Peter Okoth - Academia.edu (original) (raw)
Papers by Peter Okoth
African agriculture is highly diverse, with major farming systems matched to the major agroecolog... more African agriculture is highly diverse, with major farming systems matched to the major agroecologies. In each country or region there are localised agroecological gradients, and large differences between regions in terms of access to markets. Within each village a wide diversity of farming livelihoods can be found-differing in production objectives and resource endowments. Differences in soil fertility are partly derived from inherent differences in properties (the 'soilscape') but are strongly influenced by past management, particularly by the rates and quality of organic manures added to the soils. It is clear that 'one-size-fits-all' or silver bullet solutions that are generally applicable for enhancement of soil fertility simply do not exist. Further, although research has focused on 'best bet' technologies for different regions, a better conceptualization is 'best fit' technologies for specific situations. Although the heterogeneity in African farming is at first sight bewildering, systematic analysis across farming systems in West, East and southern Africa reveals repeating patterns of management. These repeating patterns of allocation of nutrient resources and management methods lead to self-organization among smallholder farms. The past management of fields leads to extreme differences in fertilizer use efficiency, e.g. from 5 kg grain kg N-1 to 50 kg grain kg N-1 between fields of the same farm. By categorizing field types within agroecological zones in simple terms, easily recognizable by farmers, 'rules-of-thumb' can be derived for highly-efficient management of scarce nutrient resources in these heterogeneous environments. Success of legume-based technologies for soil fertility improvement, such as grain legume/cereal rotations or legumes for animal fodder also varies enormously depending on the soil fertility status of fields. New approaches for enhancing productivity in Africa must take account of, and harness, the dynamic nature of farming systems and the heterogeneity between regions, farmers and their fields. Our proposed approach represents a substantial shift in concept from traditional 'blanket recommendations' to focus on the targeting of bestfit technologies to different farmers and crops within production systems using simple 'rules-of-thumb' derived from scientific principles and local farmers' knowledge.
Journal of Applied Biosciences, 2011
Objectives: To investigate (i) the role of earthworm communities in the integrated soil fertility... more Objectives: To investigate (i) the role of earthworm communities in the integrated soil fertility management (ISFM) theory, and (ii) the mechanisms underlying the positive impact of earthworms on maize production. Methodology and results: A field mesocosm experiment was set up in a degraded agro-ecosystem in semideciduous forest areas in Central-West Côte d'Ivoire. Earthworm communities were composed of the association of decompacting (Hyperiodrilus africanus) and compacting (Millsonia omodeoi) native species known to be main species in natural populations and regulating soil structure in the area. In the presence of earthworms, there were significant increases in (i) maize growth 30 days after planting, and (ii) maize production (aboveground biomass, grains and root biomass). This significant impact was enhanced with inorganic fertilizers and/or earthworm inoculations. The increase in maize production in earthworm-based treatments is likely to be explained by increasing root biomass production, phosphorus and water use efficiency associated with earthworm engineering activities. Conclusions and potential application of findings: These findings highlight the crucial role played by earthworms in the ISFM theory through their engineering activities by enhancing the use of water and mineral fertilizers by maize roots. Farmers should encourage proliferation of earthworm populations in their fields as these fauna are important for sustainable agriculture production in agricultural systems.
Scientific Research and Essays, Feb 28, 2013
This study identifies the factors that influence adoption of inorganic fertilizers by maize farme... more This study identifies the factors that influence adoption of inorganic fertilizers by maize farmers in Kakamega District. A probit model was used to analyze data collected from 169 maize farmers. The results showed that growing of a cash crop, off-farm income, access to an agricultural extension agent and use of improved maize seed positively and significantly influenced adoption of inorganic fertilizer. Households with more tropical livestock units were less likely to use inorganic fertilizer and instead used animal manure. The inorganic fertilizers used supplied two nutrients mainly phosphorous (P) and nitrates (N). Potassium (K) rich fertilizers were not used despite the fact that maize requires 3 nutrients N, P and K. Almost 80% of the farmers used very low amounts (< 10 kg ha-1) of Diammonium Phosphats (18:46:0) and UREA (46:0:0) or CAN (26:0:0) in a given season. Given the low inorganic fertilizer application rates, the farmers are unable to maintain or improve high maize yield. Therefore, efficiency and targeted application of inputs among the low-input farms should be improved in order to raise maize productivity. Testing the soils for nutrient status will improve precision and efficiency of inorganic fertilizers and boost maize productivity.
