Rift Valley Area Research Articles

Spatial and temporal distribution of West Nile virus in horses in Israel (1997-2013)--from endemic to epidemics.

With the rapid global spread of West Nile virus (WNV) and the endemic state it has acquired in new geographical areas, we hereby bring a thorough serological investigation of WNV in horses in a longstanding endemic region, such as Israel. This study evaluates the environmental and demographic risk factors for WNV infection in horses and suggests possible factors associated with the transition from endemic to epidemic state. West Nile virus seroprevalence in horses in Israel was determined throughout a period of more than a decade, before (1997) and after (2002 and 2013) the massive West Nile fever outbreak in humans and horses in 2000. An increase in seroprevalence was observed, from 39% (113/290) in 1997 to 66.1% (547/827) in 2002 and 85.5% (153/179) in 2013, with persistent significantly higher seroprevalence in horses situated along the Great Rift Valley (GRV) area, the major birds' migration route in Israel. Demographic risk factors included age and breed of the horse. Significantly lower spring precipitation was observed during years with increased human incidence rate that occurred between 1997–2007. Hence, we suggest referring to Israel as two WNV distinct epidemiological regions; an endemic region along the birds' migration route (GRV) and the rest of the country which perhaps suffers from cyclic epidemics. In addition, weather conditions, such as periods of spring drought, might be associated with the transition from endemic state to epidemic state of WNV.

Drop size distribution and kinetic energy load of rainfall events in the highlands of the Central Rift Valley, Ethiopia

Knowledge of rainfall characteristics is important for estimating soil erosion in arid areas. We determined basic rainfall characteristics (raindrop size distribution, intensity and kinetic energy), evaluated the erosivity of rainfall events, and established a relationship between rainfall intensity I and volume-specific kinetic energy KEvol for the Central Rift Valley area of the Ethiopian highlands. We collected raindrops on dyed filter paper and calculated KEvol and erosivity values for each rainfall event. For most rainfall intensities the median volume drop diameter (D50) was higher than expected, or reported in most studies. Rainfall intensity in the region was not high, with 8% of rain events exceeding 30 mm h-1. We calculated soil erosion from storm energy and maximum 30-min intensity for soils of different erodibility under conditions of fallow (unprotected soil), steep slope (about 9%) and no cover and management practice on the surface, and determined that 3 MJ mm ha-1 h-1 is the threshold erosivity, while erosivity of >7 MJ mm ha-1 h-1 could cause substantial erosion in all soil types in the area.Editor Z.W. Kundzewicz; Associate Editor Q. Zhang

The emergence of begomovirus-induced yellow leaf curl disease of tomato ( Lycopersicon esculentum mill.) in Ethiopia

A systematic survey was carried out to determine the incidence and distribution of tomato virus diseases in Ethiopia. Fifty seven tomato fields were inspected, 570 plant samples were collected and tested by DAS-ELISA against eight tomato infecting viruses. The presence of a Tomato yellow leaf curl virus (TYLCV) in selected symptomatic samples was confirmed by immunocapture-polymerase chain reaction (IC-PCR). The data showed that TYLCV and Tomato mosaic virus (ToMV) were the two widespread viruses detected in 24.6% and 47.37% of the fields, respectively; whereas Tomato mild mottle virus (TMMV) followed by P otato virus Y (PVY) were detected only in few samples or completely absent in most fields in the other parts of southern and eastern parts of the country. All tomato samples were negative for Tomato spotted wilt virus (TSWV), Tomato ring spot virus (ToRSV), Tobacco mosaic virus (TMV) and Cucumber mosaic virus (CMV). High incidence (up to 95%) and prevalence of leaf curl disease was observed in fields in the Rift Valley areas (Upper Awash, Merti, Melkasa and fields along the road Mojo to Zwai). The result indicated that tomato yellow leaf curl has emerged as a major tomato virus disease causing serious losses in the fields of Rift Valley areas. Key words/phrases : Begomoviruses, DAS-ELISA, IC-PCR, Tomato.

Microbial quality of water in rural households of Ethiopia: implications for milk safety and public health.

