Highlands Of Kenya Research Articles

An integrative description of Macrobiotus paulinae sp. nov. (Tardigrada: Eutardigrada: Macrobiotidae: hufelandi group) from Kenya.

In this paper we describe Macrobiotus paulinae, a new species of the hufelandi group from the Kenyan highlands. In addition to the traditional taxonomic description, aided with morphometrics as well as light and scanning microscopy imaging, we also provide nucleotide sequences of three nuclear (18S rRNA, 28S rRNA, ITS-2) and one mitochondrial (COI) DNA fragment of the new species. The sequences allowed not only a more accurate description but also provided an independent verification of the taxonomic status of Ma. paulinae sp. nov. Such integrative approach requires a considerable number of individuals and eggs, which we have partially subsidised by employing an in vitro culture of the new species. Our analyses revealed that Ma. paulinae sp. nov. is most similar to Macrobiotus madegassus Maucci, 1993 and Macrobiotus modestus Pilato & Lisi, 2009, however it differs from these species, as well as from all other known species of the hufelandi group, by the presence of seven paired dorso-lateral patches of cuticular granulation and the presence of chorionic filaments growing out of terminal discs of egg processes. Macrobiotus paulinae sp. nov. is an example of a species with a miniaturised buccal apparatus (i.e. with reduced peribuccal lamellae and oral cavity armature, and stylet supports inserted on the buccal tube more anteriorly than in typical Ma. hufelandi group species), and it therefore resembles two recently described two-macroplacoided Minibiotus species: Mi. acadianus Meyer & Domingue, 2011 and Mi. julianae Meyer, 2012. The re-examination of the type material for these two species confirmed that they are equipped with peribuccal lamellae and therefore we transfer them to the genus Macrobiotus, specifically to the hufelandi group.

Cuticular hydrocarbons corroborate the distinction between lowland and highland Natal fruit fly (Tephritidae, Ceratitis rosa) populations.

The cuticular hydrocarbons (CHs) and morphology of two Ceratitis rosa Karsch (Diptera: Tephritidae) populations, putatively belonging to two cryptic taxa, were analysed. The chemical profiles were characterised by two-dimensional gas chromatography with mass spectrometric detection. CHs of Ceratitis rosa that originated from the lowlands and highlands of Kenya comprised of n-alkanes, monomethylalkanes, dimethylalkanes and unsaturated hydrocarbons in the range of the carbon backbone from C14 to C37. Hydrocarbons containing C29, C31, C33 and C35 carbon atoms predominated in these two populations. 2-Methyltriacontane was the predominant compound in both populations. Quantitative differences in the distribution of hydrocarbons of different chain lengths, mainly the C22, C32, C33 and C34 compounds of these two populations, were observed despite indistinct qualitative differences in these hydrocarbons. Morphological analyses of male legs confirmed that the flies belong to different morphotypes of Ceratitis rosa previously labelled as R1 and R2 for lowland and highland populations, respectively. A statistical analysis of the CH compositions of the putative R1 and R2 species showed distinct interspecific identities, with several CHs specific for each of the lowland and highland populations. This study supports a hypothesis that the taxon Ceratitis rosa consists of at least two biological species.

Neotypification of Delphinium dasycaulon (Ranunculaceae)

The afromontane species Delphinium dasycaulon Fresenius (1837: 272) is one of the three species of Delphinium Linnaeus (1753: 530) (Ranunculaceae) distributed in tropical Africa. This perennial plant has a disjunct distribution, with isolated populations in East Africa (from Djibouti and Eritrea in the North to Malawi and Zambia in the South) and West Africa (Cameroon and Nigeria) (Milne-Redhead & Turrill 1952). Interestingly, no specimen has ever been collected in the central part of the East African Rift region (Kenya and Uganda), where the two other afromontane species of the genus occur: D. macrocentrum Oliver (1886: 397) which is endemic on Mt. Elgon and in the Kenyan Highlands, and D. leroyi Franchet ex Huth (1895: 474), which has a broader distribution in tropical East Africa ranging from Ethiopia in the North to Tanzania in the South (Milne-Redhead & Turrill 1952).

