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Assesssment of the Perfomance of sun drying of maize grains on perforated surfaces
(1998) Silayo, V.C.K.; Kajuna, S.T.A.R.; Omari, B.
Sun drying of maize grains on different mesh sizes ofperjorated trays using different heights from the ground was investigated. The mesh sizes used were 1.5 mm and 3 mm at the elevations of 30, 60 and 90 cm. The results show that both mesh size and height from the ground affect the drying rate and seed viability. The combination of90 cm elevation and 3mm mesh size gave the highest drying rates and lowest seed viability loss.
Relationship between the Angle of Repose and Angle of Internal Friction for Agricultural Granular Materials
(1998) Kajuna, S.T.A.R.; Rugenga, E.
The angles of repose and internal friction are important parameters which determine the flow characteristics of agricultural granular materials, such as flour, maize, beans, wheat, sorghum and rice. The angles have a big influence on the design offlow and storage structures of agricultural materials such as hoppers, silos, bunkers and bins because they determine whether the flow will be smooth or not, and whether the bursting forces in relation to vertical forces will be great or not. An apparatus for determination of the angle of repose was specifically designed for the purpose. The a'ngles of repose for three different grains, namely maize, sorghulll and rice at four moisture content levels, namely 10, 15, 20 and 25%wb were determined using the designed apparatus. A tri-axial compression machine was used to determine the angles of internal friction for the same grains and same moisture contents. The data obtained were fed into SAS statistical software for step-wise regression analysis. A model of the form r = 22.35 + 0.013<1> 2; + 0.019[MC] 2 where r = the angle of repose, 1 = angle of intemlilfriction and MC = percent moisture content on wet basis was established, and used to predict the angleofreposefor the tested grains ~ith high accuracy (R2 = 0.97). It was concluded that the angle of repose was consistently higher than the angle of internal friction for all the granular materials tested, and the angle of internal friction was highest for maize, followed by rice and finally sorghum.
Review of rainwater harvesting techniques and evidence for their use in semi-arid Tanzania
(1999) Gowing, J.W.; Mahoo, H.F.; Mzirai, O.B.; Hatibu, N.
Raillwater h.{pvesting (RWH) ,shuuld"be 'regarded as a continuum of techniques thill' link in-situ soil-wate!: conservation at on~'exi;-'ellle to co'nventiona!irrigation {it the ·other. bHitu KWH, comprises i~ group of techniques for preventing runoff and promoting infiltration: Mic/'()-catc~mellt RWH comprises'a group'oftechniques/or collecting overlandfZow;(sheetor rill) from a catchment area and delivering it to a cropped.area in order to supplement the inadequate direc·t':air!faZ{ The transfer nomllllly occurs ·over a reJativelyshOit distance entirely withirt the land-holding of an individual farmer and the system is therefore sometimes known as 'an "illtemai cauhment" .. Macro-catchment RWH comprises a group' of techniques in which natural runoff is collected Fum a relatively large area .and. tr(1nsferred over.a longer distance. Examples of each pf these categories of RWH exist' ill p'a,t's 0/ Ta,';iania, but their potential is }eirgely neglected, by research and extension"seivices alzd they are illlder-exploited. The pUipose of this paper was to 'assess the extent to which thediflerent rainwater harvesting systeniS, are used in Tanzania. The findings show that there is a widespread practice of rainwater harvesting in Tanzania. Rainwater hmvestillg with storage of wate!' for livestock has received govemment SUppOit in the past . . However, rruzny storage reselvoir~ have been destroyed by siltation. On the other hand rainwater hmvesting for crop production has llOt received an adequate SUppOit from research and extension services. Therefore, although farmers are practiciizg rainwaterhmvesting, they are faced with sh01tage of appropriate technolo giesand know
Technical Note on Performance of Macro-Catchment Rainwater Harvesting for Maize Production: Preliminary Results
(1999) Kajiru, G.J.; Hatibu, N.; Bakari, A.M.; Kishebuka, S. R.; Young, M. D. B.
