Browsing by Author "Mahoo, H. F."
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Item Application of self-organizing-maps technique in downscaling GCMs climate change projections for Same, Tanzania(2010) Tumbo, S. D.; Mpeta, E.; Mbillinyi, B. P.; Kahimba, F. C.; Mahoo, H. F.; Tadross, M.High resolution surface climate variables are required for end-users in climate change impact studies; however, information provided by Global Climate Models (GCMs) has a coarser resolution. Downscaling techniques such as that developed at the University of Cape Town, which is based on Self-Organizing Maps (SOMs) technique, can be used to downscale the coarse-scale GCM climate change projections into finer spatial resolutions; but that must be combined with verification. The SOM downscaling technique was employed to project rainfall and temperature changes for 2046-2065 and 2080-2100 periods for Same, Tanzania. This model was initially verified using downscaled NCEP reanalysis and observed climate data set between 1979 and 2004, and between NCEP reanalysis and GCM controls (1979 - 2000). After verification, the model was then used to downscale climate change projections of four GCMs for 2046-2065 (future-A) and 2080-2100 (future-B) periods. These projections were then used to compute changes in the climate variables by comparing future-A and B to the control period (1961-2000). Verification results indicated that the NCEP downscaled climate data compared well with the observed data. Also, comparison between NCEP downscaled and GCM downscaled showed that all the four GCM models (CGCM, CNRM, IPSL, and ECHAM) compared well with the NCEP downscaled temperature and rainfall data. Future projections (2046-2065) indicated 56 mm and 42 mm increase in seasonal total rainfall amounts for March-April-May (MAM) and October-November-December (OND) (23% and 26% increase), respectively; and a temperature increase of about 2°C for both seasons. Furthermore, it was found that during MAM there will be a decrease in dry spells by 2 days, and an increase in seasonal length by 8 days, while for OND, there will be also 2 days decrease in dry spells, and 40 days increase in the seasonal length. The results for future-B shows a 4°C rise in temperature, and 46.5% and 35.8% increase in rainfall for MAM and OND, respectively. The results imply a better climatic future for the area because of the increase in the amount of rainfall and decrease in dry spells. However, it is suggested that further investigations are required to see if the projected changes will have real positive effects in agricultural production and also identify better agronomic practices that will take advantage of the opportunities.Item Comparative assessment of soil and nutrient losses from three land uses in the central highlands of Ethiopia(Academic journals, 2017) Jaleta, D.; Mbilinyi, B. P.; Mahoo, H. F.; Lemenih, M.Land use/land cover change drive changes in several ecosystem processes over short and long terms. In Ethiopia, the main land use/land cover change involves conversion of natural ecosystem into cultivated land. However, a recent change also involves conversion of cultivated and gra zing land into Eucalyptus woodlots. This study was conducted to analyse the effects of such land use/land cover change on soil and nutrient losses. Three land use/ land cove r types (cultivated land, grassland and Eucalyptus woodlot) were selected for a comparative assessment. A total of twelve runoff plots, each with 43.3 m2 area and with four replications, were installed. Rainfall depth, runoff volume and sediment samples (500 ml) were collected from each plots every morning and evening for 91 days (from 4th July to 2nd October, 2015) in the main rainy season. The sediment samples for ten consecutive days were stored in separate containers and composite sediment concentration samples were weighed after being filtered and oven dried for 24 hours at 105o c. From the samples taken at the end of the rainy season, separate composite a sample before filtration of one litre was analysed in the laboratory for nutrient losses. The effect of land use/land cover on soil and nutrients losses was statistically tested using analysis of variance. The study found that soil loss significantly differed between the land use /land cover types. Soil loss from cultivated land (16.8 ton/ha) was significantly higher than loss from grassland (7 ton/ha) and Eucalyptus stand (8.1 ton/ha). The soil and nutrient losses were positively correlated with runoff volume. There was higher nutrient (N and P) loss from cultivated land than grassland and Eucalyptus. From the results, it can be concluded that soil and nutrients losses are above tolerable limit, and perennial land covers including Eucalyptus