Arbuscular mycorrhizal fungi with different soil fertility amendment practices in agricultural landscapes of Kenyan highlands

Several interrelated and site-specific agronomic factors ranging from agroecological conditions to systems management practices have been shown to variably affect arbuscular mycorrhizal fungi (AMF) diversity in the soil. Also, there have been various attempts in the past to evaluate the potential of AMF field inoculation but a majority focussed on the use of exotic strains, disregarding the potential of the existing naturally occurring strains. In an attempt to address these problems, our study aimed to develop ‘best-bet practice’ based on soil fertility amendment practice (SFAP) that encourages occurrence and diversity of AMF in the soil. Control treatment (no application) was compared with three (3) SFAP used singly or in combination with AMF or two other soil nutrients enhancing organisms (Bacillus and Trichoderma) which included the following: (1) Mavuno (macro- and micronutrients and secondary nutrients) fertilizer, (2) calcium ammonium nitrate (CAN) plus triple super phosphate (TSP) and (3) cattle manure. Maize (Zea mays L.) and common bean (Phaseoli vulgaris L.) were planted at on-station and on-farm plots for two consecutive cropping seasons with the experiment replicated in two benchmark sites of Embu and Taita-Taveta Districts. Embu site recorded a lower soil pH and also very low phosphorus levels compared to Taita site. The number of AMF spores per kg of soil was very low, ranging from 30 to 100, at Embu in the first season and application of SFAP resulted in no significant difference. However, in the second season, use of Trichoderma + CAN plus TSP was shown to significantly stimulate AMF species in the soil, with a 250 % increase in species density compared to use of Bacillus + Manure. At Taita, after the first cropping season, significant change in spore density was only recorded from AMF applied singly with a 66.1 % increase in spore density compared to Control treatment. In comparison, after the second cropping season, use of AMF applied singly, AMF + CAN plus TSP and AMF + Manure increased spore density by 135.4, 109.6 and 100 % respectively compared to Control treatment. Use of AMF applied singly increased species density in the soil by 100 and 81.1 % compared to CAN plus TSP and Trichoderma treatments respectively after first season at Taita site: while after the second cropping season, application of AMF + CAN plus TSP, AMF + Manure and AMF + Mavuno increased AMF species density in the soil by 60.3, 51.5 and 55.9 % respectively compared to Control treatment. These findings provide evidence that it is possible to increase the number of AMF spores in the soil through inoculation with native species and also possibly stimulate dormant species through other SFAP treatments.

Vegetation response to intensive commercial horticulture and environmental changes within watersheds in central highlands, Kenya, using AVHRR NDVI data

Expansion and heterogeneous clustering of commercial horticulture within the central highlands of Kenya after the mid-1990s impact watersheds and the sustainable resource management. This is distressing since climate conditions for world horticultural regions are projected to change, making such farming extremely difficult and costly to the environment. To understand the scope of impact on vegetation, the study evaluated (1) interannual variability in averaged normalized difference vegetation index (NDVI); (2) trends in average annual NDVI before and after 1990 – the presumed onset of rapid horticulture; and (3) relationship between the average annual NDVI and large-scale commercial farms, population density, and mean annual rainfall in subwatersheds. Time-series analysis of long-term Global Inventory Modeling and Mapping Studies NDVI data were analyzed as indicator of vegetation condition. NDVI trends before 1990s (1982–1989) and after 1990s (1990–2006) were evaluated to determine the slope (sign), and the Spearman’s correlation coefficient (strength). Overall, results show considerable variations in vegetation condition due largely to mixed factors including intensive farming activities, drought, and rainfall variation. Statistical analysis shows significant differences in slopes before 1990 and after 1990 (p < 0.05 and p < 0.1 respectively). Negative (decline) trends were common after 1990, linked to increased commercial horticulture and related anthropogenic disturbances on land cover. There was decline in vegetation over densely populated subwatersheds, though low NDVI values in 1984 and 2000 were the effect of severe droughts. Understanding the linkage between vegetation responses to the effects of human-induced pressure at the subwatershed scale can help natural resource managers approach conservation measures more effectively.

