Bio

Nancy Karanja Bio

She is a Full Professor in Soil Ecology, and Director of Microbial Resources Centre, University of Nairobi. She has many years of experience in BNF with legumes in SAA including managing inoculant production and use by farmers. She has also coordinated urban agriculture and it plays in addressing food insecurity and livelihoods to the urban poor and other related issues in SSA and has published widely in this subject.

Publications


2014

2013

Largerkvist, CJ, Ngigi MW, Karanja N.  2013.  Means-end chain analysis explains soil fertility management decisions by peri-urban vegetable growers in Kenya. Abstract

Past studies of the use of soil fertility management strategies by farmers usually model input use decisions based on the neoclassical utility/profit maximization principle in which farmers use soil fertility management inputs primarily to increase revenues and profits. However, there is, to date, no study that explains exactly how this decision-making process occurs and the role which personal values play in driving the choice of soil fertility management inputs. This article systematically maps the relationship between choice of soil fertility management strategy (attributes), its outcomes (consequences) and the personal values that motivate the choice. It specifically uses the means-end chain approach to construct hierarchical value maps that relate the attributes to consequences, and ultimately to the personal values. The study finds that the use of soil fertility management strategies by peri-urban fresh vegetable growers is driven by five personal values, namely happiness, comfortable life, independence, good/healthy life and achievement of life goals. It also finds that while farmers seek to increase profit (hence incomes), profit maximization is not the end driver of the use of soil fertility management inputs. It concludes that a lot more goes into farmers’ decision-making process relating to the use of soil fertility management practices than can be explained by the neoclassical profit/utility maximization principle. The study discusses the policy implications of these findings.

Gallaher, CM, Kerr JM, Njenga M, Karanja NK, WinklerPrins AMGA.  2013.  Urban agriculture, social capital, and food security in the Kibera slums of Nairobi, Kenya. Journal of the Agriculture, Food, and Human Values Society. 30(3):389–404.
Gallaher, CM, Mwaniki D, Njenga M, Karanja NK, WinklerPrins AMGA.  2013.  Real or Perceived: The Environmental Health Risks of Urban Sack Gardening in Kibera Slums of Nairobi, Kenya. Abstract

Cities around the world are undergoing rapid urbanization, resulting in the growth of informal settlements or slums. These informal settlements lack basic services, including sanitation, and are associated with joblessness, low-income levels, and insecurity. Families living in such settlements may turn to a variety of strategies to improve their livelihoods and household food security, including urban agriculture. However, given the lack of formal sanitation services in most of these informal settlements, residents are frequently exposed to a number of environmental risks, including biological and chemical contaminants. In the Kibera slums of Nairobi, Kenya, households practice a form of urban agriculture called sack gardening, or vertical gardening, where plants such as kale and Swiss chard are planted into large sacks filled with soil. Given the nature of farming in slum environments, farmers and consumers of this produce in Kibera are potentially exposed to a variety of environmental contaminants due to the lack of formal sanitation systems. Our research demonstrates that perceived and actual environmental risks, in terms of contamination of food crops from sack gardening, are not the same. Farmers perceived exposure to biological contaminants to be the greatest risk to their food crops, but we found that heavy metal contamination was also significant risk. By demonstrating this disconnect between risk perception and actual risk, we wish to inform debates about how to appropriately promote urban agriculture in informal settlements, and more generally about the trade-offs created by farming in urban spaces

Njenga, M, Karanja N, Munster C, Iiyama M, Neufeldt H, Kithinji J, Jamnadass R.  2013.  Charcoal production and strategies to enhance its sustainability in Kenya. Development in Practice. 23(3):359-371.

