Highlands Of Kenya Research Articles

Influence of Planetary Boundary Layer (PBL) Parameterizations in the Weather Research and Forecasting (WRF) Model on the Retrieval of Surface Meteorological Variables over the Kenyan Highlands

Regional climate models (RCMs) are crucial for climate studies and may be an alternative source of meteorological data in data-scarce regions. However, the effectiveness of the numerical weather prediction (NWP) models applied in RCMs is hampered by the parameterization of unresolved physical processes in the model. A major source of uncertainties in NWP models is the parameterization of the planetary boundary layer (PBL). This study evaluates the influence of seven PBL parameterization schemes in the Weather Research and Forecasting (WRF) model on the retrieval of four meteorological variables over the Kenyan highlands. The seven PBL schemes consist of four local schemes: the Mellor-Yamada-Janjic (MYJ), Mellor-Yamada-Nakanishi-Niino (MYNN), Bougeault-Lacarrere (BouLac), quasinormal scale elimination (QNSE), and three nonlocal schemes: asymmetrical convective model version 2 (ACM2), Shin and Hong (SHIN) and Yonsei University (YSU). The forcing data for the WRF model was obtained from the fifth generation of the European ReAnalysis (ERA5) dataset. The results were validated against observational data from the Trans-African Hydro-Meteorological Observatory (TAHMO). WRF was found to simulate surface meteorological variables with spatial details coherent with the complex topography within the Kenyan highlands, irrespective of the PBL scheme. A comparison between 2-meter temperature (T2) derived from the YSU scheme and T2 from the land component of ERA5 (ERA5-Land) indicates that surface meteorological variables derived from WRF are better suited for applications over the Kenyan highlands. The choice of the PBL scheme was found to primarily influence the simulation of the 10-meter wind speed (WS10) and rainfall as opposed to T2 and the 2-meter relative humidity (RH2). The insensitivity of the 2-meter variables to the choice of the PBL scheme is attributed to the influence of the surface layer parameterization near the surface. Results from the rainfall simulation indicate that the YSU scheme provides a more realistic depiction of PBL dynamics within the study area. Hence, the YSU scheme is best suited for simulating surface meteorological variables over the Kenyan highlands.

A threshold-free approach with age-dependency for estimating malaria seroprevalence

BackgroundIn malaria serology analysis, the standard approach to obtain seroprevalence, i.e the proportion of seropositive individuals in a population, is based on a threshold which is used to classify individuals as seropositive or seronegative. The choice of this threshold is often arbitrary and is based on methods that ignore the age-dependency of the antibody distribution.MethodsUsing cross-sectional antibody data from the Western Kenyan Highlands, this paper introduces a novel approach that has three main advantages over the current threshold-based approach: it avoids the use of thresholds; it accounts for the age dependency of malaria antibodies; and it allows us to propagate the uncertainty from the classification of individuals into seropositive and seronegative when estimating seroprevalence. The reversible catalytic model is used as an example for illustrating how to propagate this uncertainty into the parameter estimates of the model.ResultsThis paper finds that accounting for age-dependency leads to a better fit to the data than the standard approach which uses a single threshold across all ages. Additionally, the paper also finds that the proposed threshold-free approach is more robust against the selection of different age-groups when estimating seroprevalence.ConclusionThe novel threshold-free approach presented in this paper provides a statistically principled and more objective approach to estimating malaria seroprevalence. The introduced statistical framework also provides a means to compare results across studies which may use different age ranges for the estimation of seroprevalence.