Though a lot has been done and achieved in erosion research and control in Kenya, most of the ero... more Though a lot has been done and achieved in erosion research and control in Kenya, most of the erosion research methods have in the past put emphasis more on quantifying soil loss or measuring soil erosion, rather than pinpointing to areas that are likely to suffer soil erosion. In most cases the erosion processes have been assumed to occur in a uniform manner at all levels of the landscape hierarchy, and hence the results of one level observation can be factored to cover other levels for which data was not collected. This has resulted in many people extrapolating site-specific point data to cover wider geographic regions, assuming uniformity of the erosion process over the region. Another interesting aspect of soil erosion is that though most attention is normally put on the negative effects of soil erosion, soil erosion has also some beneficial effects. For example, the deposition of eroded soil material to lower areas has sometimes improved the quality of the soil receiving the sediment, thereby improving agricultural productivity of the depositional areas. There have however been suggestions that the problem of soil erosion has been exaggerated and not proven to actually diminish crop yields against the background of improved crop productivity improvement techniques. All theses schisms makes it necessary to engage in soil erosion research, either to disprove the sceptics or to provide other means of assessing and viewing the problem of soil erosion. The general objective of the thesis was to develop and present a method, which can be used to assess the risk of water erosion for different levels of the landscape system hierarchy using spatial methods. The broad aim was to define relevant levels that form the basis for predicting and managing soil erosion and controlling its risk. The specific objectives were: To conceptualize and define from the landscape continuum hierarchically ordered landscape elements whose internal characteristics and parts influence the occurrence of soil erosion and whose spatial extent and geometry enable their capture and modelling by remote sensing and GIS. To prove that there are spatial features (erosion proxies) which are part-of, and internally contained in the hierarchically defined landscape elements that can aid in soil erosion risk assessment and modelling. To demonstrate that the selected erosion proxies can be related to actual occurrences of soil erosion by statistical methods and similarly be differentiated as either drivers or disrupters of erosion. To demonstrate that prediction models can be derived from field data collected on the erosion proxies and the developed models used for modelling of soil erosion risk spatially in a GIS for each of the defined levels. To test and validate the method in Kiambu. To address these objectives, concepts associated with hierarchy theory, landscape system construction, geographic information systems theories, and soil erosion theories were knitted together to develop a conceptual framework and a practical methodological approach to effect and realise the objectives. Kiambu district was selected for testing the developed methodology due to its intensive utilisation for agriculture and its location in a rugged terrain in the upper footridges and footslopes of the Aberdare Mountains where below-canopy soil erosion is obscured by vegetation vigour and intensive cropping. Soil loss studies through river sediment yields in the district, indicate that there are high amounts of soil lost annually by water erosion. These range from 20 t km -2yr -1in undisturbed forests, to 3000 t km -2yr -1in cultivated to grazing lands. Soil loss studies from runoff plots in Kiambu indicate that cultivated land loses between 20 and 30 t ha -1season -1and bare soil loses more that 70 t ha -1season -1. Other justifications were prompted by the fact that soil conservation in Kenya has been focussed to the 'Catchment Approach' without necessarily defining what the catchment means. Perception of soil erosion by farmers was also biased to visible features of erosion such as gullies and tended to ignore the finer features of erosion like rills, interill erosion and other visible forms or erosion. Recent developments in geographic information systems (GIS) technology have made it possible to model and represent geographical real world phenomena in computerised spatial databases through which they can be stored, analysed, and displayed. GIS can enable stepwise and ordered analysis of the landscape system components as deemed by the landscape researcher. Soil erosion is a product of the interaction of many geographical factors such as: soil surface cover, the erodibility of the soil mantle, the steepness and length of the eroding slope, the erosive energy of falling rain-drops and the specific management aspect of the eroding site. It can therefore be assessed and modelled in a GIS environment as is demonstrated in this thesis. Concepts The method integrates…
Geoderma, Apr 1, 2019
Ethiopia faces major food security challenges. In spite of a modest level of fertilizer use, the ... more Ethiopia faces major food security challenges. In spite of a modest level of fertilizer use, the percentage of wheat that is imported is substantial. The Ethiopian government has invested in the fertilizer sector, thereby also moving away from di-ammonium phosphate (DAP) to multi-nutrient blends (NPSZnB). Wheat fertilizer experiments were established in seven locations (three replications) in the highlands that represented the wide range of soils found in this area. The crop was exposed to DAP, NPS and to five levels of NPSZnB (50-300 kg/ha). All treatments included 100 kg/ha urea. The average wheat grain yield at the experimental sites, when all fertilizer treatments were averaged, ranged from < 2 to > 7 tons/ha. Soil sampling revealed that organic carbon (28%), total nitrogen and pH, and on the negative side, Fe and Mn concentrations, were significant drivers of yield differences. Fertilizers alone (when averaged for all experimental sites) could only explain 8% of yield differences, proving the ineffectiveness of blanket fertilizer recommendations. Blend fertilizers including micronutrients (NPSZnB) performed slightly but not significantly better than NPS alone or DAP alone. However, since the NP contents in the blend are slightly below those in NPS and DAP (particularly for P), a slight positive effect of Zn or B can be observed. On the other hand, Zn concentration in soils did not correlate significantly to wheat yields. Hence, determining the added effects of Zn and B remains subject for further research. Maximum yield gains to fertilizer application can only be achieved when fertilizers and soil property differences are analyzed jointly. In that case, 79% of yield differences were explained. Grouping soils into 'recommendation windows' then helps to come up with relevant and cost-effective fertilizer strategies. A simple calculation comparing the cost of wheat import with the cost of fertilizers needed to reach the current wheat consumption level in Ethiopia shows that the latter is by far the most cheaper option, but in need of smooth functioning of the entire value chain.
Agriculture, Ecosystems & Environment, Dec 1, 1998
Nutrient Monitoring (NUTMON) is a multidisciplinary and multi-scale approach, addressing the prob... more Nutrient Monitoring (NUTMON) is a multidisciplinary and multi-scale approach, addressing the problem of soil nutrient depletion, so far mainly in sub-Saharan Africa. It involves and aims, at the various actors in¯uencing soil nutrient management at different levels. A quantitative and qualitative diagnostic phase, to determine nutrient management and economic performance in existing farming systems, is followed by a targeted process of participatory development of Integrated Nutrient Management (INM) technologies and formulation of facilitating policy instruments. Further development of the approach is required through inclusion of social disciplines, extrapolation of results to district and national scale, better estimations of dif®cult-to-quantify'¯ows and adding policy oriented activities.
This document is printed in limited numbers to minimize the environmental impact of FAO's process... more This document is printed in limited numbers to minimize the environmental impact of FAO's processes and contribute to climate neutrality. Delegates and observers are kindly requested to bring their copies to meetings and to avoid asking for additional copies. Most FAO meeting documents are available on the Internet at www.fao.org Food and Agriculture Organization of the United Nations Organización de las Naciones Unidas para la организация О Наций Alimentación y la Agric u lt u ra Organisation Nations Unies pour l'alimentation et l'agriculture des
DOAJ (DOAJ: Directory of Open Access Journals), Oct 1, 2009
The distribution of Trichoderma species in soils of Embu and Taita benchmark sites in Kenya with ... more The distribution of Trichoderma species in soils of Embu and Taita benchmark sites in Kenya with relation to land use practices was investigated. The study areas were chosen because of their significant land use intensification and for being biodiversity hot spots. Soil washing and dilution plate techniques were used to recover Trichoderma spp from the soil samples collected from different land use types. The fungal isolates were identified and assigned to nine species from Embu soils and eleven species from the Taita soils. Greater populations were observed in Embu than in Taita. Geographic differences between the regions explained the differences in ecological niches of the two regions that result to different soil assemblages and plant types in the regions and therefore variation in available substrate for the fungus. Land use at each site affected the distribution, richness and abundance of Trichoderma with napier grass having the highest abundance in both Embu and Taita while coffee had the lowest richness and abundance. Trichoderma favoured plants with shallow and widely spreading rooting systems, compared to the deeply rooted perennial coffee and tea trees. This underpins the importance of plant type and in effect land use system in the abundance of Trichoderma. The unevenness in the distribution of Trichoderma within the LUTs suggested that other factors influenced the distribution of Trichoderma apart from the LUTs. Unevenness was greater in Embu than in Taita. The differences could mostly be attributed to soil management practices employed by different farmers while managing their land and crops. Trichoderma harziunum was the most frequently isolated species and the most abundant in both Embu and Taita. Presence of Trichoderma species in some land use types and absence in others, provided a clue on the most preferred habitats, plants and/or crops. Considering the beneficial aspects of Trichoderma such as being antagonistic to the pathogenic fungi, crops or plants such as napier grass that induce high abundance and richness of Trichoderma can be used in crop rotations or in combinations with other crops to maintain high levels of the fungus in the soil.