Comparative Population Genomics of African Montane Forest Mammals Support Population Persistence across a Climatic Gradient and Quaternary Climatic Cycles

The Eastern Afromontane biodiversity hotspot (EABH) has the highest concentration of biodiversity in tropical Africa, yet few studies have investigated recent historical diversification processes in EABH lineages. Herein, we analyze restriction-site associated DNA-sequences (RAD-Seq) to study recent historical processes in co-distributed mouse (Hylomyscus) and shrew (Sylvisorex) species complexes, with an aim to better determine how historical paleoenvironmental processes might have contributed to the EABH’s high diversity. We analyzed complete SNP matrices of > 50,000 RAD loci to delineate populations, reconstruct the history of isolation and admixture, and discover geographic patterns of genetic partitioning. These analyses demonstrate that persistently unsuitable habitat may have isolated multiple populations distributed across montane habitat islands in the Itombwe Massif and Albertine Rift to the west as well as Mt Elgon and Kenyan Highlands to the east. We detected low genetic diversity in Kenyan Highland populations of both genera, consistent with smaller historical population sizes in this region. We additionally tested predictions that Albertine Rift populations are older and more persistently isolated compared to the Kenyan Highlands. Phylogenetic analyses support greater historical isolation among Albertine Rift populations of both shrews and mice compared to the Kenyan Highlands and suggest that there are genetically isolated populations from both focal genera in the Itombwe Massif, Democratic Republic of Congo. The Albertine Rift ecoregion has the highest mammalian tropical forest species richness per unit area on earth. Our results clearly support accelerating efforts to conserve this diversity.

Early biting of the Anopheles gambiae s.s. and its challenges to vector control using insecticide treated nets in western Kenya highlands

Long term use of insecticides in malaria vector control has been shown to alter the behavior of vectors. Such behavioral shifts have the potential of undermining the effectiveness of insecticide-based control interventions. The effects of insecticide treated nets (ITNs) use on the composition, biting/feeding and sporozoite rates of Anopheles gambiae s.l. mosquitoes in Musilongo village, Vihiga County of western Kenya highlands were investigated. Adult mosquitoes were collected in selected sleeping spaces inside six randomly selected houses using miniature Centre for Disease Control and Prevention (CDC) light traps. Mosquito sampling in each house was conducted twice every week for 16 consecutive months (May 2010–August 2012). At each sampling a single trap was set in the selected space inside each house such that it collected mosquitoes alternatively from 18:00 to 21:00h and 21:00 to 06:00h every week. All collected mosquitoes were morphologically identified. Female Anopheles mosquitoes were classified according to their physiological status as unfed, fed, partially gravid and gravid, sorted and counted. Members of the A. gambiae complex were identified using a Polymerase chain reaction (PCR) method. Enzyme-linked-immunosorbent assay (ELISA) was used to determine blood meal sources and Plasmodium infection rates in A. gambiae s.l. mosquitoes. Blood meal tests were conducted on DNA extracted from gut contents of blood fed A. gambiae s.l. The head and thorax section of dried samples of A. gambiae s.l. were used in testing for the presence of Plasmodium falciparum (Pf) sporozoites. Overall, 735 adult female Anopheles comprising 708 [96.3%] A. gambiae s.l. and 27 [3.7%] Anopheles funestus mosquitoes were collected. A. gambiae s.l. population collected comprised, 615 [86.9%] unfed and 38 [5.4%] fed adult mosquitoes. The rest were either partially or fully gravid. The proportion of A. gambiae s.l. biting indoors within 18:00–21:00h was 15.8% (103/653) at a rate of 3.2bites per person per hour compared to 84.2% biting from 21:00-06:00h at a rate of 3.8 bites/per/h. An estimated 97.7% A. gambiae ss and 2.3% A. arabiensis constituted the indoor biting A. gambiae s.l. The population of An. gambiae s.l. biting from 18:00 to 21:00h had a Plasmodium faciparum (pf) sporozoite rate of 3.8% compared to 3.5% observed in populations biting within 21:00-06:00h. Human blood constituted 89% of An. gambiae s.l. blood meal sources. The risk of malaria transmission from 21:00 to 06:00h was approximately 5 fold the risk within 18:00–21:00h. Majority of the infective female A. gambiae s.l. adults were biting deep into the night than in the early hours of the night. Humans remain the preferred source of blood meal for A. gambiae s.s. the dominant malaria vector in the highlands. ITNs remain a fundamental control intervention against malaria transmission since female blood seekers were more during bed time than pre-bed time. Advocacy on enhanced net availability, integrity and usage in Kenyan highlands can reduce Pf transmission. Additional complementary interventions are required to control the biting and parasite transmission encountered before bed-time.