stand reduce soil and nutrient losses significantly. This re-affirms the multi-purpose nature of Eucalyptus not only for socioeconomic benefit but also for soil erosion control when planted in appropriate locationsItem Comparison of silicon status in rice grown under the system of rice intensification and flooding regime in Mkindo Irrigation Scheme, Morogoro, Tanzania(TAJAS, 2020) Gowele, G. E.; Mahoo, H. F.; Kahimba, Frederick C.Silicon (Si) is the second most abundant element available in the earth's crust, and is considered as a benefcial element for crop growth especially rice. A study was conducted in Mkindo irrigation scheme, Mvomero District, Morogoro, Tanzania to assess the Silicon status in rice grown under the System of Rice Intensifcation and continuous flooding at various growth stages. The experiment was laid out in a randomized complete block design (RCBD) with two treatments which were two water application regimes: T1 was alternate wetting and drying using SRI technology and T2 was continuous flooding. The treatments were replicated three times and the rice variety used was SARO 5 (TXD 306). The experiment was conducted in two seasons from October 2019 to January 2020 and from March 2020 to June 2020. Si status in rice seeds and grains as well as rice plant leaves at various growth stages were evaluated according to elemental analysis based on Energy Dispersive X- Ray Fluorescence and results were analyzed using GENSTAT software. Si content in rice seeds observed prior to the experiment was 6.76%. Si content in rice grains was gradually increasing during reproductive stage and later drops during harvest. Si content in rice plant leaves increased signifcantly from vegetative to ripening stage whereby the highest Si content was recorded in T 1 (12.37%) while T2 recorded the lowest value (10.15%). It was concluded that, the alternate wetting and drying feld conditions enhances adequate uptake of Si compared to continuous flooding practices.Item Determination of suitability levels for important factors for identification of potential sites for rainwater harvesting(2016) Tumbo, S. D.; Mbillinyi, B. P.; Mahoo, H. F.; Mkiramwinyi, F. O.Indigenous and scientific knowledge for locating potential sites for water harvesting technologies do exists, however, a simple and integrated tool to assist farmers’ support agencies, is missing. A geographic information system (GIS)-based decision support system (DSS) can be a valuable tool for such a task. However, pre-requisite for such DSS are the factors and their suitability levels, which are not well developed. This paper focused on development of suitability levels for most important factors/parameters for identification of such sites, which are soil texture, soil depth, drainage, topography and land use or cover. Specific suitability levels were obtained using both the analysis of existing RWH technology at Makanya river catchment and through literature review. Results of field survey together with literature review showed that suitability levels of factors differ with different RWH technologies. For example, suitable levels/areas for water reservoirs (ndiva) are steep slopes (>30o) with clay soils whereas suitable sites for stone terraces are moderately steep slopes (18o – 30o) with sandy loam soils. It was also found that most RWH technologies are located at a distance between 0 and 125m from cropland.Item Economics of Rainwater Harvesting for Crop Enterprises in Semi-Arid Areas: The Case of Makanya Watershed in Pangani River Basin, Tanzania(Sokoine University of Agriculture, 2005) Mutabazi, K.D.; Senkondo, E. E.; Mbilinyi, B.P.; Tumbo, D.S.; Mahoo, H. F.Contrary to irrigated agriculture that uses blue water, rainwater harvesting that uses green water as direct rain (in-field management) and runoff (spate irrigation) has been accorded little importance in terms of economic research, investment, technology transfer and management. This paper demonstrates the economic benefits of rainwater management for crop production in a semi-arid Makanya Watershed in the Pangani River Basin. The results from two seasons (2003 to 2004) of yield monitoring for maize and lablab show that rainwater harvesting for crop production has the potential for poverty reduction. During the short rainy season of 2004, which was good (above average) in terms of runoff access, maize enterprise under macro-catchment rainwater harvesting realized yield, returns to land and labour amounting to 2.9 ton/ha, US $718/ha and US $19.5/person-day respectively. For the long rainy season of 2003, which was bad (below average), the performance of maize in terms of yield, returns to land and labour improved appreciably with increasing frequency of runoff reception for spate irrigation. Performance