5 Records out of 22207 Records
Author: Aller, Deborah
Awarding University: University of Edinburgh, Scotland
Level : MSc
Holding Libraries: Institute of Commonwealth Studies Library ;
Environmental degradation, agricultural productivity, food security, fresh water scarcity, and the adaptation to and mitigation of climate change are all significant concerns of the 21st century. Biochar is a highly porous, carbon rich material which is a natural soil amendment being investigated to address these current issues. Expanding agricultural production into dryland environments where sandy soils dominate is highly likely to be of great importance for ensuring future global food security, as population and food demands continue to increase. Sandy soils have little ability to store water, making food production difficult and crop yields an unreliable source of food and income for inhabitants living in these environments. This study looked at the water holding capacity (WHC) and hydrophobicity of Eichhornia crassipes and Prosopis juliflora for use as biochar, to potentially enhance soil moisture storage and thus agricultural productivity, with a particular focus on arid and semi-arid lands (ASALs) and northern Kenya. Both are invasive species found in Kenya which was the reason for their selection for use in this study. Biochar was produced at 350?C, 450?C, and 550?C in a Carbolite furnace and also in a Sampada gasification stove, to mimic traditional kiln char production. Biochar WHC was examined at mixtures of 2%, 5%, and 7%, corresponding to a field application rate of roughly 20 t ha-1, 50 t ha-1, and 70 t ha-1, respectively. Results demonstrated that both biochars increase soil WHC the greatest at a 7% application rate. The greatest hydrophobicity values were apparent at 350?C, with E. crassipes the more hydrophobic of the two. Mercury porosimetry analysis, which compares various characteristics of the pore space in relation to physical properties of the biochar, is consistent with the WHC data, revealing that as the total intruded volume increases the water holding capacity increases. Overall E. crassipes and P. juliflora show potential for use as biochar, but P. juliflora with its greater lignin content, is likely the better choice.
Author: Abdi, Zeila Dubow
Awarding University: Kenyatta University, Kenya
Level : MES
Holding Libraries: Kenyatta University Moi Library ;
More than three decades after the introduction of prosopis species in the drylands of Kenya there is now increasing concern about the negative impacts of the plant on the livelihoods of dryland communities and on the ecological integrity of the fragile arid and semiarid lands. The extent of the species coverage in the arid and semiarid lands has, however, not been fully mapped owing in part to the recent nature of the problem. As such the aim of this study was to map out the extent of the spread of the species and propose community-friendly management options for this invasive plant. Geographic information system methodology and satellite imageries (Landsat images from 2000 and 2006), maps and GPS points were the main tools used for this work. Standard spatial statistical analysis procedures were employed using the software Erdas Imagine 8.4 and ESRI Arc View to generate land cover changes associated with prosopis species. The study found that a total of 440 square kilometres were newly colonised between the years 2000 and 2006, with Bura division having the highest area of land colonised at 143km2 (33% of total land area). The study also noted that the riverine land use/land cover system was the most infested, with 631km2 colonised. This automatically puts the livelihoods of thousands of pastoralists who depend on the River Tana ecosystem at risk. The study also employed a socio-economic survey that involved the use questionnaires and interviews to ascertain the perceptions of the local community regarding origin, impact and uses of the species. Eighty four per cent of the respondents indicated that prosopis' presence has had negative effect on the indigenous biodiversity of Garissa through loss of native vegetation. The three major local uses of prosopis were charcoal, fuelwood and animal fodder. The study shows that prosopis is a major environmental problem in the study area through its swift colonisation of strategic grazing reserves and is rapidly colonising new lands. The findings of this study call for commercialising production of prosopis for charcoal burning as a strategic management strategy for the plant. This should be accompanied with the use of efficient kilning technologies. In addition deliberate and pro-active policy changes should be put in place to delineate land specifically for this environmental business. Spread of the plant outside designated areas should be controlled by use of environment-friendly mechanical approaches. This further calls for community capacity building in partnership with key stakeholders like Kenya Forest Service. In this way, prosopis will cease to be a liability and instead contribute to community development through wealth creation.
