Browsing by Author "Adamtey, Noah"

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    Diversity and structure of prokaryotic communities within organic and conventional farming systems in central highlands of Kenya
    (PLOS, 2020-08) Karanja, Edward N.; Fliessbach, Andreas; Adamtey, Noah; Kambura, Anne Kelly; Musyoka, Martha; Fiaboe, Komi; Mwirichia, Romano K.
    Management practices such as tillage, crop rotation, irrigation, organic and inorganic inputs application are known to influence diversity and function of soil microbial populations. In this study, we investigated the effect of conventional versus organic farming systems at low and high input levels on structure and diversity of prokaryotic microbial communities. Soil samples were collected from the ongoing long-term farming system comparison trials established in 2007 at Chuka and Thika in Kenya. Physicochemical parameters for each sample were analyzed. Total DNA and RNA amplicons of variable region (V4—V7) of the 16S rRNA gene were generated on an Illumina platform using the manufacturer’s instructions. Diversity indices and statistical analysis were done using QIIME2 and R packages, respectively. A total of 29,778,886 high quality reads were obtained and assigned to 16,176 OTUs at 97% genetic distance across both 16S rDNA and 16S rRNA cDNA datasets. The results pointed out a histrionic difference in OTUs based on 16S rDNA and 16S rRNA cDNA. Precisely, while 16S rDNA clustered by site, 16S rRNA cDNA clustered by farming systems. In both sites and systems, dominant phylotypes were affiliated to phylum Actinobacteria, Proteobacteria and Acidobacteria. Conventional farming systems showed a higher species richness and diversity compared to organic farming systems, whilst 16S rRNA cDNA datasets were similar. Physiochemical factors were associated differently depending on rRNA and rDNA. Soil pH, electrical conductivity, organic carbon, nitrogen, potassium, aluminium, zinc, iron, boron and micro-aggregates showed a significant influence on the observed microbial diversity. The observed higher species diversity in the conventional farming systems can be attributed to the integration of synthetic and organic agricultural inputs. These results show that the type of inputs used in a farming system not only affect the soil chemistry but also the microbial population dynamics and eventually the functional roles of these microbes.
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    The response of soil physicochemical properties to tillage and soil fertility resources in Central Highlands of Kenya
    (Pagepress, 2020) Kiboi, Milka N.; Muriuki, Anne; Ngetich, Felix K.; Adamtey, Noah; Mugendi, Daniel N.
    To attain agricultural sustainability, use of soil resources and tillage requires equal consideration for chemical and physical components of soil fertility. We assessed responses of selected soil physical and chemical properties to tillage and soil fertility amending resources. The study was carried out in Meru South and Kandara sub-counties located in the Central Highlands of Kenya for four cropping seasons. The experimental design was split-plot with tillage as the main factor - conventional (D15) - and minimum (D0) tillage and soil fertility resources (SFR) as sub-factors - mineral fertilizer (F), crop residues + fertilizer (RF), residues + fertilizer + animal manure (RFM), residues + Tithonia diversifolia + manure (RTiM), residues + Tithonia diversifolia + phosphate rock (Minjingu) (RTiP), residues + manure + legume intercrop (RML) and control (no input). Compared with control, aggregate stability was significantly higher on average under SFRs with sole organics by 19% in Meru South. Total N and available P were higher under integration of fertilizer and organics in both sites. Calcium increased under sole organic or integration with fertilizer in Meru South and under sole organics in Kandara. Magnesium significantly increased under all SFRs compared with control in Kandara. Soil organic carbon significantly (P=0.02) increased under D0 by 6% compared to D15 in 0-5 cm depth in Kandara. Application of RTiM had the highest SOC in all depths’ at Meru South. SOC significantly increased under RTiP and RML by 11% in 0-5 cm depth and under RML by 13% in 5-10 cm depth at Kandara. Mineral-N (NO3 –-N and NH4 +-N) was higher under D0 at planting compared with D15 in Meru South. In Kandara, NO3 –-N and NH4 +-N were significantly higher by 17% and 30%, respectively under D0 compared with D15 at planting during SR16 season. Higher mineral N was recorded under F application on the 30th and 45th days in both sites. The highest mineral-N content was on the 45th day after planting during SR16 season and on the 30th day during LR17 season at Meru South. In Kandara, NO3 –-N and NH4 +-N were highest on the 45th day and 30th day, respectively, during SR16 season. During LR17 season, mineral-N was highest on the 30th day in Kandara. The study highlights that minimal soil disturbance and organic inputs use or integration with fertilizers are feasible alternatives for improving soil fertility in the Nitisols of Central Highlands of Kenya.
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    Suitability of different data sources in rainfall pattern characterization in the tropical central highlands of Kenya
    (Heliyon, 2020-11) Oduor, Nathan O.; Ng'etich, Felix K.; Kiboi, Milka N.; Muriuki, Anne; Adamtey, Noah; Mugendi, Daniel N.
    Uncertainty in rainfall pattern has put rain-fed agriculture in jeopardy, even for the regions considered high rainfall potential like the Central Highlands of Kenya (CHK). The rainfall pattern in the CHK is spatially and temporally variable in terms of onset and cessation dates, frequency and occurrence of dry spells, and seasonal distribution. Appraisal of the variability is further confounded by the lack of sufficient observational data that can enable accurate characterisation of the rainfall pattern in the region. We, therefore, explored the utilisation of satellite daily rainfall estimates from the National Aeronautics and Space Administration (NASA) for rainfall pattern characterisation in the CHK. Observed daily rainfall data sourced from Kenya meteorological department were used as a reference point. The observation period was from 1997 to 2015. Rainfall in the CHK was highly variable, fairly distributed and with low intensity in all the seasons. Onset dates ranged between mid-February to mid-March and mid-August to mid-October for long rains (LR) and short rains (SR) seasons, respectively. Cessation dates ranged from late May to mid-June and mid-December to late December for the LR and SR, respectively. There was a high probability (93%) of dry spell occurrence. More research needs to be done on efficient use of the available soil moisture and on drought tolerant crop varieties to reduce the impact of drought on crop productivity. Comparison between satellite and observed rain gauge data showed close agreement at monthly scale than at daily scale, with general agreement between the two datasets. Hence, we concluded that, given the availability, accessibility, frequency of estimation and spatial resolution, satellite estimates can complement observed rain gauge data. Stakeholders in the fields of agriculture, natural resource management, environment among others, can utilise the findings of this study in planning to reduce rainfall-related risks and enhance food security.