2012

Okello, JJ;, Lagervisk CJ;, Ngigi M;, Karanja N.  2012.  Role of Farmers’ Personal Values in Soil Fertility Management Decisions: Evidence from Means-End Chain Analysis of Peri-urban Leafy Vegetable Production in Kenya. Abstract

Peri-urban areas play a major role in the supply of vegetables consumed in urban areas. In order to meet high demand for aesthetic quality characteristics, peri-urban farmers use intensive production practices characterized by use external inputs. This paper uses Means-End Chain analysis approach to examine the role farmers’ personal values play in the decision to use soil fertility improvement inputs namely, animal manures (organic fertilizer) and inorganic fertilizers. It found that use of animal manures and inorganic fertilizers was driven by the need to earn higher profit margins thus making more money in order to meet family needs. This in turn met farmers’ personal values relating to, among others, happiness, leading a comfortable life, independence and healthy life. The major implication of these findings was that farmers’ private goals could, with the urging of the market that demands unique aesthetic quality characteristics, promote intensive applications of both the organic and inorganic inputs with potential negative environmental consequences.

Karuku, GN, Gachene CKK, Cornelis W, Verplancke H, Kironchi G.  2012.  Soil hydraulic properties of a nitisol in Kabete, Kenya. AbstractWebsite

Water relations are among the most important physical phenomena that affect the use of soils for agricultural, ecological, environmental, and engineering purposes. To formulate soil-water relationships, soil hydraulic properties are required as essential inputs. The most important hydraulic properties are the soil-water retention curve and the hydraulic conductivity. The objective of this study was to determine the soil hydraulic properties of a Nitisol, at Kabete Campus Field Station. Use of an internal drainage procedure to characterize the hydraulic properties and soil and water retention curves allowed for the establishment of the moisture and matric potential at field capacity and permanent wilting point. The Bt2 (84 -115) and Bt3 (115 - 143 cm) had the highest clay contents of 619 compared to Ap, AB and Bt1 horizons. The PWP was attained at soil moisture contents of 0.223, 0.284, 0277, 0.307 and 0.314 m3m-3 in the Ap, AB, Bt1, Bt2, and Bt3 horizons, respectively. Horizontal saturated hydraulic conductivity (Ksat) was high at 6.0 cm hr-1 in Ap horizon and decreased to 0.4 cm hr-1 in the subsurface horizon (Bt3). Ksat in the vertical direction was higher than horizontal and ranged from 8.3 cm hr-1 in surface layer to 0.6 cm hr-1 in Bt3 horizon, with exception of Bt1 and Bt2 where horizontal Ksat was greater than vertical. The Ap horizon also had the highest crop extractable water. Though the AB and Bt1 had the same water content at low matric suction, the variation was very wide as the SWRC approached saturation point. Bt1 and Bt2 also had similar water contents at suction range of – 7kPa after which Bt1, tended towards Bt3. Bt3 had the narrowest range of crop extractable water and thus was attributed to texture. The Bt3 retained the most amount of water at 0.314 m3m-3concluding that θPWP increased with depth. The total available water capacity between FC and PWP in the profile was 79.2 mm m-1. The study observed that the field capacity, crop available water contents and hydraulic conductivities were influenced positively by soil organic matter. The Van Genuchten parameters of air entry value (α) and pore size distribution (n) indicated that pore size distribution was not even in the AP and AB horizons. The field capacity was attained at higher matric potential at -5kPa for Bt1 while Bt2 and AP, AB, Bt2 and Bt3 was at -10kPa.The functional relationship, K(θ) = aθb that deals with water redistribution as a result of soil hydraulic properties and evaporative demand of the atmosphere was highly correlated to soil moisture content and texture with R2 values > 0.85.

Lagerkvist, CJ, Ngigi M, Okello J, Karanja N.  2012.  Means-End Chain approach to understanding farmers’ motivations for pesticide use in leafy vegetables: The case of kale in peri-urban Nairobi, Kenya. Abstract

