Browsing by Author "Uwingabire, Solange"

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Agroforestry for sustainable bioenergy and improved soil fertility in two agro-ecological zones, Rwanda
(Sokoine University of Agriculture, 2024) Uwingabire, Solange
In Rwanda, the demand for food and energy is high and rising due to population growth. Furthermore, in rural households, the primary energy supply is from fuelwood combusted in inefficient cookstoves, resulting in fuel wastage and health issues associated with smoke in the kitchen. Biochar produced in cooking stoves can contribute to negative carbon emissions through sequestration of biomass Carbon while also providing other benefits for sustainable development, including provision of clean renewable energy and increased yields in tropical agriculture. In addition, B has low nutrient content and is recalcitrant to biodegradation; supplementing B with a fast-releasing nutrient source may contribute to improving soil fertility and physical conditions and lead to increased crop productivity. The reported research aimed to assess the impact of introducing Biochar-producing cooking stoves on household energy access and vegetable production, both on smallholder farms and experimental stations, in two agro-ecological zones (AEZs) of Rwanda. Participatory research on B production and use was conducted with 60 smallholder farmers selected purposively to evaluate the potential of Biochar – producing cooking stoves to address the interconnected challenges of household energy access and low vegetable productivity in Rwanda. The study compared two top-up lift draft (TLUD) gasifier types (Gastov and Karundura) with a three-stone fire (TSF) cookstove, using a standardized cooking test (SCT) and a household survey. Key indicators included cooking time, firewood usage and Biochar yield while the survey collected informationii about fuel availability, frequency of use, gasifier design, benefits and challenges. In addition, a three-season field study was done in two AEZs to assess the Biochar effects on vegetable yields after application to soil, where Biochar from gasifier stoves was applied in furrows (2-3 cm deep) in the gardens of French beans (Phaseolus vulgaris) at a rate of 3 tons per hectare (t/ha) using randomized paired design. Yield and the soil’s physical and chemical properties were analyzed. Concurrently, another, three- season field study (on station trials) was conducted in two AEZs to assess the synergistic effect of five types of Biochar (from S. sesban, G. sepium, A. angustissima, Eucalyptus, and Grevillea sp.) alone or mixed with livestock manure (LM) and applied at 1 and 3 t/ ha using French bean as a test crop. The key indicators were French bean yields, and soil chemical properties of soils. The study utilized descriptive statistics, one-way analysis of variance (ANOVA) using a generalized model in R, linear fixed effect model and the difference between means was examined using Tukey’s test at p<0.05. The study revealed that the TSF stove cooked a standardized meal faster than the gasifier stove did but the later reduced fuelwood consumption by 25-50% and produced biochar. The household survey responses revealed low firewood availability, but with the ability of firewood, savings when using gasifier stove. Gasifier stoves provided benefits through temperature control, reduced need for constant supervision, Biochar production, and reduced time needed for fuelwood collection, more hygienic and attractive appearance cooking. Most household cooks reported that the gasifier stoves produced less smoke and were safer for children and women’s health. The findings from on-farm trialsiii showed a consistently positive response in French bean yield following a one-time application of B in both sites. The B-treated plots were significantly (P<0.05) higher in pH, plant available nutrients (available Phosphorus (P), total Nitrogen (TN) and exchangeable bases), and soil nutrient retention capacity (high cation exchange capacity (CEC)). Soil porosity, plant available water (PAW), were significantly increased by B application while reducing soil bulk density (BD). The B produced by the TLUD gasifiers was perceived as positive as it combines B production and bioenergy, reduces off-farm biomass gathering, improves energy security and produces sufficient B to improve soil productivity in home gardens. For the on-station trials, the seasonal increase in yield has been recorded in combined plots with the high yield found in B-LM, each at the level of 3 t/ha, compared to the sole application of LM or B and the control treatment. The main factors for the increase of the French bean yield in the study areas are improved soil properties, including high pH; high nutrients content (Avail P, TN), soil OC and soil CEC. The application of B, either alone or in combination with LM, positively increased soil nutrients and French bean yield. The improvement became better as the B rate increased and when mixed with LM than sole application of B or LM. Increased vegetable yield enables enhanced nutrition and/or market opportunities and the adoption of the TLUD stoves may contribute to energy sustainability through the reduction of fuel use. The study recommends considering the combination of B with LM as an effective land rehabilitation strategy to improve soil fertility and increase vegetable yield in Rwanda. This technology of using B and LM is a low-cost technology foriv managing acidic sandy soils of Rwanda. The technology offers significant contributions in terms of improving soil fertility, increasing bioenergy output, mitigating climate change by sequestering atmospheric carbon in the soil and reducing greenhouse gas emissions associated with traditional cooking methods, particularly for women and children, thus improving the overall well-being and socio-economic stability of rural communities.