of maize and maize-lablab intercrop improved with increasing frequency of runoff access. Respective returns to land and labour under rainfed (no runoff) were only US $122.5/ha and US $3.3/person-day compared to US $1,011.9/ha and US $26.9/person-day with three incidences of runoff reception. Seasonal returns to land and labour exceed the national annual per caput income of US $280 and the global poverty line of US $1/person/day. These findings justify investment and technology transfer in rainwater harvesting for crop production in the upper watersheds of our major river basins.Item Effect of Eucalyptus expansion on surface runoff in the central highlands of Ethiopia(SpringerOpen., 2017) Jaleta, D.; Mbilinyi., B. P.; Mahoo, H. F.; Lemenih, M.Over the last century, Eucalyptus has rapidly expanded across the globe. It has become the most planted tree species. Environmentalists fear this for the perceived negative eco-hydrological impact. Foresters and wood industries support its expansion looking at its socio-economic benefits. Ethiopia is one of the countries where Eucalyptus dominates forest development gains in the last century. The main purpose of this review is to evaluate the expansion, benefit and challenges of Eucalyptus in Ethiopia. Eucalyptus was introduced to Africa, and Ethiopia, around the end of the 19th century, in 1890s. Since then it has continued to expand to cover wider geographic areas within Ethiopia: highland and lowland. It is providing multiple purposes, economic and social, for millions of households in urban and rural areas. It has substituted effectively some of the natural forest’s functions, principally in wood supply; hence this way it has contributed to reducing pressure and in slowing down deforestation. Yet Eucalyptus sustained blame for ecosystem water and soil nutrient drains, and allelopathic effect to suppress native flora growth. Studies on these aspects of the genus are inconclusive. Some argue the extravagant use of water and nutrient, while others argue otherwise. There are studies that show water and nutrient use of Eucalyptus is based on availability: for instance, dry season and wet season uses are not the same. The most known about Eucalyptus is its high nutrient and water use efficiency. Therefore, when evaluated on per volume of water, nutrient and land allocated for biomass production, Eucalyptus will provide the highest biomass return. This may make it the preferred species. The paper concludes that the development of Eucalyptus forestry is crucial in narrowing the gap between forest product demand and supply in the current context of Ethiopia and most African countries, but such development should be managed with proper silviculture: Planted in the right site and tended properly to optimize its positive values and reduce possible negative effects.Item Enhancing response farming for strategic and tactical management of risks of seasonal rainfall variability(2014) Admassu, H.; Mahoo, H. F.; Rwehumbiza, F. B. R.; Tumbo, S. D.; Mogaka, H.Seasonal rainfall variability, particularly the uncertainty with respect to the direction and extent that variability will assume in a given season, forms the greatest source of risk to crop production in semi-arid areas of Ethiopia. Equipping vulnerable communities, in advance, with the expected date of onset of a cropping season, is crucial for smallholder farmers to better prepare to respond and manage the uncertainties. Therefore, rainfall prediction, particularly development of models that can foretell the date of onset of next cropping season is crucial in facilitating strategic agronomic planning and tactical management of in-season risks. A twenty-four-year climatic data study was conducted for Melkassa Agricultural Research Centre (MARC) in semi arid Ethiopia, to develop onset date prediction models that can improve strategic and tactical response farming (RF). A sequential simulation model for a build up of 15 to 25 mm soil water by April 1st, was conducted. Simulation results revealed a build up of soil water up to 25 mm, to be the most risk-wise acceptable time of season onset for planting of a 150-day maize crop. In the context of response farming, this was desirable as it offers the opportunity for farmers to consider flexible combination production of maize (Zea mays L.) varieties of 120 and 90 days in the event of failure of earliest sown 150-day maize crop. Thus, to allow for flexible combination production of the three maize varieties, predictive capacity was found crucial for April onset of the next crop season. Accordingly, based on the consideration of pre-onset rainfall parameters, the first effective rainfall date varied considerably with the date of onset of rainfall. Regression