Browsing by Author "Gweyi-Onyango, Joseph"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Effects of different nitrogen forms on growth, phenolics, flavonoids and antioxidant activity in amaranth species
    (Society for Tropical Plant Research, 2017) Munene, Rozy; Changamu, E. O.; Korir, Nicholas; Gweyi-Onyango, Joseph
    Higher plants, accumulate large number of polyphenolic compounds which are believed to act as defence compounds against different environmental constraints. Nitrogen (N) is a critical element for plant growth, absorbed as (NH4 + ) and (NO3 - ), which affects plant growth and to some extent contributes to secondary metabolites accumulation. Greenhouse experiment was carried out to determine the effect of N forms on growth and phytochemical accumulation in Amaranthus species. Two amaranth varieties; AB6 and AB7 constituted the main plot while three N forms; ammonium, nitrate, ammonium nitrate and control (no N form) represented the subplot. Destructive sampling was done and plant height was recorded. Folin-Ciocalteu’s and aluminium trichloride methods were used to determine total phenolic content (TPC) and total flavonoid content (TFC) respectively. DPPH (diphenylpicrylhydrazyl) radical scavenging activity assay was used to obtain total antioxidant activity. Nitrogen forms significantly (p≤0.05) affected plant height between two amaranth varieties. Under nitrate treatment, AB7 exhibited greater height (40.2 cm) than AB6 (35.2 cm). Furthermore, N effect was more evident in AB6 variety, where by compared to the control, NO3 - as exclusive N source enhanced shoot length by 64% in AB6 and 51% in AB7 which was twice that of the NH4 + -N treated plants. Sole NH4 + and no N form enhanced accumulation of both TFC and TPC, unlike nitrate and ammonium-nitrate mixture. Compared to NH4 + treatment, NO3 - reduced TFC by 17.4% in AB6- variety and 14.7% in AB7 variety and TPC accumulation by 23% AB6 and 20% AB7 varieties respectively. Correspondingly, NH4 + - N form resulted to superior antioxidant DPPH scavenging activity indicated by high scavenging activity and lower IC50 value (concentration which scavenged 50% of the DPPH radicals). Plant height displayed a significant negative correlation with TFC and TPC accumulation of r= 0.75 and r= 0.81 respectively. The results indicated that ammonium-induced stress enhanced total flavonoids and phenolics accumulation; a salient phytochemical plasticity observed during plant growth and survival trade-off in a vegetable amaranth.
  • Thumbnail Image
    Item
    Green Pepper Growth and Yield Response to the Integration of Mulching Materials and Row Plant Spacing
    (Academic Research Publishing Group (ARPG), 2017) Ocharo, Edgar N.; Korir, Nicholas K.; Gweyi-Onyango, Joseph
    An experiment was conducted at the Crops Research Station of the Kenya Agricultural and Livestock Research Organization Alupe, Busia County. The experiment was performed to find out the most suitable mulching material and an ideal spacing for green pepper cultivation under Busia County Conditions. The experiment was laid out in a Factorial Randomized Block Design with three replications. The treatments comprised of four mulching materials viz. black plastic mulch, transparent plastic mulch, straw mulch and bare soil which was the control with three row spacings viz. 30 x 50 cm, 40 x 40 cm and 50 x 40 cm. Data collected was subjected to SAS statistical software for analysis and means separated using LSD at P≤0.05. Significant responses on plant height and number of branches per plant were observed for both seasons due to spacing and mulching treatments. The highest branches (6.97) per plant were recorded in the 40 by 40 cm spacing under the transparent mulch with the lowest (2.83) shown under the same spacing in the straw mulch of California Wonder variety. The widest spacing elicited the highest number of fruits per plant (7.37) in the black plastic mulch while only a mean of 1 fruit per plant was recorded in the mulch control during the short rain season. The highest fruit mean yield per plant of 1556 g and 1533 g was recorded in the widest spacing (50 by 40cm) during the long and short rain seasons respectively. Therefore this study recommends the use of plastic mulches at wider spacing.
  • Thumbnail Image
    Item
    Interaction Effect of Growth Regulators and Irrigation Schedules on Growth and Yield of French Beans in Kiambu County, Kenya
    (SCIENCEDOMAIN International, 2018) Kalawa, Ikiba L.; Wafula, Wekha N.; Korir, Nicholas K.; Gweyi-Onyango, Joseph
    Inadequate and unreliable rainfall distribution in Kenya has affected negatively agricultural yields and family incomes. Integration of growth regulators can stimulate favorable crop growth under limited moisture, but there has been scarce research and documentation on them. Therefore the gibberellic acid and cytokine in effect on French beans growth and yield was assessed under different irrigation schedules at Kenyatta University Field Station in two seasons of 2014/2015. The experiment was set in Randomized Complete Block Design (RCBD) in split-plot arrangement with three levels of each hormone as sub-plots and three watering regimes as main plots and replicated three times. The results showed that optimum rates of growth regulators positively improved the growth and yield components of French beans. Significant differences between the treatments at P<0.05 were observed on the leaf area where the 0.50ml level of cytokine in had the greatest at week nine after sowing with 1335.3 cm2 during the first season and 1343.1 cm2 during the second season at a daily watering regime. Consequently, this led to significantly the highest pod fresh yield of the French beans with 58.97 g/plant and 84.99 g/plant for the first and second seasons respectively at week nine in the same treatment combination. The highest level of gibberellic acid (0.675 ml) led to the lowest fresh pod yields at week six, seven and eight, while the highest rate of cytokine in (0.750 ml) had the least fresh pod yield at week nine showing the negative effect of excessive application of growth regulators on French beans, yield components. The study, therefore, recommends an application of cytokinin at a rate of 0.50ml to achieve maximum yields in French beans.
  • Thumbnail Image
    Item
    Review of Scientific Advances and Importance of Biochar for Agricultural and Industrial Uses
    (International Journal of Bioresource Science, 2024-12-07) Mwadalu, Riziki; Ndufa, James; Maitra, Sagar; Gweyi-Onyango, Joseph; Gitari, Harun
    Biochar has been known as an effective soil amendment with capabilities of boosting soil moisture storage, increasing soil fertility, and enhancing crop productivity. Biochar also has the potential for industrial use for wastewater treatment, water purification, steel making, building insulation, and air pollution control. The current metadata analysis evaluated the importance of biochar for agricultural and industrial uses and its relevance for use in Kenya. A total of 120 reference materials comprising journal papers, conference proceedings, and book chapters were used. Numerous studies conducted across the globe have documented the positive effects of biochar in increasing available soil nutrients (increased by 28.6% and phosphorus by 2 folds), lowering bulk density by 3-31%, enhancing soil moisture storage by 18-108%, and boosting microbial activities in the soil thus enhancing nutrient cycling. The metadata analysis also showed that biochar can reduce CO2 emissions by up to 33% thereby mitigating climate change. Biochar equally increased maize yield by 32-135% and rice yield by 8.5-10.7%. The review also showed that biochar can play a crucial role in different industrial uses such as wastewater treatment, steel making, and water purification. Some of the main impediments to the adoption of biochar were; the lack of a regulatory framework to govern the sector and the lack of a decision support system for use by end users.