School of Agriculture and Biotechnology
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Item Integrating Cordia Africana Trees on Farms Differentially Improves Soil Properties in Small Holder Farms in Kirinyaga County, Kenya(2023-08-08) Kamau, Miriam; Kinyanjui, Mwangi; Kamiri, HellenTree-based solutions are more efficient in nutrient cycling in farming systems and hence ideally suited for impoverished farmers experiencing food insecurity. Agroforestry trees have a positive effect on soil fertility through litter fall by the canopies compared to that of the adjacent open fields. Field sampling involved selecting mature Cordia africana trees from ten farms and collecting soil samples at varying distances from the tree trunks and at two depths (0-15 and 15-30cm). For each selected farm, soil samples were collected at three sampling points defined by distance from the tree base thus: - 5M (under the tree canopy), 11M (at the edge of the crown), and 30M (from the tree's influence. Laboratory analyses measured concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, and organic carbon. The soil parameters investigated (Nitrogen, Phosphorus, Soil organic carbon, Potassium, and Calcium) were significantly higher in the topsoil than in the subsoil. The horizontal effect of trees with increasing distance from the tree on soil nitrogen, organic carbon, and phosphorus is minimal, the effect being more on vertical distribution (across depth). Differences in nutrient contents in soil nutrient variables between agroforestry and cropped land showed that soil nutrients within the Cordia africana system were higher than those under cultivated land implying that Cordia africana has a positive effect on soil quality. Thus, the study emphasizes the adoption of Cordia africana in agroforestry practices with a view to increase soil fertility and improve crop yields in sustainable farming. There is therefore need for the formulation of appropriate measures of soil management based on the characteristics of the sites.Item Effects of Land Use Change on Banana Production:A Case Study of Imenti South Sub-County of Meru County in Kenya(Britain International of Exact Sciences Journal, 2020-09) Nyamamba, Kevin A.; Ouna, Tom O.; Kamiri, Hellen; Pane, ErwinMost high agricultural potential regions in Kenya such as Imenti South (Meru County) have exceeded their population density and have been associated with sharp decline in farm productivity. There has been a systematic transformation of land use for banana production in the area. This has led to reduction in land acreage under other crops and increase in land acreage under banana farming. This study focused on land use and banana production trends between the years 2000 to 2019 in Imenti South. To achieve the objective, the study used mixed research design that involved qualitative and quantitative approaches. A sample size of 377 respondents was identified using simple random sampling. Banana yields and land acreage data were obtained from Imenti South Agricultural office for the study period. The mainresearch instruments were questionnaires for households and key informants. Majority of the respondents (72%) in the study region admitted to have changed the land use and type of crops they have been farming during the study period whereas 28% changed from other crops to banana farming. Land acreage and banana production have been increasing during the study period in the area. The study revealed there is positive and statistically significant relationship (r = .617; p = .004) between land under banana and production. The study recommends that stakeholders in County governments should establish departments that independently identify, analyses, monitor and educates the famers on the new technologies that improves and increases banana productionItem Influence of Vegetation Cover and Topographic Position on Water Infiltration, Organic Matter Content and Aggregate Stability of Grassland Soils in Semi-Arid Kenya(Advances in Agricultural Science, 2019) Mutuku, Daisy; Kamiri, Hellen; Ndufa, James; Kiama, Stephen; Mware, MugoA study was conducted in Mpala and Ilmotiok ranches in Laikipia County, Kenya, to investigate the influence of vegetation cover and topographic position on soil organic matter, bulk density, aggregate stability and water infiltration rate. Three vegetation cover types; (Tree, Grass and Bare) and four topographic positions (Hillslope, Headwater, Riparian, and Plateau) were evaluated. Soil samples were collected along the topographic positions and within the vegetation cover types at five levels of depth; 0-10, 10-20, 20-30, 30-40, 40-50 cm during the dry season May to August 2016. The samples were analyzed for soil organic matter, bulk density and soil aggregate stability. Water infiltration rate was measured in situ on the soil surface using a mini-disk Infiltrometer. Soil aggregate stability varied significantly between topographic zones (p=0.0124) but not between the vegetation cover types and soil depth in Ilmotiok site. Mpala site showed a significant difference in aggregate stability between the topographic zones (p=0.0152). However, no significant difference was observed in variation of aggregate stability between the vegetation cover types and soil depth (p=0.8998; p=0.8284) respectively. In Ilmotiok site, the highest infiltration rate was recorded in the Tree covered fields (73.3 mm/hr) and decreased in Grass fields and Bare grounds at 25 and 17 mm/hr, respectively. The Headwater zones had the highest infiltration rates (73.3 mm/hr) while the lowest infiltration rates were (0 mm/hr) in the Hillslope zones. The infiltration rates in Mpala site were highest in Bare grounds (37.8 mm/hr) and lowest in Tree fields with 5.7 mm/hr. The Headwater zones had the highest infiltration rates followed by Hillslope zones with (8.9 mm/hr) while the Riparian zones had the lowest infiltration rates (0.00 mm/hr). Soil organic matter (SOM) differed significantly at P (<0.0001) among the vegetation cover types, topographic zones and soil depth for both sites. In Ilmotiok site, the mean soil organic matter was highest (1.96%) in Hillslopes zones and lowest in Grass covered fields (0.30%). In Mpala, SOM content was highest in Tree covered fields at 2.28%, and lowest in Grass covered fields at 0.38%, for RIP and PLA zones respectively. Topographic positions and grazing management influenced soil properties in the semi-arid grasslands, hence the need for strategies in grazing management that will promote restoration of these degraded areas.Item Socioeconomic Determinants of Banana Farmers’ Perception to Climate Change in Nyeri County, Kenya.