Biodiversity and Conservation, Dec 1, 2010
... Jérôme E. Tondoh Arnauth M. Guéi Csaba Csuzdi Peter Okoth ... unpublished data). Soils ... more ... Jérôme E. Tondoh Arnauth M. Guéi Csaba Csuzdi Peter Okoth ... unpublished data). Soils of the area are Oxisols with homogeneous distribution across the landscape but with some differences related to topography (Angui unpublished data). ...
Table of contents Acknowledgement iv Glossary of definitions vii CHAPTER 1 1 1 Introduction 3 1.1... more Table of contents Acknowledgement iv Glossary of definitions vii CHAPTER 1 1 1 Introduction 3 1.1 Why the research? 3 1.2 Current conceptual flaws in water erosion research in Kenya 6 1.2.1 Lack of a hierarchical perspective in tackling the problem of soil erosion 6 1.2.2 Terminology use 9 1.2.3 Obscurity of soil erosion with increase in population 10 1.2.4 Perception of soil erosion 1.3 Existing opportunities for tackling the hazard of soil erosion 1.4 Thesis objective 1.4.1 Specific objectives 1.5 Scope, limitations, and outline of the thesis 1.5.1 Scope 1.5.2 Limitations 1.5.3 Thesis outline CHAPTER 2 2 Theory, concepts and literature review 2.1 Introduction and background 2.1.1 Landscape construction and soil erosion 2.1.2 The confusion with scale 2.1.3 The development of dynamic and hierarchical systems thinking 2.2 Hierarchies, the concepts and principles 2.2.1 Principles of hierarchy theory 2.2.2 Linking the principles with soil erosion 2.2.3 Role of object boundaries and the emergence of the holon within hierarchies 2.3 Concepts of spatial modelling in a GIS 2.3.1 Modelling approaches 2.3.2 The land mosaic 2.3.3 Hierarchies on land 2.3.4 Extraction of landscape objects for use in a GIS 2.3.5 Data structures 2.3.6 Data quality and sources of errors in a GIS 2.4 Capture of the spatial features from the space domain 2.4.1 Spatial extraction of objects from aerial photographs or satellite images 2.4.2 Visual verses digital data extraction 2.5 Statistical theory 2.6 Soil erosion theories and assessment 2.6.1 Water erosion processes 2.6.2 Soil erosion and risk assessment methods 2.6.3 Water erosion assessment methods used in Kenya so far Table of Contents ii CHAPTER 3 3 A new framework for hierarchical modelling of soil erosion 3.1 An overview of the methodology and model 3.1.1 Underlying concepts 3.1.2 The conceptual model 3.1.3 What the method seeks to achieve? 3.1.4 Strengths of the methodology and model 3.1.5 Modelling the landscape system 3.1.6 Weaknesses of the model 3.2 Implementing the model and methodology 3.2.1 Step 1 Defining the hierarchies 3.2.2 Step 2 Setting the research scene for statistical sampling 3.2.3 Step 3 Creating spatial datasets for hierarchical modelling 3.2.4 Step 4 Determining statistical relationships and developing prediction models 3.2.5 Step 5 Producing outputs and validating predicted erosion risk for decision support CHAPTER 4 4 The study area 4.1 Location of the study area 4.2 Climate and agro-climatic zones 4.3 Geology and geomorphology of the study area 4.4 Soils of the study area 4.4.1 General 4.4.2 Sampled soil properties 4.5 Land use, land tenure and its history 4.5.1 Current land use 92 4.5.2 History of the land use in the area 93 4.6 Population CHAPTER 5 5 Capture of the spatial data using satellite images, aerial photographs and GIS 5.1 Holons of the three hierarchical levels 98 5.1.1 Description of the landscape holons 5.
Nutrient Cycling in Agroecosystems
There is an urgent need to increase cereal yields in the Ethiopian Highlands to ensure national f... more There is an urgent need to increase cereal yields in the Ethiopian Highlands to ensure national food security. A major crop response-to-fertilizer program was set up in 2017–2019 as part of the CASCAPE project in the Ethiopian Highlands. It covered 33 experiments on maize, teff and wheat in five reference soil groups (Nitisols, Luvisols, Vertisols, Leptosols and Andosols). Five levels of multi-nutrient fertilizer (50–300 kg NPSZnB ha− 1 and 100 kg urea ha− 1) were applied. At the lower fertilizer level, average yields were 5500, 1500 and 3300 kg ha− 1 for maize, teff and wheat, respectively. At the highest rate, yields were 7900, 2100 and 5000 kg ha− 1. Maize and wheat yields were strongly correlated to the reference soil groups, but not to rainfall differences. Wheat yields were also positively correlated to soil organic carbon levels, underpinning the need to apply integrated soil fertility management. Comparing NPSZnB fertilizers with NPS and DAP fertilizers revealed a lack of st...