Macro-catchment raiilwater harvesting (RWH) describes those techniques witll much larger Catchment Areas (CAs) (generally > > Iha) which generally do not fall witllin a farmer's land. The CAs and Cropped basins (CBs) will often be very different in character and tlle transfer d.istance may be in tile range of a few hundred metres to several kilometres'- Although runotf efficiency is relatively lower tllan thy. 'microcatchment systems, runoff volumes will still be large because of tlle size of tlle CA. If the transfer distance is very large, it is also possible for tlle CA to receive rain and produce runoff for a CB which has received no rain. Macro-catchment RWH systems include: hillside systems such as tlle "ma jaluba" system of tlle Lake Zone of Tanzania (Meertens et aZ" 1999) where, water is ~hannelled intp bunded rice padis by small channekconstructed across ,tlle slope on grazing land; stream-bed systems which spread water tlowing in ephemeral streams using permeable stone dams or earth b~nds (van Dijk and Ahmed, 1993); and stt-eam diversion systems which chamlel water , trbm ephemeral streams into water-spreading s&uctures such a~ tlle "Caag" system of Somalik (Reij, 1991) The mairi problems with these : s~stems are, in controlling tlle sometimes very high volumes of runoff and preventing erosion. I The risk of too' much water washing away tiblds is a major problem in Western Pare I - Lowlands (WPLL).
Performance of maize under micro-catchment rainwater. harvesting in western Pare lowlands and Morogoro, Tanzania
(1999) Hatibu, N.; Gowing, l.W.; Mzirai, O.B.; Mahoo, H.P.
Micro-catchment Rainwater Harv.esting. (RWH) has been defined as a method of collecting run-off from a Catchment Area (CA) over short distances not exceeding 100 m and supplying it to an adjacent Cultivated Basin (CB). It is a system that is designed to concentrate rainwater so as to utilize it more effe"ctively in areas- where. the seasonal. rainfall amounts are frequently lower than crop water requirements. The Catchment to Basin Area Ratio (CBAR) is an important parameter in the design of micro-catchment systems. It usually varies between 1:1 and 10:1. However, methodsfor deciding the optimumle·ve! of CBAR for differef!t farming systems are not available. The purpose of the experiments reported here was to evaluate the CBARfor maize production in semiarid areas of Tanzania. The experiments were run between 1992 and 1995. in semi-arid areas of Morogoro and Mwanga Districts of Tanzania, to assess the peiformance of maize grown in microcatchment systems with CBAR varying from 0:1 to 4:1. Maize var. TMVI was grown in Mwanga District while maize-var. Staha was used as a test crop in Morogoro District. Grain was harvested in five out of six experimental seasons in Mwanga (Masika 1993, 1994 and 1995 and Vuli 199411995 and 199511996). In Morogoro, grain harvest was obtained only in two seasons (Masika 1993 and 1994) out offour. The results showed that micro-catchment RWH farming is feasible during Vuli. The yield benefits due to RWH were found to be 120 - 152· % and significant at P = 0.05. The benefits during Masika were found to be very low at only 12 - 17 % and not significant at P = 0.05.
Soil nitrogen dynamics and relationships with maize yields in a gliricidia–maize intercrop in Malawi
(Kluwer Academic Publishers, 1999-04) Ikerra, Susan T.; Maghembe, Jumanne A.; Smithson, Paul C.; Buresh, Roland J.
Many soils of southern Africa are severely N deficient, but inorganic fertilizers are unaffordable for most sub- sistence farmers. Rotations and intercrops of legumes with crops may alleviate N deficiency through biological N 2 fixation and redistribution of subsoil N to the surface. We monitored soil inorganic N dynamics for two seasons in a gliricidia [Gliricidia sepium (Jacq.) Walp.] – maize (Zea mays L.) intercrop in the unimodal rainfall area of southern Malawi. One maize crop per year was grown with or without interplanted gliricidia, in factorial combination with three rates of N (0, 24 or 48 kg N ha −1 ). Application of gliricidia prunings increased (p < 0.001) topsoil (0 to 20 cm) inorganic N at the end of the dry season and during the early rains. Differences between plus and minus gliricidia treatments were less when total inorganic N to 1-m depth was summed. A greater proportion of the total inorganic N to 1-m depth occurred in the topsoil (0 to 20 cm) when gliricidia was present, suggesting that redistribution of subsoil N to the surface accounted for part of the N increase by gliricidia. Gliricidia lowered (p < 0.05) subsoil water content during drier periods. Gliricidia plots accumulated more (p < 0.01) ammonium-N during the dry season. Nitrate-N remained constant during the dry season but rose rapidly in gliricidia plots after the onset of rains. A 2-factor model including preseason inorganic N and anaerobic N mineralization potential accounted for 84% of the variability in maize yields for the two seasons’ data combined. The combination of preseason inorganic N and potential N mineralization appears to provide a good estimate of N supply to maize in systems receiving both organic and inorganic sources of N.