(Journal of Arts & Humanities, 2019-08-29) Karienye, David; Nduru, Gilbert; Kamiri, Hellen;Climate change is one of the key constraints to banana production globally. The extent of the climate change impacts depends largely on farmers’ awareness, perceptions and responses to climate change. This study examined the perception of farmers in Mt Kenya region, Nyeri County-Kenya of climate change impacts on banana value chain and analysed the socio-economic factors that influenced these perceptions. The study sites were purposively selected to include areas where banana production had been practiced since the 1980s. Data was collected from a hundred and thirty farming households between February and April 2018. Results indicated that 78.2% of the respondents perceived increase in rainfall and temperature as what constituted climate change. The major perceived effects of climate change to be high transport cost of banana to the market, low prices during rainy season and high demand of the produce during dry season. Results of logit model analysis indicated that gender of household head, farming system, type of farming and access to weather information influenced farmers’ perception towards climate change. Even though majority (78.5%) of the farmers perceived climate change to have changed over the years, 47.7% recommended accessibility of weather information on onset of the rainfall period, while 49.2% preferred information on rainfall distribution within the seasons in order to respond to climate change occurrences. These findings show that there is need to integrate policies that safeguard the smallholder farmers from adverse effects of climate change.Item Dynamics of agricultural use differentially affect soil properties and crop response in East African wetlands(Springer Science, 2013) Kamiri, Hellen; Kreye, Christine; Becker, MathiasAgricultural land use changes differen- tially affect soil fertility and crop production potential of wetlands. We studied East African wetlands with contrasting hydro-geological characteristics (high- and lowland floodplains and valley swamps). Land uses ranged from no use and grazing over crop production in flooded and drained fields to abandon- ment. We classified the dynamics of wetlands’ con- version into agricultural sites and assessed selected soil fertility attributes associated with land use changes, and their effect on the crop production potential in aerobic and anaerobic soils. A conversion of pristine wetlands, differing in soil physical and chemical attributes, into sites of production tended to negatively affect soil total C and N. Effects were stronger with soil drainage and in the coarse-textured soils of the lowland floodplain and the mid-hill valleys. Mineral P application in drained valleys significantly increased available soil P. Crop response followed these patterns with usually higher biomass accumulation and nutrient uptake in flooded than aerobic soils. Wetlands of fine soil texture in the highlands appeared more resilient than coarse-tex- tured soils, particularly when drained. Enhanced crop performance in flooded soils indicates the possibility for partial recovery of the production potential and the rehabilitation of some wetlands. Keywords Carbon Drainage Floodplain Inland valley Nitrogen Oryza glaberrimaItem Plant Communities Changes in Relation to Land Uses and Soil Properties in Malinda Wetland, Tanzania(2016) Kamiri, Hellen; Mogha, Neema; Handa, Collins; Alvarez, Miguel; Möseler, BodoItem Effect of management and soil moisture regimes on wetland soils total carbon and nitrogen in Tanzania(Geophysical Research Abstracts, 2013) Kamiri, Hellen; Kreye, Christine; Becker, MathiasWetland soils play an important role as storage compartments for water, carbon and nutrients. These soils implies various conditions, depending on the water regimes that affect several important microbial and physical-chemical processes which in turn influence the transformation of organic and inorganic components of nitrogen, carbon, soil acidity and other nutrients. Particularly, soil carbon and nitrogen play an important role in determining the productivity of a soil whereas management practices could determine the rate and magnitude of nutrient turnover. A study was carried out in a floodplain wetland planted with rice in North-west Tanzania- East Africa to determine the effects of different management practices and soil water regimes on paddy soil organic carbon and nitrogen. Four management treatments were compared: (i) control (non weeded plots); (ii) weeded plots; (iii) N fertilized plots, and (iv) non-cropped (non weeded plots). Two soil moisture regimes included soil under field capacity (rainfed conditions) and continuous water logging compared side-by-side. Soil were sampled at the start and end of the rice cropping seasons from the two fields differentiated by moisture regimes during the wet season 2012. The soils differed in the total organic carbon and nitrogen between the treatments. Soil management including weeding and fertilization is seen to affect soil carbon and nitrogen regardless of the soil moisture conditions. Particularly, the padddy soils were higher in the total organic carbon under continuous water logged field. These findings are preliminary and a more complete understanding of the relationships between management and soil moisture on the temporal changes of soil properties is required before making informed decisions on future wetland soil carbon and nitrogen dynamics.