Browsing by Author "Okalebo, J.R."
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Item Analysis of Maize-Common Bean Intercrops in Semi-Arid Kenya(1994) Okalebo, J.R.; Pilbeam, C.J.; Simmonds, L.P.; Gathuka, K.W.; Chemistry Division, National Agricultural Research Centre - Muguga; Department of Soil Science, University of Reading, LondonMaize (Zea mays L.) and common bean (Phaseolus vulgaris L.) were each sown at four plant densities, including zero, in a bivariate factorial design at Kiboko Rangeland Research Station, Kenya during the long and short rains of 1990. The design gave nine intercrops with different proportions of maize and beans, and six sole crops, three of maize and three of beans. Seed Yields in both the sole crops were not significantly affected by plant density, so the mean yield was used to calculate the Land Equivalent Ratio (LER), which averaged 1·09 in the long rains but only 0·87 in the short rains. These low values were apparently due to the fact that beans failed to modulate and fix nitrogen in the study area, The difference in LER between seasons was probably caused by differences in the amount and distribution of rain in relation to crop growth. Maize was more competitive than bean, each maize plant being equivalent to between 0·7 and 3-4 bean plants depending upon the treatment and the season.Item Comparison Between dry. and wet Ashing Techniques for Phosphorus Potassium Calcium and Magnesium Analysis of Plant Material in A Single Digestion(1975) Okalebo, J.R.; E.A.A.F.R.OIn plant nutrition studies, it is common practice to observe effects of treatments or soil amendments by the analysis of plant material for contents of major nutrients N, P K, Ca, mainly. Most analytical methods have therefore been devised, emphasizing on accuracy, precision and speed.Item Effects of Form and Method of Phosphate Fertilizer Application on Maize, Sorghum And Millet Growth in a Semi-Arid Environment Of Kenya. I. Effect on Maize and Sorghum(1990) Njuho, P.M.; Okalebo, J.R.; Gathua, K.W.In a study to investigate maize and sorghum response to three types of phosphate fertilizers (DAP, TSP and SSP), uniform crop emergence and rapid growth to maturity resulted mainly from adequate rainfall, evenly distributed over the major development stages (vegetative, f10weringlsilking and grain filling). At harvest, the crops attained the highest grain yield of 2,970 and 2,250 kglha for maize and sorghum respectively. Grain yield levels from banding or broadcasting P were statistically similar for the two cereals, which implies that a farmer may select anyone of the methods for fertilizer P application. Phosphate fertilizers (DAP, BP and SSP) did not give significant grain yield increases, possibly as a result of adequate available P levels in soils on the test site (31 ppm P by Bray No 2 extraction). Moreover, with sorghum, grain yeild reduction from fertilizer applications were observed and the cause of yield depression has to be sought. The differences in performance of three P sources with respect to maize and sorghum production were evident mainly from the vegetative to f10weringlsilking stages of growth. In this period, rapid uptake of P and subsequent high dry matter yield of tops were observed from the highly soluble DAP. But the use of super phosphate (TSP and SSP) seemed to give higher final grain yield. Further studies are suggested in semi-arid areas (particularly in P deficient soils) to establish the economical levels of P application, suitable forms of phosphate and to identify easier and effective methods of P application.Item A Field Comparison Study of Ammonium Phosphates and Superphosphate-Urea or Ammonium Nitrate on Corn (Zea Mays L.) Growth in Five Quebec Soils(1978) Okalebo, J.R.; MacKenzie, A.F.; Macdonald College of McGill Univ., Ste.Anne de Bellevue, Quebec, CanadaEffects of mono-, diammonium, and superphosphate with added urea or ammonium nitrate on corn (Zea mays L.) growth were studied in the field in 1971 and 1972. At the rate of 100 kg P2O5/ha, none of the carriers affected emergence of seedlings in five Quebec soils. Leaf P content at silking time was of little benefit in predicting P status of the plants, or in differentiating among the carriers. Phosphorous applications gave significant corn yield increases, with carriers performing alike when averaged over all sites. However, some yield differences among carriers occurred on some soil types and seasons. These carrier differences were not consistent and remain to be clarified. The ammonium phosphates compared with the check generally hastened maturity but reduced potassium levels in leaf tissue of corn.Item Field Evaluation Study of Mono and Diammonium Phosphate And Superphosphate of Maize (Zea Mays L.) Growth in Five Quebec Soils(1973) Okalebo, J.R.Performance of mono- and diammonium phosphates and super phosphate with urea or ammonium nitrate on maize (Zea Mays L.