PROF. MUNGAI DAVID N

During the last 40 years, water development in the southern Marsabit District of Kenya concentrated mainly on drilling boreholes and constructing large dams and pans which are difficult to maintain without financial aid. In order to make the nomads independent of outside aid, the Marsabit Development Programme has introduced animal traction for dam and pan construction and promotes the management of shallow wells. This paper reports the experiences encountered so far in the integration of water development within the natural resource improvement programme and discusses lessons learnt during the 1991/2 drought in the area in terms of water development and nomadic lifestyle.

This paper examines the anomalies in the sedimentation rating equations in terms of existing notions of statistical analysis and concludes that c=aqb is the preferred relationship. The method of estimating parameters a and b through ordinary least squares and the method of prediction using the log normal probability distribution of the error component z (c=aqbz) is presented using data for the Mathare river at Kabete, Kenya. The need for nonlinear least squares for estimation of parameters a and b is discussed in relation to the additive nature of the error component (c=aqb + z) n the nonlinear form of rating equation. The equation c=Faqb (where F is a correction factor arising due to log normal distribution of the error term z) predicted the sediment yield of the Mathare catchment quite well for 61 days during the long rainy season of 1991.

This paper briefly presents a methodology for planning development in arid and semi-arid areas. It highlights the issues of problem identification and assessment of the natural and socio-economic environment, and describes the database contained in the Range Management Handbook. The handbook makes available baseline data for planning development in arid and semi-arid areas following a successful Farm Management Handbook that covers the high- and medium-potential areas of Kenya. In three parts, the Range Management Handbook covers: the status, principles and applications in Kenya; texts and maps relating to climate, landforms and soils, vegetation types, water sources, range unit inventory, livestock marketing and human ecology; special reports (guide to tolerant plants, pictorial key for goat stocking rates, large scale remote monitoring of vegetation, and a survey method for classification of range conditions) relevant to land planning and use in arid and semi-arid areas

This paper describes a "near-farmer" applied research project working on 10 field stations scattered through the arid and semi-arid lands of Embu, Meru and Isiolo Districts of Esatern Province, Kenya. The objective of the research was to define better extension messages for resource-poor farmers to enable them to improve their land and water management techniques for improved and sustained yields. Most of the trials related to soil fertility and soil moisture, as well as trials on the use of Vetiver grass for soil conservation, control of the legume root parasite Alectra vogelii, and new introductions such as groundnuts, simsim (sesame), tubers, fodder crops and fruits.

This paper presents results of a study aimed at quantifying soil and water management practices and identifying major constraints and implications for future adoption of appropriate technologies. The study was conducted in the Machakos and Makueni Districts of Kenya. Approximately 83% of the farmers interviewed were using manure, while only 4% use fertilizer. 60% had fanya juu terraces on their land, while only 13% were using grass strips. The study concluded that finance is a major constraint limiting farmers' adoption of practices enhancing soil fertility and that lack of conservation practices on grazing land is of great concern. The lack of knowledge of possible benefits of soil and water management practices is noted.

Preliminary findings on the effects of land use in the Masinga Dam catchment, Kenya, on the storage capacity of the reservoir are presented. Remote sensing and GIS techniques, supplemented with ground reports, were used to determine areas most susceptible to erosion. A representative catchment was then chosen for rainy season monitoring of soil loss, river suspended sediments and discharge response to rainfall. In addition, Gerlach-type traps were used to evaluate erosion rates under different crop covers and slope gradients. A sample of 200 households was interviewed about their perceptions of erosion problems on their farms. Preliminary results suggest that the major sediment-contributing areas are the densely populated and intensively cultivated foothills of the Aberdares, rather than the semi-arid lowlands directly bordering the reservoir. Poorly drained sealed and murram roads, together with footpaths, cattle tracks and gullies, act as extensions of the drainage network during storms, channelling sediment-laden runoff from bare areas around homesteads and schools directly into the river. Subsistence crops, particularly mono-cropped maize, appear to provide poor cover for a major part of the wet season.

