Browsing by Author "Gikonyo, E.W."
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Item Dynamics Of Current And Residual Phosphorus In Tropical Acid Soil(Universiti Putra Malaysia, 2006) Gikonyo, E.W.The United Nations millennium development programme among other goals, aims at reducing extreme poverty and hunger by 50% between the years 1990 - 2015. This can be achieved through increased and sustainable agricultural production, particularly in developing countries where >60% of the population's livelihood depend on agriculture (Paarlberg, 2002). Halving hunger by 2015 will be achieved through intensification of crop production (Millenium Taskforce on Hunger, 2004). In many acidic soils in developing countries, P deficiency exacerbated by the high P fixing capacities are the main limiting factors for crop production and therefore, P remains, one of the main keys for agricultural sustainability (Chien and Menon, 1993). Therefore, P replenishment is indisputable and requires application of external P sources (Mokwunye and Bationo, 2002) for improvement and sustainability of agricultural production.Item Dynamics of Current and Residual Phosphorus in Tropical Acid Soil(Esther Wakiuru Gikonyo, 2006) Gikonyo, E.W.The United Nations millennium development programme among other goals, aims at reducing extreme poverty and hunger by 50% between the years 1990 - 2015. This can be achieved through increased and sustainable agricultural production, particularly in developing countries where >60% of the population's livelihood depend on agriculture (Paarlberg, 2002). Halving hunger by 2015 will be achieved through intensification of crop production (Millennium Taskforce on Hunger, 2004). In many acidic soils in developing countries, P deficiency exacerbated by the high P fixing capacities are the main limiting factors for crop production and therefore, P remains, one of the main keys for agricultural sustainability (Chien and Menon, 1993). Therefore, P replenishment is indisputable and requires application of external P sources (Mokwunye and Bationo, 2002) for improvement and sustainability of agricultural production.Item Field And Laboratory Research Manual For Integrated Soil Fertility Management In Kenya(Kenya Soil Health Consortium, 2016-05) Mangale, N.; Muriuki, A.; Kathuku-Gitonga, A.N.; Kibunja, C.N.; Mutegi, J.K.; Esilaba, A.O.; Ayuke, F.O.; Nguluu, S.N.; Gikonyo, E.W.; Kenya Agricultural and Livestock Research OrganizationIn Kenya research efforts have generated numerous Integrated Soil Fertility Management (ISFM) technologies with potential for increasing food production and rural incomes (Jama et al., 2000; Lekasi et al,. 2001; TSBF, 2005; Salasya, 2005; Ojiem, 2006; AGRA, 2007; Misiko, 2007; Okalebo, et al., 2007; WAC, 2008; FAO, 2009; Rockstrom et al., 2009). However, these technologies have had limited impact on smallholder farmers’ fields. The gap between research and application of ISFM guidelines is wide and evidenced by the low uptake and utilization of recommended ISFM technologies by smallholder farmers. Reasons for this unfortunate scenario include incoherent and conflicting recommendations for ISFM technologies because generators of ISFM technologies and innovations hardly collaborate and/or share their research outputs with each other or with end users. This also results in many inappropriate technology recommendations that confuse target farmers and lower technology adoption. These are the major reasons why farmers have been unable to realize the full benefits of the potential productivity gains possible from growing improved crop varieties, although adoption of these varieties is now widespread in the country (Rukandema, 1984; Omiti et al., 1999). Although it is evident that appropriate use of ISFM can transform agriculture, the level of production with ISFM in Kenya has remained low. Part of the reason for low production ISFM can be traced to poor research. Successful ISFM research with a potential of increasing food production and incomes is best driven by appropriate field and laboratory research methods. In Kenya different laboratories use different methods to analyze for the same elements, often generating varying results for the same soil and plant samples. For example there are more than three methods for determination of soil and plant phosphorus levels used in different laboratories