Assessment of mosquito larval productivity among different land use types for targeted malaria vector control in the western Kenya highlands.

BackgroundMosquito larval source management (LSM) is likely to be more effective when adequate information such as dominant species, seasonal abundance, type of productive habitat, and land use type are available for targeted sites. LSM has been an effective strategy for reducing malaria morbidity in both urban and rural areas in Africa where sufficient proportions of larval habitats can be targeted. In this study, we conducted longitudinal larval source surveillance in the western Kenya highlands, generating data which can be used to establish cost-effective targeted intervention tools.MethodsOne hundred and twenty-four (124) positive larval habitats were monitored weekly and sampled for mosquito larvae over the 85-week period from 28 July 2009 to 3 March 2011. Two villages in the western Kenya highlands, Mbale and Iguhu, were included in the study.After preliminary sampling, habitats were classified into four types: hoof prints (n = 21; 17 % of total), swamps (n = 32; 26 %), abandoned goldmines (n = 35; 28 %) and drainage ditches (n = 36; 29 %). Positive habitats occurred in two land use types: farmland (66) and pasture (58). No positive larval habitats occurred in shrub land or forest.ResultsA total of 46,846 larvae were sampled, of which 44.1 % (20,907) were from abandoned goldmines, 30.9 % (14,469) from drainage ditches, 22.4 % (10,499) from swamps and 2.1 % (971) from hoof prints. In terms of land use types, 57.2 % (26,799) of the sampled larvae were from pasture and 42.8 % (20,047) were from farmland. Of the specimens identified morphologically, 24,583 (52.5 %) were Anopheles gambiae s.l., 11,901 (25.4 %) were Culex quinquefasciatus, 5628 (12 %) were An. funestus s.l. and 4734 (10.1 %) were other anopheline species (An. coustani, An. squamosus, An. ziemanni or An. implexus). Malaria vector dynamics varied seasonally, with An.gambiae s.s. dominating during wet season and An.arabiensis during dry season. An increased proportion of An. arabiensis was observed compared to previous studies.ConclusionThese results suggest that long-term monitoring of larval habitats can establish effective surveillance systems and tools. Additionally, the results suggest that larval control is most effective in the dry season due to habitat restriction, with abandoned goldmines, drainage ditches and swamps being the best habitats to target. Both farmland and pasture should be targeted for effective larval control. An increased proportion of An. arabiensis in the An. gambiae complex was noticed in this study for the very first time in the western Kenya highlands; hence, further control tools should be in place for effective control of An. arabiensis.

Focal Screening to Identify the Subpatent Parasite Reservoir in an Area of Low and Heterogeneous Transmission in the Kenya Highlands.

Mass screening and treatment currently fails to identify a considerable fraction of low parasite density infections, while mass treatment exposes many uninfected individuals to antimalarial drugs. Here we test a hybrid approach to screen a sentinel population to identify clusters of subpatent infections in the Kenya highlands with low, heterogeneous malaria transmission. Two thousand eighty-two inhabitants were screened for parasitemia by nested polymerase chain reaction (nPCR). Children aged ≤ 15 years and febrile adults were also tested for malaria by rapid diagnostic test (RDT) and served as sentinel members to identify subpatent infections within the household. All parasitemic individuals were assessed for multiplicity of infections by nPCR and gametocyte carriage by nucleic acid sequence-based amplification. Households with RDT-positive individuals in the sentinel population were more likely to have nPCR-positive individuals (odds ratio: 1.71, 95% confidence interval, 1.60-1.84). The sentinel population identified 64.5% (locality range: 31.6%-81.2%) of nPCR-positive households and 77.3% (locality range: 24.2%-91.0%) of nPCR-positive individuals. The sensitivity of the sentinel screening approach was positively associated with transmission intensity (P = .037). In this low endemic area, a focal screening approach with RDTs prior to the high transmission season was able to identify the majority of the subpatent parasite reservoirs.