Peri-urban farmers play a significant role in the production of vegetables consumed in the urban centers in most African countries. The production of vegetables in the peri-urban areas in these countries is strategic with most farmers targeting the lucrative and better-paying urban markets. However, the decline in agricultural land in the peri-urban due to competition from housing for urban workers has led peri-urban farmers to use intensive means of agricultural production. Decreasing land sizes imply that peri-urban lands are continuously under production resulting in the build-up of pests and diseases. Further, the tropical climate generally increases the outbreak and rapid multiplication of pests and diseases. These problems and the urban consumers’ demand for clean and spotlessness vegetables encourage the excessive use of pesticides. Additionally, the desire to reduce losses and waste can cause farmers to violate the recommended intervals between pesticide application and harvest. Consequently, there have been concerns about the excessive application of pesticides in vegetables produced in the peri-urban areas. The study applies the Means-End Chain (MEC) approach accompanied by the laddering technique to assess the motivations for peri-urban farmers to use pesticides as opposed to other crop protection methods in the production of fresh vegetables. It specifically examines the relevant attribute econsequenceevalue relations by setting up relevant hierarchical value maps. The study is based on a random sample of 54 kale farmers in three peri-urban areas of Nairobi. It finds that farmers apply pesticides at different times mainly for the purpose of improving their efficacy in protecting kale against pests and diseases. Protection of kale improves its aesthetic quality attributes resulting in higher prices and hence profit margins. Examination of the hierarchal value maps further reveals that the other motivations for pesticide use include benevolence value (being helpful and honest to trading partners), power (social recognition or good reputation as a good farmer), hedonism (happiness for being a successful farmer), security (having good health) and self-direction (independence or being self-supporting from vegetable income). Clearly, the motivations suggest a dilemma in safe use of pesticides. While some motivators dictate less use of pesticides, others can promote indiscriminate use of pesticides. The study discusses the implication of these findings for sustainable and environmentally friendly production of safe leafy vegetables in peri-urban areas.

Lelei, DK, Karanja NK, Ayuke FO, Kibunja CN, Vanlauwe B.  2012.  EFFECTS OF SOIL FERTILITY MANAGEMENT PRACTICES ON SOIL AGGREGATION, CARBON AND NITROGEN DYNAMICS. E. Afr. agric. For. J. 113-118. 78(1):113-118.
Carl, JL, Julius O, Nancy K.  2012.  Anchored vs. relative best–worst scaling and latent class vs. hierarchical Bayesian analysis of best–worst choice data: Investigating the importance of food quality attributes in a developing country. Abstract

Applying best–worst (BW) scaling to a multifaceted feature, e.g. food quality, is challenging as attribute non-attendance or lack of attribute discrimination risks invalidating the transformation of choice data to unidimensional scale. The relativism of BW scaling also typically prevents distinction of respondents or groups of respondents based on similarities to the study object. A dual-response BW scaling method employed here to obtain an anchored scale allowed comparisons of importance ratings across individuals. Attribute importance ratings and rankings obtained were compared with those from relative BW scaling. Latent class (LC) and hierarchical Bayesian (HB) analyses of individual specific BW choice data were also compared for ability to consider within- and between-respondent choice heterogeneity. Personal interviews with 449 consumers provided data on the importance of 16 food quality attributes of kale produced in peri-urban farming in Kenya. Major findings were that the anchoring model improved individual choice predictions compared with conventional relativistic BW scaling, i.e. was more reliable in measuring consumer preferences, and that HB analysis fitted the data better than LC analysis. HB analysis also successfully obtained individual parameter estimates from sparse data and is thus a promising tool for analysis of BW choices in sensory and consumer-orientated research.

Courtney, GM, John KM, Mary N, Nancy KK, Antoinette MG, WinklerPrins A.  2012.  Urban agriculture, social capital and food security in the Kibera slums of Nairobi, Kenya.

2011

Mary, N, Nancy K, Gordon P, Diana L-S, Michael P.  2011.  Gender mainstreaming in organisational culture and agricultural research processes. Abstract

Despite increased attention to gender issues in the international development arena since the rise of feminism in the 1970s, few agricultural research organisations have integrated gender in their problem diagnosis and technology development. Gender mainstreaming can significantly enhance the impact of research and technology development. Entrenching gender mainstreaming in organisations and their research agendas remains a challenge. To overcome it requires political will, accountability, a change in organisational culture, and technical capacity within an organisation. This article presents an illustration of gender-mainstreaming practice in the institutional culture and agricultural research processes by Urban Harvest and the International Potato Centre (CIP).

