buildup of organic matter and supply of nutrients to plants. However, undecomposed plant residues reduce crop establishment and plant stand. Therefore, there is need to determine suitable time for green manure incorporation before planting. The effect of time after incorporation of lablab green manure on soilborne pathogens and bean crop establishment was evaluated by incorporating 12t/ha of lablab green manure at planting and at 7, 14, and 28 days before planting. Soil samples were collected before and after incorporation of green manure at planting, and at two, four and six weeks after planting. Data was collected on crop emergence, plant stand, yield, incidence and severity of root rot, and population of root rot pathogens. Incorporation of lablab residues 28 days before planting resulted in 21% improvement in germination, with corresponding reduction in root rot incidence and severity of 8% and 36%, respectively, compared to plots incorporated with green manure at planting. Plots incorporated with lablab green manure earlier before planting had reduced population of root rot pathogens, while those incorporation at planting excited the population of root rot pathogens and also had up to 71% reduction in grain yield compared to plots where lablab residue was incorporated 28 days before planting. The results of the study showed that a period of 28 days between Lablab green manure incorporation and planting is necessary to allow for proper decomposition, resulting in a reduction in root rot incidence and an increase in grain yield.