Waterborne pathogenic agents affect the health of people either by direct consumption of contaminated water or by its indirect use in food production and/or processing. Studies on the microbiological quality of water in rural areas of Ethiopia are still limited, especially at the household level. The aim of the present study was to assess the microbial quality of water from different sources in rural households in two districts of the Ethiopian Rift Valley area. The correlation between E. coli counts in water and milk was also investigated. In total, 233 water samples (126 collected in dry and 107 in wet season) and 53 milk samples (19 from raw milk and 36 from processed milk products) were analyzed for E. coli contamination. The overall prevalence of E. coli in water samples was 54.9% (n = 233). In most of the analyzed samples, a higher prevalence of E. coli was recorded during the wet compared to the dry season. The highest load of E. coli was detected in water samples from dugouts. The quality of raw milk and traditionally-processed milk products showed variations between districts, and the traditionally-processed milk products were found to contain higher E. coli loads than raw milk. The correlation between the E. coli counts in water and milk only showed a weak but positive relationship (r = 0.1). Taking E. coli as a proxy for water quality, the microbiological quality of water consumed in the study area was found to be very poor, posing a potential food safety and health risk to the rural communities.

Constraints and challenges of meeting the water requirements of livestock in Ethiopia: cases of Lume and Siraro districts

Compared to the total water use in livestock production systems, water for livestock drinking is small in amount but is an important requirement for health and productivity of animals. This study was carried out to assess constraints and challenges of meeting drinking water requirements of livestock in rural mixed smallholder crop-livestock farming districts in the Ethiopian Rift Valley area. Data was collected by individual interviews with randomly selected respondents and farmer group discussions. Farmers ranked feed and water scarcity as the two most important constraints for livestock husbandry, although the ranking order differed between districts and villages. Poor quality water was a concern for the communities in proximity to urban settlements or industrial establishments. Water provision for livestock was challenging during the dry season, since alternative water sources dried up or were polluted. Though rainwater harvesting by dugout constructions was practiced to cope with water scarcity, farmers indicated that mismanagement of the harvested water was posing health risks on both livestock and people. A sustainable water provision for livestock in the area, thus, depends on use of different water sources (intermittent or perennial) that should be properly managed. Industrial establishments should adopt an environment-friendly production to minimize pollution of water resources used for livestock consumption. Technical support to farmers is required in proper design and use of existing rainwater harvesting systems. Further investigations are recommended on effect of poor quality water (perceived by farmers) on performance of livestock.

Expansion of Eucalypt Farm Forestry and Its Determinants in Arsi Negelle District, South Central Ethiopia

Declining natural forests and growing demands for wood products are encouraging the rapid expansion of eucalypt farm forestry in Ethiopia, and Arsi Negelle district represents areas with recent plantation expansion in the Rift Valley area of Ethiopia. This study assessed trends in eucalypt planting over the last five decades, identified the determinants, and examined perceptions of local stakeholders towards this expansion in the district. Quantitative data were gathered through a household survey and farm level inventory. About 90% of the respondents had planted eucalypts, and 52% of them were engaged in planting since the late 1990s. About 11% converted cropland to eucalypt woodlots, which is also a growing trend in the area. Proximity to Arsi-Forest Enterprise (P < 0.01) and area of land holding (P < 0.01) positively and significantly affected both decision to plant and land area allocated to eucalypts plantings. Active labour in the family negatively and significantly (P < 0.05) affected planting decisions, while education level of the household head positively and significantly (P < 0.05) affected land area allocated to eucalypts plantings. Despite strong policy discouragement and perceived adverse ecological effects by the farmers themselves, 96% of them and 90% of the district experts support the expansion. Eucalyptus has become the most desired and planted tree genus, and economics not ecology appears to drive its expansion. Unless better alternative sources of cash income and substitutes for energy and construction materials are found, its expansion is likely to continue even at the expense of cropland. It is concluded that research is needed to fine-tune current eucalypt farm forestry practices to reduce the associated ecological externalities, rather than grossly banning eucalypt planting by smallholders.

