Nancy Karanja

University of Nairobi | UON · Department of Land Resource Management & Agricultural Technology

Background. Soil macrofauna are key components of agricultural processes due to their ability to enhance major soil functions such as nutrient cycling and organic matter decomposition. Yet, in the Democratic Republic of Congo, their compositions and dynamics are threatened by the intensification of agricultural activities on small pieces of land ch...

In Africa, banana is mainly produced by smallscale farmers under complex production systems for both home consumption and income generation. Low soil fertility continually constraints its production and farmers are embarking on emerging technologies such as improved fallow, cover crops, integrated soil fertility management, agroforestry with fast g...

Declining soil fertility and climate change have led to a reduction in potato yield and thus negatively affected the livelihood of communities that rely on the crop. A study was conducted in Nyandarua County, Kenya, for two seasons to evaluate the potential of potato-legume intercropping in enhancing N and P uptake and use efficiencies and on potat...

Background: Crop production in the arid and semi-arid lands (ASALs) is constrained by erratic rainfall and poor soil fertility. Therefore, climate smart agriculture mechanisms such as in-situ rainwater harvesting technologies and recommended fertilizer rates would be vital for ensuring food security. Objective: To evaluate selected in-situ water ha...

p> Background: Crop production in the arid and semi-arid lands (ASALs) is constrained by erratic rainfall and poor soil fertility. Therefore, climate smart agriculture mechanisms such as in-situ rainwater harvesting technologies and recommended fertilizer rates would be vital for ensuring food security. Objective : To evaluate selected in-situ wate...

An accurate estimation of crop evapotranspiration and soil water balance under potato-legume intercropping is important for improving the crop water productivity of rainfed potato. This study quantified the evapotranspiration, yield, and soil water balance of potato (Solanum tuberosum L.) intercropped with lima bean (Phaseolus lunatus L.) or dolich...

Declining soil fertility in Nitisols and Planosols which dominate major potato growing areas of Kenya is a hindrance to sustainable production of the crop. A study was conducted in Nyandarua County, Kenya to assess performance of potato (Solanum tuberosum L.) and the agronomic efficiencies of three fertilizer types namely Di Ammonium Phosphate (DAP...

Low nutrients have been reported in potato-growing areas of Kenya, prompting a need for nutrient management research. A study was designed to determine the effect of omitting nutrients on potato growth, yield and harvest index. On-farm nutrient omission trials were set during the long rains (LR) and short rains (SR) of 2016 in which the treatments...

A large portion of sub-Saharan Africa is situated in belts of uncertain rainfall and are characterized by low soil fertility with limited capacity to adapt to and mitigate the impacts of climate change. A field study was conducted in the semi-humid potato-growing belt of Kenya to test the effect of legume intercropping and water soluble silicon (or...

Inherent low soil fertility remains a hindrance to potato production in Kenya and continues to pose a threat to food security. A study was conducted in Nyandarua and Meru counties to assess the soil fertility status in smallholder potato farms. Soil and plant tissue samples were collected and analysed for selected nutrients (pH, OC, N, P, K, S, Ca,...

Negative nitrogen balance represents a major factor causing low potato yield in potato growing areas of Kenya while its excessive surplus poses a significant environmental concern. In order to synchronize this tradeoff, a field trial integrating potato (Solanum tuberosum L.) with lima bean (Phaseolus lunatus L.) and dolichos (Lablab purpureus L.) i...

Conversion of forests to cultivated farms through slash-and-burn or chop-and-char practices often results in rapid loss of soil organic matter (SOM) or conversion of inherent SOM into pyrogenic organic matter (PyOM). However, there is little knowledge about the short-term changes in soil macrofauna that may occur when large amount of biochar are ad...

Phosphorus (P) is an essential element and its efficient use is of global importance. This study evaluated the effect of growing potato under leg-ume intercrops on P uptake and use efficiency indices: P harvest index (PHI), P uptake efficiency (PuPE), P partial factor productivity (PPFP) and P partial balance (PPB). The experiment was carried out f...

Soil organic matter (SOM) is considered an important determinant of soil fertility in tropical agroecosystems. While numerous studies have shown the value of agroforestry in increasing soil nutrients and improving crop yield, few have addressed the systematic impacts of duration of cultivation on soil aggregation and C storage in such systems. A st...

In order to enhance sustainable intensification of potato-based cropping systems, especially in sub-Sa-haran Africa (SSA), there is a need to investigate the economic viability of investing in this lucrative venture. This study evaluated the economic returns under legume intercropping systems using value/cost ratio (VCR) and benefit/cost ratio (BCR...

Use of inorganic fertilizers in smallholder cropping systems in Africa is often becoming inefficient due to increasing unresponsiveness to fertilizer application. A study was conducted for 2 years (four seasons) to assess the effects of biochar made from Prosopis juliflora (Sw.) DC. biomass on nutrients, fauna abundance and subsequent influence on...