analyses revealed the first effective rainfall date to be the best predictor of the date of onset (R2 = 62.5%), and a good indicator of the duration of next season (R2 = 42.4%). The identified strategic predictor, the first effective rainfall date, enabled prediction of time of season onset and season length by a lead time of two to three months. This markedly improved Stewart’s RF. The date of onset of the next crop season was also found to be a useful predictor of season duration (R2 = 87.3%). Strategic agronomic planning should be adjusted according to the first effective rain date, and tactically according to what date of rainfall onset informs us about expectations in the duration and total season water supply.Item Estimation of environmental flows in the Great Ruaha River Catchment, Tanzania: use of the desktop reserve model(WATERNET/WARFSA/GWP-SA, 2006) Kashaigili, J. J.; Mccartney, M.; Mahoo, H. F.For the past eleven years, the Great Ruaha River which flows through the Ruaha National Park, has ceased flowing during the dry season, with extended periods of zero flow. The drying up has resulted in social conflicts between upstream and downstream users. It has also caused adverse impacts on the ecosystem of the Ruaha National Park, disrupting the lives of many animals and causing changes in their behavior. In this paper we present the findings of a hydrological study conducted to estimate environmental flow requirements. The desktop reserve model was used to determine maintenance high and low flows, and drought low flow requirements within the Ruaha National Park. The results indicate that to maintain the basic ecological functioning of the river requires an average annual allocation of 635.3 Mm3 (equivalent to 21.6% of mean annual runoff). This is the average annual maintenance flow; comprising of maintenance low flows (i.e. 15.9 % MAR; 465.4 Mm3) and maintenance high flows (i.e. 5.8% of MAR; 169.9 Mm3). The absolute minimum water requirement was estimated to be 0.6 m3s-1 with the probability of exceedance of 0.99. The study confirms that in the absence of ecological information hydrological indices can be used to provide a first estimate of environmental water requirements. However, before being applied, greater understanding of the relationships between flow and the ecological condition of the riverine ecosystem is required.Item GIS-based decision support system for identifying potential sites for rainwater harvesting(Physics and Chemistry of the Earth, 2007) Mbilinyi, B. P.; Tumbo, S. D.; Mahoo, H. F.; Mkiramwinyi, F. O.Identification of potential sites for rainwater harvesting (RWH) is an important step towards maximizing water availability and land productivity in the semi-arid areas. However, selection of appropriate sites for different RWH technologies on a large scale presents a great challenge, since the necessary biophysical data and infrastructure are often lacking. This paper presents a geographic information system (GIS)-based decision support system (DSS) that uses remote sensing (RS), limited field survey to identify potential sites for RWH technologies. The input into the DSS include maps of rainfall, slope, soil texture, soil depth, drainage and land use/cover and the outputs are maps showing potential sites of water storage systems (ndiva), stone terraces, bench terraces and borders. The Model Builder in the Arc View GIS was used as a platform for the DSS. Two sites in the Makanya watershed, in Kilimanjaro Region, Tanzania, were used for testing and validation of the DSS. The results reflect specific suitability levels of parameters and weight of factors; for example, near streams (drainage) with slope ranges from moderately steep to steep (10 –30 ) are potential sites for ndiva locations whereas moderately undulating to steep slopes (5 –30 ) with unstable soils are potential sites for stone terraces. Moderately undulating slopes (5 –10 ) with clay, silt clay and sandy clay soils are potential sites for bench terrace and gently undulating slopes (2 –5 ) with clay, silt clay and sandy clay soils are potential sites for borders. The results from testing and validation of the developed DSS indicated that the tool can be used reliably to predict potential sites for RWH technologies in semi-arid areas. Most of predicted RWH technologies during testing were found within very highly and highly suitable locations (41.4% and 40%, respectively) also in validation 36.9% of RWH technologies were found within the moderately suitable followed by very highly suitable and highly suitable both with 23.6%. Despite the good results, it is recommended that more work be carried out to refine the model and to include other pertinent ancillary data like socio-economic factors to increase its