TP53 mutations, human papilloma virus DNA and inflammation markers in esophageal squamous cell carcinoma from the Rift Valley, a high-incidence area in Kenya

BackgroundSquamous Cell Carcinoma of Esophagus is one of the most common malignancies in both men and women in eastern and south-eastern Africa. In Kenya, clinical observations suggest that this cancer is frequent in the Rift Valley area. However, so far, there has been no report on the molecular characteristics of esophageal squamous cell carcinoma (ESCC) in this area.ResultsWe have analyzed TP53 mutations, the presence of human papilloma virus (HPV) DNA and expression of inflammation markers Cyclooxygenase 2 (Cox-2) and Nitrotyrosine (NTyR) in 28 cases (13 males and 15 females) of archived ESCC tissues collected at the Moi Teaching and Referral Hospital in Eldoret, Kenya. Eleven mutations were detected in TP53 exons 5 to 8 (39%). All ESCC samples were negative for HPV 16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 70, 73 and 82. Immunohistochemical analysis of Cox-2 and NTyR showed a low proportion of positive cases (17.4% and 39.1%, respectively). No association between the above markers and suspected risk factors (alcohol or tobacco use, hot tea drinking, use of charcoal for cooking) was found.ConclusionOur findings suggest that mechanisms of esophageal carcinogenesis in eastern Africa might be different from other parts of the world. Low prevalence of TP53 mutation compared with other intermediate or high incidence areas of the world highlights this hypothesis. Our data did not support a possible ole of HPV in this series of cases. Further studies are needed to assess and compare the molecular patterns of ESCC from Kenya with those of high-incidence areas such as China or Central Asia.

Reading the Landscape Past: Explaining the Lack of On-Farm Tree Planting in Ethiopia

Abstract Although tree planting initiatives by the state began by the end of the nineteenth century, on-farm tree planting has not been widespread, particularly on plots outside homesteads. Farmers particularly in central and northern Ethiopia are limited to growing trees mainly at homesteads indicating the need to identify the underlying discouraging factors. This paper examines the historical trend and current status of tree planting by smallholder farmers. In addition to reviewing historical and legal documents, the study solicited farmers' opinions and used maps and satellite images to examine past and recent features of a site in southern Ethiopia that represents the southern Rift Valley areas of the country and is characterised by low to medium tree cover. Major policy failures identified, and which persisted over a long period of time, include lack of tenure security, historical background that promoted free grazing, political and institutional instability, abrupt and radical changes in rural development policies and strategies and market distortions due to de facto open access of forest resources on the one hand and price control and lengthy permit requirements to sell wood and wood products produced on farms on the other. Unless these issues are addressed, the degrading landscapes will be worse off. The study clearly demonstrates that, in developing countries like Ethiopia, stable institutions, secure tenure and enabling policies are critical if tree planting is to be promoted for meeting farmers' own needs and growing market demands and thus increasing rural household income.

Soil water property variations in three adjacent land use types in the Rift Valley area of Ethiopia

This study investigated the effects of land use change on infiltration and moisture content of soils in three land use types. A total of 81 soil and core samples (3 replications × 3 treatments × 3 profiles × 3 soil depths) were used to determine parameters that may affect the infiltration properties of soils. The infiltration rate was measured in the field using double-ring infiltrometer with three replicates in each land use type. Results showed that infiltration rates were generally slow in the open grazed and cultivated lands suggesting high potential for runoff, limited percolation, and very low amount of water available in the soil profiles. The accumulated infiltration in soils under cultivation and open-grazing was smaller than the controlled grazing by approximately 57%. Similarly, cultivation and open-grazing had reduced the soil moisture content by 29 and 33%, respectively, compared to the controlled grazing. Surface soil compaction, higher dry bulk density and lower soil organic carbon, appeared to be the principal factors for the low infiltration capacity and moisture content of the soils. Therefore, dry land management, with long term tree cover and well regulated grazing system, is very crucial for the sustainable ecosystem functioning of this environmentally fragile area.