Effect of Varying Ratios and Rates of Enriched Cattle Manure on Leaf Nitrogen Content, Yield and Quality of Tea (Camellia sinensis)

Tea (Camelia sinensis) a major cash crop in Kenya is normally grown on highly weathered and strongly acidic soils. Non-judicial use of the recommended inorganic compound fertilizer 25:5:5:5s acidifies the soil and pollutes water masses. Integrated soil fertility management, the combined use of organic and inorganic fertilizer is recommended for higher tea yield and soil health. An experiment was carried out in the Eastern Highlands of Kenya to determine the effect of different ratios and rates of enriched cattle manure on leaf nitrogen content, yield and quality of tea. Inorganic compound fertilizer 25:5:5:5s led to the highest N level in the mature leaf. Enriching organic manures with inorganic fertilizers increased the yield but reduced the quality. Tea quality parameters Theaflavins (TF) and Thearubigins decreased with increase in fertilizer rate irrespective of fertilizer type. Caffeine content however increased with increasing rate fertilizer especially in the case of inorganic compound fertilizer 25:5:5:5. Enriching organic manures with inorganic fertilizers increased the N content in the mature leaf and crop yield but reduced the quality. The study showed the beneficial effect of enriched manures in tea production.

Impacts of Benthic Coarse Particulate Organic Matter variations on Macroinvertebrate Density and Diversity in the Njoro River, A Kenyan Highland Stream

ABSTRACT An investigation to assess the relationship between coarse particulate organic matter (CPOM) and macroinvertebrate communities was undertaken in the Njoro River, Kenya during 2010. Significantly lower macroinvertebrate densities and diversities were observed in study sites with low Coarse Particulate Organic Matter (CPOM) content. The Mugo study site had the highest CPOM content and macroinvertebrate density and diversity. The unidentifiable detritus category (i.e. small CPOM fragments) had the highest influence on macroinvertebrate taxa whereas twigs had the least influence. The benthic samples were dominated by detritivores, but no shredders were recorded. Our results suggest that CPOM is an important determinant of the macroinvertebrate assemblages in streams. Given this, we believe that it is important to conserve tropical stream riparian vegetation due to their important role as a source of CPOM in streams.

Low parasitemia in submicroscopic infections significantly impacts malaria diagnostic sensitivity in the highlands of Western Kenya.

Asymptomatic malaria infections represent a major challenge in malaria control and elimination in Africa. They are reservoirs of malaria parasite that can contribute to disease transmission. Therefore, identification and control of asymptomatic infections are important to make malaria elimination feasible. In this study, we investigated the extent and distribution of asymptomatic malaria in Western Kenya and examined how varying parasitemia affects performance of diagnostic methods including microscopy, conventional PCR, and quantitative PCR. In addition, we compared parasite prevalence rates and parasitemia levels with respect to topography and age in order to explore factors that influence malaria infection. Over 11,000 asymptomatic blood samples from children and adolescents up to 18 years old representing broad areas of Western Kenya were included. Quantitative PCR revealed the highest parasite positive rate among all methods and malaria prevalence in western Kenya varied widely from less than 1% to over 50%. A significantly lower parasitemia was detected in highland than in lowland samples and this contrast was also observed primarily among submicroscopic samples. Although we found no correlation between parasitemia level and age, individuals of younger age group (aged <14) showed significantly higher parasite prevalence. In the lowlands, individuals of aged 5–14 showed significantly higher prevalence than those under age 5. Our findings highlight the need for a more sensitive and time-efficient assay for asymptomatic malaria detection particularly in areas of low-transmission. Combining QPCR with microscopy can enhance the capacity of detecting submicroscopic asymptomatic malaria infections.