usefulness.Item Hydrological modelling to assist water management in the Usangu wetlands, Tanzania(JRBM, 2008) McCartney, M.P.; Kashaigili, J.J.; Lankford, B.A.; Mahoo, H. F.The Usangu wetlands, containing the Ihefu swamp, are one of the most valuable inland wetlands in Tanzania. Over the last decade, outflow from the swamp has ceased for extended periods in the dry season. This has had severe consequences for downstream ecosystems, including the Ruaha National Park. Results from a simple hydrological model developed for the Ihefu swamp indicate that, between 1958 and 2004, dry season inflows declined by approximately 60% and the dry season area of the swamp decreased by approximately 40% (i.e. from 160 km2 to 93 km2 ). The model also shows that to maintain minimum downstream environmental flows requires a minimum inflow of 7 m3 s−1 , which is approximately 65% greater than occurs currently. There is significant potential for improving water use efficiency. However, given the socio-economic importance of current levels of water withdrawal, this inflow may be difficult to achieve. Consequently consideration needs to be given to other options, including upstream storage and water management within the wetland itself. This paper highlights that a simple model supplying relatively low-confidence, but indicative, results can provide a useful basis for contemplating water management options.Item Identification of suitable indices for identification of potential sites for rainwater harvesting(2013) Tumbo, S.D.; Mbilinyi, B. P.; Mahoo, H. F.; Mkilamwinyi, F.O.Although indigenous and scientific knowledge for locating potential sites for water harvesting technologies do exist, a simple and integrated tool to assist farmers’ support agencies, is missing. A geographic information system (GIS)-based decision support system (DSS) can be a valuable tool for such a task. However, key to such DSS are the factors and their suitability levels, which are not well developed. This study therefore focused on the development of suitability levels for most important factors/parameters for identification of such sites. The factors included rainfall, soil texture, soil depth, drainage, topography and land use or cover. Specific suitability levels were derived from analysis of existing RWH technologies in Makanya river catchment. Results showed that suitability levels of factors differ with different RWH technologies. Suitable areas for ndiva is on steep slopes (18o-30o) with clay soils, stone terraces is on moderately steep slopes (10o – 18o) with sandy clay loam soils, bench terraces (5o-18o slopes, clay or silt clay soils) and “boda” (2o-5o slopes, slit clay or clay soils). It was also found that ndiva, “boda”, stone terrace and bench terrace are located at a distance within 125m from cropland. Testing of the developed parameters using ArcView-based DSS framework showed that 81.4% RWH technologies were located in the very high and high suitability levels, indicating the usefulness of the developed parameters and their suitability levels.Item Identification of suitable indices for identification of potential sites for rainwater harvesting(Tanzania Journal of Agricultural Sciences, 2014) Tumbo, S. D.; Mbillinyi, B. P.; Mahoo, H. F.; Mkilamwinyi, F. O.Although indigenous and scientific knowledge for locating potential sites for water harvesting technologies do exist, a simple and integrated tool to assist farmers’ support agencies, is missing. A geographic information system (GIS)-based decision support system (DSS) can be a valuable tool for such a task. However, key to such DSS are the factors and their suitability levels, which are not well developed. This study therefore focused on the development of suitability levels for most important factors/parameters for identification of such sites. The factors included rainfall, soil texture, soil depth, drainage, topography and land use or cover. Specific suitability levels were derived from analysis of existing RWH technologies in Makanya river catchment. Results showed that suitability levels of factors differ with different RWH technologies. Suitable areas for ndiva is on steep slopes (18o-30o) with clay soils, stone terraces is on moderately steep slopes (10o – 18o) with sandy clay loam soils, bench terraces (5o-18o slopes, clay or silt clay soils) and “boda” (2o-5o slopes, slit clay or clay soils). It was also found that ndiva, “boda”, stone terrace and bench terrace are located at a distance within 125m from cropland. Testing of the developed parameters using ArcView-based DSS framework showed that 81.4% RWH technologies were located in the very high and high suitability levels, indicating the usefulness of the developed parameters and their suitability levels.Item Impact of