Analysis of Kenya’s Atmospheric Moisture Sources and Sinks

Abstract Achievement of the United Nations Sustainable Development Goals (SDGs) is contingent on understanding the potential interactions among human and natural systems. In Kenya, the goal of conserving and expanding forest cover to achieve SDG 15 “Life on Land” may be related to other SDGs because it plays a role in regulating some aspects of Kenyan precipitation. We present a 40-yr analysis of the sources of precipitation in Kenya and the fate of the evaporation that arises from within Kenya. Using MERRA-2 climate reanalysis and the Water Accounting Model 2 layers, we examine the annual and seasonal changes in moisture sources and sinks. We find that most of Kenya’s precipitation originates as oceanic evaporation but that 10% of its precipitation originates as evaporation within Kenya. This internal recycling is concentrated in the mountainous and forested Kenyan highlands, with some locations recycling more than 15% of evaporation to Kenyan precipitation. We also find that 75% of Kenyan evaporation falls as precipitation elsewhere over land, including 10% in Kenya, 25% in the Democratic Republic of the Congo, and around 5% falling in Tanzania and Uganda. Further, we find a positive relationship between increasing rates of moisture recycling and fractional forest cover within Kenya. By beginning to understand both the seasonal and biophysical interactions taking place, we may begin to understand the types of leverage points that exist for integrated atmospheric water cycle management. These findings have broader implications for disentangling environmental management and conservation and have relevance for large-scale discussions about sustainable development.

Larval flushing alters malaria endemicity patterns in regions with similar habitat abundance

A model of Anopheles gambiae populations dynamics coupled with Plasmodium falciparum transmission dynamics is extended to include mechanisms of larval flushing which are known to occur. Flushing dynamics are modeled using a simulation that incorporates seasonal, autocorrelated, and random components based on 30 years of rainfall data for the Kakamega District of the western Kenya highlands. The model demonstrates that flushing phenomena can account for differences between regions with the same annual larval habitat pattern, changing the World Health Organization endemicity classification from either hyperendemic or holoendemic to hypoendemic disease patterns. Mesoendemic patterns of infection occur at the boundary of the holoendemic to hypoendemic transition. For some levels of flushing the entomological inoculation rate drops to an insignificant amount and disease disappears, while the annual indoor resting density remains well above zero. In these scenarios, the disease is hypoendemic, yet the model shows that outbreaks can occur when disease is introduced at particular time points.

Uptake of integrated soil fertility management technologies in heterogeneous smallholder farms in sub-humid tropics

Low soil fertility strongly affects environmental sustainability and Sustainable Development Goals (SDGs) worldwide. Integrated soil fertility management (ISFM) is a potential remedy for declining soil fertility. We addressed determinants of ISFM technologies and identified the sources of soil fertility information using cluster and ordered probit analyses in two counties of the Central Highlands of Kenya. In Tharaka-Nithi county, the uptake of ISFMclass1 (Animal manure +anti-erosion + inorganic fertilizer +crop rotation + legume intercrop), positively correlated with membership to cooperatives, religious groups, SACCOs, and ownership of wheelbarrow but negatively associated with gender, level of education, low farming experience and increased off-farm income. The uptake of ISFMclass2 (Compost +Tithonia diversifolia +minimum tillage +agroforestry + crop residue retention) significantly correlated with religious group membership and ownership of radio. The uptake of ISFMclass3 (sole green manure) positively correlated with a household with an adult offering outside labor but negatively associated with distance to agro-dealers. In Murang'a, ISFMclass2 (Animal manure +inorganic fertilizer +anti-erosion + legume intercrop) is positively associated with farmers' age, membership to cooperatives, television ownership, and access to handhoe and distance to tarmacked roads. Access to drought power, distance to tarmacked road, and buyers positively correlated with ISFMclass1 (Agroforestry +green manure +minimum tillage +crop residue retention + crop rotation). There was a positive correlation between access to drought power and uptake of ISFMclass3 that combined compost and Tithonia diversifolia. We conclude that the region's uptake of unique ISFM combinations is influenced by socioeconomic, bio-physical determinants, and farmers' perception of soil fertility status. We thus recommend that increased upscaling of uptake of unique combinations of ISFM technologies require robust collaboration among various local development stakeholders to address the prohibitive factors while strengthening enabling ones.