This paper presents results from a trial in Swara Farm, Njoro, Kenya, in which a field was sown with Sorghum almum on a volcanic ash soil. Immediately after sowing, 14 strips measuring 156 m x 9 m were marked out and alternate strips were oversown with inoculated seed of lucerne cv. Hairy Peruvian. During the first year of the trial no differences were noticed in the growth of S. almum, but during the second year it grew better when associated with lucerne. After two years the field was ploughed and sown with wheat. The strips were harvested separately with a combine harvester. Mean yields after S. almum were 2,708 kg/ha and after the S.almum/lucerne mixture were 3,244 kg/ha.

The results of soil surveys at the ICIPE research site at Ungoye, South Nyanza, and the Ngori Ngori toposequence in Narok, Kenya, are discussed to provide insight into the applicability of soil survey information to soil and water management. It is concluded that soil survey information in soil and water management programmes can be used through understanding and appreciation of the criteria used in categorizing soils and their management implications. From the examples given it is noted that chemical aspects of the soil should be viewed not just as a means to assess its fertility, but also as a base to predict the behaviour of the soils when subjected to different types of management.

The existing soil erosion damage caused by water drained from minor roads in the Nyeri District of Kenya was assessed and the soil conservation works needed to stabilize the waterways and gullies along the roads are specified. The study evaluated the land affected by road drains/culverts on 25 minor roads with a total length of 149 km. Of the total of 321 culverts identified, 171 (53%) were found to require channel rehabilitation. 68% of the culverts discharged onto steep slopes (>10%). Erosion was found to be more severe in the coffee-growing zones than in tea-growing areas. In the plateau areas, soil erosion from the culvert outlets was minimal. Due to gentle slopes and more perennial vegetation. 20,346 m of channel excavation was needed to provide artificial waterways for the discharge of water drained from the roads. Channel stabilization with grass cover or installation of scour checks was necessary on very gentle slopes. Steep slopes required stone check-dams and single-row post/stone check-dams. Very steep slopes also required lock-and-spill drains and post/stone/wire check-dams. Gabions (57 crossings) were needed mainly for rehabilitation of large gullies along with double-row post/stone check-dams and post/stone/wire check dams. Cut-off drains were necessary in some cases to divert water from the culvert outlets. In areas where vegetation was easily accessible, brushwood check-dams could be used.

The Arpolo gullying control project in the West Pokot Region of Kenya is described. This is an example of conservation work done to protect the Arpolo dispensary which cost >KES350,000 to put up and serves about 3,000 people and is threatened by a fast-growing gully. The initial proposal for a concrete wall in the first phase of implementation was not feasible since it would be undermined during the rains. The alternative was to plan, design and apply water-harvesting methods and implement biological measures that would reduce the erosive energy of the surface runoff. The design of the water-harvesting structures is shown. The success of the project shows that land and water management requires skillful planning and design, especially where soils are vulnerable to erosion. The physical and chemical properties of the soils in the area are described. Given proper hydraulic designs, water-harvesting measures are still a reliable means of soil conservation.

This paper reflects on the role of root crops (cocoyam, Colocasia esculenta or C. antiquorum) as a case study in riverbank protection and food security in Kenya. Field performance, water erosion control, ecologically friendly production and food value were studied. It is concluded that the national relevance of cocoyam cultivation lies in its role in its conservation through erosion control and soil fertility maintenance; its low energy input; its potential to supplement per capita calories through high yield per unit area; its perpetuity; its multiple nutritive value, ease of preparation and digestibility; and its industrial potential and competitive market opportunity for various end-products.

This paper explores the potential of agroforestry in arid and semi-arid areas, presents various management practices and identifies a suitable agroforestry extension programme. Natural, social and economic environments, and their interactions with agroforestry practices are discussed for Tharaka Division of Tharaka-Nithi District, Sololo Division of Marsabit District and Central Division of Mandera District, Kenya

This paper examine past and present trends in the development of Kenyan water resources, and the status of Kenya's arid and semi-arid lands. It considers the parameters linked with soil erosion and sedimentation processes and suggests means of combating the problem.

