Agricultural Engineering and Land Planning Collection

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Plant-water status and grain yield of maize (zea mays l) in relation to soil water status at Morogoro, Tanzania.
(Sokoine University of Agriculture, 1987) Rwehumbiza,Filbert Bartazar Rwabulala
Analysis was made of reference crop evapotranspiration (Eto) and rainfall (R) data on a 10-day basis over a 10-year period (1973/74 - 1982/83).On the average, ETo exceeds R during the entire short rain season thus making production of crops other than those tolerant to water stress a risky undertaking.The effects of soil water holding capacity (WHC), cultivars,and water regimes on soil ~ and plant - water status, growth, grain yield and yield components of maize (Zea mays L) were identified.The study was conducted during short rains on two soils (both Ferralsols) one x
Assessment of the utilization, management and operating costs of agricultural tractors in the Chemelil Sugar Belt in Kenya.
(Sokoine University of Agriculture, 1992) Onyango, Ogweno Samuel Roger
The research undertook to study the utilization, management and operating costs of agricultural tractors used in the Chemelil sugar belt in Western Kenya. Historical cost data spread over a span of 16 years were obtained for 141 tractors operated by three different owners in the belt. The data was used to assess the level of utilization and operating costs and to test mathematical models for predicting tractor resale values, repair and maintenance costs, annual operating costs as well as establishing the factors that influence them. It was found that tillage tractors in the belt had an average annual use of 1040 hours and transport tractors 1230 hours and that both category of tractors had restricted utilization due to limits imposed by maximum hectarage for tillage tractors and queuing discipline at the sugar factory and in the fields for cane transport tractors.Mathematical models were formulated and tested for relation between ratio of tractor resale value to its current purchase and repair initial and depreciation age,maintenance costs purchase price and relation expressed tractor between cumulative as a percentage, of cumulative depreciation against tractor age and resale value to its annual operating cost against tractor age. Multiple regression computer software in the MSTATC version facility package was used to test the 1 .41 models. Important empirical relations were derived from the results of the tests. Qualitative factors were the investigated quantities shown to influence quantitatively and that the control of the qualitative factors could reduce operating costs.A relation for predicting annual operating costs of a tractor basing on its replacement value was found. The relation could also be used to predict the tractor’s optimal replacement point similar given the future substitutive models. found to defy prices of or The trend of actual depreciation was basic the depreciation models. Purchase assumptions of accounting It was demonstrated that due to high inflation rates it is not possible to assign terminal salvage values to tractors notwi thstandi ng.in good running order, their age not with standi ng.
Sprinkler perfomance evaluation at Mtibwa Sugar Estates
(Sokoine University of Agriculture, 1994) Emmanuel,Marealle
ABSTRACT A perfomance evaluation study aimed at evaluating Mtibwa sprinkler irrigation system was carried out at Mtibwa sugar estates,Morogoro. The specific objectives were:(1)To investigate whether the application rate,duration of application and operating pressure of the current system meet the sugar cane water reqirement with respect to the prevailing soil moisture deficit.(2) To investigate sprinkler irrigation performance parameters whether the system is operating as designed and give recommendatons in relation to low yield difference between irrigated and rainfed cane.The results showed that about 20 % of all sprinkler irrigated blocks had coefficient of uniformity below 80 %.The pressure recorded ranged from 1.8 to 3.2 bar and 73 % of all blocks had sprinklers operating below the designed pressure of 3.2 bar.From the performance parameters the study showed that about 38 % of all blocks required longer duration of irrigation than the current practiced one. The longer required duration per set is identified to be due to low application rate which is also caused by low operating pressure at the pump stations and consequently to the sprinklers. Therefore,the low yield and insignificant yield differences between irrigated and rainfed sugar cane is caused by poor performance of the sprinkler system.This led to inadequate application of water.
Sustainability of irrigation schemes for small scale farmers: a case study of furrow irrigation scheme at Buleya Malima, Gwembe Valley Zambia.