viz: Infra-red spectroscopy (IR), Bray II, Olsen, Mehlich I, II and III and the Truog methods. Recommendations based on the variable results from these methods are difficult to validate for reliability. Often this may lead to confusion and generation of wrong fertilizer recommendations leading to inappropriate use of farm inputs, soil acidification, low crop yields, low adoption, food insecurity and low household incomes. The Kenya Soil Health Consortium (KSHC) has developed this manual of field and laboratory methods through consultation with the major national, regional and international research and learning institutions to guide implementation of agricultural research in Kenya. This protocol highlights among others; the process of research formulation, process of project implementation, field research methodology and approaches, plants-soil sampling and analysis, soil chemical analysis methods, fertilizer recommendation and use efficiency, and data management. The protocol is intended to act as a reference material and as a guide for future agricultural research and development in Kenya. This protocol is of great benefit to a wide range of stakeholders involved in agricultural research, agricultural extension, capacity building, and agricultural policy development.Item Phosphate Sorption Isotherms Of Selected Soils Of Kenya(University Of Nairobi, 1997) Gikonyo, E.W.Phosphate sorption characteristics of eight selected soils of Kenya were determiner order to establish the influence of previous manure and phosphate (P) fertilizer applications. The soils were two ando-humic Nitisols, orthic acrisol, humic Nirisol, dystromollic Nitisol, mollic Nitisol and a ferralo-chromic Acrisol. A greenhouse experiment with maize was performed to determine the external P requirement for maximum dry matter yield (DMY) of eight-week old plants. Phosphate sorption data were generated by equilibrating soil samples at room temperature with O.OlM KCI solutions containing various concentrations ofP (0.05 to 3.0 mg P/kg soil). P sorbed was taken as the difference between the initial P concentration and the final P concentration in the equilibrium solution. Sorption curves were plotted using: h,.· data obtained. The ando-humic Nitisols gave the steepest curves and the highest Standard Phosphate Requirement (P required to raise the soil to 0.2 mg PI kg soil). They had a Standard Phosphate Requirement (SPR) of 380 mg P/kg soil (760 kg P/ha) and 340 mg P/kg soil (680 kg/ha). The lowest sorbing soil was the orthic acrisol with zero SPR. Phosphate characteristics of the soils were mainly influenced by soil pH (r = 0.619***), organic carbon (r = 0.581 ***), clay content (r = 0.438*), Base Saturation (r = 0.596***) and iron and aluminium extracted by both dithionite citrate bicarbonate (Fed' Aid) and ammonium oxalate (Fe., Alo)' Phosphate sorption was positively correlated to the Fe and .'.j contents: AIJ (r = 0.822***), Alo (r = 0.794***), FeJ (r =:: 0.740***) and Fe, (r = 0.512"'*). *, ** and *** means significant at 0.05, 0.01 and 0.001 level respectively. viii Manure increased P sorption in four soils and reduced in the other four. Effect of manure on P sorption was indirectly through its influence on the Fe and Al levels. Manure could probably increase or decrease the Fe and Al levels and hence reduce or increase P sorption respectively. Phosphate application reduced P sorption through its effect on the soil sorption complex by narrowing the ratio ofR20):P20s (where R stands for Fe or AI) which led to reduced P sorption. Results from the greenhouse showed that maize dry matter yields increased to a maximum (42.17 to 53.3 g/pot) with increasing P concentration up to 0.6 mg P/kg soil after which the yields started decreasing except in the andosol where the maximum was not achieved with the P levels tested. For soils tested in.this study, maximum dry matter yield can be obtained by fertilizing the soils to 0.6 mg P/kg soil equilibrium solution P level though the amounts of P required will depend on the phosphate buffering capacity of the soils. Phosphate sorption of the soils may be reduced by application of manure but increased sorption may result in some soils and, therefore, a need for further research is necessary. Phosphate applied in previous applications is useful in that it reduces subsequent P sorption and hence P requirement.