Determinants of farmers’ knowledge on soil and water conservation technologies in dry zones of Central Highlands, Kenya


 
 
 This study ascertained the socioeconomic determinants of farmers’ knowledge on soil and water conservation technologies in Dry zones of Central Highlands of Kenya involving 400 farming households. Results showed that the majority of the farmers had inadequate knowledge on the use and benefits of soil and water conservation technologies. The socio-economic factors that influence knowledge levels of the knowledge-intensive technologies were education level, gender, perceptions on soil fertility, farmer group membership, access to training, farm size, access to credit, number of livestock kept and access to farm equipment. This implies that there is the need to come up with an all-inclusive policy that can be employed in improving farmer’s level of knowledge through the use of more innovative methods of information dissemination. This can be done by strengthening the existing farmer groups, enhancing extension services, and also formulating gender-friendly policies.
 
 

Forage diversity and fertiliser adoption in Napier grass production among smallholder dairy farmers in Kenya

Feed scarcity is one of the major challenges affecting smallholder dairy production in Kenya. Forages are the foundation of livestock nutritional requirements; forage diversification and fertiliser are intensification options that can increase productivity. A sample of 316 and 313 smallholder farmers were surveyed in eastern midlands and central highlands of Kenya, respectively, to establish the types of forages cultivated and the factors that influence fertiliser adoption in Napier grass ( Cenchrus purpureus Schumach.) production. Independent t -tests were applied to compare the effect of continuous variables on social economic and institutional characteristics between adopters and non-adopters on fertiliser and area allocated to different forages. Chi-square tests were used to compare nominal variables for the proportion of farmers growing different forages, criteria they consider in selection of suitable forages, and social economic and institutional characteristics of adopters and non-adopters of fertiliser. Binary logistic regression was used to determine factors that influence fertiliser adoption. The study revealed that forage diversification was low with Napier grass being the only forage cultivated by most farmers (~90%). Urochloa ( Urochloa spp ), Rhodes grass ( Chloris gayana Kunth.) and Guinea grass ( Megathyrsus maximus Jaq.) were cultivated by less than 11% of farmers. The fertiliser adoption rate was high (77%) and was influenced by gender of household head, membership of groups, access to extension services and labour. Future research should focus on promoting of forage diversification and investigate quantity and fertiliser application regimes in order to enable development of appropriate advisory services.

Response of potato to fertilizers applied on different soil types in Kenyan Highlands

AbstractDeclining soil fertility in Nitisols and Planosols, which dominate major potato (Solanum tuberosum L.) growing areas of Kenya, is a hindrance to sustainable production of the crop. A study was conducted in Nyandarua County, Kenya, to assess performance of potato and the agronomic efficiencies of three fertilizer types: diammonium phosphate (DAP) (N–P2O5–K2O: 18–46–0), Mavuno Peas, Beans and Root Vegetables (MRV) (15N:8 P2O5:15 K2O plus S, Ca, Mg, Fe, Cu, Zn, B, Mn, Mo), and new Mavuno blend (18N:24 P2O5:10 K2O plus 5S, 0.04B, 0.02 Zn). The experiments were established on Nitisol and Planosol soil types in farmers’ fields. Two potato varieties were evaluated in a split plot layout design. Diammonium phosphate had the highest and significant influence on potato haulm, giving 16.5 and 15.5 g plant–1 on variety Sherekea growing on Nitisol and Planosol, respectively. Fertilizer type significantly influenced potato yield, which was recorded at 29.2 t ha–1 with DAP and 26.6 t ha–1 with new Mavuno on variety Sherekea grown on Nitisol. A significant positive interaction (P < .05) of fertilizer type and soil type was observed. Fertilizers also gave significant effect on agronomic efficiency of N, P, and K. Potato yield and agronomic nutrient use efficiency were dependent on the fertilizer types used as well as soil type. Diammonium phosphate and new Mavuno were the best fertilizer types.