Bala, Abdullahi; Karanja, N; MM; LL; AR; GK.  2011.  Production and use of Rhizobial inoculants in Africa. Abstract

Inoculation studies have been conducted in Africa since the 1950s and the benefits of inoculation of legumes with suitable rhizobial strains have been amply demonstrated. Despite the clear evidence of response to inoculation by legume crops, there is relatively little use of inoculants by smallholder farmers in sub-Saharan Africa. Several programmes aimed at promoting the use of inoculants in smallholder farms have been supported by national governments, especially in East and southern Africa (e.g. Malawi, Zambia and Zimbabwe). Such programmes were often run with funding from international agencies, such as the Food and Agricultural Organisation (FAO), United Nations Educational, Scientific and Cultural Organisation (UNESCO) and the International Atomic Energy Agency (IAEA). While the projects lasted, some increase in inoculant use was often recorded. However, the scale of adoption declined once the projects came to an end. The various regions within sub-Saharan Africa have had varying degrees of success in promoting inoculant production and use. Table 1 shows some of the existing inoculant plants and their capacity. Some of the problems identified for the lack of sustainability of inoculant production in Africa include poorly developed marketing channels, inadequate quality assurance as well as inadequate capacity within the extension sector.

Mutua G.K, Karanja N.K, F A, H N, Kimenju J.W.  2011.  The potential of Bacillus subtilis and Rhizobium leguminosarum in controlling plant-parasitic nematodes in farmers’ fields. Abstract

Assessment of the potential of dual inoculation of Bacillus subtilis and Rhizobium leguminosarum biovar phaseoli strain USDA 2674 on plant parasitic nematodes in bean was carried out on farmers’ fields. Bean seeds variety Rose Coco, were treated with three B. subtilis isolates namely K158, K194 and K263 singly or in combination with Rhizobium and then planted in nematode infested fields. Plant parasitic nematodes in the genera Meloidogyne, Pratylenchus and Scutellonema were dominant. Nematode diversity assessed by Shannon, Simpson’s, Trophic and Maturity indices declined with increased length of cultivation. Plant parasitic index was 63% higher in the cultivated farms compared to the natural forest. The dual innoculant enhanced nodulation variably depending on the length of cultivation and increased bean yields compared to the control. Bacillus subtilis isolates K194, K158 and K263 suppressed plant parasitic nematodes by 42, 36 and 28%, respectively. The potential of dual inoculation of Bacillus and Rhizobium in addressing nematode and soil fertility challenges was demonstrated in this study. Key words: Diversity, Kakemega, Kenya, nodulation, Phaseolus vulgaris

2010

Cheryl, R;L, Shirley W;, Flatt MS;, La Jolla CA;, Karanja N;, Cynthia T;, Nancy SE.  2010.  Two-Year Results From a Multi-Site Randomized Trial of a Commercial Weight Loss Program. Abstract

Commercial weight loss programs may contribute to efforts to reduce the prevalence of obesity, although evidence of efficacy and effects on metabolic and cardiovascular risk factors is critical in evaluating the likelihood of sustained benefits. The Jenny Craig (JC) program involves individualized diet and exercise counseling (provided either in-person at community-based sites or by telephone), prepackaged foods and a low-energy density diet. The aims of this study are (1) To test, in a multi-site randomized controlled trial, whether the JC Centre-based and/or JC Direct (telephone-based) interventions promote greater weight loss and maintenance of that loss in overweight or obese women over a 24-month period compared to usual care (UC) conditions; and (2) To describe the effect of the program (vs. UC conditions) on selected biochemical factors, cardiopulmonary fitness, quality of life (QOL) and eating attitudes and behaviors. At randomization, participants (n=442) were 44(10) (mean[SD]) yrs, with BMI 33.8(3.4) kg/m2, weight 92.1(10.7) kg, and waist circumference 108.6(9.6) cm. Two-year data are available for 91% of study participants (n=406), and weight loss is - 8.1(8.6), -6.7(9.3), and -2.2(7.4) kg for the JC Centre- based, JC Direct, and UC groups, an average weight reduction of -8.7%, -7.3%, and -2.4% of initial weight, respectively. The proportion of women at highest risk (CRP>3 mg/L) in the JC arms decreased significantly from 53% at enrollment to 33% at two years, but was unchanged in the UC arm. Interim analysis also shows the JC intervention to promote favorable changes in lipid, leptin and carotenoid levels, and improved cardiopulmonary fitness