Validation of crop weather models for crop assessment arid yield prediction under Tanzania conditions
(2000) Kihupi, N.; Dihenga, B.O.; Ntella, P. M.
Information gatheringfor early warning and crop assessment in Tanzania is based on physical inspection of standing crop in sample jields. This process is subject to human error, inadequate and is also time consuming. Recent developments in computer simulation have paved the way for more efficient methods of analysing datafor purposes of early warning and crop assessment. Two such sch~mes based on soil water balance simulation, viz. IRSIS and CRPSM models were used in this study fo see how closeZv they could predict grain yieldsfor selected stations in Tanzania. Inputfor the models comprised of weather, crop and soil data collected from jive selected stations. Simulation results show that IRSIS model tends to over predict grain yields of maize, sorghum and wheat, a fact that could be attributed to the inadequacy of the model to accurately account for rainfall excess. On the other hand, the CRPSA1 model simulated results were not significantZv different (P>O. 05) from the actual grain yields ojmaize, sorghum,. wheat and beans. Although the agreement between actual and simulated yield data was good, it was observed that mean valuesfor predicted grain yields were consistently lower thanfor actual grain yields. This could be attributed to the use of approximate rather than location specific input parameters required by the CRPSM model. Locally calibrated input parameters in the CRPSM model could filrther improve the accuracy of the model and hence its ability to predict grain yields.
Effects on direct sun drying of maize grains on perforated and unperforated surface
(2000) Silayo, V.C.K.; Woods, J. L.
Sun drying ofmqize grains on unperforated and perforatedsurfaceswas conducted under simulated solar radiation intensity of afJout 800 Wlm: and in the field, where solar radiation intensity was variable. ,The drying depths employed were 10, 20, 30 and 40 mm under simulated solar radiation conditions and 20 and 40 mm in the field The response variables measured were weight loss at all depths and moisture content and temperature distributions in the 40-mm depth bed The results in terms of overall drying rates indicate that, at depths greater than 10 mm, the perforated surface was superior (P < 0.05) to the unperforated and at 40 mm th.e efJectwas about double that of the contro/. Changi,!gof dryingdepthfrom 10 to. either 20 or 30 mm on the perforated surface did not affoct the specific drying rates significantly (P < 0.05) 'except on 40/,;;n depth. On the unperforated surface the overall specific drying rates decreased significantly (P
Investigation of laser and ultrasonic ranging sensors for measurements of citrus canopy volume
(American Society of Agricultural Engineers, 2002) Tumbo, S. D.; Salyani, M.; Whitney, J. D.; Wheaton, T. A.; Miller, W. M.
This study compared ultrasonic and laser measurements of citrus canopy volume with manual measurement methods. Fifteen trees with different canopy heights and volumes were used. Manual and ultrasonic measurements provided dimensions for computing the canopy volume whereas laser measurements gave information that could be used to compute a ‘laser canopy volume index.’ Ultrasonic and laser methods agreed with manual methods (R2 > 0.85, RMSE < 2.15 m3). Laser showed better prediction of canopy volume than the ultrasonic system because of the higher resolution. Ultrasonic or laser sensors can be used for automatic mapping and quantification of the canopy volumes of citrus trees.
Failure of the Mtera-Kidatu reservoir system in the Early 1990s
(SUA, 2003) Yawson, D.K.; Kachroo, R.K.; Kashaigili, J.J.
Four possible causes for the failure of the Mtera-Kidatu Reservoir System within the Rufiji River Basin in Tanzania in the early 1990s were investigated. These were sudden decrease in inflows, sudden increase in losses, sudden increase in hydropower generation, and unnecessary spills; or a combination of these, and it was found out that unaccounted for and unnecessary spillage was the main cause. This paper proposes that consideration of the flows that are generated within the intervening catchment (i.e. catchment between Mtera and Kidatu) and the operational policy that maximum power is produced at Kidatu most of the time must be the core in the management of the reservoir system. If this was the case in the past then the Mtera Reservoir should not have gone dry in the 1991-1994 period. The validity of this assertion was tested with the TALSIM 2.0 model and an efficiency of 95% was achieved, indicating a very good correlation with the investigative techniques employed in this study.