Integrating crop species with different photosynthetic pathways has great potential to increase efficiency in the use of scarce resources. In order to tap the resource complementarity emanating from this mix, this study intercropped potato (Solanum tuberosum L.) with lima bean (Phaseolus lunatas L.) and dolichos (Lablab purpureous L.), and related...

Intercropping is rarely practiced among smallholder potato farmers in sub-Saharan Africa and currently not included in official recommendations. This is partly due to lack of science-based evidence on intercropping combinations that guarantee high yield and resource use efficiency. In this regard, the International Potato Center, University of Nair...

Over the past few decades elite strains of rhizobia have become commercially available for agricultural production. However, these elite rhizobia are often not as competitive as native strains under adverse edaphic conditions, primarily concerning tolerance to soil desiccation. Biochar has been proposed as a soil amendment to reduce water stress. T...

Continuous cultivation of potato (Solanum tuberosum L.) in monoculture systems represents the greatest factor deteriorating soil organic matter (SOM) in smallholder farms. With an aim to breaking this norm, a 2-year field trial intercropping potato with two legumes: lima bean (Phaseolus lunatus) and dolichos (Lablab purpureus), was conducted in the...

Soil and nutrient losses due to soil erosion are pronounced in potato growing areas of East Africa due largely to the rugged topography and high soil disturbance associated with potato cultivation. This study intercropped potato (Solanum tuberosum L.) with three grain legumes: lablab bean (Lablab purperous L.), garden pea (Pisum sativa L.) and clim...

Aims To assess the effects of potato-legume intercropping on selected soil physical and chemical properties after four consecutive growing seasons (from the short rains in 2014 to long rains 2016). Methods The experiment was laid out in a randomised complete block design with four replicates. The treatments were potato-dolichos (PD); potato-garden...

Abstract Eradicating poverty and achieving food and nutrition security in a sustainable environment is difficult to achieve without adequate access to affordable cooking fuel. It is therefore important to understand the common sources of cooking energy used by people in rural areas and the challenges faced in making fuel sources economically viable...

Abstract Background Pasture enclosures play an important role in rehabilitating the degraded soils and vegetation, and may also influence the emission of key greenhouse gasses (GHGs) from the soil. However, no study in East Africa and in Kenya has conducted direct measurements of GHG fluxes following the restoration of degraded communal grazing lan...

Abstract Background Rehabilitation of degraded rangelands through the establishment of enclosures (fencing grazing lands) is believed to improve soil quality and livelihoods, and enhance the sustainability of rangelands. Grazing dominated enclosure (GDE) and contractual grazing enclosure (CGE) are the common enclosure management systems in West Pok...

Dung beetles are crucial in livestock systems due to their contribution to dung removal, nutrients cycling, carbon sequestration and sustainable pasture production. There are limited studies to elucidate abundance and species diversity across different ecosystems. Since utilization of dung beetles in promoting ecosystem functions such as dung remov...

Soil organic matter (SOM) losses due to soil erosion may be considered low in continuous potato (Solanum tuberosum L.) cropping systems, but cumulated over time may cause considerable soil degradation. A field study was conducted in Kabete, Kenya, during the 2014 to 2015 rainy seasons to determine the effect of sediment particle size distribution o...

Bacterial wilt disease, race 3 biovar 2A, is a devastating disease of potato and other important solanaceous crops, with no chemical control method. The current studies were, therefore, undertaken to assess the efficacy of biocontrol agent (BCA) and organic amendments to manage bacterial wilt (BW) of potato caused by Ralstonia solanacearum, under c...

Competition for nitrogen (N) and phosphorous (P) under potato-based intercropping systems decreases the level of nutrients available for potato and subsequently influences nitrogen and phosphorous use efficiency. A field trial was conducted for four consecutive seasons between 2014 short rains and 2016 long rains to assess the effect of incorporati...

This study evaluated the effect of potato-grain legume intercropping systems on best land equivalent yield ratios, crop water productivity and net profits in field trials conducted in three agro-ecologies of Kenya: upper highland with seasonal rainfall of 592 mm and altitude of 2550 m, lower highland (505 mm, 1879 m) and lower midland (356 mm, 1522...

The charcoal sector constitutes an important source of employment and revenue for many tropical agroecosystems. Better understanding of the effects of charcoal-making is thus warranted to guide actions aimed at minimising environmental externalities. Conversion of trees to charcoal eliminates canopy effects associated with the living trees while at...

Soil macrofauna contribute to key soil functions underpinning soil-mediated ecosystem services. There is limited understanding about the role of trees as ‘resource islands’ for soil macrofauna in agricultural landscapes and how this interaction is affected by soil degradation status. The study assessed the spatial influence of three dominant trees...