Soil property changes following conversion of acacia woodland into grazing and farmlands in the Rift Valley area of Ethiopia

AbstractContinued conversion of woodlands into grazing and farmland is seriously undermining the natural ecosystem of the dry and fragile Rift Valley areas of Ethiopia. This study investigated the effects of land‐use change on soil organic carbon (SOC), total nitrogen (N), pH, exchangeable bases, cation exchange capacity (CEC) and base saturation (per cent) in three adjacent land‐use types: controlled grazing, open‐grazing and farmland. A total of 81 soil samples were collected and analysed. Contents of SOC and total N decreased drastically in open‐grazing and farmland (p &lt; 0·001), and were significantly higher in the top 0·2 m than in the subsurface soil layer. Compared with the controlled grazing, reductions in the contents of SOC and total N in the top 1 m soil layer were 22–30 and 19 per cent, respectively, due possibly to the decrease in plant biomass input into the soil and the fast decomposition of organic materials. Long‐term cultivation had significantly increased the concentration of exchangeable K. Exchangeable Na was high in the lower layers, while Mg was higher in the top surface soil. CEC also varied with soil depth (p = 0·016); it was higher in the topsoil than in the subsurface soil, which may be, among others, due to the differences in soil organic matter distribution with depth. Although these semi‐arid soils are known to have low organic carbon and CEC levels, the values from the current study area are critically low, and may indicate the further impoverishment of the soils under high agricultural and grazing pressures. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Evaluation of Deltamethrin applications in the control of tsetse and trypanosomosis in the southern rift valley areas of Ethiopia

A study aimed at evaluating the efficacy of Deltamethrin (0.4% impregnated targets and 1% pour-on formulation) in controlling tsetse and trypanosomosis was carried out in two selected 10 km × 10 km Universal Transverse Mercator Grids of the Southern Tsetse Eradication Project (STEP) area in the southern rift valley of Ethiopia. The Grids selected were H3 (site I) and G5 (site II) in two districts of the Wolaita Zone. The trial was underway from September 2003 to April 2004. The strategy followed to accomplish the trial was a pre-intervention phase (entomology and parasitology) and an intervention phase with insecticide (Deltamethrin 0.4%)-impregnated odour-baited targets in site I and Deltamethrin 1% ‘pour-on’ application to cattle in site II. The intervention phase was monitored on a monthly basis. Following the deployment of 460 targets at a density of 4 targets per km 2 in trial site I, the relative abundance of tsetse fly ( Glossina pallidipes) declined from a pre-intervention mean catch of 1.35 flies per trap per day to 0.05 flies per trap per day at final monitoring. These resulted in an 88.9% overall reduction. Similarly, an 83.25% reduction was recorded in the incidence of trypanosomosis in sentinel cattle as it dropped from 10.75% (first monitoring) to 1.8% (last monitoring). The corresponding measures of packed cell volume (PCV) have shown a significant improvement from a mean of 21.8% (95% confidence interval (CI): 20.7–22.9) at first monitoring to 25.5% (95% CI: 24.3–26.7) of last monitoring ( P < 0.01). In site II, the trial was started by spraying Deltamethrin 1% pour-on to 409 cattle at a rate of 1 ml/10 kg body weight. Pour-on treatment was repeated every month throughout the trial period. A sharp drop in the relative abundance of tsetse fly was revealed soon after. The catch was nil at fourth monitoring as it declined from 0.91 flies per trap per day of pre-intervention ( P < 0.01). A 94.9% overall reduction was achieved. The incidence of trypanosomosis in sentinel cattle also declined from 10% (first monitoring) to 0.95% (last monitoring) with about 90.5% decline. An improvement in the overall mean PCV was seen as it rose from a mean of 24.1% (95% CI: 22.9–25.3) at first monitoring to 27.2% (95% CI: 26.2–28.1) at last monitoring which revealed a significant increase ( P < 0.01) until the third monitoring and maintained a stable state thereafter. This work finally disclosed that a relatively better efficacy was attained by using Deltamethrin pour-on formulation than targets in controlling tsetse and trypanosomiosis. However, this difference did not prove an apparent significance ( P > 0.05). So it is recommended to continue the current tsetse suppression by using the integrated approach of both techniques under consideration.