Potential Predictability of Malaria in Africa Using ECMWF Monthly and Seasonal Climate Forecasts

AbstractIdealized model experiments investigate the advance warning for malaria that may be presently possible using temperature and rainfall predictions from state-of-the-art operational monthly and seasonal weather-prediction systems. The climate forecasts drive a dynamical malaria model for all of Africa, and the predictions are evaluated using reanalysis data. The regions and months for which climate is responsible for significant interannual malaria transmission variability are first identified. In addition to epidemic-prone zones these also include hyperendemic regions subject to high variability during specific months of the year, often associated with the monsoon onset. In many of these areas, temperature anomalies are predictable from 1 to 2 months ahead, and reliable precipitation forecasts are available in eastern and southern Africa 1 month ahead. The inherent lag between the rainy seasons and malaria transmission results in potential predictability in malaria transmission 3–4 months in advance, extending the early warning available from environmental monitoring by 1–2 months, although the realizable forecast skill will be less than this because of an imperfect malaria model. A preliminary examination of the forecasts for the highlands of Uganda and Kenya shows that the system is able to predict the years during the last two decades in which documented highland outbreaks occurred, in particular the major event of 1998, but that the timing of outbreaks was often imprecise and inconsistent across lead times. In addition to country-level evaluation with district health data, issues that need addressing to integrate such a climate-based prediction system into health-decision processes are briefly discussed.

Economic Evaluation of Foliar NPK Fertilizer on Tea Yields in Kenya

Economic evaluation analysis of foliar (NPK) fertilizer on tea yields was investigated on three varieties of tea grown in the Kenyan Highlands. Foliar fertilizers trial was setup on three sites, Meru, Kirinyaga and Kericho, comprising of 36 plots per site. Two foliar fertilizer types, Foliar Fertilizer 1 (FF1) and Foliar Fertilizer 2 (FF2), a positive control of Soil Fertilizer (SF) and a blank (FF0) were used to standardize the method. Yield analysis in Meru site showed significant increase (HSD=4.9, p?0.05) after FF1 full rate application. SF had significant yield increases for all its rates from zero rate (HSD= 49, 44, 19, p?0.05) for half, full and double rates respectively. FF2 had no yield increase after its application. The economic rates were determined to be full rate for FF1 and SF and half rate for FF2 in Kericho site; half rate for all fertilizer types Kirinyaga site; double rate for FF2 and SF and full rate for FF1 in Meru site. The profitable rates were: double rate for SF across all sites and for FF1 and FF2 in Meru site; full rate for FF1 and half rate for FF2 in Kericho and Kirinyaga sites respectively.

Active case surveillance, passive case surveillance and asymptomatic malaria parasite screening illustrate different age distribution, spatial clustering and seasonality in western Kenya.

BackgroundEpidemiological characteristics of clinical malaria may differ from asymptomatic infections, thus both cross-sectional parasite screening and longitudinal clinical case surveillance are necessary for malaria transmission monitoring and control.MethodsIn order to monitor malaria transmission, surveillance of clinical malaria from two years of active case surveillance in three cohorts of 6,750 individuals, asymptomatic parasitaemia cases of 5,300 individuals and clinical cases in three study areas were carried out in the western Kenyan highlands in 2009 and 2010. Age distribution, seasonality and spatial clustering were analysed.ResultsThe results revealed a significant difference in the age distribution of clinical cases between passive and active case surveillance, and between clinical case rate and asymptomatic parasite rate. The number of reported cases from health facilities significantly underestimated clinical malaria incidence. The increase in asymptomatic parasite prevalence from low to high transmission seasons was significantly higher for infants (<two years) and adults (≥15 years) (500% increase) than that for children (two to 14 years, 65%), but the increase in clinical incidence rates was significantly higher for children (700%) than that for adults (300%). Hotspot of asymptomatic infections remained unchanged over time, whereas new clusters of clinical malaria cases emerged in the uphill areas during the peak season.ConclusionsDifferent surveillance methods revealed different characteristics of malaria infections. The new transmission hotspots identified during the peak season with only active case surveillance is an important observation with clear implications in the context of malaria elimination. Both mass parasite screening and active case surveillance are essential for malaria transmission monitoring and control.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0551-4) contains supplementary material, which is available to authorized users.

