Agricultural Engineering and Land Planning Collection

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Relating erosivity factors to soil loss: a case study of Hombolo and Morogoro sites.
(Sokoine University of Agriculture, 1996) Ngalesoni, Gabriel Simon
This study was conducted at Morogoro and Hombolo, as part of the ongoing research under the department of Agricultural Engineering and Land Planning.This report acts as interim findings of the research. Ten run off plots were established, four at Hombolo and the rest at Morogoro. Five erosivity factors were regressed to ascertain the best fit on the soil loss.The plots had different treatments of canopy cover for each of the seven rainstorms recorded during the cropping season. El 30 compound erosivity factor and runoff mination of proved to have 0.92 and 0.69,high coefficients respectively.There deter was a significant difference in soil loss between bare plots and other plots with crop cover.However,the difference in runoff amounts was insignificant.
Performance of centre pivot sprinkler irrigation system: a case study of Ubombo Sugar Estate, Swaziland
(Sokoine University of Agriculture, 2014) Msibi, Sandile Trevor
The centre pivot irrigation system is increasingly becoming popular among farmers around the world on account of the benefits the system can offer compared to other methods. Hence evaluation of system performance with the ultimate aim of attaining greater irrigation efficiency and better manage irrigation is paramount. The study evaluated the performance of centre pivot sprinkler irrigation system and its effect on sugarcane yield at Ubombo Sugar Estate in the Lubombo Region of Swaziland. Four centre pivots (EEL09, NKA21, CAS02 and SMB) were selected from 106 centre pivot machines for purposes of evaluation. Information collected included meteorological data, design parameters, water application uniformity, system operating pressure, tyre pressure, system flow rate, sprinkler nozzle discharge and pressure, crop data and planted area, harvesting programs, pumps and motor specifications, pumping hours, cost of power and actual flow rates. Drive speeds of 15%, 20%, 30% and 40% of the centre pivot systems were examined to determine their significance on system performance parameters on the basis of common field operations. Water and power budgeting systems utilized were assessed to determine adequacy of irrigation water supply and implications on system and crop performance. Irrigation water quality, soil physical and chemical properties, soil infiltration characteristics and soil compaction were also examined to determine their influence on system performance and sugarcane yields. Data analysis was carried out using Microsoft Excel, ETo Calculator, Instat, Statistical Package for Social Sciences (SPSS), ArcGIS and HPen32 software. Results demonstrated that centre pivots were accurately designed and properly installed as they adequately supplied water to meet sugarcane demand of 7.5 mm/day. Performance indicators showed that centre pivots were relatively performing well as uniformity indices (CU and DU) were within acceptable standards, i.e. above the base values of 85% for CU and 75% for DU. Recommendedapplication efficiencies (AELQ and PELQ) were only achieved by CAS02 and SMB centre pivot systems as they were above the minimum of 90%. Speed effect results showed a general decline in CU and DU with an increase in centre pivot speed as opposed to an increase in application efficiency. CU for SMB declined from 88.9% at 15% speed to 86.9% at 40% speed setting. A similar trend was evident for both NKA21 and EEL09.PELQ for SMB increased from 93.1% to 98.0%% and AELQ from 92.6% to 100%. A parallel trend was also observed for NKA21 and EEL09. Analysis of variance for these results showed that the performance indicators were not significantly different (p<0.01) among treatments. This demonstrated the ability of the centre pivot irrigation system to apply water uniformly and efficiently across the field at different speeds. Water and power budgets were not satisfactory in meeting estate crop water demand since they did not capture and consolidate relevant parameters needed to accurately define budgets.Water supply was determined by capacities of irrigation structures used and losses were incurred during periods of low demand. Electricity budgets were based on historical power records which affected overall water supply and caused water stress to the crop. Quality of irrigation water was within acceptable levels and had no negative impact on system, crop and soil. Soil physical