Teaching and Learning Guide for: Africa’s Linguistic Diversity

African languages have played an important role in the development of linguistic theory but their role in the fields of historical linguistics and linguistic typology has been less prominent. Africa’s linguistic diversity has been long underestimated given the dominance of the four-family model proposed by Joseph Greenberg. Criticism of this model has long held among specialists in some of Africa’s smaller and lesser-known language families, but has only recently become more widely acknowledged among linguists. Archaeologists, geneticists, and others continue to model African prehistory based on African linguistic classifications, which are outdated and which have failed to withstand scrutiny. This teaching and learning guide suggests a program to train scholars in recognizing and evaluating the standards by which various African language classifications have been made. Africa’s linguistic diversity will be shown to be far greater than what is suggested by the four-family model.

Molecular phylogenetic investigations of the Viviparidae (Gastropoda: Caenogastropoda) in the lakes of the Rift Valley area of Africa

The freshwater gastropod family Viviparidae is nearly cosmopolitan, but absent from South America. On the African continent, two genera are recognized; the widespread Bellamya and the monotypic Neothauma, which is confined to Lake Tanganyika. Most of the African Bellamya species are confined to the major lakes of the Rift Valley area in Africa, i.e. Lake Albert, Lake Malawi, Lake Mweru, and Lake Victoria. The phylogenetic analyses of mitochondrial (COI and 16S) and nuclear (H3, 18S and 28S) DNA inferred three major lake-clades; i.e. Lake Victoria/Kyoga/Albert, Lake Malawi and Lake Mweru/Bangweulu. The endemic B. rubicunda from Lake Albert and B. unicolor from Lake Kyoga were inferred to be part of the Lake Victoria clade. Bellamya capillata as identified by shell characters was polyphyletic in gene trees. The monophyletic Bellamya species radiation in Lake Malawi was most nearly related to the Lake Victoria/Kyoga/Albert-clade. Taxa from the Zambian lakes, Mweru and Bangweulu, were inferred together and placed ancestral to the other lakes. Neothauma tanganyicense was inferred as the sister-group to the Zambian Bellamya. Within the lake-clades the endemic radiations show very low genetic diversities (0–4.1% in COI), suggesting much faster morphological divergence than molecular divergence. Alternatively, Bellamya in Africa constitutes only a few species with several sub-species or eco-phenotypic morphs. The African viviparids were inferred to be the sister-group to a clade comprising Asian species, and the relatively low genetic diversity between the clades (12.6–15.5% in COI) makes a recent Miocene dispersal event from Asia to Africa much more likely than an ancient Gondwana vicarience distribution.

Zoonotic intestinal parasites in Papio anubis (baboon) and Cercopithecus aethiops (vervet) from four localities in Ethiopia

A total of 59 faecal samples from ranging Papio anubis (baboons) and another 41 from Cercopithecus aethiops (vervet) from the Rift Valley areas of Ethiopia were microscopically examined to determine the prevalence and species of major gastro-intestinal parasites of zoonotic importance. Faecal smears were prepared from fresh faecal samples, stained using modified Ziehl–Neelsen method and microscopically examined. About 3 gm of the dropping was also preserved separately in clean and properly labelled containers containing 10% formalin. The specimens were microscopically examined after formalin-ether concentration for ova, larvae, cysts and oocyst of intestinal parasites. The results of microscopic examination of faecal samples of baboons demonstrated the presence of Trichuris sp. (27.1%), Strongyloides sp. (37.3%), Trichostrongylus sp. (8.5%), Oesophagostomum sp. (10.2%), Schistosoma mansoni (20.3%), Entamoeba coli (83.1%), Entamoeba histolytica/ dispar (16.9%), Blastocystis hominis (3.3%), Cyclospora sp. (13.3%) and Cryptosporidium sp. (11.9%). Likewise, the results of microscopic examination of faecal samples of vervets demonstrated the presence of Trichuris sp. (36.6%), Oesophagostomum sp. (4.9%), E. coli (61.0%), E. histolytica/ dispar (24.4%), B. hominis (34.2%), Cyclospora sp. (22.0%) and Cryptosporidium sp. (29.3%). The presence of parasitic protozoa and helminths in baboons and vervets in the study areas is a high risk to human welfare because these non-human primates use the same water sources as humans and range freely in human habitats. An implication of such parasitic infection for the control programme is discussed.