The effects of P supply (0, 20, 40, 80, 160 and 320 kg/ha) on growth and nodulation of cowpeas (Vigna unguiculata) cv. Vita 4 and Ife Brown grown in a podzolic soil (Haplustult) was studied in a greenhouse trial. The seeds were inoculated with Bradyrhyzobium CB 756. Plants were harvested at the beginning of flowering. The number of trifoliate leaves and DM yield in both cv. increased with increasing P application. The yield of the tops of Vita 4 was maximum at 160 kg P/ha and that of Ife Brown at 320 kg P/Ha. Extractable P related linearly to the rate of applied P, and DM yield increased with increase in extractable P. Plants grown without P had fewer and smaller nodules. An increase in P from 1 to 160 kg/ha increased the number of nodules/plant from 16 to 113 in Vita 4 and from 14 to 70 in Ife Brown. Similarly, increasing P increased nodule dry weight. The P conc. of the youngest fully expanded leaf (YFEL) and in the whole plant top increased with increasing P supply in both cv. and was generally higher in the YFEL than in the whole top. A critical P conc. of 0.3 and 0.25% was found in the YFEL and the whole top, resp., for cv. Vita 4.

Stover placement (surface mulch, incorporated or a mixture of mulch and incorporation) was compared with stover removal in the presence and absence of 50kg N fertilizer/ha in trials over two successive seasons in continuous maize cropping systems in two regions in Kenya. Stover applied at 4 tonnes DM/ha was found to have highly variable effects on maize growth and yield according to site., method of stover placement, N application and season. Relative to controls without stover, stover incorporation reduced yield by 39% in the first season, followed by yield increases of 15% in the second season. In the first season there was little or no response to N in the presence of stover. Low N uptake and N use efficiency suggested N immobilization in the incorporation treatment. Yield responses and large N uptake in the following season suggested mineralization of N immobilized in the previous season. Surface mulching at the Kabete site increased grain yields in the first season by 39% and 6% compared to stover removal without and with fertilizer, resp. In the second season, surface mulching markedly reduced yields possibly due to a combination of reduced phytotoxicity and N immobilization. At the Katumani site, stover amendments increased yields compared to removal in both seasons with incorporation results being superior to surface mulch. At this site, in both seasons, application of N reduced the effect of stover mulching and incorporation. You must log in to CAB Direct in order to view search results. If you have forgotten your log

Trends in land use practices in the Lake Nakuru catchment area and, in particular, the causes and impacts of deforestation, which threaten the lake's unique ecology. It addresses the importance of natural forests for the successful management of the lake's watershed area. Findings are all discussed in the broader, national context and some suggestions for programmes of action to alleviate problems caused by deforestation are presented.

This paper outlines the development of a new methodology to modify and improve the indigenous practices of soil fertility management in Eastern and Southern Africa and suggests requirements for involvement by collaborating institutions. It provides a brief history of the Tropical Soil Biology and Fertility (TBSF) Programme in Africa, ongoing resource integration work in Zimbabwe, proposed work in Kenya and team development in Zimbabwe.

This paper describes earthflow features in Nyairoko sub-location of Ol Joro Orok Division, Kenya. In 1989 more than 900 earthflows were counted in Nyandarua District, most of them in Ol Joro Orok and Ol Kalou Divisions. Individual flows affected areas between a few square metres and two hectares. More than 50% of the farms in the area were affected by earthflows. Such earthflows occurred only on grazing land and on convex slopes and were usually the result of extremely slow processes. Soils in the area are mainly moderately well drained, dark reddish brown Luvisols and well-drained, red to reddish-brown Nitisols. The first visible signs were usually shallow scars along the contour, breaking up the grass vegetation. Subsequent soil movement was very gradual. According to old residents of the area some of the earthflow features had been observed as long as 60 years ago and could not be attributed to land use change. One earthflow studied in detail revealed that soil stratification impeded drainage, leading to oversaturation of the topsoil layers and that seasonal subsurface flow generally seemed to be responsible for the soil movement. No obvious triggering could be identified.