Lime, manure and Inorganic Fertilizer Effects on Soil Chemical Properties, Maize Yield and Profitability in Acidic Soils in Central Highlands of Kenya

In Sub-Saharan Africa (SSA), acidic soil covers 29% of the total area. About 13% of the Kenyan total land area has acidic soils, widely distributed in croplands of the central and western Kenyan regions. The high soil acidity, coupled with soil nutrient depletion, negatively affects crop productivity in the region. We conducted an on-farm experiment to determine the effect of lime, manure, and phosphatic fertilizer application, either solely or combined, on soil chemical properties, maize yield, and profitability in acidic soils of Tharaka Nithi County, Kenya. The treatments were different rates of manure, lime, and P fertilizer. The experiment was designed as a randomized complete block design replicated ten times in farmer’s fields. Soil sampling was done at a depth of 0-20 cm prior to the start of the experiment, after crop harvest of SR2016 and LR2017 seasons. The samples were analyzed in the laboratory following standard methods. Results showed that lime significantly increased soil pH by 10.6% during the SR2016 and by 17.7% during the LR2017. Similarly, treatments with lime reduced exchangeable acidity and increased soil available P. Treatments with inorganic fertilizers had significantly higher maize grain yield in comparison with treatments with the sole application of lime, manure, and lime + manure. Lime + fertilizer + manure treatment gave the highest average maize grain yield (5.1 t ha−1), while control gave the lowest (1.5 t ha−1) during the LR2017 season. Economic returns were low due to the prevailing low rainfall experienced during the study period during the SR2016 season. Lime combined with inorganic fertilizer treatment recorded the highest returns (128.75 USD ha-1) followed by sole inorganic fertilizer (105.94 USD ha-1) during the LR2017 season. The study recommends a combination of both lime and inorganic fertilizer for enhanced maize production and profitability in Tharaka-Nithi County, Kenya.

Tillage system and integrated soil fertility inputs improve smallholder farmers’ soil fertility and maize productivity in the Central Highlands of Kenya

We designed and implemented an on-farm trial in Meru South and Gatanga sub-counties to understand the effects of integrated soil fertility management (ISFM) technologies on soil nitrogen (N), phosphorus (P), potassium (K), and maize productivity. The technologies included combinations of mineral fertiliser and maize stover (CrMf); crop residue, Tithonia diversifolia and rock phosphate (CrTiP); crop residue, Tithonia diversifolia and goat manure (CrTiMan); crop residue, inorganic fertiliser and goat manure (CrMfMan); crop residue, goat manure and Dolichos lablab (CrManLeg), and sole inorganic fertiliser (Mf) executed under conventional (ConC) and minimum (MinTill) tillage methods. We interviewed the farmers who participated in implementing the trials at the end of the study to understand the likelihood to uptake the technologies. We observed that the technologies increased soil N, P, K, and maize productivity compared to ConC (the control). There was a high likelihood of uptake of high-performing ISFM technologies. We recommend CrTiP for the two sub-counties for the short-term. However, a long-term experiment is needed to evaluate performances of CrTiMan, CrTiP, CrMfMan, and CrManLeg under the two tillage methods for site-specific recommendations taking into consideration rainfall variations.

Coupled Model Intercomparison Project phase 6 evaluation and projection of East African precipitation

