Browsing by Author "Nyabundi, J.O."
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Item Effect of Proximity between Inter Cropped Maize and Beans on Growth and Yield of Maize under Varying Nitrogen Levels(1994) Nyabundi, J.O.; Cheminin'gwa, G.N.In a field study, planting patterns of maize (Zea mays L.) and beans (Phaseolus vulgaris L.) and nitrogen fertilisation were evaluated for two seasons. Plant population of each species was 53,330 plants/ha. The planting patterns consisted of sole maize. Maize and beans intercropped in alternate rows. Maize and beans intercropped as alternate plants in the same row, and maize and beans intercropped in the same hill. The N levels were, 50, 100 and 150 kg N/ha. Yield of beans was not affected by the planting patterns. Increasing die intimacy between maize and beans increased maize biomass and yield under low N levels (0 and 60kg/ha), but had no effect at high N levels. At low N, intercropping maize and beans in the same hill out yielded all the other treatments, while intercropping in alternate rows gave the lowest yield. Increasing N application rates increased the yield of both maize and beans, but the optimal N level was lower (50 kg/ha) for maize and beans planted in the same hill Chan for monocrop maize or maize planted with beans in alternate rows (100 kg/ha). Effect of increased intimacy on maize biomass occurred later in the season compared to that of applied N. These results suggest that bean plants contributed N to the associated maize plants, largely from dead and decomposing bean roots and root nodules. The contribution was enhanced by interspecific intimacy.Item Effects of Water Stress on Growth and Yield of Field-Grown Tomatoes I : Canopy Development and Biomass Accumulation(1989) Nyabundi, J.O.; Hsiso, T.C.; University of CaliforniaIn tomato plants subjected to different levels of water stress under field conditions of deep soils, it was found that drought had little or no effect on leaf water potential. However, biomass and leaf area developments were markedly depressed. Photosynthesis of the upper-most mature leaves was also affected, but this effect was largely attributed to leaf age; the dry treatment had older leaves with low photosynthetic efficiency. It was concluded that water stress depressed biomass accumulation mainly by inhibiting leaf area development. This occurred in two ways: first, through the reduced photosynthetic area arising from a small canopy, and second, since water stress depressed leaf area development, canopies of stressed plants consisted of a relatively large proportion of old leaves, which have low photosynthetic rates. This led to lower photosynthetic efficiency in such canopies.Item Effects of Water Stress on Growth and Yield of Field-Grown Tomatoes. II: Biomass Partitioning between Vegetative and Reproductive Growth(1989) Hsiso, T.C.; Nyabundi, J.O.; University of CaliforniaMuch work has been done in attempts to understand crop water requirements during different phenological stages with a view to increasing crop yields under conditions of rainfall limitation. Many of these studies have been based on the hypothesis that moisture availability at certain phenological stages is critical to crop yield (Salter and Good, 1967). Identification of such stages would allow selective water application thus economizing on water and reducing irrigation OASIS whilst minimizing yield losses. In rained agriculture, timing of planting would be adjusted so that the critical phases would not occur during periods of drought.Item Evaluation of Sesame Cultivars for Resistance to Cercospora Leaf Spot(1995) Ayiecho, P.O.; Nyanapah, J.O.; Nyabundi, J.O.White leaf spot and angular leaf spot caused by Cercospora sesami and C. sesamicola respectively were monitored in plots of 16 sesame accessions at Siaya Farmers' Training Centre and Kibwezi Dryland Research Field Station, Kenya, to determine the relative susceptibility of these accessions. Increases in percentage diseased leaves and percent defoliation fitted the Gompertz model more closely than the logistic model. Rates of disease increase in inte:cted leaves and defoliation as well as areas under disease progress curves (AUDPC) varied among the 16 accessions. Accessions with larger AUDPC generally had faster rates of disease progress, although this was not always the ~ase. The most susceptible accessions to both diseases were SPS 071 and SIK 134. Accession SIK Ol3, and accessions SIK 031 and SPS 045 exhibited the least susceptibility to white leaf spot and angular leaf spot, respectively and are suggested as future standards for comparing reaction of other genotypes to Ce,.cospo/,a leaf diseases of sesame.