(Sokoine University of Agriculture, 1995) Masinja,Rusmus
This study was carried out to determine factors that influence sustainability of smallholder irrigation schemes in Zambia.This was against background the that many schemes have been opened by the government to resettle people and have operated smoothly under its management. But upon government withdrawal, farmers have failed to manage these schemes. The study was carried out at Buleya Malima smallholder irrigation scheme.The objectives of study were; (a) to evaluate the schemes using technical and socio-economic parameters inherent current practices in the scheme, and, (c) improving the performance assess the to make recommendations for of the (b)scheme to and management practices. The average results for technical study were: 26.4%, 64.5% and 9.2% for application efficiency, tailwater ratio and deep percolation ratio respectively. The results revealed thSustainability of irrigation schemes for small at there was a waste of water by farmers through tailwater runoff. Thus, the system was performing poorly, and could not be sustained at these levels of water loss.The study on socio economic revealed that irrigated farming could be sustainable if properly designed and planned with the involvement of the farmers. The big problem was lack of managerial ability innovativeness and by the scheme management to provide farmers with enabling environment to form their own viable organisations which could see the continuity of the scheme even after the government had withdrawn. Farmer Participation in planning,decision-making and implementation of these decisions is advisable in order to sustain the scheme operations. Enabling environment for Management should create farmers to form viable associations through which farmers and management would co ordinate their operations. Formal and informal training in technical operations of irrigation infrastructure and new agricultural practices should be provided, so that farmers are able to operate the irrigation system with minimum dependence on management trained management Therefore, personnel to provision of well impart appropriate knowledge on the operations and maintenance of irrigation system is advisable.
Evaluation of sprinkler irrigation performance at Simunye Sugar Estate in Swaziland.
(Sokoine University of Agriculture, 1995) Magongo,Bongani Harmon
The performance the evaluated study irrigation system at Simunye,objectiveswere:parameters,(1)To identify the original parameters,(2)To investigate performance parameters,whether the system is operating as designed,and (3)To recommend suitable changes in the operation and system configurations that could be implemented to improve the irrigation efficiency. The results showed that there were no available design parameters on which the system of Simunye Sugar Estate was designed. The system showed a uniformity coefficient (Cu)of 76%,which is within recommended Cu range for design market acceptance.The Distribution uniformity obtained was 61% and the potential application efficiency for the low-quarter (PELQ) was found to be 54%.Both of these parameters were lower than the recommended ones, and they were significantly different when compared with the recommended ones of at least 67% and 75-85%, respectively.The actual application efficiency for the lower-quarter (AELQ) was found to be 45% which is too low when compared to the PELQ.The minimum basic infiltration rate of the soils irrigated by sprinkler system was 5 mm/h. Factors which contributed to the non-uniformity of the system were wind velocity and wind the direction operating pressure (which was too high or lower than the recommended one for the system), evaporation losses,and the sprinkler spacing. From the results it was shown that management of the irrigation system had an effect on the poor performance of the system.
Technical and economic comparison of performance between farmer and government managed irrigation schemes in Tanzania: a case study of Kapunga irrigation project
(Sokoine University of Agriculture, 1996) Chemka, David Nyakamwe
This study compares the performance of government-managed irrigation schemes (GMIS) to farmer-managed irrigation schemes (FMIS) at Kapunga rice irrigation project in Mbeya region in Tanzania. The specific objectives were to evaluate: (i) organisational structure of the two systems; (ii) water management aspects of the two systems; productivity and Appropriate (iii) economic performance of the two systems. Indicators been have used to quantify performance of the two types of management of irrigation. Results of the study show that the farmer-managed scheme, performed better than the government-managed scheme in attaining scheme irrigation efficiency, productivity,economic, and productivity, irrigation scheme financial in profitability. Applicable indicators for the farmer-managed irrigation schemes are quantified as shown below. Those of the government-managed scheme are indicated in brackets. efficiency was 61% (29%) ;Its overall irrigation average productivity was 3.2 ton/ha (2.2 ton/ha); economic profitability: internal rate of return was 3.2% (5%), benefit/cost ratio 0.6 (0.14); while its financial profitability: internal rate of return was 3.9% (5.1%), benefit/cost ratio 0.6 (0.13). The organisation of both the government and farmer-managed irrigation schemes were appropriate, however, both schemes were weak in irrigation management as the essential operation and maintenance activities were not carried out effectively. Schemes Both the government and the farmer-managed had canal maintenance problem. There was corresponding big error in water adequacy of 86% and 98% respectively arising from improper water control at the secondary canals offtake.Paddy nurseries in the government-managed scheme had undesirable water stress. However, both schemes were able to distribute water equitably, reliably, as well as maintaining a correct field water depth from tillering to flowering and grain formation stages.