projected climate change on agricultural production in semi-arid areas of Tanzania: A case of Same district(2012) Tumbo, S. D.; Kahimba, F. C.; Mbilinyi, B. P.; Rwehumbiza, F. B.; Mahoo, H. F.; Mbungu, W. B.; Enfors, E.Sub-Saharan Africa is one of the most vulnerable regions in the World to climate change because of widespread poverty and limited adaptive capacity. The future climate change is likely to present an additional challenge to the agricultural sector. Therefore, the effects of climate change on the current agronomic management practices were investigated using Same District, Tanzania as a case study area. APSIM software was used to investigate the response of maize (Zea mays L.) yield to different agronomic management practices using current and future (2046 - 2065) climate data. The climate change projections data from global climate models were downscaled using self-organising maps technique. Under the conventional practices, results show that during long rainy season (from March to May) there is yield decline of 13% for cultivar Situka, no change for cultivar Kito and increase of 10% and 15% for cultivars Sc401 and TMV1, respectively. Under the recommended practices, cultivars TMV1 and Sc401 are projected to register a 10% yield increase whereas cultivars Situka and Kito are projected to register a decrease of 10% and 45%, respectively. Also, under both conventional and recommended management practices, results showed that during short rainy season (from October to December/January) all cultivars are projected to register between 75% and 146% increase in maize yields. This implies that future climate change is going to have positive effects on current management practices during short rainy seasons and it will have negligible impact during long rainy seasons.Item Integrated catchment characteristics, runoffwater reservoir capacities and irrigation - requirement for bean productivity(2013) Singa, D. D.; Tumbo, S. D.; Mahoo, H. F.; Rwehumbiza, F. B. R.; Lowole, M. W.Crop production in semi-arid Sub-Saharan Africa (SSA) is limited by over-reliance on rainfall, which is erratic and inadequate. Rainwater conservation and irrigation are needed to avert drought effects and dry spells, and extend crop production activities to dry seasons. A study was conducted from 2011 to 2013 at Ukwe area in Malawi, to determine the size of seasonal open surface reservoir and crop field in relation to catchment characteristics among smallholder farming communities, using beans as a case study crop. There is positive linear relationship between seasonal harvested watershed runoff and rainfall (over 75%). Based on the catchment characteristics and crop water requirement, catchment/cultivated area ratio was 2.1. Harvested runoff water is linearly related to seasonal rainfall amount. About 6000 m3 of water was required to irrigate a hectare of beans. Total volume harvested was estimated to support six-fold the current field area at bean water productivity of 0.7 g L-1. It is possible to determine dry season bean water productivity based on integrated effects of catchment characteristics, runoff water reservoir capacities and irrigation water requirement.Item Knowledge Sharing and Communication Tools for Dialogue Issues on Productivity of Water in Agriculture in Mkoji Sub-catchment, Tanzania(Sokoine University of Agriculture, 2003) Kasele, S. S.; Mlozi, M. R. S.; Hatibu, N.; Mahoo, H. F.The concept of productivity of water in agriculture is new and is understood differently by different stakeholders. Yet to apply it, all stakeholders require a common understanding. Currently there is limited understanding of how the concept can be communicated to different stakeholders. This limits the potential for dialogue to enable concerns to be resolved. This study investigated knowledge-sharing and communication tools suitable in facilitating dialogue among different stakeholders on the productivity of water in agriculture in Mkoji sub-catchment in the upper part of the Rufiji Basin, Tanzania. The study was based on a survey of multiple stakeholders of water in the study area, including direct water users in agriculture, namely farmers; water resources and agricultural experts; and water managers, especially in irrigated systems. A high proportion (87.5%) of the smallholder farmers indicated low awareness of the concept as universally defined. The experts were aware of the basic definition of productivity of water in agriculture as the ratio of total crop yield to the volume of water used. Given past experience in the study areas, knowledge sharing through farmer training, demonstration plots, field visits, radio and posters will assist in increasing the understanding of different stakeholders and thus improve dialogue.