Mary, N, Dannie R, Nancy K, Kuria G;, Stephen K, Sammy C, Will F.  2010.  Recycling Nutrients from OrganicWastes in Kenya’s Capital City. Abstract

The question how much of the potential soil nutrients contained in urban wastes are being used and what processes are involved led to this study in the early 2000s. The issue is of central importance to understanding the potential benefits of a properly managed urban agriculture sector, since soil fertility is a major problem in Sub- Saharan Africa and urban wastes represent a large potential source of nutrients (Savala et al. 2003). Mougeot (1993, p.114) highlighted the importance of solid waste management and offered insights into the use of organic wastes by farmers as compost for their crops. When the Consultative Group on International Agricultural Research (CGIAR) was starting up its new system-wide program – Urban Harvest – in Africa in late 2000, stakeholders called for better documentation of these processes. In response, we came together from a number of institutions in Kenya to identify and map out the basic market and material flows for composts and manure in Nairobi and identify opportunities for improving the functioning of the system. Several of us were also involved in a UN meeting at the end of 2001 on the links between waste management and urban agriculture (Kahindi et al. 2001), and the two CGIAR centres based in Nairobi both had a stake in the issue. The International Livestock Research Institute (ILRI) had done some preliminary work in 15 countries on crop–livestock system intensification in peri-urban areas (Staal 2002), and the World Agroforestry Centre (ICRAF) was interested in market chains involving urban nurseries using compost and manure. Coming as well from a local NGO and a national research organization, we formed an interdisciplinary team. Participatory methods were employed because a basic value underlying our collective approach was that research has a greater impact if the potential users of its results are engaged in the process and have a stake in the outcome.

Mutua, GK;, Kinyari P;, Githuku C;, Kironchi G;, Kang’ethe E;, Prain G;, Njenga M;, Karanja NN.  2010.  Assessment of environmental and public health hazards in wastewater used for urban agriculture in Nairobi, Kenya. Abstract

Thirty percent of residents in Nairobi practise urban agriculture (UA) with a majority of the farmers using untreated sewage to irrigate crop and fodder. Due to the environmental and health risks associated with wastewater irrigation, a study was carried out in partnership with farmers in Kibera and Maili Saba which are informal settlements along the Ngong River, a tributary of the Nairobi River Basin. Soil, water, crops and human faecal samples from the farming and non-farming households were analysed to elucidate sources, types and level of heavy metal pollutants in the wastewater and the pathogen loads in humans and vegetable crops. Heavy metal accumulation in soils collected from Kibera and Maili Saba were Cd (14.3 mg kg-1), Cr (9.7 mg kg-1) and Pb (1.7 mg kg-1) and Cd (98.7 mg kg-1), Cr (4.0 mg kg-1) and Pb (74.3 mg kg-1), respectively. This led to high phytoaccumulation of Cd, Cr and Pb in the crops that exceeded the maximum permissible limits. No parasitic eggs were detected in the vegetables but coliform count in the wastewater was 4.8 x108±2.2 x1011/100ml. Soils irrigated with this water had parasitic eggs and non-parasitic larvae counts of 54.62 and 27.5/kg respectively. Faecal coliform and parasitic eggs of common intestinal parasites increased in leafy vegetable sampled from the informal markets along the value chain.

2009

Njenga, M;, Karanja N;, Magoiya J.  2009.  Risks Associated with Urban Wastewater Irrigation and Production of Traditional African Vegetable (TAVs) Seeds in Nairobi, Kenya. Abstract

Globally farmers use wastewater to irrigate crops because it also supplies plant nutrients and ensures all year round food availability. A study was carried out in Nairobi with farmers who used wastewater to produce both food and fodder along the Ngong/Motoine River to obtain an understanding of the benefits and risks associated with wastewater farming and to identify mitigation strategies. Farmers cultivated plots below 0.5 acres where they grew vegetables for home consumption, sale for employment. Analysis of the wastewater samples showed that heavy metal contents were within acceptable limits. However, investigation done on plant samples taken from selected crops showed that there was bioaccumulation of cadmium, chromium and lead to levels that were several times higher than the recommended critical limits. Determination of biological contamination samples from these farms and from the wet markets showed that produce from the markets had higher loads of faecal colifoms and parasitic eggs than vegetables irrigated with untreated water. One strategy for mitigating health risks associated with consumption of the contaminated vegetables was to introduce an alternative farming activity to farmers which in this case was to introduce production of Traditional African Vegetables seeds. Eight farmers have for two seasons been able to produce 30 kg of assorted seeds valued at KShs 30000 or USD 400. This has increased both income and assets for farming households and availability of quality seed for rural and urban farmers.