African agriculture is highly diverse, with major farming systems matched to the major agroecolog... more African agriculture is highly diverse, with major farming systems matched to the major agroecologies. In each country or region there are localised agroecological gradients, and large differences between regions in terms of access to markets. Within each village a wide diversity of farming livelihoods can be found-differing in production objectives and resource endowments. Differences in soil fertility are partly derived from inherent differences in properties (the 'soilscape') but are strongly influenced by past management, particularly by the rates and quality of organic manures added to the soils. It is clear that 'one-size-fits-all' or silver bullet solutions that are generally applicable for enhancement of soil fertility simply do not exist. Further, although research has focused on 'best bet' technologies for different regions, a better conceptualization is 'best fit' technologies for specific situations. Although the heterogeneity in African farming is at first sight bewildering, systematic analysis across farming systems in West, East and southern Africa reveals repeating patterns of management. These repeating patterns of allocation of nutrient resources and management methods lead to self-organization among smallholder farms. The past management of fields leads to extreme differences in fertilizer use efficiency, e.g. from 5 kg grain kg N-1 to 50 kg grain kg N-1 between fields of the same farm. By categorizing field types within agroecological zones in simple terms, easily recognizable by farmers, 'rules-of-thumb' can be derived for highly-efficient management of scarce nutrient resources in these heterogeneous environments. Success of legume-based technologies for soil fertility improvement, such as grain legume/cereal rotations or legumes for animal fodder also varies enormously depending on the soil fertility status of fields. New approaches for enhancing productivity in Africa must take account of, and harness, the dynamic nature of farming systems and the heterogeneity between regions, farmers and their fields. Our proposed approach represents a substantial shift in concept from traditional 'blanket recommendations' to focus on the targeting of bestfit technologies to different farmers and crops within production systems using simple 'rules-of-thumb' derived from scientific principles and local farmers' knowledge.
African agriculture is highly diverse, with major farming systems matched to the major agroecolog... more African agriculture is highly diverse, with major farming systems matched to the major agroecologies. In each country or region there are localised agroecological gradients, and large differences between regions in terms of access to markets. Within each village a wide diversity of farming livelihoods can be found-differing in production objectives and resource endowments. Differences in soil fertility are partly derived from inherent differences in properties (the 'soilscape') but are strongly influenced by past management, particularly by the rates and quality of organic manures added to the soils. It is clear that 'one-size-fits-all' or silver bullet solutions that are generally applicable for enhancement of soil fertility simply do not exist. Further, although research has focused on 'best bet' technologies for different regions, a better conceptualization is 'best fit' technologies for specific situations. Although the heterogeneity in African farming is at first sight bewildering, systematic analysis across farming systems in West, East and southern Africa reveals repeating patterns of management. These repeating patterns of allocation of nutrient resources and management methods lead to self-organization among smallholder farms. The past management of fields leads to extreme differences in fertilizer use efficiency, e.g. from 5 kg grain kg N-1 to 50 kg grain kg N-1 between fields of the same farm. By categorizing field types within agroecological zones in simple terms, easily recognizable by farmers, 'rules-of-thumb' can be derived for highly-efficient management of scarce nutrient resources in these heterogeneous environments. Success of legume-based technologies for soil fertility improvement, such as grain legume/cereal rotations or legumes for animal fodder also varies enormously depending on the soil fertility status of fields. New approaches for enhancing productivity in Africa must take account of, and harness, the dynamic nature of farming systems and the heterogeneity between regions, farmers and their fields. Our proposed approach represents a substantial shift in concept from traditional 'blanket recommendations' to focus on the targeting of bestfit technologies to different farmers and crops within production systems using simple 'rules-of-thumb' derived from scientific principles and local farmers' knowledge.
Tropical and Subtropical Agroecosystems, 2009
A survey was carried out to establish the effects of Land Use Types (LUTs) on Arbuscular Mycorrhi... more A survey was carried out to establish the effects of Land Use Types (LUTs) on Arbuscular Mycorrhiza Fungi (AMF). AMF spore abundance and colonization were evaluated. The percentage root colonization was assessed in trap plants only. AMF were identified and enumerated from spores extracted directly from field soils. Soils were sampled from 60 points occurring in central Kenya. A total of 17 AMF species were isolated and 14 identified to species level. The spore community was dominated by Acaulosporaceae, and Glomaceae. Land use type had no significant (p
Land degradation occurs at varied temporal and spatial scales making its quantification a great c... more Land degradation occurs at varied temporal and spatial scales making its quantification a great challenge. Assessment of land degradation patterns and types can be done at different scales: plot, farm, landscape, and national/continental and global levels. The benefit of the hierarchical approach is that the findings from one scale can be used to verify the interpretation of information from other scales. Despite this recognition, most studies on land degradation have stopped at their respective scales of assessment with little if any scaling up or out of the results to explore implication at the next scales. This study assessed long term spatial and temporal patterns of land degradation in Kenya using multi-scale satellite data sets and detailed field observations and measurements. At national level, the study determined areas at risk of degradation using Normalize Difference Vegetation Index (NDVI) as a proxy. Systematic site characterization and soil sampling was then undertaken ...
Land degradation remains a major challenge to food production and environmental integrity particu... more Land degradation remains a major challenge to food production and environmental integrity particularly for sub-Saharan Africa. Once productive soils have been ruined due to human and natural degradation processes, the mapping of the patterns of degradation in order to propose intervention approaches is a challenge. This study employed the use of Normalized Difference Vegetation Index (NDVI) as a proxy to assess land degradation patterns in Kenya. The study employed the use of 500 m, Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index (MODIS/NDVI) and the gridded climate CRU TS 3.1 (0.5 • × 0.5 •) data for the period (2000-2009). The relationship between annual green biomass (as reflected by NDVI) and mean annual precipitation (MAP) dynamics was computed using Pearson's correlation coefficient while linear regression was performed to determine the magnitude of change of the NDVI over time (inter-annual change in NDVI). All computations were done in a GIS environment using ArcGIS 9.2. Mean precipitation over the 10 year period ranged between 550 and 870 mm at national level. There was relatively reduced precipitation in years 2000, 2003, 2005 and 2008. Despite the annual fluctuations, there was a general increase in mean precipitation at national level over the period of assessment. Correlation between NDVI and MAP at national and regional levels revealed clear patterns of NDVI change and hence potential for degradation or improvement. The degrading areas span across different agroecological zones humid (Kakamega, Kisii) to arid (Kitui, Narok, Turkana, Garissa) lands suggesting that there are various drivers of degradation in these respective regions. Positive and significant changes in the NDVI slope were observed for some selected locations such as Wajir and Baringo that are located in the dryland areas implying the 'greening' of the drylands. Despite the assessment showing solid visual extent of the land degradation problem, assessments using NDVI do not identify the actual causes of degradation or improvements. There is need to follow up such assessments with detailed field observations at selected georeferfenced sites to ascertain the causes of the patterns observed.