The effects of rainfall and catchment characteristics on runoff yield in semi-arid areas of Tanzania
(Sokoine University of Agriculture, 1996) Ojesi,Samson Oscar Frackson
A complete randomised block design three replications (viz :at 6%,experiment with (CRDB) and 15% 18% slope) was conducted in Kisangara, Tanzania from November, 1994 to May,1995. The experiment consisted of catchment length (viz: 6 m and soil surface cover treatments and 12 m) (viz:natural vegetation and bare-and-compacted) . The study period covered two rainy seasons, short rainy season (locally known as Vuli) and rainy long of objectives season the study Masika). (locallyknown wereinvestigate to as The effects of rainfall and catchment characteristics on runoff yield and to use the data obtained to develop and test an empirical model for semi-arid conditions of Tanzania.Runoff yield from 60 m2 (10 m x 6 m) and 120 m2 (10 m x 12 m) catchments was measured using a runoff collecting system.Rainfall, soil particle size distribution, soil moisture, infiltration rate and soil bulk density for the catchments were also monitored throughout the two rainy seasons. The results generated a showed that catchments at 18 percent slope significantly higher mean runoff yield than the catchments at 6 percent slope equal to or more than 6 mm. (p< 0.05) at rainfall amount similarly catchments at 15 percent slope generated a significantly higher mean runoff yield than catchments of 6 percent slope (p< 0.05) at a rainfall amount equal to or more than 6 mm. However, the mean runoff yield generated from catchments at both 15 and 18 percent was not significantly different (p< 0.05). The mean runoff yield per unit area of catchment was not significantly different from the 6 m and 12 m length catchments. However, the total mean runoff yield generated from the 6 m length catchments was 9 percent- more than the total mean runoff yield generated from the 12 m length catchments for the two rainy seasons studied. The mean runoff yield from bare and compacted catchments was significantly different from the mean runoff yield generated from natural vegetated catchments (p< 0.01).The mean runoff yield from bare and compacted catchments at 18 percent slope was highly correlated with the rainfall characteristics (r> 0.95).Overall correlation coefficient between mean observed and mean predicted runoff of the empirical model developed was high (0.84) indicating that the model is suitable for semi arid conditions of Tanzania and can reliably be used to predict runoff in areas where no such measurements are made to design harvesting. The optimal micro-catchments for rain water.
Effects of Mswiswi watershed degradation on stream flow in Usangu village irrigation project
(Sokoine University of Agriculture, 1997) Malongo,Gerald Wanda Sere
The effect of Mswiswi watershed degradation on stream flow was investigated as one of 5 watersheds used by Usangu Irrigation Project as source of water. The watershed was calibrated upon itself by establishing four watershed degradation scenarios as the basis for comparison of watershed degradation parameters and stream flow characteristics. The established degradation scenario were 1960-65, 1965-75, 1975- 86 and 1986-92. The 1960-65 degradation scenario was taken as the control period i.e the period for which watershed degradation was at the minimum level. Therefore all parameters of watershed degradation and stream flow of certain probabilities in 1960-65 were compared with the same parameters in other three scenarios.Watershed degradation evidence analyzed from aerial photographs of 1977 and 1992 shows that: watershed forest loss was 0.105 , 0.032 and 0.497 km2/year for mixed forest,forest reserve and low dense miombo woodland, respectively. Soil degradation through gully expansion was 0.049 km2/year.The study shows that precipitation in Mswiswi watershed is decreasing from 1963-1986. This has been evidenced by decreasing trend of 5-year moving averages of precipitation and precipitation of certain probabilities. Comparison of watershed degradation parameters in four degradation scenarios shows that there were a differences among scenarios as a result of degradation. There was a general decreasing trend of parameters such as watershed storage and watershed loss factor from degradation scenario of lower order (1960-65) to scenario of higher order (1986-92). This means that the trend of decrease in watershed degradation parameters was from 1963-1989. Watershed degradation parameters such as curve number and watershed degradation factor were, on the contrary, increasing from 1963-1989. The decrease of watershed loss and watershed storage indicate that watershed was degrading as has been evidenced by watershed forest loss. Similar indication of watershed degradation was shown by increase of curve number and watershed degradation factor. This study shows that there was a relationship between increasing trend of runoff and increasing or decreasing trend of watershed degradation parameter from one degradation scenario to another for a particular probability of exceedance. Runoff of 10 % probability was increasing from watershed degradation scenario of lower order to scenario of higher order as watershed storage and loss factor of the same probability was decreasing. The trend of changes in base flow of particular probability of exceedance was more related to the trend in which watershed degradation factor of the same probability was varying. Stream flow from Mswiswi watershed is affected by both climatic changes and watershed degradation. To evaluate the effect of watershed degradation alone, the developed runoff and base flow models were run for equal rainfall events, so as to see how the watershed in the process of degradation in different periods was responding or would respond to the same rainfall events. The results of model utilization show that runoff was increasing as the watershed was degrading for equal rainfall events. In the case of base flow, the results of model utilization show that watershed degradation was causing cyclic trends of base flow variability. The maximum and minimum base flow for equal rainfall were having recurrence intervals of ten years. The magnitude of maximum and minimum base flow was decreasing with time as watershed was degrading for equal rainfall events.