Factors Affecting Technical Efficiency of Passion Fruit Producers in the Kenya Highlands

The importance of passion fruit in livelihood improvement has been a key driver among rural households production participation in Kenya. The frequency of harvest and income flows compared to other farm enterprises in the fruit growing regions has been high. However, the productivity of the fruit remains low; an indicator of low technical efficiency. Using a semi-structured questionnaire, cross sectional data from 123 randomly selected passion fruit producers was used in the study to assess factors that contribute to purple passion fruit production efficiency in the Kenyan highlands. The study established a mean technical efficiency of 58.66%. Orchard age, credit amount used, non-passion fruit income and County variables significantly and positively influenced TE at 5% level. The level of education, extension advice use frequency and market access positively and significantly influenced technical efficiency at 10% level. In order to amend the current efficiency status upwards, passion fruit producers and support institutions should incorporate innovative measures towards resource use efficiency for increased productivity.

Lime-Aluminium- Phosphorus Interactions in Acid Soils of the Kenya Highlands

Liming and phosphorus (P) applications are common practices for improving crop production in acid soils of the tropics. Although considerable work has been done to establish liming rates for acid soils in many parts of the world, information on the role of the lime-Al-P interactions on P fertility management is minimal. A green house pot experiment was conducted at Waruhiu Farmers Training Centre, Githunguri to evaluate the lime-Al-P interactions in acid soils of the Kenya highlands. Extremely acidic (pH 4.48) and strongly acidic (pH 4.59) soils were used for the study. Four lime (CaO) rates and phosphorus (Ca (H2PO4)2 rates were used. The liming rates were: 0, 2.2, 5.2 and 7.4 tonnes ha -1 for extremely acidic soil and 0, 1.4, 3.2, and 4.5 tonnes ha -1 for the strongly acidic soil. Phosphorus applications rates were: 0, 0.15, 0.30 and 0.59 g P kg soil for the extremely acidic soil and 0, 0.13, 0.26, and 0.51 g P kg -1 for the strongly acidic soils. The experiments were a 4 factorial laid in a randomized complete block design (RCBD) and replicated Original Research Article Muindi et al.; AJEA, 9(4): 1-10, 2015; Article no.AJEA.20220 2 three times. Data collected included: soil chemical properties and P adsorption. The soils had high exchangeable Al (>2 cmol Al kg -1 ), Al saturation of (>20% Al) and low P. Lime-Al-P interaction significantly (P≤0.05) increased soil pH, extractable P, reduced exchangeable Al, Al saturation, P adsorption and standard phosphorus requirements (SPR). Use of 7.4 tonnes ha lime in extremely acidic soils and 4.5 tonnes ha -1 lime in strongly acidic soils significantly reduced exchangeable Al and SPR by >70%. Lime positively correlated with soil pH, extractable P, and Langmuir maximal adsorption constant and negatively correlated with SPR and exchangeable Al. It was therefore concluded that lime and P positively interact to reduce Al and P adsorption rates in acid soils in the Kenya highlands.