Identification of effective indigenous Bradyrhizobium strains which nodulate soybean varieties could trigger development of an industry for inoculant production with use of strains adapted to local conditions. This study was conducted to identify and select effective local rhizobia strains nodulating soybean in South Kivu soils. One hundred and sev...

Identification of effective indigenous Bradyrhizobium strains which nodulate soybean varieties could trigger development of an industry for inoculant production with use of strains adapted to local conditions. This study was conducted to identify and select effective local rhizobia strains nodulating soybean in South Kivu soils. One hundred and sev...

One of the 'grand challenges' of this age is the anthropogenic impact exerted on the nitrogen cycle. Issues of concern range from an excess of fixed nitrogen resulting in environmental pressures for some regions, while for other regions insufficient fixed nitrogen affects food security and may lead to health risks. To address these issues, nitrogen...

This paper presents the effect of potato (Solanum incunumL) cropping systems on soil and nutrient losses and highlights the role of surface runoff in this process. The findings show the need to incorporate indeterminate leguminous cover crops to minimize losses due to erosion.

Adoption of legume inoculation with rhizobia by small-scale farmers in East Africa, and the resultant increase in biological nitrogen fixation requires that quality inoculants meet minimum standards. BIOFIX is one of the commercially available rhizobia/legume inoculants in East Africa, whose standard is at least 109 rhizobia g-1. We examined the ef...

A sustainable increase in agricultural productivity is essential in assuring food security in developing countries. Low soil fertility is a major contributing factor to the current vicious cycle of low agricultural productivity and inadequate livelihoods among smallholder farmers. Integrated soil fertility management (ISFM) is one way of achieving...

Studies document increases in biological nitrogen fixation (BNF) following applications of biochar. However, the underlying mechanisms for this response remain elusive. Greenhouse experiments were conducted to test the effects of biochar mineral nutrients, pH, and volatile matter (VM) on BNF in common beans (Phaseolus vulgaris L.). Biochars were pr...

The main input of nutrients in agroforestry systems is achieved through biomass decomposition. A study was carried out to determine the rates of decomposition and N and P release pattern from T. vogelii and T. candida plant residues using litterbag experiments in Malawi. The plant residue treatments included Tephrosia biomass alone or in combinatio...

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 t...

As many countries in sub-Saharan Africa undergo rapid urbanization, a growing number of people are joining the ranks of the urban poor. Urban agriculture is a livelihood strategy used by the poor to improve their well-being, but it has remained largely inaccessible to inhabitants of slums, who generally lack access to land to farm. However, in the...

Background and aims Degradation of physical, chemical and biological properties of soils in sub-Saharan Africa mainly results from little or no organic resource application coupled with sub-optimal fertilizer application. A study was conducted over three seasons, from March 2010 to August 2011, to evaluate potential of six organic materials (bagass...

Purpose – The purpose of this paper is to examine consumers’ perception of food safety for vegetables at traditional urban market outlets in a developing country context and test whether curiosity-motivated information acquisition and personal control over choice of stimuli influence consumer involvement, resulting in more differentiated mental mo...

Here is a very useful book that tells you not only how to make compost but also why. It has emerged out of a lot of collaboration among several institutions that work with low-income urban and peri-urban farmers and composting groups during the last decade, since the mid nineties. Most of this work was done in Kenya, but it applies equally well to...

Assessing potential of human faecal matter as a fertilizer material

Rising demand for energy is one of the major challenges facing the world today and charcoal is a principal fuel in Kenya. Faced with energy poverty many poor households turn to briquette making. This study assessed the additional cooking fuel obtained from recycling charcoal dust into charcoal briquettes. It applied Life Cycle Assessment (LCA) to a...

The soil water storage, soil water content, available water content and soil water balance under various cover crop residue management practices in a Nitisol were evaluated in a field experiment at the Kabete Field Station, University of Nairobi. The effects of surface mulching, above and below ground biomass and roots only incorporated of (mucuna...

Need”for”affordable”and”cleaner”cooking”fuel”

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-ma...

Severe health, safety and environmental hazards are being created by the growing population of urban poor in low-income countries due to lack of access to sanitation and to inadequate existing sanitation systems. We developed a multi-faceted motivational framework to examine the constituents that explain user motivation regarding a personalised san...

Maize production in Malawi is limited mainly by low soil N and P. Improved fallows of N-fixing legumes such as Tephrosia and Sesbania offer options for improving soil fertility particularly N supply. The interactions of Tephrosia fallows and inorganic fertilizers on soil properties, N uptake, and maize yields were evaluated at Chitedze Research Sta...

rainfed agriculture and simulated irrigation requirement for tomato production in the Kabete Field Station. The model predicted increased irrigation requirement for a tomato crop of 33.1, 28.1 and 36.6 mm of water, in the 1st, 2nd and 3rd 10-day periods of development stage, respectively. The crop evapotranspiration (ETc) requirements by tomato cro...