Farmers’ utility of irrigation water supply as a method of assessing irrigation system’s performance.
(Sokoine University of Agriculture, 1997) Makongoro, Elfariji Kohi
A model which employ Farmers’ Utility of Irrigation Water Supply (FUIWS) in assessing irrigation system’s performance has been developed in this study. The methodology was tested through a Case Study at Lower Moshi Farmer Managed Irrigation Scheme (Lower Moshi FMIS). The main objective was to investigate FUIWS as a method of assessing the performance of irrigation systems. Strong relationship was observed between Relative Water Supply (RWS) and FUIWS. Wherever RWS was high FUIWS was also high and vice versa as proved by positively large covariance value obtained. However, this relationship was identified as non linear correlation by significance correlation coefficient test. The graphs plotted showed relationship of the type: R = aen Where:R = RRWS in paddy fields. U' = UFUIWS. a and n are constants. In this particular Study, the scheme model obtained was: R = 0.377e,1,2SU Similar block models were established. The homogeneity test on the block mean values showed that; RWS have the same degree of variability for all levels of FUIWS. This indicated the ability of the scheme model to be used in place of block models. Different "a" and "n" constant values obtained between blocks indicated different irrigation management levels between blocks. The method was tested in paddy rice only, therefore more work is needed to test it in upland crops; traditional and improved Farmer Managed Irrigation Scheme (FMIS). Also, more research is required to establish whether threshold values "a" and "n" are universal or not and what factors influencing them.
Intervention measures and their effects on farmer managed irrigation schemes in Tanzania:a case study of Musa Mwinjanga irrigation scheme.
(Sokoine University of Agriculture, 1997) Omari,Juma Mzee
The study aimed at evaluating the effects emanating from intervention on farmer managed irrigation schemes (FMIS) was carried out at Musa Mwinjanga Irrigation scheme. The specific objectives were: (I) To evaluate the scheme rehabilitation status; (ii) To investigate the causes and magnitude of water losses; (iii) To evaluate water supply requirements; (iv) To assess and evaluate water management aspects of the system. Results showed that the scheme has been operating at low efficiency. The conveyance, distribution, application and project efficiencies were found to be 53.6%, 53%, 59.8% and 31.7% respectively. Low irrigation efficiencies have been attributed to high conveyance losses due to the pervious nature of volcanic soils and poor command of the canals. Most of the canals were found running below the field levels. Other reasons include high’operation losses due to poor water management practices; lack of water control facilities; and application losses arising from poor land levelling. The seasonal mean relative water supply (RWS) for plots varied between 0.96 and 2.92 due to inadequate irrigation scheduling and lack of flow measuring facilities. The overall seasonal mean RWS for the plots was found to be 1.83 with coefficient of variation of 0.354 and standard deviation of 0.647, indicating inequity of water distribution among the plots.T-test results of RWS within blocks showed no significant difference in adequacy of • supply at 5% significance level. This implies that farmers in sampled blocks were adequately irrigating at more or less equal proportion as per crops water requirements.Organisation of the scheme was found to be fairly appropriate. However, operation and maintenance activities are not timely, effectively and efficiently carried out.•Natural drainage and slopes within the scheme are not efficiently used and managed hence the waterlogging problems in lowland areas of the central part of the scheme. From the study, it is recommended that outstanding physical works left during phase-I should be accomplished. Damaged facilities should be repaired and farmers should be trained on proper water management aspects.
Use of landsat thematic mapper and ancillary data in assessing potential areas for rainwater harvesting cropping systems
(Sokoine University of Agriculture, 1997) Kweka,Amini Rabi
Rain Water Harvesting (RWH) is a system which can store and redistribute the moisture needed to enhance yields, in areas where rainfall distribution limit dryland crop production. In regions where rainfall is insufficient to produce’ even a minimum crop, water harvesting offers the potential to bring those areas under cultivation. However, in many areas,conventional planning data for selecting prospective sites for RWH cropping system is in most cases not easily available or not up to date. This study assess the possibility of using satellite images to improve and up-date the required data.This study used a nested procedure, combining a coverage of a small sample area by Landsat Thematic Mapper (TM) satellite imagery,conventional photo interpretation and analysis of soil and topographic maps to identify potential areas for RWH cropping system. Computer pattern recognition techniques were used to discriminate soil information from the Landsat Thematic Mapper (TM) satellite data on a sample area. Soil mapping units photo from a conventional soil survey and aerial interpretation were matched to the spectral map for interpretation and classified soil description of the generated classes. Field investigations were done to confirr the results of the sample area which was then extended to
Pricing of irrigation water in a farmers-managed irrigation scheme in Tanzania: a case study of lower Moshi.