Karanja N.K, F.O A, E.M M, B.K M.  2009.  Soil macrofauna community structure across land use systems of Taita, Kenya. Abstract

This paper presents data on diversity and abundance of soil macrofauna in various land use systems in Taita (natural forest, plantation forest, fallow, coffee, napier, and maize, Horticulture. Each was sampled for macrofauna using three sampling methods (monolith, transect and pitfall trapping). Seventy eight (78) genera/species were recorded across the different land use systems of Taita. Rényi diversity profile indicated no significant differences in species richness across land use systems as reflected by the very close diversity profiles at α = 0. However, the two diversity indices (Shannon index: α = 1 and Simpson’s index: α = 2) indicated that plantation forest was the most diverse of the land use systems, while fallow and maize were least diverse. Rényi evenness profile indicated that the plantation forest was most even in terms of species distribution which was least in maize. However because some of the profiles for some land use systems cross each other, they could not be ranked. The major macrofauna groups recorded in the Taita benchmark site included: Hymenoptera, Isoptera, Coleoptera, Oligochaeta and Orthoptera and Arenae. Generally Hymenoptera were the most abundant of the macrofauna groups constituting about 36% of the total followed by Isoptera (22%), Oligochaeta (16%), Coleoptera (10%). The other macrofauna (Arenae, Diplopoda, Diptera, Orthoptera, Blattidae, Isopoda, Chilopoda- Geopholomorpha, Hemiptera, Opiliones,Chiopoda-Scolopendromorpha, Lepidoptera, Dermaptera, Phasmidae, Blattelidae and Mantodea each constituted <10% of the total macrofauna recorded. Hymenoptera was ranked 1st as it had the highest total abundance (59,440 individuals m-2), while Mantodea was ranked 18th and had the lowest total abundance (6 individuals m-2). Generally macrofauna density was higher in arable systems than forests, although the differences were not always significant. Except for Chilopoda-Geopholomorpha, Chilopoda- Scolopendromorpha and Isopoda, all the other macroafauna groups were not significantly different across land use systems. The three groups (Chilopoda- Geopholomorpha, Chilopoda- Scolopendromorpha and Isopoda) were significantly highest in the forests than in all the other land use systems. These variation appear to be associated with management practices that consequently results in the destruction of nesting habitats, modification of soil microclimate within these habitats and removal of substrate, low diversity and availability of food sources for the associated macrofauna groups. The significant correlations between some soil macrofauna groups with selected soil chemical properties too show that, soil chemical characteristics may indirectly play a role in influencing the density, distribution and structure of macrofauna communities. This indicates the potential of using these fauna groups as bio-indicators of soil productivity. Key words: Macrofauna; community structure; diversity; abundance; land use systems.

Erastus, K’etheK, Violet N K, Brigid MD;, Delia G, K.Lang’at A, Monica W K, Nancy K.  2009.  A trans-disciplinary study on the health risks of cryptosporidiosis from dairy systems in Dagoretti, Nairobi, Kenya: study background and farming system characteristics. Abstract

Cryptosporidium was conducted with 20 farmers randomly selected from the 29 farmers in the wider survey who were considered at high risk because of farming system. We found that around 1 in 80 urban households kept dairy cattle with an average of three cattle per household. Cross-breeds of exotic and local cattle predominate. Heads of dairykeeping households were significantly less educated than the heads of non-dairy neighbours, had lived in Dagoretti for significantly longer and had significantly larger households. There was a high turnover of 10 % of the cattle population in the 3-month period of the study. Cattle were zero grazed, but productivity parameters were sub-optimal as were hygiene and husbandry practices. In conclusion, dairy keeping is a minor activity in urban Nairobi but important to households involved and their community. Ecohealth approaches are well suited to tackling the complex problem of assessing and managing emerging zoonoses in urban settings. Keywords Urban dairy . Cryptosporidiosis . Ecohealth . Kenya