AbstractThis study evaluates the performance of 43 Coupled Model Intercomparison Project phase 6 (CMIP6) models in reproducing annual cycle, climatology, and trend of observed precipitation over East Africa during 1950–2014. The results show that the CMIP6 models display good performance in simulating the annual cycle (i.e., bimodal pattern) of East African precipitation; however, most models and the multimodel ensemble mean (ENSEM) underestimate the March to May (MAM) precipitation while overestimating the October to December (OND) precipitation. Spatially, most models seem to perform relatively better in simulating OND precipitation compared to MAM season, despite wet (dry) biases over most parts of East Africa with the wettest (driest) biases over the Lake Victoria basin (southeastern Tanzania) during OND (MAM). The metrics have shown that nine models (i.e., MPI‐ESM1‐2‐HR, AWI‐CM‐1‐MR, MPI‐ESM1‐2‐LR, IPSL‐CM6A‐LR, CAS‐ESM2‐0, BCC‐CSM2‐MR, NorESM2‐LM, CESM2‐WACCM, and CMCC‐CM2‐SR5) outperform the other individual models during both OND and MAM. Compared with individual models, the ENSEM better agrees with the observation. Besides, the ENSEM and most models can reproduce the increasing trend in OND precipitation as observed over East Africa. However, for the secular change of MAM precipitation, given that half of the models show increasing trends, the ENSEM simulation produces an inconsistent trend with the observation. The ensemble of the above nine models with better performance projects an increase of precipitation averaged over East Africa in both MAM and OND by the end of the 21st century, with larger changes under SSP5‐8.5 than under SSP2‐4.5. Spatially, the largest percentage increase in MAM precipitation is projected to occur in central Tanzania and northwestern Kenya, while southeastern Tanzania shows the greatest percentage decrease. The projected percentage increases in OND precipitation are larger in the northeastern highlands of Tanzania and northwest Kenya.

Economic evaluation and socioeconomic drivers influencing farmers’ perceptions on benefits of using organic inputs technologies in Upper Eastern Kenya

Declining soil fertility in Sub-Saharan Africa (SSA) is a significant constraint towards increasing agricultural productivity. Soil fertility decline coupled with rapid population growth and low use of organic soil fertility technologies has threatened the population's economic status that lives in the rural area and relies on rain-fed agriculture. We conducted a cross-sectional household survey in the Central Highlands of Kenya (Gatanga and Meru South sub-counties) to determine farmers’ perception of the benefits of using organic resources technologies, socioeconomic drivers influencing their perceptions, and financial returns from the technologies. The selected technologies were; sole animal manure and a combination of animal manure with inorganic fertilizer. We based the benefits of using the selected soil fertility management technologies on four variables; potential to improve soil fertility, crop yields, profitability, and labor requirement. The majority of the farmers strongly agreed that using the selected technologies improved soil fertility, crop yields and were profitable. On the contrary, they agreed it was labor-intensive. Gender of the household head, household size, Tropical Livestock Unit (TLU), access to external labor, access to credit, total land cultivated, age, and years of farming experience were the socioeconomic drivers that significantly influenced farmers’ perception of the use of sole animal manure and animal manure combined with inorganic fertilizer. Results showed that animal manure had the highest financial returns of US$ 440.74 in Gatanga, while in Meru South, animal manure combined with inorganic fertilizer had the highest returns of US$ 456.25. The study highlights that the use of sole animal manure and animal manure combined with inorganic fertilizer is perceived positively by the smallholder farmers and has better financial returns than sole inorganic fertilizer. Thus, the use of selected organic resource technologies should be encouraged by creating more awareness through farmers’ training programs.

Determinants of farmers' perceptions of climate variability, mitigation, and adaptation strategies in the central highlands of Kenya

Climate variability in recent decades has intensified in the SSA region, which makes it imperative to explore adequate adaptation and mitigation strategies to offset its current and future adverse impacts. Farmers' perception of climate variability can significantly influence their coping, mitigation, and adaptation potential. This study assessed farmers' perceptions of indicators and consequences of climate variability and explored factors influencing their perception of climate variability and adoption of climate coping strategies. A cross-sectional survey design was used to sample 300 farmers in the Central Highlands of Kenya. Binary logistic regression models were used to determine factors that influenced the perception of climate variability, adaptation, and mitigation strategies based on three predictor sets, including socioeconomic, institutional, and environmental dimensions. Three climate adaptation and mitigation strategy groups adopted by farmers, including crop adjustment, nutrient management, and soil and water management practices, were subjected to binary logistic regression models. The core determinants of farmers' perception of climate variability included tropical livestock unit (TLU, p = 0.008), access to agricultural training (p = 0.022), change in agricultural production (p = 0.005), change in forest cover (p = 0.014), soil fertility status (p = 0.039), and perceptions of soil erosion (p = 0.001). Most farmers reported changes in all climatic indicators during the decade preceding the survey, including increasing temperature (80%), reduced precipitation (78%), and declining season lengths (76%). There were significant relationships between climate variability perceptions and coping strategies, with the soil and water management set showing stronger links with climate perceptions compared to crop adjustment and nutrient management strategies. Critical mitigation and adaptation strategies to cope with climate variability implemented by farmers included the use of fertilizer and manure in combination (71%), terracing (66%), and crop rotation (60%). Farmers' perceptions significantly determined the adoption of climate-smart agriculture technologies, and environmental determinants strongly influenced climate variability coping strategies. Therefore, while formulating climate sustainability-related policies, farmers' perceptions should be considered.