Some biological characteristics that foster the invasion of Prosopis juliflora (Sw.) DC. at Middle Awash Rift Valley Area, north-eastern Ethiopia

A study on some biological features of Prosopis juliflora, a multipurpose leguminous species introduced to Ethiopia, was carried out at Melka-Worer, North-east Ethiopia. The study focused on the number of seeds produced in a pod during the study period, seed dispersal through droppings of animals, soil seed banks, seed germination and stumping height of trees and coppicing ability of P. juliflora. The overall mean number of seeds was 23±4 seeds/pod. The width and length of seeds ranged between 0.8–1.7 and 8–29 cm, respectively. The mean weight of a seed of Prosopis was 0.0275 g±0.001 (S.E.) while there were 36,000–37,000 seeds/kg. The number of seeds recovered from 1 kg of droppings of each animal ranged between 760 (goats) and 2833 (cattle), suggesting that cattle are the major dispersers of seeds of the study species followed by warthogs, camels and goats. There was a highly significant difference in vertical distribution of the seed density of P. juliflora recovered from the soil samples while the horizontal distribution exhibited a great disparity in the density of soil seeds among the sample plots. The total mean soil seed density, in the litter layer and down to 9 cm depth, was 1932 seeds/m 2 (±307 S.E.). Germination of seeds of P. juliflora differed significantly among the various treatments. The highest germination percentage was obtained from seeds that were treated with mechanical scarification (100%) and sulfuric acid for 15–60 min (97–99%). About 37% and 47% of the seeds recovered from droppings of goats and warthogs, respectively, germinated. All stumped trees of P. juliflora produced coppices except those stumped at 10 cm below ground. The overall mean number of coppices at the studied plots was 17.8±0.9 (S.E.) while the overall mean height of coppices, in 6 months after stumping, was 68.4 cm±2.7 (S.E.). The results clearly demonstrated that Prosopis is equipped with a number of biological characteristics that foster its rapid invasion of new areas. These include: (i) production of many, small and hard seeds capable of surviving passage through the digestive system of animals, entering into the soil to form soil seed banks and remaining viable until favorable conditions for germination and seedling establishment appear; (ii) attractive and rewarding pods for animals, containing fleshy and sweet mesocarp embodying the numerous small seeds, which is sought after by both domestic and wild animals, meant for long-distance dispersal; (iii) accumulation of dormant but long-lived viable seed reserves that would serve as sources of regeneration of new Prosopis plants in the event of disturbance that might eliminate the above-ground stands; (iv) production of a mixture of seeds, with a few capable of germinating immediately after dispersal to exploit the favorable conditions that might exist at the time of dispersal, while the majority remain dormant for spreading germination over time and space; and (v) great ability of resprouting and fast coppice growth from stumped/damaged trees, making it a very strong competitive invader combined with its sexual reproduction. Combinations of all these characteristics make Prosopis a powerful noxious invader as can be evidenced from its rampant invasion in the study site and elsewhere in the tropics. Therefore, any effort in the management, control or elimination of Prosopis, which does not take these biological characteristics is bound to fail. The results also revealed that stumping trees at 10 cm below the ground eliminates the chance of resprouting of Prosopis and, hence, might offer a viable option for controlling and even eliminating the plants from areas where they are undesirable. The fact that Prosopis has great ecological and socio-economical importancce, which have not been fully realized in Ethiopia, makes its control through utilization a very attractive, purposive and viable option.