This paper examines the impact of sand harvesting from rivers on the environment, land use and social life in the Masinga Division, Machakos District, Kenya. Sand acts as a safe aquifer for water flowing below and through it. Removal of sand results in destruction of underground aquifers and loss of safe water. sand scooping adversely affects surface water quality and quantity and damages the aquatic ecosystem. Haulage of sand by heavy trucks causes environmental degradation by accelerating soil erosion and affecting soil stability. Storage of sand causes destruction of surface areas through clearing of vegetation and uses land that could be used for agriculture. Related social and health problems include prostitution and high school drop-out rate leading to serious social and health problems. The beneficial effects of sand harvesting include local employment; however, the share of monetary benefits to locals is minimal. The results show that the local community gains the least from sand harvesting, but stands to suffer the most if the degradation of the river system continues. Suggestions are made for safe and sustainable methods of managing sand harvesting, in which greater local involvement and stricter enforcement of regulations to protect the environment are vital.

This paper is concerned with policy and development issues relating to the planning of rural land use in Kenya. The central theme of the analysis is the critical and urgent need for sustainable land use. Based on a study of land considerations in past development policies and of current land use issues, the paper discusses current development strategies and issues. Pitfalls likely to be encountered in future land use planning in rural Kenya are discussed.

Long-term use of compost (4, 8, 12 or 125 kg/ha for maize and 10, 20, 30 or 200 kg/ha for beans) on improving crop yields and soil physical characteristics was studied at the steep-land research site, Kabete campus, Kenya. Preliminary results showed that maize yields under compost were lower than under diammonium phosphate (DAP). Compost increased the maize yield by 15% compared to an increase of 50% caused by DAP. Bean yield did not show any response to any rates of compost or DAP. The use of compost improved soil physical conditions, mainly bulk density and infiltration rates

The effect of wind erosion in areas subjected to continuous pastoral use compared with the effects of rangeland rehabilitation in areas subjected to natural recovery were studied at four sites in eco-climate zone VI in the Marsabit District of Kenya. The study was conducted using erosion pins and comparing organic and soil texture changes within the first 10cm of the soil. The soils ranged from loamy sand in the rehabilitation enclosure to sandy soils in the area with continual use. In all cases the soils had poor aggregate stability. An average annual soil loss of 95t/ha was observed in the areas under continuous use where vegetation was minimal, whilst soil was deposited at a rate of 446t/ha annually in the rehabilitation enclosure in which there was plentiful Indigofera dwarf shrubland vegetation

A stream flow model was developed for use in rural catchments in Kenya. In the model the physical environment was divided into three zones: the unsaturated zone (consists of multiple hydrological response units defined by homogenous land use and soil type in which a daily soil moisture balance is maintained), shallow saturated and deep saturated zones which were modelled as regional aquifers. Rainfall and evapotranspiration were distributed according to altitude, and runoff was determined using the curve number method devised by the US Soil Conservation Service: a function of five-day antecedent precipitation. Evapotranspiration was varied according to the soil moisture content, and the weather generator allowed Monte Carol simulations over a long period. The data consisted of daily rainfall, mean daily evaporation for each month, land use/vegetation and soil type. The ARC-INFO GIS package was used to assemble the topographical, hydrological, land use/vegetation type and soil information in different layer. The model was tested on the Naro Moru catchment (172kn2) in Kenya, which has climatic conditions that vary from the glaciated peaks of Mount Kenya (5,200 m) to the semi-arid Laikipia plateau (1,800 m). The model was calibrated over a two-year period and validated over a different two-year period. A comparison of the observed and simulated stream flow showed that minimal calibration was required. The simulated stream flow compared well with the observed values for both the calibration and the validation periods (70-85% for the 10-day period) indicating that the model is appropriate for ungauged catchments.

Runoff and soil loss was studied on steep terraced slopes containing various combinations of lines of Grevillea robusta, hedgerows of Calliandra calothyrsus and strips of Pennisetum purpureum in Kabale, southwest Uganda. A factorial design, replicated three times, included three levels of intra-row spacing (0, 3 and 5m) of Grevillea spp. and three understorey types (none, Pennisetum and Calliandra spp). The understorey and Grevillea were interplanted along a contour in the middle of the terrace parallel to the two adjacent risers. Results indicate that when contour lines of trees are on fallow ground there is little or possibly a negative effect in controlling soil and water loss. When contour lines are on steep cultivated terraces they have a significant effect in reducing losses. The understoreys appear to filter out much of the sediment from the runoff, holding it in or above the contour line of the vegetation. The potential for using contour lines of Pennisetum and Calliandra for controlling soil and water loss is discussed.