African agriculture is highly diverse, with major farming systems matched to the major agroecolog... more African agriculture is highly diverse, with major farming systems matched to the major agroecologies. In each country or region there are localised agroecological gradients, and large differences between regions in terms of access to markets. Within each village a wide diversity of farming livelihoods can be found-differing in production objectives and resource endowments. Differences in soil fertility are partly derived from inherent differences in properties (the 'soilscape') but are strongly influenced by past management, particularly by the rates and quality of organic manures added to the soils. It is clear that 'one-size-fits-all' or silver bullet solutions that are generally applicable for enhancement of soil fertility simply do not exist. Further, although research has focused on 'best bet' technologies for different regions, a better conceptualization is 'best fit' technologies for specific situations. Although the heterogeneity in African farming is at first sight bewildering, systematic analysis across farming systems in West, East and southern Africa reveals repeating patterns of management. These repeating patterns of allocation of nutrient resources and management methods lead to self-organization among smallholder farms. The past management of fields leads to extreme differences in fertilizer use efficiency, e.g. from 5 kg grain kg N-1 to 50 kg grain kg N-1 between fields of the same farm. By categorizing field types within agroecological zones in simple terms, easily recognizable by farmers, 'rules-of-thumb' can be derived for highly-efficient management of scarce nutrient resources in these heterogeneous environments. Success of legume-based technologies for soil fertility improvement, such as grain legume/cereal rotations or legumes for animal fodder also varies enormously depending on the soil fertility status of fields. New approaches for enhancing productivity in Africa must take account of, and harness, the dynamic nature of farming systems and the heterogeneity between regions, farmers and their fields. Our proposed approach represents a substantial shift in concept from traditional 'blanket recommendations' to focus on the targeting of bestfit technologies to different farmers and crops within production systems using simple 'rules-of-thumb' derived from scientific principles and local farmers' knowledge.
Journal of Applied Biosciences, 2011
Objectives: To investigate (i) the role of earthworm communities in the integrated soil fertility... more Objectives: To investigate (i) the role of earthworm communities in the integrated soil fertility management (ISFM) theory, and (ii) the mechanisms underlying the positive impact of earthworms on maize production. Methodology and results: A field mesocosm experiment was set up in a degraded agro-ecosystem in semideciduous forest areas in Central-West Côte d'Ivoire. Earthworm communities were composed of the association of decompacting (Hyperiodrilus africanus) and compacting (Millsonia omodeoi) native species known to be main species in natural populations and regulating soil structure in the area. In the presence of earthworms, there were significant increases in (i) maize growth 30 days after planting, and (ii) maize production (aboveground biomass, grains and root biomass). This significant impact was enhanced with inorganic fertilizers and/or earthworm inoculations. The increase in maize production in earthworm-based treatments is likely to be explained by increasing root biomass production, phosphorus and water use efficiency associated with earthworm engineering activities. Conclusions and potential application of findings: These findings highlight the crucial role played by earthworms in the ISFM theory through their engineering activities by enhancing the use of water and mineral fertilizers by maize roots. Farmers should encourage proliferation of earthworm populations in their fields as these fauna are important for sustainable agriculture production in agricultural systems.
Scientific Research and Essays, Feb 28, 2013
This study identifies the factors that influence adoption of inorganic fertilizers by maize farme... more This study identifies the factors that influence adoption of inorganic fertilizers by maize farmers in Kakamega District. A probit model was used to analyze data collected from 169 maize farmers. The results showed that growing of a cash crop, off-farm income, access to an agricultural extension agent and use of improved maize seed positively and significantly influenced adoption of inorganic fertilizer. Households with more tropical livestock units were less likely to use inorganic fertilizer and instead used animal manure. The inorganic fertilizers used supplied two nutrients mainly phosphorous (P) and nitrates (N). Potassium (K) rich fertilizers were not used despite the fact that maize requires 3 nutrients N, P and K. Almost 80% of the farmers used very low amounts (< 10 kg ha-1) of Diammonium Phosphats (18:46:0) and UREA (46:0:0) or CAN (26:0:0) in a given season. Given the low inorganic fertilizer application rates, the farmers are unable to maintain or improve high maize yield. Therefore, efficiency and targeted application of inputs among the low-input farms should be improved in order to raise maize productivity. Testing the soils for nutrient status will improve precision and efficiency of inorganic fertilizers and boost maize productivity.