Parameterization, calibration and validation of the DNDC model for carbon dioxide, nitrous oxide and maize crop performance estimation in East Africa

Dynamic biogeochemical models are crucial tools for simulating the complex interaction between soils, climate and plants; thus the need for improving understanding of nutrient cycling and reduction of greenhouse gases (GHG) from the environment. This study aimed to calibrate and validate the DeNitrification-DeComposition (DNDC) model for soil moisture, temperature, respiration, nitrous oxide and maize crop growth simulation in drier sub-humid parts of the central highlands of Kenya. We measured soil GHG fluxes from a maize field under four different soil fertility management practices for one year using static chambers and gas chromatography. Using experimental data collected from four management practices during GHG sampling period, we parameterized the DNDC model. The results indicate that the DNDC model simulates daily and annual soil moisture, soil temperature, soil respiration (CO2), nitrous oxide (N2O), N2O yield-scaled emissions (YSE), N2O emission factors (EFs) and maize crop growth with a high degree of fitness. However, the DNDC simulations slightly underestimated soil temperature (2–6%), crop growth (2–45%) and N2O emissions (5–23%). The simulation overestimated soil moisture (9–17%) and CO2 emissions (3–10%). It however, perfectly simulated YSE and EFs. Compared to the observed/measured annual GHG trends, the simulation results were relatively good, with an almost perfect fitting of emission peaks during soil rewetting at the onset of rains, coinciding with soil fertilisation. These findings provide reliable information in selecting best farm management practice, which simultaneously improves agricultural productivity and reduces GHG emissions, thus permitting climate-smart agriculture. The good DNDC simulated YSE and EFs values (Tier III) provide cheaper and reliable ways of filling the huge GHG data gap, reducing uncertainties in national GHG inventories and result to efficient targeting of mitigation measures in sub-Saharan Africa.

432 Centuries of Recorded Science and Technology in Black Africa

Abstract During the 1970s and 1980s, American and European investigators discovered evidence of such African scientific achievements as the following: (1) the domestication of assorted plants in The Egyptian Nile Valley ca. 18000 BP; and domesticated cattle in the Kenyan Highlands, ca, 15000 BP. These were achieved thousands of years before plant and animal domestication in South west Asia, the hitherto presumed place where domestication first occurred; and (2) the making of Carbon steel in Tanzania, in the 1st c. BC, using techniques the discoverers called “semi-conductor technology – the growing of crystals”. These and other records of advanced scientific achievements, and at such dates, should prompt a profound revision of our understanding of the scientific knowledge developed by pre-20th century Africans before Europeans conquered and colonized and shattered African societies. They should also prompt a revision of the history of science in the world. In this article I shall present 13 exhibits drawing from the history of spectacular African achievements in science and technology. They range in time from ca. 43200 BC to 1952 AD. And they cover, geographically, Lesotho in Southern Africa; to Kenya, Uganda and Tanzania in East Africa; to the Democratic Republic of the Congo in Central Africa; to Egypt in North Africa; and to Liberia and Nigeria in West Africa.

