Browsing by Author "Kibunja, C.N."
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Item Effects of Soil Fertility Management Practices on Soil Aggregation, Carbon and Nitrogen Dynamics(2013) Lelei, D.K.; Karanja, N.K.; Ayuke, F.O.; Kibunja, C.N.; Vanlauwe, B.; University of Nairobi, P.O Box 30197-00100, Nairobi, KenyaPoor resource farmers cultivate steep slopes without soil conservation measures and apply insufficient plant nutrients thus degrading the soils. Use of organic and inorganic sources of nutrients is one of the approaches being advocated to farmers as a way of improving soil health and increasing crop 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 Impact of Long-Term Application of Organic and Inorganic Nutrient Sources in a Maize-Bean Rotation to Soil Nitrogen Dynamics and Soil Microbial Populations and Activity(National Agricultural Research Laboratories, 2007) Kibunja, C.N.; National Agricultural Research LaboratoriesDeclining crop productivity is a big challenge to both the smallholder farming community and the researchers in crop production in Kenya. Nitrogen (N) is recognized as one of the most limiting nutrients to agricultural productivity in sub Saharan Africa. The high cost of mineral fertilizers and the adverse effects of continued fertilization have led to a search for alternative sources of nutrient supply. The effect of land management on soil nitrogen dynamics, microbial diversity and land sustainability in a long-term field experiment situated at the National Agricultural Research Laboratories, Kabete, near Nairobi, forms the subject of this thesis. The trial was established in 1976 to study the effect of continuous use of farmyard manure (FYM), crop residues and chemical fertilizers on crop yields and soil properties in a maize-bean rotation. A study was carried out to assess the effect of land management on soil physio-chemical properties and microbial populations. Soil chemical properties declined over time, while acidity and bulk density increased under continuous cropping with no inputs. The effect of organic and inorganic inputs on soil microbes, number and activities of various groups of microorganisms was monitored for one year in the 0 -15 and 15 -30 cm soil layers. Use of FYM alone or combined with chemical fertilizers gave significantly higher (p=0.05) numbers of microbes, microbial respiration and soil enzymatic activity than plots with no-inputs or with chemical fertilizers alone. The topsoil layer had significantly (p=0.05) higher microbial activity than the sub-soil regardless of treatment. Bacteria were more numerous (1 x 105 g dry soil -I) than fungi (Ix 103 g dry soil -I), which may lead to more SOM mineralization and less SOM retention in this cropping system. To study the dynamics of fertilizer nitrogen (N), labeled 15N fertilizer as calcium ammonium