(Sokoine University of Agriculture, 1999) Mutabuzi,Lutatina James
A computer program model for pricing irrigation water among beneficiaries, was developed by the use of Turbo Pascal language. The data that was used to test the model was collected from Lower Moshi Farmer-Managed Irrigation System (FMIS) in Northern part of Tanzania as a Case Study area.The aim was to evaluate the costs involved in the process of allocating irrigation water with the objective of developing a computer program model appropriate for pricing irrigation water in FMIS in Tanzania. Allam’s (1987) mathematical model for allocating irrigation water price which was developed in Egypt, was adopted and adapted for the purpose. The results show that the irrigation water prices obtained differ between different blocks within the same system, and also there is significant difference of irrigation water prices between two systems that exist in Lower Moshi Irrigation System (LMIS) i.e Rau and Mabogini. By manual calculations, Mabogini irrigation system’s water price ranges from 8,276 Tshs/ha to 14,972 Tshs/ha; while for Rau system it ranges from 3,896 Tshs/ha to 13,857 Tshs/ha; with their mean values of 11,940 Tshs/ha and 10,538 Tshs/ha respectively.The computer program model produced irrigation water prices ranging from 8,479 Tshs/ha to 15,200 Tshs/ha for Mabogini system; while for Rau system they range from 3,913 Tshs/ha to 13,858 Tshs/ha, with their mean values of 12,151 Tshs/ha and 10,414 Tshs/ha respectively. The mean value was adopted as the system irrigation water price in each system. The farmers’ capacity to pay Irrigation Service Fee (ISF) was also assessed and found to be 154,309 Tshs and 194,309 Tshs for tenant and landowner farmers respectively.The irrigation water pricing computer program model was tested for one cropping season. Therefore, more work is required to test it for the two cropping seasons, and in other FMIS so as to develop universal model. This will make it more universally applicable in Tanzania.
Modelling the water balance of a small catchment: A case study of Muhu catchment in southern highlands of Tanzania
(Sokoine University of Agriculture, 2000) SHIBA, S1PHO SIMEON S. T.
I'he water balance ol'Muhu catchment located in the Southern Highlands of Tanzania in Iringa region was modelled by establishing the empirical relations that exist between storage parameters, rainfall parameters and runoff components. Storage parameters included soil moisture storage and interception. Rainfall parameters included rainfall amount, intensity, duration. throughfalL stemflow and evaporation. Runoff components included total runoff, direct runoff and base How. The catchment's physical and hydrological characteristics that affect these parameters were determined. 1 he assessment of hydrological and physical properties showed that the soils were predominantly sandy clay, having high organic matter content, with a moderately rapid hydraulic conductivity (Ks) of 4.2 cm/h and infiltration rale of 3.8 cm/ h. The bulk density was generally low with an average of 0.9 g/cnT for 0-15 cm depth: 1.1 Ig/cm5 for 15-30 cm depth and 1.30 g/cm’ for 30 - 45 cm depth. The catchment had a slope steepness of 35 % and a varying vegetal percentage cover of about 56 %. The 1997/98 waler year was exceptional with high rainfall (1934 mm) mainly due to the El-nino phenomenon. Sixty-seven percent of the rainfall received in the catchment penetrated the canopy to reach the forest floor as throughfalL On average 3.3 % of the rainfall reached the forest floor as stem flow' while 25.5% of the rainfall was intercepted by the canopy. ThroughfalL stemflow and interception were linearlyIll related to rainfall. Die regression coefficients of all the relationships were significantly different from zero al 1% level (fteO). With increasing percentage surface cover, interception increased while throughfall decreased. The storage capacity of the forest cover was estimated to be 0.7 mm.