Though a lot has been done and achieved in erosion research and control in Kenya, most of the ero... more Though a lot has been done and achieved in erosion research and control in Kenya, most of the erosion research methods have in the past put emphasis more on quantifying soil loss or measuring soil erosion, rather than pinpointing to areas that are likely to suffer soil erosion. In most cases the erosion processes have been assumed to occur in a uniform manner at all levels of the landscape hierarchy, and hence the results of one level observation can be factored to cover other levels for which data was not collected. This has resulted in many people extrapolating site-specific point data to cover wider geographic regions, assuming uniformity of the erosion process over the region. Another interesting aspect of soil erosion is that though most attention is normally put on the negative effects of soil erosion, soil erosion has also some beneficial effects. For example, the deposition of eroded soil material to lower areas has sometimes improved the quality of the soil receiving the sediment, thereby improving agricultural productivity of the depositional areas. There have however been suggestions that the problem of soil erosion has been exaggerated and not proven to actually diminish crop yields against the background of improved crop productivity improvement techniques. All theses schisms makes it necessary to engage in soil erosion research, either to disprove the sceptics or to provide other means of assessing and viewing the problem of soil erosion. The general objective of the thesis was to develop and present a method, which can be used to assess the risk of water erosion for different levels of the landscape system hierarchy using spatial methods. The broad aim was to define relevant levels that form the basis for predicting and managing soil erosion and controlling its risk. The specific objectives were: To conceptualize and define from the landscape continuum hierarchically ordered landscape elements whose internal characteristics and parts influence the occurrence of soil erosion and whose spatial extent and geometry enable their capture and modelling by remote sensing and GIS. To prove that there are spatial features (erosion proxies) which are part-of, and internally contained in the hierarchically defined landscape elements that can aid in soil erosion risk assessment and modelling. To demonstrate that the selected erosion proxies can be related to actual occurrences of soil erosion by statistical methods and similarly be differentiated as either drivers or disrupters of erosion. To demonstrate that prediction models can be derived from field data collected on the erosion proxies and the developed models used for modelling of soil erosion risk spatially in a GIS for each of the defined levels. To test and validate the method in Kiambu. To address these objectives, concepts associated with hierarchy theory, landscape system construction, geographic information systems theories, and soil erosion theories were knitted together to develop a conceptual framework and a practical methodological approach to effect and realise the objectives. Kiambu district was selected for testing the developed methodology due to its intensive utilisation for agriculture and its location in a rugged terrain in the upper footridges and footslopes of the Aberdare Mountains where below-canopy soil erosion is obscured by vegetation vigour and intensive cropping. Soil loss studies through river sediment yields in the district, indicate that there are high amounts of soil lost annually by water erosion. These range from 20 t km -2yr -1in undisturbed forests, to 3000 t km -2yr -1in cultivated to grazing lands. Soil loss studies from runoff plots in Kiambu indicate that cultivated land loses between 20 and 30 t ha -1season -1and bare soil loses more that 70 t ha -1season -1. Other justifications were prompted by the fact that soil conservation in Kenya has been focussed to the 'Catchment Approach' without necessarily defining what the catchment means. Perception of soil erosion by farmers was also biased to visible features of erosion such as gullies and tended to ignore the finer features of erosion like rills, interill erosion and other visible forms or erosion. Recent developments in geographic information systems (GIS) technology have made it possible to model and represent geographical real world phenomena in computerised spatial databases through which they can be stored, analysed, and displayed. GIS can enable stepwise and ordered analysis of the landscape system components as deemed by the landscape researcher. Soil erosion is a product of the interaction of many geographical factors such as: soil surface cover, the erodibility of the soil mantle, the steepness and length of the eroding slope, the erosive energy of falling rain-drops and the specific management aspect of the eroding site. It can therefore be assessed and modelled in a GIS environment as is demonstrated in this thesis. Concepts The method integrates…
Geoderma, Apr 1, 2019
Ethiopia faces major food security challenges. In spite of a modest level of fertilizer use, the ... more Ethiopia faces major food security challenges. In spite of a modest level of fertilizer use, the percentage of wheat that is imported is substantial. The Ethiopian government has invested in the fertilizer sector, thereby also moving away from di-ammonium phosphate (DAP) to multi-nutrient blends (NPSZnB). Wheat fertilizer experiments were established in seven locations (three replications) in the highlands that represented the wide range of soils found in this area. The crop was exposed to DAP, NPS and to five levels of NPSZnB (50-300 kg/ha). All treatments included 100 kg/ha urea. The average wheat grain yield at the experimental sites, when all fertilizer treatments were averaged, ranged from < 2 to > 7 tons/ha. Soil sampling revealed that organic carbon (28%), total nitrogen and pH, and on the negative side, Fe and Mn concentrations, were significant drivers of yield differences. Fertilizers alone (when averaged for all experimental sites) could only explain 8% of yield differences, proving the ineffectiveness of blanket fertilizer recommendations. Blend fertilizers including micronutrients (NPSZnB) performed slightly but not significantly better than NPS alone or DAP alone. However, since the NP contents in the blend are slightly below those in NPS and DAP (particularly for P), a slight positive effect of Zn or B can be observed. On the other hand, Zn concentration in soils did not correlate significantly to wheat yields. Hence, determining the added effects of Zn and B remains subject for further research. Maximum yield gains to fertilizer application can only be achieved when fertilizers and soil property differences are analyzed jointly. In that case, 79% of yield differences were explained. Grouping soils into 'recommendation windows' then helps to come up with relevant and cost-effective fertilizer strategies. A simple calculation comparing the cost of wheat import with the cost of fertilizers needed to reach the current wheat consumption level in Ethiopia shows that the latter is by far the most cheaper option, but in need of smooth functioning of the entire value chain.
Agriculture, Ecosystems & Environment, Dec 1, 1998
Nutrient Monitoring (NUTMON) is a multidisciplinary and multi-scale approach, addressing the prob... more Nutrient Monitoring (NUTMON) is a multidisciplinary and multi-scale approach, addressing the problem of soil nutrient depletion, so far mainly in sub-Saharan Africa. It involves and aims, at the various actors in¯uencing soil nutrient management at different levels. A quantitative and qualitative diagnostic phase, to determine nutrient management and economic performance in existing farming systems, is followed by a targeted process of participatory development of Integrated Nutrient Management (INM) technologies and formulation of facilitating policy instruments. Further development of the approach is required through inclusion of social disciplines, extrapolation of results to district and national scale, better estimations of dif®cult-to-quantify'¯ows and adding policy oriented activities.
This document is printed in limited numbers to minimize the environmental impact of FAO's process... more This document is printed in limited numbers to minimize the environmental impact of FAO's processes and contribute to climate neutrality. Delegates and observers are kindly requested to bring their copies to meetings and to avoid asking for additional copies. Most FAO meeting documents are available on the Internet at www.fao.org Food and Agriculture Organization of the United Nations Organización de las Naciones Unidas para la организация О Наций Alimentación y la Agric u lt u ra Organisation Nations Unies pour l'alimentation et l'agriculture des
DOAJ (DOAJ: Directory of Open Access Journals), Oct 1, 2009
The distribution of Trichoderma species in soils of Embu and Taita benchmark sites in Kenya with ... more The distribution of Trichoderma species in soils of Embu and Taita benchmark sites in Kenya with relation to land use practices was investigated. The study areas were chosen because of their significant land use intensification and for being biodiversity hot spots. Soil washing and dilution plate techniques were used to recover Trichoderma spp from the soil samples collected from different land use types. The fungal isolates were identified and assigned to nine species from Embu soils and eleven species from the Taita soils. Greater populations were observed in Embu than in Taita. Geographic differences between the regions explained the differences in ecological niches of the two regions that result to different soil assemblages and plant types in the regions and therefore variation in available substrate for the fungus. Land use at each site affected the distribution, richness and abundance of Trichoderma with napier grass having the highest abundance in both Embu and Taita while coffee had the lowest richness and abundance. Trichoderma favoured plants with shallow and widely spreading rooting systems, compared to the deeply rooted perennial coffee and tea trees. This underpins the importance of plant type and in effect land use system in the abundance of Trichoderma. The unevenness in the distribution of Trichoderma within the LUTs suggested that other factors influenced the distribution of Trichoderma apart from the LUTs. Unevenness was greater in Embu than in Taita. The differences could mostly be attributed to soil management practices employed by different farmers while managing their land and crops. Trichoderma harziunum was the most frequently isolated species and the most abundant in both Embu and Taita. Presence of Trichoderma species in some land use types and absence in others, provided a clue on the most preferred habitats, plants and/or crops. Considering the beneficial aspects of Trichoderma such as being antagonistic to the pathogenic fungi, crops or plants such as napier grass that induce high abundance and richness of Trichoderma can be used in crop rotations or in combinations with other crops to maintain high levels of the fungus in the soil.