Tillage, Mulching and Nitrogen Fertilization Differentially Affects Soil Microbial Biomass, Microbial Populations and Bacterial Diversity in a Maize Cropping System

Determination of biologically active components of the soil organic matter, such as soil microbial biomass carbon (C) and nitrogen (N) can be used as indicators for variations in soil productivity due to changes in soil management. Soil agronomic management practices bring about changes in the physical and chemical properties of the soil, resulting in variations in soil microbial biomass and microbial diversity. The effects of tillage, mulch and inorganic fertilizers on soil microbial biomass C and N, microbial populations and bacterial diversity were determined from the treatment combinations which had been applied for 5 years in Central Kenyan Highlands. The test crop used was maize (Zea mays L.). The study involved conventional and minimum tillage systems, mulching and inorganic fertilizers (120 kg N/ha). Tillage (P < 0.001), mulch (P < 0.001), and fertilizer (P = 0.009) significantly affected soil microbial biomass C and N whereby minimum tillage and mulch increased soil microbial biomass C and N. Interestingly, minimum tillage and mulch recorded the highest bacteria and fungi CFUs compared to conventional tillage and inorganic fertilizers. Only fertilizer and mulch (P < 0.001) had significant effect on actinobacteria CFUs. Amplified ribosomal DNA analysis (ARDRA) showed that the highest genetic distance of 0.611 was recorded between treatments conventional tillage + no mulch + no NPK fertilizer and conventional tillage + no mulch + NPK fertilizer. The results demonstrate that minimum tillage and mulching are attractive soil agronomic management practices since they increase soil microbial biomass and bacterial diversity in agricultural soils.

Comparison between observed and DeNitrification-DeComposition model-based nitrous oxide fluxes and maize yields under selected soil fertility management technologies in Kenya

Process-based biogeochemical models can be used to simulate soil nitrous oxide (N2O) fluxes and maize yields and draw insights on yields improvement and climate change mitigation options. We compared both observed and DeNitrification-DeComposition (DNDC) simulated soil N2O fluxes and maize yields. We used DNDC model to simulate soil N2O fluxes and maize yields under four soil fertility treatments (inorganic fertiliser, animal manure, animal manure + inorganic fertiliser and control,) replicated thrice for 1 year in Central Highlands of Kenya. We sampled soil N2O fluxes using static chambers installed in each plot. We analysed soil N2O using gas chromatography and calculated cumulative fluxes using trapezoidal rule linear interpolation between sampling dates. DNDC showed poor results in simulating daily N2O fluxes (157.16% ≤ normalised root mean square error (nRMSE) ≤ 324.01% and 0.90 ≤ modelling efficiency (NSE) ≤ 0.96), good to excellent performance in simulating cumulative annual soil N2O fluxes (6.16 ≤ nRMSE ≤12.86 and 0.63 ≤ NSE ≤ 0.86) and good to excellent performance in simulating maize yields (1.15% ≤ nRMSE ≤13.86% and 0.51 ≤ NSE ≤ 0.88) across all soil fertility treatments. The DNDC model had good to excellent performance in simulating cumulative soil N2O fluxes and crop yields across treatments. Though the model captured yield-scaled N2O fluxes and N2O emission factors across treatments, they were underestimated under manure treatment. There is a need to continue calibrating the DNDC model for improved capture of daily N2O fluxes and uptakes on Kenyan soils.

Abundance and Distribution of Malaria Vectors in Various Aquatic Habitats and Land Use Types in Kakamega County, Highlands of Western Kenya.

Management of malaria transmission relies heavily on vector control. Implementation and sustenance of effective control measures require regular monitoring of malaria vector occurrences, species abundance and distribution. The study assessed mosquito larval species composition, distribution and productivity in Kakamega County, western Kenya. A cross-sectional survey of Anopheline larvae was conducted in various aquatic habitats and land use types in Kakamega County, highlands of western Kenya between the month of March and June 2019. One thousand, five hundred and seventy six aquatic habitats were sampled in various land use types. The mean densities of An. gambiae s.l (46.2), An. funestus (5.3), An. coustani (1.7), An. implexus (0.13) and An. squamosus (2.0) were observed in fish ponds, burrow pits, drainage ditches, and tire tracks, respectively. High mean densities of An. gambiae s.l was reported in farmland (20.4) while high mean abundance of An. funestus s.l (8.2) and An. coustani s.l (4.0) were observed in artificial forests. The study revealed that the productivity of anopheles larvae varied across various habitat types and land use types. Therefore, treatment of potential breeding sites should be considered as an additional strategy for malaria vector control in Kakamega County, western Kenya.