Pedological Characterization of Soils Developed from Volcanic Parent Materials of Northern Province of Rwanda
(Science publishing group, 2016-10) Uwitonze, Providence; Msanya, Balthazar Michael; Mtakwa, Peter Wilson; Uwingabire, Solange; Sirikare, Sylvere
Soils formed from volcanic materials have high potential for agricultural production and support high human population densities. This study was carried out on soils developed from volcanic parent materials of Northern Province of Rwanda aiming largely on pedological characterization but to a certain extent on assessment of potentials of soils for production of major crops in the area. Three representative pedons namely Kinigi Pedon 1 (KNG-P1), Kinigi Pedon 2 (KNGP2) and Gahunga Pedon 1 (GHNG-P1) were identified and described. Sixteen soil samples were collected from different pedogenic horizons and analyzed in the laboratory for physico-chemical properties. Pedons were classified using USDA Soil Taxonomy and FAO-WRB for Soil Resources. Potentials and limitations of the soils were also identified. Results show that soils were shallow to very deep and well drained. Topsoils were very dark coloured with colour values of ≤ 2 in all pedons. Texture was generally loamy with bulk densities of < 0.47 g/cm3 in Pedons KNG-P1 and KNG-P2 while they ranged from 0.94 to 1.34 g/cm3 in Pedon GHNG-P1. Topsoils were medium acid (KNG-P1, KNG-P2) and mildly alkaline (GHNG-P1), with high to very high OC ranging from 3.97 to 13.03%. CECsoil was high (> 32 cmol (+)/kg) in Pedons KNG-P1 and KNG-P2. Base saturation was low (< 30%) in Pedons KNG-P1 and KNG-P2 while it was high (> 50%) in Pedon GHNG-P1. pHNaF was > 9.5 in Pedons KNG-P1 and KNG-P2 reflecting exchange complex dominated by amorphous materials and/or humus complexes. Phosphorus retention capacity ranged from 6.25% to 99.58% and only Pedons KNG-P1 and KNG-P2 met the “andic properties” requirement of PRC ≥ 85%. Melanic index values indicated that these two pedons were characterized more by fulvic than humic acids. Nutrient imbalance with reference to basic cations was common in all studied soils, implying suboptimal nutrient uptake and toxicity. Fe2O3, SiO2 and Al2O3 were the dominant oxides in the studied soils. Degree of weathering of studied soils was low as indicated by their weathering indices. Using field and laboratory data, Pedons KNG-P1 and KNG-P2 classified as Andisols/Andosols and GHNG-P1 as Mollisols/Phaeozems. Land units represented by Pedons KNGP1 and KNG-P2 were rated as marginally suitable while land unit represented by Pedon GHNG-P1 was rated as moderately suitable for the major crops of the area. Application of P fertilizers coupled with efficient placement was recommended to enhance P, and soil conservation should be underscored in study area.
Pedological characterization of soils developed on gneissic granites in the Congo Nile watershed divide and central plateau zones, Rwanda
(2016-09) Uwingabire, Solange; Msanya, Balthazar Michael; Mtakwa, Peter Wilson; Uwitonze, Providence; Sirikare, Sylvere
Pedological characterization was carried out on soils developed on gneissic granites of Southern Province of Rwanda. Three representative soil profiles (GSK-PI, GSK-P2 and TMB-PI) were identified, described and sampled using standard manuals. A total of nineteen soil samples were analyzed in the laboratory for physicochemical properties. Soil classification was carried out using two international systems of classification. The potentials and limitations of the soils were also identified. All studied pedons were very deep, well drained with loamy to clayey topsoil textures overlying dominantly clayey subsoil textures. The deeper subsoil ofPedon TMBPI consisted of loamy and sandy textures. Pedons GSK-PI and GSK-P2 depicted eluviation-illuviation process as indicated by presence of clay cutans in subsoils. Analytical data showed low bulk and particle densities and high porosity in topsoils ranging from 1.02 to 1.34 g/crrr', from 2.18 to 2.59 g/cm! and from 48.34 to 53.23%, respectively. Topsoilsof studied soils were strongly to slightly acidic with pH ranging from 5.49 to 6.59 while subsoils were strongly acidic to medium acidic with pH range between 5.13 and 5.86. The studied pedons had very low to medium total nitrogen and organic carbon respectively ranging from 0.15 to 0.24% and from 1.6 to 2.5%, both decreasing with depth. Topsoil and subsoil cation exchange capacity of the soils respectively ranged from low (9.8 - 21.6 cmol (+)/kg) to medium (4.2 - 13.2 cmol (+)/kg). Base saturation of the studied pedons was rated as low « 50%) throughout all horizons of studied pedons. Whereas topsoil available phosphorus ranged from low to medium (6.4 - 15.7 rug/kg) and decreased with depth, phosphorus retention capacity was < 50% and increased with depth in Pedons GSK-PI and GSK-P2 but didnot show any definite trend in PedonTMB-PI. All studied pedons indicated suboptimal nutrient ratios with reference to the basic cations, implying potential nutrient imbalance and toxicity of these nutrients. SiD" AI,O, and Fe,O, ranged from 45.4 to 58.4%, 17.0 to 27.0% and 16.7 to 24.3%, respectively. On the basis of silt/clay ratios, the degree of weathering of the studied pedons followed the trend GSK-PI>GSK-P2>TMB-PI. According to USDA Soil Taxonomy, the studied pedons classified as Ultisols (GSK-PI and GSK-PI) and Inceptisols (TMB-PI), respectively, correlating to Alisols and Cambisols of WRB for Soil Resources. The studied soils were generally rated as having low fertility and only marginal suitability for the major crops of the area. Specific land management and cropping systems were recommended for sustainable utilization of soils.