Effects of Lime-Aluminium-Phosphate Interactions on Maize Growth and Yields in Acid Soils of the Kenya Highlands

Soil acidity and phosphorus (P) deficiency are some of the major causes of low maize yields in Kenya. Although considerable work has been done to establish liming rates for acid soils in many parts of the world, information on the effects of the lime-Al-P interactions on maize growth and yield is limiting. A green house pot experiment was conducted at Waruhiu Farmers Training Centre, Githunguri to evaluate the effects of lime-Al-P interactions on maize growth and yield in acid soils of the Kenya highlands. Extremely acidic (pH 4.48) and strongly acidic (pH 4.59) soils were used for the study. Four lime (CaO) rates and phosphorus (Ca (H2PO4)2 rates were used. The liming rates were: 0, 2.2, 5.2 and 7.4 tonnes ha-1 for extremely acidic soil and 0, 1.4, 3.2, and 4.5 tonnes ha-1 for the strongly acidic soil. Phosphorus applications rates were: 0, 0.15, 0.30 and 0.59 mg P kg-1 soil for the extremely acidic soil and 0, 0.13, 0.26, and 0.51 mg P kg-1 for strongly acidic soil. The experiments were a 42 factorial laid down in a Randomized Complete Block Design (RCBD) and replicated three times. Data collected included: plant height, number of leaves, P-uptake and maize dry matter yield. Lime-Al-P interaction significantly (P≤ 0.05) increased P concentrations in maize tissues, maize height, dry matter yields. Use of 7.4 tonnes ha-1 in extremely acidic soils and 4.5 tonnes ha-1 in strongly acidic soils significantly (P≤ 0.05) increased maize height compared to lower lime rates. Phosphorus uptake and dry matter yields did not however, vary when 7.4 tonnes ha-1 lime was combined with either 0.59 mg P kg-1 or 0.3 mg P kg-1 in extremely acidic soils, and 4.5 tonnes ha-1 was combined with either 0.51 mg P kg-1 or 0.26 mg P kg-1 in strongly acidic soils. It was, therefore, concluded that lime and P positively interact to reduce Aluminium toxicity in the soils and improve maize growth, P uptake and yields in acid soils in the Kenya highlands. However, further research is required to evaluate long term effects of the interactions on crop yields, uptake of plant nutrients under field conditions.

Current Mathematical Models for Analyzing Anti-Malarial Antibody Data with an Eye to Malaria Elimination and Eradication

The last decade has witnessed a steady reduction of the malaria burden worldwide. With various countries targeting disease elimination in the near future, the popular parasite infection or entomological inoculation rates are becoming less and less informative of the underlying malaria burden due to a reduced number of infected individuals or mosquitoes at the time of sampling. To overcome such problem, alternative measures based on antibodies against specific malaria antigens have gained recent interest in malaria epidemiology due to the possibility of estimating past disease exposure in absence of infected individuals. This paper aims then to review current mathematical models and corresponding statistical approaches used in antibody data analysis. The application of these models is illustrated with three data sets from Equatorial Guinea, Brazilian Amazonia region, and western Kenyan highlands. A brief discussion is also carried out on the future challenges of using these models in the context of malaria elimination.

The Effects of Maize Planting Density and Weeding Regimes on Light and Water Use

Light and water are among essential resources required for production of photosynthates in plants. A study on the effects of weeding regimes and maize planting density on light and water use was conducted during the 2001/2 short and 2002 long rain seasons at Muguga in - the central highlands of Kenya. Weeding regimes were: weed free (W1), weedy (W2), herbicide (W3) and hand weeding twice (W4). Maize planting densities were 9 (D1) and 18 plants m -2 (D2) intercropped with Phaseolus vulgaris (beans). The experiment was laid as randomized complete block design replicated four times and repeated twice. All plots were thinned to 4 plants m -2 at tasseling stage (96 DAE) and thinnings quantified as forage. Soil moisture content (SMC), photosynthetically active radiation (PAR) interception, evapo-transpiration (ET crop), water use efficiency (WUE), and harvest index (HI), were determined. Percent PAR was higher in D2 than in D1 before thinning but higher in D1 than in D2 after thinning in both seasons. PAR interception was highest in W2 but similar in W1, W3 and W4 in both seasons. SMC was significantly lower in W2 but similar in W1, W3 and W4. D2 had lower SMC than D1 in season two. Weeding regime significantly influenced ET crop, while planting density and weeding regime significantly influenced WUE and HI. D2 maximizes water and light use for forage production but results to increased intra-specific plant competition for water and light severely before thinning (96 DAE) that reduce grain yield in dual purpose maize, relative to D1.