Effects of farmer-initiated modifications of water control structures on performance of irrigation system:a case study of Mkindo Scheme, Morogoro, Tanzania
(Sokoine University of Agriculture, 2000) Matiku,John Magorombe
A study to assess the effects of farmer-initiated modifications of water control structures on the performance of the irrigation system in Tanzania was carried out at Mkindo farmer managed irrigation scheme (FMIS) in Morogoro region. The scheme had two phases. The changes made on the original water control structures were assessed, the performance of the existing water distribution system, and the effect of the existing water control structures on performance of the irrigation system was evaluated. The result of the study shows that changes were made by farmers on the original design of already constructed water control structures in the scheme as follows: some of the field canals and the original centrally located field drains were removed by farmers in order to increase irrigable area (bigger utilised land area). Therefore, some farmers were doing field-to-field irrigation method; the main drainage for phase-I has been converted to field irrigation canal by nearby farmers; dimension of existing paddy field earth bunds and secondary canal banks were smaller than original ones; water harvesting from main and secondary canal by farmers outside the scheme exists and no water control gates (wooden stop-logs originally provided) exists at division box openings and at turnout level for the scheme. Applicable indicators for the performance of FMIS are quantified as follows:-Overall irrigation efficiencies were 6% and 8.3% for phase-I and phase-II of the scheme respectively: Average productivity dropped from 6.6 ton/ha in 1995/96 to 3.1 ton/ha in1998/99 season. The organisation of Mkindo FMIS was appropriate, however, the scheme was weak in irrigation management as the essential operation and maintenance activities were not carried out effectively. The scheme had canal maintenance problem. There was a corresponding big error in waler adequacy of 72% and 68% for both phase- I and phase-II of the scheme respectively arising from improper water control along the main canal and at secondary canal offtake. Both phase-I and phase-II of the scheme were not able to distribute water equitably, reliably as well as maintaining a correct field water depth from tilling to flowering and grain formation stage. This was shown by relatively high error of equity of 18% and 20% for both phases respectively. These figures are far greater than zero, which is the indicator for highest performance. Therefore, the FMIS in Tanzania may perform better, or be sustainable, if original design of already constructed water control structures are maintained (i.e. not changed) by farmers at operation stage. This emphasises farmer’s involvement and empowerment at planning, design and construction stages of the scheme.
Major factors influencing the occurrence of landslides in the northern slopes of the Uluguru mountains, Tanzania
(2000) Kilasara, M.; Mtakwa, P. W.; Poesen, J.; Deckers, J. N.
Landslide mitigation largely depends on the understanding of the nature of the factors that have direct bearing on the occurrence oflandslides. Identification of these factors is of paramount importance in setting out appropriate and strategic landslides control measures. The present study focused on the identification of the major factors influencing the occurrence oflandslides in the Northern slopes of the Uluguru Mountains, Tanzania. The main objective was to establish relationship between spatial distribution of landslides and their causative factors. Such information would enable the planning of appropriate and strategic control measures. Aerial photographs, field survey and Geographic Information System (GIS) techniques were employed to identify the landslides features which occurred during EL NINO rains, spatial distribution and their corresponding factors. The results show that landslides dominate the geomorphic units with slope gradient ranging from 25% to over 80%. The most affected geomorphic units are in the order: debris slopes> incisions and V-shaped valleys > amphitheatres. Factors which cause theoccurrence of landslides are both soil and terrain related. The most important soil characteristics are presence of shallow soil solum with low bulk density and high macro porosity overlying a relatively less porous saprolite or hard bed rock. The terrain related factors include: undercutting of slopes by roads and pathways and presence of very steep concave side slopes. Water flow from roads and pathways and seepage from irrigation channels are precursors for the triggering oflandslides in the study area.
Irrigation scheduling of varied flow in irrigation canal systems: a case study of Ruaha Mbuyuni irrigation scheme, Iringa, Tanzania.
(Sokoine University of Agriculture, 2000) Subira,Nesphory Kisyeri
A study in irrigation scheduling of varied flow canal systems is considered in this research. A mathematical model was modified to suit irrigation scheduling of varied flow in irrigation canal systems. Four out of seventeen field canals and twelve fields plots were selected randomly on the basis of location representation. Different sets of data were collected at Ruaha Mbuyuni traditional irrigation scheme was taken as a case study. A modified model for prediction of water volumes in the scheme during irrigation event was developed. Irrigation intervals and water volumes computed using the model were termed as simulated irrigation intervals and simulated water volumes respectively. Comparison between the simulated, designed and observed parameters was performed, using t-student distribution test. The test showed that, canal one, three and four the difference is not significant at 1% significant level. In canal two, the difference is significant at 5% significant level. It may be because the agricultural management practiced in the irrigation area is not similar for the whole farm. Thus the model can be adopted to predict the irrigation intervals. Similarly, simulated and observed irrigation intervals for selected canals were compared using t-student distribution test. The test revealed that, in canal one and three the difference is not significant at 5% significant level. In canal two and four the test showed that there is a significant difference at 5% significant level. However, comparison between the measured and the simulated water volumes using the same t-test distribution was performed. The test showed that, in canal one and three the difference is not significant at 5% significance level. In canal four the difference is no significant at 1% significant level. It was concluded that, the irrigation intervals (scheduling) and water volumes in the fields are fairly well predicted by the model, provided the agricultural management is maintained similar for the whole farm under irrigation. A computer program was developed to reduce the tedious calculations involved in the process of computing/determining the irrigation intervals by simply entering the raw data or some processed data and hence serves some time. It also helps to eliminate some simple errors that could be encountered in the calculation process. Further study is necessary in different traditional irrigation schemes so as to validate the model as a useful tool for predicting irrigation interval for the varied flow canal systems. The model used in this study was tested in a traditional lowland paddy only, and performed sufficiently for varied flow canal system in one scheme, therefore, research work is needed to test it in other traditional irrigation schemes, so as to make it more widely applicable.