Water productivity indicators in great Ruaha river basin: analysis and implications for decision-making and allocating water
(SUA, 2003) Mdemu, M.; Lankford, B.; Kadigi, R.M.J.; Cour, J.; Kashaigili, J. J.
The assessment of benefits from water by applying the concepts of water productivity is gaining momentum for managing water resources in river basins. A number of institutions have been in the forefront of spearheading the concept. The attractiveness of the water productivity concept is partly due to its diversified nature in looking at benefits of water use, both intended and unintended in a particular system. The benefits may include area irrigated, number of families depending on a particular source of water, number of jobs created as a result of presence of water. This paper explores water productivity indicators and their implications for allocating water drawing the example from the Great Ruaha River Basin. In addition to the primary and secondary indicators of productivity, the paper develops the concept of tertiary indicators (labelled ‘specific hydrovalue’) to express the economic benefits gained per person per cubic metre of water used. The paper concludes that water productivity indicators (WPIs) can be used as a tool for analysing the tradeoffs and prioritising of water use and allocation in competing and non-competing water uses but that much more conceptual and computational analysis is required
Modelling the Mtera-Kidatu reservoir system to improve integrated water resources management
(Hydro Africa, 2003) Yawsona, D.K.; Kashaigili, J.J.; Kachroo, R.K.; Mtalo, F.W.
Failure of the Mtera-Kidatu Reservoir System within the Rufiji River Basin in Tanzania in the early 1990s is investigated by considering four possible causes (i.e. sudden decrease in inflows, sudden increase in losses, sudden increase in hydropower generation or unnecessary spills; or a combination of these) and it was found out that unaccounted spillage seems to be the main cause. Consequently, the system’s simulation model has been proposed in this paper that takes into consideration the flows that are generated in the intervening catchment (i.e. catchment between Mtera and Kidatu) with the operational policy that maximum power is produced at Kidatu most of the time because Kidatu has higher head for greater power generation than at Mtera. The paper shows that if this proposed model had been in place then the Mtera Reservoir should not have gone dry in the 1991-1994 period. The validity of the proposed model is tested with the TALSIM 2.0 Model and the regression analysis of the water levels at Mtera Reservoir produced by the models had an efficiency of 95%, indicating a very good correlation. The proposed model operates the reservoir system in an integrated manner by considering the flows into the Mtera Reservoir as well as accounting for the flows generated by the intervening catchment.
Rice production economics at the local and national levels: the case of Usangu plains in Tanzania
(International Water Management Institute (IWMI), 2003) Kadigi, Reuben M. J.
This report explores the production economics of paddy at the basin (Usangu), district (Mbarali), regional (Mbeya) and national (Tanzania) levels. The important features of the report are summarized in the document.
Mapping uses and competition for shared water resources: conflicts and values in Mkoji sub-catchment, Tanzania
(Loskopdam, South Africa, 2004) Hermans, Leon M.; Kadigi, Reuben M. J.; Mahoo, Henry F.; Halsema, Gerardo E. van
Conflicts over water are a common feature in closing basins and the difficulties in resolving them provide a serious barrier for the formulation of an effective IWRM strategy. Understanding the specifics of a conflict, including its dynamics and its evolution, provides an essential basis for subsequent efforts towards conflict resolution. Since conflicts are driven by interests and values of stakeholders, insight into the values underlying conflicts may further help the identification of promising ways to resolve them. Especially the latter is of crucial importance, as the identification of effective solutions to conflicts still remains more of an art than a craft. This paper discusses the use of two analytic frameworks that support a better understanding of local conflicts over water: conflict analysis and value- focused thinking. It illustrates the use of these frameworks to analyse local water conflicts in a closed sub-catchment in Tanzania. It shows how these frameworks support the identification of solutions that can help local stakeholders to “create value” in closing basins. On the basis of this illustrative analysis, the paper argues that these two frameworks deserve a wider use in the field of local water management.
Using the PT model to determine appropriate water management for maize production: A case study of Fulwe village in Morogoro district
(2005) Pangapanga, C. P.; Marijani, B. J.; Tumbo, S. D.; Mpulila, T.; Rwehumbiza, F. B.