Phosphorus availability and exchangeable aluminum response to phosphate rock and organic inputs in the Central Highlands of Kenya

Soil acidity and phosphorus deficiency are some of the constraints hampering agricultural production in tropical regions. The prevalence of soil acidity is associated with phosphorus (P) insufficiency and aluminum saturation. We conducted a two-seasons experiment to evaluate soil phosphorus availability and exchangeable aluminum in response to phosphate rock and organic inputs in acidic humic nitisols. The field experiment was installed in Tharaka Nithi County in the Central Highlands of Kenya. The experimental design was a randomized complete block design with treatments replicated thrice. The treatments were: Green manure (Tithonia diversifolia Hemsl.) (60 kg P ha−1), phosphate rock (60 kg P ha−1), goat manure (60 kg P ha−1), Tithonia diversifolia (20 kg P ha−1) combined with phosphate rock (40 kg P ha−1), manure (20 kg P ha−1) combined with phosphate rock (40 kg P ha−1), Triple Super Phosphate combined with Calcium Ammonium Nitrate (TSP + CAN) (60 kg P ha−1) and a control (no input). During the long rains of the 2018 season (LR2018), Tithonia diversifolia + phosphate rock had a significantly higher reduction (67%) of exchangeable aluminum than the sole use of Tithonia diversifolia. Grain yield under TSP + CAN was the highest, followed by the sole organics during the LR2018. Tithonia diversifolia + phosphate rock resulted in a 99% and a 90% increase in NaHCO3-Pi compared to sole phosphate rock and sole Tithonia diversifolia, respectively. Tithonia diversifolia led to 14% and 62% higher resin-Pi and NaOH-Pi, respectively, compared to manure in the short rains of 2017 (SR2017). The increase in NaOH-Po after the two seasons was statistically significant in sole TSP + CAN. Based on the observed reduced exchangeable aluminum and additional nutrients like Ca, Mg, and K in the soil, sole organic inputs or in combination with phosphate rock treatments are feasible alternatives for sustaining soil phosphorus. Our findings underscore an integrated approach utilizing organic amendments combined with phosphate rock in acidic humic nitisols' phosphorus nutrient management.

Land use change, but not soil macrofauna, affects soil aggregates and aggregate-associated C content in central highlands of Kenya

Though land use change has been shown to have great influence on soil structure and C storage, little is still known how these effects change over the long term, especially in Africa. Thus, a study was conducted in central highlands of Kenya to evaluate changes in soil aggregates and aggregate-associated C content across four land use types. The four land use types included (1) an undisturbed bush land, (2) over 50 years old grazed pasture, (3) over 80 years old coffee plantation, and (4) a maize field cultivated continuously for 3 years. It was hypothesized that soil aggregates and aggregate-associated C would decrease with increasing soil disturbance caused by tillage or exerted by livestock hooves, with the magnitude of these effects being reduced by abundance of earthworms and termites. Land use type significantly affected soil aggregates especially, large macroaggregates and microaggregates. The weight of large macroaggregates in bush land (14.4 g 100 g−1 soil) was more than 20 times higher than in maize field (0.6 g 100 g−1). On the contrary, the weight of microaggregates in maize field (41.2 g 100 g−1) was more than double that recorded in bush land (18.8 g 100 g−1). Aggregate-associated C showed magnitude of differences similar to those of soil aggregates. However, the abundance of earthworms and termites generally showed weak or no correlation with soil aggregate fractions and aggregate-associated C. Our results shows that land use change can significantly influence soil aggregation and C content, which could have far-reaching implications for the long term C sequestration.