Biodiversity and Conservation, Dec 1, 2010
... Jérôme E. Tondoh Arnauth M. Guéi Csaba Csuzdi Peter Okoth ... unpublished data). Soils ... more ... Jérôme E. Tondoh Arnauth M. Guéi Csaba Csuzdi Peter Okoth ... unpublished data). Soils of the area are Oxisols with homogeneous distribution across the landscape but with some differences related to topography (Angui unpublished data). ...
Table of contents Acknowledgement iv Glossary of definitions vii CHAPTER 1 1 1 Introduction 3 1.1... more Table of contents Acknowledgement iv Glossary of definitions vii CHAPTER 1 1 1 Introduction 3 1.1 Why the research? 3 1.2 Current conceptual flaws in water erosion research in Kenya 6 1.2.1 Lack of a hierarchical perspective in tackling the problem of soil erosion 6 1.2.2 Terminology use 9 1.2.3 Obscurity of soil erosion with increase in population 10 1.2.4 Perception of soil erosion 1.3 Existing opportunities for tackling the hazard of soil erosion 1.4 Thesis objective 1.4.1 Specific objectives 1.5 Scope, limitations, and outline of the thesis 1.5.1 Scope 1.5.2 Limitations 1.5.3 Thesis outline CHAPTER 2 2 Theory, concepts and literature review 2.1 Introduction and background 2.1.1 Landscape construction and soil erosion 2.1.2 The confusion with scale 2.1.3 The development of dynamic and hierarchical systems thinking 2.2 Hierarchies, the concepts and principles 2.2.1 Principles of hierarchy theory 2.2.2 Linking the principles with soil erosion 2.2.3 Role of object boundaries and the emergence of the holon within hierarchies 2.3 Concepts of spatial modelling in a GIS 2.3.1 Modelling approaches 2.3.2 The land mosaic 2.3.3 Hierarchies on land 2.3.4 Extraction of landscape objects for use in a GIS 2.3.5 Data structures 2.3.6 Data quality and sources of errors in a GIS 2.4 Capture of the spatial features from the space domain 2.4.1 Spatial extraction of objects from aerial photographs or satellite images 2.4.2 Visual verses digital data extraction 2.5 Statistical theory 2.6 Soil erosion theories and assessment 2.6.1 Water erosion processes 2.6.2 Soil erosion and risk assessment methods 2.6.3 Water erosion assessment methods used in Kenya so far Table of Contents ii CHAPTER 3 3 A new framework for hierarchical modelling of soil erosion 3.1 An overview of the methodology and model 3.1.1 Underlying concepts 3.1.2 The conceptual model 3.1.3 What the method seeks to achieve? 3.1.4 Strengths of the methodology and model 3.1.5 Modelling the landscape system 3.1.6 Weaknesses of the model 3.2 Implementing the model and methodology 3.2.1 Step 1 Defining the hierarchies 3.2.2 Step 2 Setting the research scene for statistical sampling 3.2.3 Step 3 Creating spatial datasets for hierarchical modelling 3.2.4 Step 4 Determining statistical relationships and developing prediction models 3.2.5 Step 5 Producing outputs and validating predicted erosion risk for decision support CHAPTER 4 4 The study area 4.1 Location of the study area 4.2 Climate and agro-climatic zones 4.3 Geology and geomorphology of the study area 4.4 Soils of the study area 4.4.1 General 4.4.2 Sampled soil properties 4.5 Land use, land tenure and its history 4.5.1 Current land use 92 4.5.2 History of the land use in the area 93 4.6 Population CHAPTER 5 5 Capture of the spatial data using satellite images, aerial photographs and GIS 5.1 Holons of the three hierarchical levels 98 5.1.1 Description of the landscape holons 5.
Nutrient Cycling in Agroecosystems
There is an urgent need to increase cereal yields in the Ethiopian Highlands to ensure national f... more There is an urgent need to increase cereal yields in the Ethiopian Highlands to ensure national food security. A major crop response-to-fertilizer program was set up in 2017–2019 as part of the CASCAPE project in the Ethiopian Highlands. It covered 33 experiments on maize, teff and wheat in five reference soil groups (Nitisols, Luvisols, Vertisols, Leptosols and Andosols). Five levels of multi-nutrient fertilizer (50–300 kg NPSZnB ha− 1 and 100 kg urea ha− 1) were applied. At the lower fertilizer level, average yields were 5500, 1500 and 3300 kg ha− 1 for maize, teff and wheat, respectively. At the highest rate, yields were 7900, 2100 and 5000 kg ha− 1. Maize and wheat yields were strongly correlated to the reference soil groups, but not to rainfall differences. Wheat yields were also positively correlated to soil organic carbon levels, underpinning the need to apply integrated soil fertility management. Comparing NPSZnB fertilizers with NPS and DAP fertilizers revealed a lack of st...