Forty controlled gullies distributed in Kiambu, Murang'a and Nyeri Districts of Central Province, Kenya, were randomly selected to evaluate their control measures. A recording schedule was developed to assist in collecting pertinent information. Results indicate that the failure of gully control in Central Province can be attributed to lack of technically skilled personnel and poor maintenance of gully control structures. It is concluded that there is a great need to impart technical knowledge to technical staff, and that it is essential to intensify research on gully control techniques and that there is regular and proper maintenance of all gully control structures after rainstorms.

The possible environmental impacts of water development projects and land use practices such as deforestation and over grazing on water supply in Kenya are reviewed. Measures that can be taken in conjunction with properly conducted environmental impact assessments to mitigate adverse impacts are suggested

A review of available literature on the hydrologic impacts of drainage is presented and management practices that reduce such impacts are identified. Factors that influence the impact of drainage include land use, soil type, drainage density, type and condition of the drains, size and duration of the storm, and extent and location of the drainage. Suggested options for minimising impacts include: appropriate land use (fish ponds, duck farming, harvesting natural products, dry season grazing or cultivation); controlled drainage through use of shallow drains, drainage for growing water-loving plants, land preparation (hilling, cambered beds), and blocking drains at the end of the rains; and water storage (dams along the river or farm ponds).

The effectiveness of different grass spp. in reducing runoff and soil loss was studied at Kabete campus, University of Nairobi, Kenya. Half metre wide strips of Napier grass (Pennisetum purpureum), Nandi setaria (Setaria anceps) and tall Signal grass (Brachiaria ruziziensis) were established on 11m x 2m runoff plots, and runoff and soil loss were monitored for each rainfall event during the long and short rains of 1990. In terms of runoff control, there was no significant difference between treatments during early establishment; however, runoff form plot with filter strips was always lower than controls. B. ruziziensis was most effective at runoff and soil loss reduction and this was attributed to growth habit and slow rate of establishment. The capability of the strips to impede runoff improved with time.

A model of the Ndarugu riverbank intake, Kenya, was used to test various possibilities of weir construction. It was found that by narrowing the river near the intake to increase velocity, sedimentation was drastically reduced. This solution was found to be economically feasible and easy to implement.

The effects of three different micro-catchment sizes on survival and growth of plant species was assessed and success in establishment and growth of Croton megalocarpus and Cassia spectabilis was compared in a semi-arid region of Kitui District, Kenya. Both species were planted in 25 x 25 cm, 45 x 45 cm, and 65 x 65 cm spherical micro-catchments. Height and diameter were measured and a survival count was taken. Results show that then micro-catchment size influenced (P>0.05) lateral growth of both species. Lateral growth of C. spectabilis in the smaller two micro-catchments (3.66 and 4.60 cm, resp.) was not significantly different (P>0.05), but was less than in the largest micro-catchment(5,31 cm). These results indicate that the two species are suitable for afforestation in these areas and that their survival is not limited by provision of a catchment in the area.

The implications of global climatic change on water resource development and management in Kenya was examined. The extent to which the water resources of the various regions of Kenya will be affected and the effects on streamflow regimes, rainfall amount, frequency and distribution patterns and the overall effects of these on socio-economic development are discussed. It is suggested that increased drought could occur in low-potential regions of Eastern, Rift valley and North Eastern Provinces, whilst regions that already receive a favourable amount of rainfall could have even higher amounts. Changes in rainfall patterns and stream discharge may require translocation of current water development projects with possible high costs and dire consequences for those dependent upon such projects. The increases aridity in the arid and semi-arid lands may lead to increased salinity of groundwater, limiting it's use. Recommendations include water conservation strategies, groundwater basin recharge, inter-basin water transfer from high to low potential zones, cloud seeding above arid and semi-arid areas, better soil and water conservation strategies, and controlling the use of products contributing to global warming.