An integrated geophysical analysis of the upper crust of the southern Kenya rift

SUMMARY Previous interpretations of seismic data collected by the Kenya Rift International Seismic Project (KRISP) experiments indicate the presence of crustal thickening within the rift valley area beneath the Kenya dome, an uplift centred on the southern part of the Kenya rift. North of the dome, these interpretations show thinning of the crust and an increase in crustal extension. To the south near the Kenya/Tanzania border, crustal thinning associated with the rift is modest. Our study was aimed at further investigating crustal structure from this dome southwards via a detailed analysis focused on upper crustal structure. We used results from surface geological mapping, drill hole data from water wells and geothermal exploration wells, KRISP 85 seismic data for a profile across the rift, KRISP 85 and 90 seismic data for a profile along the rift axis and KRISP 94 seismic data for a profile crossing southernmost Kenya to constrain gravity modelling and construction of integrated models of crustal structure. Our integrated analysis produced the following results concerning the structure and evolution of the southern Kenya rift: (1) the graben master faults are consistently located along the western margin of the rift valley, and there is no evidencefor half-graben polarity reversals for a distance of about 300 km; (2) there is no axial (north‐south) crustal symmetry with respect to the apex of the Kenya dome, and the crustal thickness may be as much related to pre-rift crustal type and thickness as it is to crustal thickening and modification by magmatic processes; (3) the pre-existing lithospheric contrast between the Archaean and Proterozoic basement terranes played a significant role in the location and structural geometry of the rift; (4) south of latitude 1uS, low velocities and densities observed under the western flank of the rift probably represent reworked Archaean Tanzanian craton; (5) magmatic modification of the upper crust is modest except near the major Quaternary volcanic centres that produce a series of isolated axial gravity highs; (6) the other element of the axial gravity high is an intrarift horst block that extends along the axis of most of the rift valley.

A Note on Risk Factors for Calf Mortality in Large-Scale Dairy Farms in the Tropics : A Case Study on Rift Valley Area of Kenya

A Note on Risk Factors for Calf Mortality in Large-Scale Dairy Farms in the Tropics : A Case Study on Rift Valley Area of Kenya

Starch-hydrolyzing bacteria from Ethiopian soda lakes.

Alkaliphilic bacteria were isolated from soil and water samples obtained from Ethiopian soda lakes in the Rift Valley area--Lake Shala, Lake Abijata, and Lake Arenguadi. Starch-hydrolyzing isolates were selected on the basis of their activity on starch agar plate assay. Sixteen isolates were chosen, characterized, and subjected to 16S rRNA gene sequence analysis. All the isolates were gram positive and catalase- and beta-galactosidase positive. All isolates except one were motile endospore-forming rods and were found to be closely related to the Bacillus cluster, being grouped with Bacillus pseudofirmus, Bacillus cohnii, Bacillus vedderi, and Bacillus agaradhaerens. The one exception had nonmotile coccoid cells and was closely related to Nesterenkonia halobia. The majority of the isolates showed optimal growth at 37 degrees C and tolerated salinity up to 10% (w/v) NaCl. Both extracellular and cell-bound amylase activity was detected among the isolates. The amylase activity of two isolates, related to B. vedderi and B. cohnii, was stimulated by ethylenediaminetetraacetic acid (EDTA) and inhibited in the presence of calcium ions. Pullulanase activity was expressed by isolates grouped with B. vedderi and also most of the isolates clustered with B. cohnii; cyclodextrin glycosyltransferase was expressed by most of the B. agaradhaerens-related strains. Minor levels of alpha-glucosidase activity were detected in all the strains.

Research on nutrient flows and balances in west Africa: state-of-the-art

West Africa is poorly endowed when it comes to soil fertility. Unlike for example the Rift Valley area, west African soils never enjoyed volcanic rejuvenation. At low agricultural intensity, this does not matter as nutrients cycle through the soil and the natural vegetation and losses are few. However, the past decades have shown high population increases, the breakdown of traditional shifting cultivation systems, and a rapid decline of land productivity and soil fertility in particular. The present review paper shows how much is known about the severity of this process and the technologies at hand that can stop it. The information provided shows that on the technical side much is known now, but research output still is poorly integrated into development efforts.

Research on nutrient flows and balances in East and Southern Africa: state-of-the-art

East and Southern Africa have soils that are still relatively fertile, notably those in the Highlands, associated with the Rift valley area. The lower areas are less well-endowed when it comes to soil fertility. At low agricultural intensity, this does not matter as nutrients cycle through the soil and the natural vegetation and losses are few. However, the past decades have shown high population increases, the adoption of continuous cultivation in areas that used to be under traditional shifting cultivation, and a decline of land productivity. The present review paper shows how much we know about the severity of this process and the technologies at hand that can stop it. The information provided shows that on the technical side much is known now, but research output is still poorly integrated into development. Although integrated nutrient management has been shown to be a panacea to combat nutrient depletion, there is a serious crisis of primary data on this subject.