Land suitability evaluation for the production of the major crops in the southwestern part of the Uluguru Mountains, Morogoro rural district, Tanzania
(Sokoine University of Agriculture, 2001) Kimaro, D. N.; Msanya, B. M.; Mwango, Sibaway, B.; Kimbi, Gerald, G.; Kileo, Emmanuel, P.
Land evaluation study was conducted on the southwestern slopes of the Uluguru Mountains in Morogoro Rural District, Tanzania to assess the potentials and constraints of the various land units for the production of low input rainfed cabbage, round potato and arabica coffee. The study area is located between latitudes 7 o 0000 and 7 o 1123.5S and longitudes 37 o 3000 and 37 o 3836.6E covering the villages of Kibaoni, Langali, Bunduki, Bumu, Kikeo, Luale, Mwarazi, Nyandira, Kibuko and Tchenzema. The areal extent is 419.64 km 2 (41,964 ha) with an average elevation ranging between 900 - 2700 m a.s.l. The mean annual rainfall in the study area ranges from 1065 mm to 2450 mm. The rainfall distribution pattern is monomodal with the rainy season starting from December to May. The peak rainfall occurs in April in most places of the study area. The high altitude areas receive more rainfall than the lower areas. In some areas rainfall distribution tends more to be bimodal with two peaks occurring in October and in April. There is considerable temperature variability in the study area with the mean monthly temperature ranging from 17.4 o C (July) to 22.4 o C (December). At high elevations temperatures are much cooler. The shortest reference length of growing period is 180 days while the longest is 270 days. The geology of the study area consists of a mixture of banded pyroxene granulites with occasional biotite-rich bands, foliated mica gneisses, hornblende gneisses and granulites and some iron-rich meta-anorthositic rocks, all belonging to the Usagaran system. In some places alluvial deposits and kaolinitic clays of Neogene age are found. The study area consists of strongly dissected mountains with very steep plateau and ridge slopes of about 30-60% and narrow valleys and incisions. Lukwangule plateau is the highest peak in the study area reaching an altitude of 2,623 m a.s.l. The Lukwangule plateau is only slightly dissected and the surface forms quite a mature relief. Two distinct drainage patterns exist in the study area. A sub-radial pattern which is related to the horse-shoe of high mountains from Mkumbaku through Lukwangule and Magari to Lupanga, which is currently represented by some of the larger rivers such as Mngazi, Mbakana and, in part, the Mgeta. A rectilinear pattern is exhibited where secondary streams and many main rivers show adjustment to geological structure and rock type. The pattern of the minor rivers follows the geological structure more closely and has resulted in river capture, reversed drainage and wind gaps. The edge of the meta-anorthosite is marked by the Mgeta, Mfunesi and Lukangazi river valleys for about two-thirds of its circumference, and this weakness is presumably the cause of the spiral course of the Mgeta River as it cuts back along the junction of rocks, capturing successively all the radial drainage from the north and west of the high level plateaux.
Irrigation scheduling based on penetrometer depth technique.
(Sokoine University of Agriculture, 2001) Moses, Chibuye Mambwe
Efficient and profitable irrigation scheduling strategies are needed particularly in the arid and semi arid regions where available water resources are becoming more limited due to population growth and/or climate. Salinisation of ground water resources due to inappropriate water use is equally threatening large areas of productive irrigated land. To help sharpen the predictive capability of farmers with regard to soil water status, a study to model a simplified approach to irrigation scheduling based on soil resistance to penetration was undertaken at Sokoine University of Agriculture in Tanzania. Two locations representing two different soil types namely clay soil (SI) and sandy clay loam soil (S2) were used. Each location comprised of three blocks which were further subdivided into three plots. Three irrigation timing schedules were allocated to the plots in a Complete Randomised Block Design. Penetration depth at randomly selected spots was measured before and after irrigation for all the plots. The gravimetric determination of soil moisture content for each of the four penetrometer legs up to the penetration depth was done.Thereafter, two of the plants around the penetrometer were randomly selected, dug out and their tap length measured. The corresponding soil moisture content for the root length starting from average penetration depth to the entire extent of the root was then determined. The results showed that penetration depth is linearly related (r = 0.91 for SI and r = 0.82 for S2) to soil moisture content within the zone of penetration. Beyond average penetration depth, the soil moisture content for SI correlated poorly (r = 0.32) with average penetration depth while S2 correlated relatively high (r = 0.78). However, the multi variable model (i.e. root length and average penetration depth as variables) showed improved and highly positive correlation coefficients (r = 0.94 for SI and r = 0.96 for S2) with root zone moisture content beyond the penetration depth. Calibration of an individual soil type would make possible the relationship to be developed between penetration depth and depth of irrigation application otherwise the models would simulate soil moisture content.Model validation by using the t-test showed no significant difference (p < 0.05) between observed and simulated values for all the three models developed. The observed and simulated moisture contents of both models 2 and 3 in each of S1 and S2 were compared by using the t-test. The results showed no significant difference (p<0.05) although the mean simulated root zone moisture content of model 2 was closer to the mean observed root zone moisture content than the mean simulated value of model 3 for both locations. The results have shown that the penetrometer depth approach can be used to indicate soil moisture status and/depth of irrigation application in the upper soil of 0 - 30 cm which is used by farmers as an indicator of the soil water status and hence influences irrigation scheduling decisions.