} growth was studied in the field in 1971 and 1972. At the rate of 100 kgP 20Sha- l , carriers did not appear to damage seedlings at emergence. Phosphorus application gave significant maize yield increases, with carriers performing alike when averaged over all sites. However, some yield differences among carriers varied with soil type and season. Although differences were not significant, in 1971 diammonium phosphate produced higher mean grain yields on more acid, high phosphorus test soils whereas mono ammonium phosphate and super phosphate-nitrogen mixtures gave higher mean grain yields on less acid, low phosphorus test soils.Item An Infrared Spectroscopic Study of Hydrogen Bonding in Benzyl Alcohol and Certain Ortho- and Para-substituted Benzyl alcohols(John Robert O, 1972) Okalebo, J.R.The infrared absorption in the hydroxyl-stretching region of benzyl alcohol, and its 2,- and ,E-chloro- and E.- and ,E-nitroderivatives,in tetrachloroethylene solutions dilute enough to make intermolecular hydrogen bonding insignificant, has been examined under conditions of high resolution.Item Maize Response to Three High Analysis Phosphate Fertilizers in Some Soils of East Africa(1977) Okalebo, J.R.; Kenya Agricultural Research Institute, Box 30148, NairobiPart II presents information on the efficiency of triplesuperphunphale (TSP) monosenmonium phosphate (MAP) and diammonium phosphate (DAP) in relation to the uptake and recovery of applied phosphate by maize.Item Response of Sorghum to Fertilizer Nitrogen And Phosphorus in Semi-Arid Areas of Machakos and Kitui Districts in Kenya(1989) Okalebo, J.R.; Keter, J.K.A.; Ssali, H.; University of NairobiField trials were carried out in 1979/80 at one site to study sorghum responses to direct and residual phosphate fertilizer application and in 1981 to investigate direct N and P fertilizer responses in three other sites of marginal rainfall, Machakos and Kitui Districts of Kenya. Yields of grain varied with site and season, but the lowest was 950 kg grain/ha, whereas the highest was 4200 kg/ha. Although N and P applications generally improved sorghum yields, a significant grain yield increase was obtained at Ithookwe Sub-station, where 60 kg N/ha and 40 kg P/ha fertilizer combination gave a grain yield increase of 1700 kg/ha (79%) over the control treatment yield. This site was characterized by low levels of N and P in soils at the beginning of cropping and by high rainfall. Variability in major nutrient levels in soils within experimental plots very likely influenced N and P responses, particularly in two other sites with adequate high rainfall. Consecutive cropping of sorghum on the same piece of land resulted in yield reductions, possibly due to the decline in soil fertility. At harvest, sorghum accumulated up to 75 kg N/ha and 9.6 kg P/ha in grain and stalk, yielding 0 to 7 tons/ha in one growing season. N and P accumulation in these two sorghum components also varied with season and site. More work is suggested in the studies of N and P fertilizer responses, with attention to factors such as site selection, mineral N measurements, and sorghum variety.Item The Use of Manure on Smallholders' Farms in Semi-Arid Eastern Kenya(1995) Probert, M.E.; Okalebo, J.R.; Jones, R.K.The manure that is returned to croplands each year is an important resource in the subsistence farming systems of eastern Kenya. Measurements on several farms have shown that the manure being used is of very poor quality. Analyses of soil samples from beneath the bomas (small enclosures) where animals are kept indicate that substantial losses of nutrients occur through leaching; ammonia volatilization and denitrification may also be involved. Current practice is to apply the manure at rates that appear to make poor use of this scarce resource. The findings are discussed in terms of what changes to the system may be feasible to reduce losses of nutrients, and to improve the quality of the manure and the effectiveness of its use.