This paper looks at factors which influence land allocation and crop production patterns in Botswana, across traditional and commercial farmers. It found that, among smallholder traditional farmers, less land is used (on average 5.6 ha) and is subdivided into the growing of three major crops: sorghum, maize and beans, with more land allocated to sorghum, the main staple and more adaptable to the climate. The small amount of cultivated land is attributed to lack of capital, transport and labour. Although large areas of land are owned by commercial farmers a high percentage is left idle due to constraints such as poor marketing systems, poor storage facilities and shortage of labour

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

Department of Periodontology/ Community and Preventive Dentistry, School of Dental Sciences, University of Nairobi, P.O. Box 19676 - 00202, Nairobi, Kenya. OBJECTIVE: To determine the influence of oral hygiene habits and practices on the risk of developing oral leukoplakia. DESIGN: Case control study. SETTING: Githongo sublocation in Meru District. SUBJECTS: Eighty five cases and 141 controls identified in a house-to-house screening. RESULTS: The relative risk (RR) of oral leukoplakia increased gradually across the various brushing frequencies from the reference RR of 1.0 in those who brushed three times a day, to 7.6 in the "don't brush" group. The trend of increase was statistically significant (X2 for Trend : p = 0.001). The use of chewing stick as compared to conventional tooth brush had no significant influence on RR of oral leukoplakia. Non-users of toothpastes had a significantly higher risk of oral leukoplakia than users (RR = 1.8; 95% confidence levels (CI) = 1.4-2.5). Among tobacco smokers, the RR increased from 4.6 in those who brushed to 7.3 in those who did not brush. Among non-smokers, the RR of oral leukoplakia in those who did not brush (1.8) compared to those who brushed was also statistically significant (95% CL = 1.6-3.8). CONCLUSION: Failure to brush teeth and none use of toothpastes are significantly associated with the development of oral leukoplakia, while the choice of brushing tools between conventional toothbrush and chewing stick is not. In addition, failure to brush teeth appeared to potentiate the effect of smoking tobacco in the development of oral leukoplakia. Recommendations: Oral health education, instruction and motivation for the improvement of oral hygiene habits and practices; and therefore oral hygiene status, should be among the strategies used in oral leukoplakia preventive and control programmes.

This paper examines the land use patterns in the upper Tana river basin, Kenya, and the resultant erosion that is responsible for the continued loss of storage capacity of the Masinga reservoir. The main Tana branch of the Masinga reservoir contributes about 85% of the total sediment inflow to the reservoir. The high production rates of sediment are linked to the rivers that feed this branch passing through intensively cultivated slopes of the Aberdares and Mount Kenya. Lack of adequate ground cover and the steep slopes often being cultivated without soil conservation measures result in increased surface runoff and soil loss. The need for effective soil conservation in the catchment area is stressed to prevent the expected lifespan of the reservoir form being reduced dramatically.

The role of probability theory in providing information on the critical dry and wet periods using daily rainfall data was studied. The methodology was illustrated using the daily rainfall data from Kibwezi rainfall station, Kenya, with 55 years of records. The theory of runs, conditional probability, Poisson probability density and Chi-square statistics were used in the analysis. The model performed well and simulated the critical dry and wet periods (days) adequately. Results showed that one may expect the critical dry period to be about 24 and 12 days during the long and short rainy seasons, resp. Similarly, the critical wet spell is expected to last for 5 and 6 days, resp. It is suggested that drought analysis in the Kibwezi region should be based on the dry periods of the long rainy season, and runoff, soil erosion and rain harvesting analysis on the wet periods of the short rainy season.

Farmers of the Sagana irrigation project, Kenya, have identified fluctuating and low prices for their agricultural produce as their main constraint. This paper reports results from a study carried out to identify an alternative cropping system that could be used to optimize their returns by harvesting their crops when the market price is highest. The study shows that there is a complex interaction of factors affecting the selection of a cropping system: climatic, water requirements, marketing and farmer preferences. It also illustrates how proper planning of the cropping calendar can reduce irrigation water requirements and maximize project benefits.