Establishment of digital land resources database for land use planning: a case study of eastern Morogoro rural district, Tanzania
(Sokoine University of Agriculture, 2001) Munisi, Abbas Idriss Mawenya
A study was conducted in the eastern part of Morogoro Rural District to establish digital land resources database which could be used when making decision on land use planning. Four Divisions namely; Mkuyuni, Matombo, Mvuha and Bwakira Chini were included in the study. Land resources data for climate (rainfall and temperature), physiography and soils and socio-economic were collected and compiled from field survey and other sources. The data were analysed, characterised and computerized to generate digital land resources database. The generated databases were stored, manipulated and geoproccssed using computer and various softwares to produce digital spatial and non-spatial information which included thematic maps for elevation, climate, length of growing period (LGP), soils and agroecological zones. Tables on land attribute database, descriptive soil legend and reports were other digital products generated. The digital databases were then used to run land evaluation for the area. Automated land evaluation system (ALES) was employed to compute physical land suitability Evaluation for specified land utilization types (LUTs) i.e. maize, rice, citrus and sesame. The results of the suitability evaluation showed that 57% of the area could be used to produce maize, 85% to produce citrus, 22% paddy and 78% to produce sesame; with production potentials ranging from moderate to poor for all studied LUTs. The major limitations were erosion hazard, nutrient availability, rooting condition and wetness. Citrus was more suited to the area, followed by sesame, maize and lowland rice. The study has demonstrated that greater capability for storing, displaying spatial and non-spatial data in different forms and scales, data analysis and computation of land evaluations exist when land resources data are captured in digital format. Basing on this conclusion, it is highly recommended that land resources data at any level should be inventoried and automated to simplify the process of land use planning.
Assessment of the land use changes due to traditional irrigation activities: the case study of four villages around Ruaha Mbuyuni, Iringa and Morogoro Tanzania
(Sokoine University of Agriculture, 2002) Rugenga Elizabeth
The study on assessment of land use changes due to traditional irrigation activities was conducted in four villages around Ruaha Mbuyuni from June 2000 to June 2001. Three sets of aerial photographs (1955, 1976 and 1999) were used, interpreted on mirror stereoscope and analysed using GIS-ARC/INFO program. The area of each class was' calculated for each data set from which the rate of expansion of irrigated farms was determined. The questionnaire survey was conducted to collect information on the historical changes in natural resources and socio-economic activities responsible for land use changes and analysed using SPSS program. Stratified random sampling was also conducted for soil physical and chemical analyses. By using rating procedures the contribution of soil properties in land use changes was carried out. The results showed that irrigated fields expanded by 2056.8ha and 1528.6ha with expansion rate of 97.94ha/yr and 66.46ha/yr from 1955 to 1976 and 1976 to 1999 respectively. Human population increased from 2886 to 16877people between 1967 and 1998. Irrigation activities have been observed to increase the extent of socio-economic activities like firewood gathering and building. The results for soil analysis indicated that, total nitrogen, available phosphorus and organic matter content was low in all fields and therefore low soil fertility in the area. Exchangeable Na were observed to be high in some fields and having high potential to cause soil salinity and sodicity. Other chemical properties i.e pH values, Ca, Mg and CEC were observed to be within the acceptable range for irrigation activities and crop productivity. The soil physical properties indicated that the bulk density of the soil were within the acceptable range for water infiltration and plant roots penetration. The soil textural class was observed to range from sand loam to sand clay loam for the topsoil and sand to clay for the subsoil. Generally, the results have shown that the pattern of land use changes in the study area were due to irrigation activities taking place in the area which has influenced population growth and socio-economic development.

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