Author: Muuo, Moses Kagiri
Awarding University: Jomo Kenyatta University of Agriculture and Technology, Kenya
Level : MSc
Holding Libraries: Jomo Kenyatta University of Agriculture and Technology Library ;
Prosopis juliflora has been spreading rapidly colonizing pasturelands, farms and forming dense impenetrable thickets in Marigat division. In this study, Thematic Mapper (TM) images for 1986 and 1989 and Enhanced Thematic Mapper plus (ETM +) images for 2000 and 2003 were used as source of remotely sensed data for mapping the spread of Prosopis juliflora and perform land cover change in the division. Structured questionnaires were used to evaluate people's perceptions on the effects of Prosopis juliflora. Supervised classification approach was used to obtain classified images for 1986, 1989,2000 and 2003. The images depicted land covers such as shrub land, grass cover, Prosopis juliflora, wetlands, agricultural fields and bare land. On accuracy assessments, Kappa stastic yielded 0.6, 0.6, 0.7 and 0.7 for images of 1986, 1989,2000 and 2003 respectively while overall accuracy yielded 65%, 63%, 75% and 79% for the same images. Statistical analysis showed that between 1986 to 2003, spatial areas covered by Prosopis juliflora, wetlands, agricultural fields and bare land increased by 101 %, 50%, 4.5% and 86% respectively while areas covered by grass cover and shrub land declined by 86%, and 12% respectively. Results from questionnaires indicate livestock production has been adversely affected by the invading Prosopis juliflora. The critical grass and forage species have been eliminated and hence affecting pastoralism, which is the main lifestyle and source of livelihood for local people in Marigat division. On animal health, the respondents stated when their animals feed on Prosopis juliflora pods, they develop teeth complications. The fresh and sugary pods are sticky and hence collect around the base of the teeth leading to massive teeth decays, wearing and loosening. The animal cannot chew regurgitated bolus because of weak teeth, most of them falling off and hence eventually dies as a result of starvation. Similarly, areas under farming activities have been reduced by the invading Prosopis juliflora and hence affecting food production in Marigat division. Therefore, if unchecked, Prosopis juliflora has the potential to wipe out pastoralism and farming activities in the near future. However, some of the respondents cited benefits accrued from its product such as building posts, fuel wood and pods (animal feed). Many of the households rely on charcoal and poles from Prosopis juliflora for sale and domestic uses. The pods of Prosopis juliflora are popular source of fodder for livestock during dry seasons. The vigorous and continous flowering of the species has made bee keeping a popular economic activity in the division. Therefore, the study recommends enhanced use of products from Prosopis juliflora through their proper processing and marketing. Periodical monitoring of the spread of Prosopis julifora by using GIS, SRS and GPS is also highly recommended. Further studies on impact of Prosopis juliflora on soil physical and chemical properties should be carried out to compliment this study. Finally, these research findings could be used in the management and control of Prosopis juliflora not only in Marigat division but also in other arid and semi - arid areas affected by the spread.
Author: Kahi, Hemru Chore
Awarding University: University of Nairobi, Kenya
Level : MSc
Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;
Subject Terms: Soils/Trees/Prosopis juliflora/Acacia tortilis/Njemps Flats/ ;Abstract:
ABSTRACT NOT AVAILABLE
Author: Nyamai, Daniel Odinde
Awarding University: University of Oxford, England
Level : Phd
Holding Libraries: Kenya Forestry Research Institute Library ;
Leucaena leucocephala, Calliandra calothyrus, Gliricidia sepium, Prosopis juliflora and Cassia siamea are among the most important leguminous trees in the tropics. Although their potential role in agroforestry system has been recognised, integration with arable crops is rare. The rapidly increasing populations in the tropical countries, especially Kenya where the birth rate is currently estimated to be 4.3% per annum have resulted in a great demand for land, leading to environmental degradation and a decline in soil fertility. In an attempt to improve or sustain productivity in Kenya without costly inputs such as chemical fertilizers, which are too expensive for peasant farmers, an investigation into low input crop production in an intercropping system using leguminous trees was undertaken. Special emphasis was placed on the use of tree prunings as sources of manures either from the intercropped trees or brought in from other areas. Three field experiments were conducted in Kenya. The effects of manures on soil environment and crop production and also the effects of intercropping Prosopis and Cassia with crops on yield and soil nutrients were examined. Greenhouse and laboratory experiments in Oxford investigated in more detail the amount of N fixed and made available to millet in association with the trees under different management systems. The laboratory experiment concentrated on the relative rates of decomposition and release of nitrogen from tree foliage. Application of manures resulted in an average increase in maize yield by between 11 and 22% and greatly increased the level of soil N but least organic C. Soil N was found to be a reliable predictor of grain yield. The manures conserved soil moisture by lowering soil surface temperatures. Decomposition of manures was fastest in Leucaena and slowest in Terminalia. The laboratory investigation also showed that Leucaena had the fastest rate of decomposition and highest rate of release of N while Cassia had the slowest and least. Intercropping with Prosopis resulted in an average increase of 13 and 4% in grain yield of maize and sorghum, respectively but no increase in beans. It significantly improved soil N in all the treatments. The spacing did not affect yields until the third season, but affected the dry matter yield per ha of Prosopis and Cassia. Close in-row spacing of Cassia resulted in intra and inter-specific competition before coppicing. The amount of N fixed by Leucaena and the soil N were significantly affected by the treatment. The management of the hedges and of the trees mixed with millet was crucial in determining their effects on crops. Manured pure millet and millet mixed with Leucaena gave the highest yields, growth, and soil and foliar N contents. Significant differences occurred amongst the tree species in the amount of N fixed and made available to millet.