African agriculture is highly diverse, with major farming systems matched to the major agroecolog... more African agriculture is highly diverse, with major farming systems matched to the major agroecologies. In each country or region there are localised agroecological gradients, and large differences between regions in terms of access to markets. Within each village a wide diversity of farming livelihoods can be found-differing in production objectives and resource endowments. Differences in soil fertility are partly derived from inherent differences in properties (the 'soilscape') but are strongly influenced by past management, particularly by the rates and quality of organic manures added to the soils. It is clear that 'one-size-fits-all' or silver bullet solutions that are generally applicable for enhancement of soil fertility simply do not exist. Further, although research has focused on 'best bet' technologies for different regions, a better conceptualization is 'best fit' technologies for specific situations. Although the heterogeneity in African farming is at first sight bewildering, systematic analysis across farming systems in West, East and southern Africa reveals repeating patterns of management. These repeating patterns of allocation of nutrient resources and management methods lead to self-organization among smallholder farms. The past management of fields leads to extreme differences in fertilizer use efficiency, e.g. from 5 kg grain kg N-1 to 50 kg grain kg N-1 between fields of the same farm. By categorizing field types within agroecological zones in simple terms, easily recognizable by farmers, 'rules-of-thumb' can be derived for highly-efficient management of scarce nutrient resources in these heterogeneous environments. Success of legume-based technologies for soil fertility improvement, such as grain legume/cereal rotations or legumes for animal fodder also varies enormously depending on the soil fertility status of fields. New approaches for enhancing productivity in Africa must take account of, and harness, the dynamic nature of farming systems and the heterogeneity between regions, farmers and their fields. Our proposed approach represents a substantial shift in concept from traditional 'blanket recommendations' to focus on the targeting of bestfit technologies to different farmers and crops within production systems using simple 'rules-of-thumb' derived from scientific principles and local farmers' knowledge.
African agriculture is highly diverse, with major farming systems matched to the major agroecolog... more African agriculture is highly diverse, with major farming systems matched to the major agroecologies. In each country or region there are localised agroecological gradients, and large differences between regions in terms of access to markets. Within each village a wide diversity of farming livelihoods can be found-differing in production objectives and resource endowments. Differences in soil fertility are partly derived from inherent differences in properties (the 'soilscape') but are strongly influenced by past management, particularly by the rates and quality of organic manures added to the soils. It is clear that 'one-size-fits-all' or silver bullet solutions that are generally applicable for enhancement of soil fertility simply do not exist. Further, although research has focused on 'best bet' technologies for different regions, a better conceptualization is 'best fit' technologies for specific situations. Although the heterogeneity in African farming is at first sight bewildering, systematic analysis across farming systems in West, East and southern Africa reveals repeating patterns of management. These repeating patterns of allocation of nutrient resources and management methods lead to self-organization among smallholder farms. The past management of fields leads to extreme differences in fertilizer use efficiency, e.g. from 5 kg grain kg N-1 to 50 kg grain kg N-1 between fields of the same farm. By categorizing field types within agroecological zones in simple terms, easily recognizable by farmers, 'rules-of-thumb' can be derived for highly-efficient management of scarce nutrient resources in these heterogeneous environments. Success of legume-based technologies for soil fertility improvement, such as grain legume/cereal rotations or legumes for animal fodder also varies enormously depending on the soil fertility status of fields. New approaches for enhancing productivity in Africa must take account of, and harness, the dynamic nature of farming systems and the heterogeneity between regions, farmers and their fields. Our proposed approach represents a substantial shift in concept from traditional 'blanket recommendations' to focus on the targeting of bestfit technologies to different farmers and crops within production systems using simple 'rules-of-thumb' derived from scientific principles and local farmers' knowledge.
Tropical and Subtropical Agroecosystems, 2009
A survey was carried out to establish the effects of Land Use Types (LUTs) on Arbuscular Mycorrhi... more A survey was carried out to establish the effects of Land Use Types (LUTs) on Arbuscular Mycorrhiza Fungi (AMF). AMF spore abundance and colonization were evaluated. The percentage root colonization was assessed in trap plants only. AMF were identified and enumerated from spores extracted directly from field soils. Soils were sampled from 60 points occurring in central Kenya. A total of 17 AMF species were isolated and 14 identified to species level. The spore community was dominated by Acaulosporaceae, and Glomaceae. Land use type had no significant (p
Land degradation occurs at varied temporal and spatial scales making its quantification a great c... more Land degradation occurs at varied temporal and spatial scales making its quantification a great challenge. Assessment of land degradation patterns and types can be done at different scales: plot, farm, landscape, and national/continental and global levels. The benefit of the hierarchical approach is that the findings from one scale can be used to verify the interpretation of information from other scales. Despite this recognition, most studies on land degradation have stopped at their respective scales of assessment with little if any scaling up or out of the results to explore implication at the next scales. This study assessed long term spatial and temporal patterns of land degradation in Kenya using multi-scale satellite data sets and detailed field observations and measurements. At national level, the study determined areas at risk of degradation using Normalize Difference Vegetation Index (NDVI) as a proxy. Systematic site characterization and soil sampling was then undertaken ...
Land degradation remains a major challenge to food production and environmental integrity particu... more Land degradation remains a major challenge to food production and environmental integrity particularly for sub-Saharan Africa. Once productive soils have been ruined due to human and natural degradation processes, the mapping of the patterns of degradation in order to propose intervention approaches is a challenge. This study employed the use of Normalized Difference Vegetation Index (NDVI) as a proxy to assess land degradation patterns in Kenya. The study employed the use of 500 m, Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index (MODIS/NDVI) and the gridded climate CRU TS 3.1 (0.5 • × 0.5 •) data for the period (2000-2009). The relationship between annual green biomass (as reflected by NDVI) and mean annual precipitation (MAP) dynamics was computed using Pearson's correlation coefficient while linear regression was performed to determine the magnitude of change of the NDVI over time (inter-annual change in NDVI). All computations were done in a GIS environment using ArcGIS 9.2. Mean precipitation over the 10 year period ranged between 550 and 870 mm at national level. There was relatively reduced precipitation in years 2000, 2003, 2005 and 2008. Despite the annual fluctuations, there was a general increase in mean precipitation at national level over the period of assessment. Correlation between NDVI and MAP at national and regional levels revealed clear patterns of NDVI change and hence potential for degradation or improvement. The degrading areas span across different agroecological zones humid (Kakamega, Kisii) to arid (Kitui, Narok, Turkana, Garissa) lands suggesting that there are various drivers of degradation in these respective regions. Positive and significant changes in the NDVI slope were observed for some selected locations such as Wajir and Baringo that are located in the dryland areas implying the 'greening' of the drylands. Despite the assessment showing solid visual extent of the land degradation problem, assessments using NDVI do not identify the actual causes of degradation or improvements. There is need to follow up such assessments with detailed field observations at selected georeferfenced sites to ascertain the causes of the patterns observed.