2008

Kamweti, D, Michieka RW;, Karanja N.  2008.  Tree Species Composition And Spacing In Agroforestry System Of Embu District, Kenya. Abstract

In agroforestry systems, farmers plant or retain different tree species because of their different roles. In selection of tree species, farmers seek fast growing trees, which can generate income from sale of timber and woodfuel. Other attributes to such tree crop competition and soil enrichment are borne in mind during tree species screening and selection by farmers. An investigation of tree species composition and spacing in any agroforestry system is a prerequisite to determination of growth and yield of wood resources in agroforestry system. The main objective of this study was to determine relative frequency of the common tree species and their spatial distribution in agroforestry areas of Embu District, Kenya.

2007

Ayuke, FO;, Karanja NK;, Wickama J;, Awiti A;, Hella J.  2007.  Soil fauna community structure across land manage ment systems of Kenya and Tanzania..

2006

Gudu, SO, Woomer PL, Karanja NK, Okalebo R, Othieno CO, Serem C, Maritim HK, Sanginga N, Bationo A, Muasya RM.  2006.  The African Green Revolution and the Role of Partnerships in East Africa. Abstract

Sub-Saharan African (SSA) region continues to experience perennial hunger, poverty and poor health of its people. Agricultural production has remained low over decades and is declining to extremely low staple maize yields below 0.5 t ha–1 season–1 at the smallholder farm scale, against the potential of 4–5 t ha–1 season–1 given modest levels of inputs and good crop husbandry. Constraints contributing to low productivity are numerous, but the planting of poor-quality seed, declining soil fertility, poor markets and value addition to products significantly contribute to poor productivity. Partnerships for development are weak even though there are numerous technologies to improve and sustain agricultural production arising from extensive research and extension in SSA. But, technology adoption rates have been extremely slow, and in some cases we find no adoption. In this chapter we highlight constraints which are bottlenecks for achievement of a green revolution in Africa. Success efforts are reported, but we moot a focus on efficient utilization of abundant and affordable African natural resources, such as phosphate rocks to replenish depleted phosphorus in soils. We argue that to achieve an African green revolution, partnerships with concerned global communities and national institutions, including universities, NGOs, CBOs and farming communities, need to be strengthened. Specifically, human capacity at all levels should be built through training. Without private sector’s strong participation on acquisition of inputs and marketing proven products, it will be difficult to achieve a green revolution

2005

Gichangi, EM, Karanja NK, Wood W.  2005.  The potential of agro-organic wastes to reduce nitrogen losses from cattle manure used by smallholder farmers in the central Kenyan highlands.. Abstract

Livestockmanure is a valuable source of plant nutrients for crop production in the Central Kenyan highlands but its quality in terms of available nitrogen is low due to considerable nitrogen losses through ammonia olatilization. This study aimed at assessing the potential of agro-organic wastes to reduce nitrogen losses from manure heaps during the storage period. Three organic amendments selected from a laboratory simulation experiment were evaluated under farmers' conditions based in Karura, Kiambu District for their ability to reduce nitrogen losses from cattle manure heaps. The effect of a polyethylene sheet covering of manure heaps on nitrogen retention was also determined. There were eight treatments that comprised three agro­organic amendments (maize stover, coffee pulp and sawdust) and the control. Agronomic effectiveness of the treated manure samples and N uptake by maize seedlings were evaluated in a glasshouse experiment. 19% and 46% of the initial nitrogen respectively. Maize growth improved significantly (p:s;0.05) with increasing rates of manure irrespective of the organic treatments except for manure amended with sawdust. Treatments that received the recommended rate of nitrogen at 100 kg N ha-' had significantly higher (p:S;0.05) biomass of 21.55 g/p1ant while the control produced 2.78 g/p1ant only. Nitrogen uptake increased with increasing rates of manure and was higher (p-;O.O5) with manure amended with coffee pulp. Covering manure heaps to reduce moisture loss would also be beneficial in reducing nitrogen losses.

2004

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