Fulwe village is located in Mikese ward, some 30 kilometres east of the Morogoro Municipality, along the Morogoro - Dar es Salaam highway. It is located at longitude 37º53’60’’ East, and the latitude is 6º46’ south. The annual rainfall ranges from 700mm to 1000 mm. The short rainy season (Vuli) starts in mid-October and ends in December while the long rains (Masika) start in February and ends in mid May. The dry season extends from June to October. The annual average maximum and minimum temperatures are 26ºC and 21ºC respectively. Soils are acidic lithosols and ferralitic latosols with deeper deposits of ferruginous sandy clay. Fulwe villagers depend mostly on rainfed agriculture and maize is the main staple food and also one of the major sources of income. Other crops cultivated include beans, soybeans and horticultural crops.
Determinants of farm-level adoption of water systems innovations in dryland areas: The case of Makanya watershed in Pangani river basin, Tanzania
(2005) Masuki, K.F. G.; Mutabazi, K. D; Tumbo, S. D.; Rwehumbiza, F. B.; Mattee, A. Z.; Hatibu, N.
Water system innovations such as rainwater harvesting involve abstraction of water in the upper catchments. Increasing adoption of rainwater harvesting in the riparian catchments could have hydrological impacts on downstream flows in the river basin, but it is assumed to have overall gains and synergies when efficient use of rainwater is optimized at farm-level. This paper examines the main determinants of adoption of water system innovations with specific emphasis on the intensity of adoption and adoption lag, using a cross-sectional sample of 234 farmers in the Makanya watershed. Censored Tobit models were used to estimate the coefficients of intensity of adoption and adoption lag of water system innovations. Group networking, years spent in formal education, age of respondent, location and agricultural information pathways were found to be major determinants of intensity of adoption at farm-level. It was also found that intensity of adoption and frequency of attendance to collective action are strong determinants of adoption lag of water system innovation in Makanya watershed. Empirical knowledge of the determinants of adoption of water system innovations is critical for an effective scaling out of best practices of water harvesting in the Basin.
Crop water productivity of an irrigated maize crop in Mkoji sub-catchment of the Great Ruaha River Basin, Tanzania
(Elsevier, 2006-09-16) Igbadun, Henry E; Mahoo, Henry F; Salim, Baanda A; Tarimo, Andrew K. P. R.
Crop water productivity (CWP) is a quantitative term used to define the relationship between crop produced and the amount of water involved in crop production. It is a useful indicator for quantifying the impact of irrigation scheduling decisions with regard to water management. This paper presents CWP quantified from field experimental data. Three fields were cultivated to maize under irrigation during the 2004 dry season in a traditional irrigation scheme in Tanzania. The maize crop was irrigated at eight different seasonal water application depths: 400, 490, 500, 510, 590, 600, 610 and 700 mm, in two of the three fields, and at five water application depths: 400, 590, 600, 610 and 700 mm in the third field. The variation in seasonal water application depth was achieved by skipping the weekly irrigation once after every other irrigation at some pre-defined stages of the crop growth. CWP were computed in terms of …
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.
Evaluation of a variable rate controller for aldicarb application around buffer zones in citrus groves
(2007-01-25) Tumbo, S. D.; Miller, W. M.; Salyani, M.; Sweeb, R.; Buchanon, S.
Advances in precision farming technologies have facilitated controlled application of agrochemicals and documentation procedures to follow environmental regulations. This paper details evaluation of a commercial variable rate (VR) controller for preventing aldicarb applications in the buffer zones around potablewater wells of citrus groves. The controllerwas coupled to two common drive mechanisms, a ground-driven electric clutch-engaged (GDEC) and pulse-width-modulation motor-driven (PWMM). The evaluation involved determination of dynamic performance of the VR application system through quantification of reaction times and rate transition distances and determination of appropriate “look-ahead” times for each of the drive mechanisms. Without a look-ahead (zero) setting, the mean midpoint reaction distances were about 1.8 and 3.6m for the GDEC and PWMM mechanisms, respectively, at 7.0-km/h ground speed. For the GDEC, a look-ahead time of 1 s gave the mean midpoint reaction distances of −0.06 and 0.04m during step-up and step-down of the rate, respectively. For PWMM, the best look-ahead times were 1 and 2 s during step-up and step-down of the rate, respectively.However, since the prototype unit could not accommodate two look-ahead times, the compromise look-ahead time for both step-up and -down was 2 s. Validation in the actual buffer zone showed that, at 95% confidence level, the buffer zone should be increased by 2.5 or 3.3m in commercial applications using GDEC or PWMM systems, respectively.
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.

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