and chemical properties indicated that soils were inherently sandy and ideal for sugarcane growth save for shallow profiles with low water holding capacities. Soil compaction as a result of mechanical harvesting was a major cause of significant reduction in soil infiltration rates, water storage capacity and hence runoff. Significantly higher soil compaction values at 0 to 15 cm depth (p<0.0l) were associated with EEL09 centre pivot with an average of 3 210 kPa compared to those of NKA2I at 596 kPa, CAS02 at 447 kPa and SMB at 1 389 kPa. Identical observations were made at 0 to 30 cm depth where higher compaction values were associated with EEL09 and SMB. EEL09, a sandy textured field measured a basic infiltration rate of 6 mm/h as a result of compaction while the other less compact sandy textured fields had infiltration rates greater than 70 mm/h. Yields were variable as EEL09 achieved a low yield of 71 t/ha against 147 t/ha for CAS02, 124.8 t/ha for NKA21 and 106 t/ha for SMB. Findings indicate that centre pivots are performing well although potential system performance and sugarcane yields are constrained by limited water and power supply,pressure variations, clogging of sprinklers, rutting of un-gravelled tracks, soil compaction,low water holding capacities, reduced infiltration rates and game encroaching sugarcane fields. It is therefore recommended that constant system checks, improvement of traction on centre pivot wheels, development of new model for water and power budgets as well as undertaking of extensive research on the effects of mechanical harvesting be done so as to improve centre pivot irrigation system performance and sugarcane yields at Ubombo Sugar Estate.
Auger metering studies for fine prilled URSA
(Sokoine University of Agriculture, 1988) Mwombeki, Francis Fabian
ABSTRACT Tne performance of sheet ana 'wire au6ers was studied for meterin6 prilleu urea fertilizer. First the physical characteristics of prilled urea was established. It was found that the angle of repose and the coefficient of fricition on galvanized steel surface increased with increased moisture content.The opening of the hopper bottom, inclination of hooper walls and modes of agitation were studied for uiiximizing fertilizer flow into the metering chamber. A bottom opening width of jO mm, hopper wall angle of 60 o with the horizontal and a rotary or eliptical agitation modes aere founu to provide optimum flow.Succeeding experiments were conducted to study the rate and consistency of fertilizer metering by sheet and wire auoer unaer varying pitch/diameter ratio,delivery tube in .ination, au6er speed and fertilizer moisture.Rate of fertilizer injection into flooded soils was studied under simuxared field conditions. Assessment was also made of the amount of r.-rti 1 i zer adhering to the augers during metering. A pitch diameter ratio of 1.25 give a maximum found to diecharge. Also, fertilizer discharge increased with greater inclination of the delivery tube and decreased with increasing fertilizer moisture contents.The metering accuracy generally decreased with greater inclination of the delivery tube fertilizer granule size decreased metering accuracy.The experiments, of injecting fertilizer in flooded soils were conducted in a rotating soil bin to simulate actual field conditions.The inclination of the delivery tube along the direction of the bin movement gave a higher injection rate than an inclination against the bin movement. The wire auger exhibited a greater injection capability than the sheet auger and produced higher pressure at the tube opening.This auger also encountered less sticking of fertilizer on the flight than the sheet auger.
The Mechanics of a disc plough
(Sokoine University of Agriculture, 1985) Kiriama,L.L.
ABSTRACT An angle attachment was designed to enable disc axis orientation with the soil bin facility developed at the College.A force prediction model by Godwin et al at Silsoe College was used to predict the magnitude of forces to be expected.- The effect of change in axis angle on draught,- vertical and side forces was studied and the results compared with the prediction. It was found that there.was a significant effect in changing the disc axis angle, The draught and side forces were found to be less at 15° than at 0^ 0° axis angle, angle. The optimum axis angle at 25° sweep was found to be about 15 o ’where the maximum downward vertical force occured. Since the experimental and predicted results did not compare well, an exploration of the force prediction model was suggested.Whilst for global prediction the model seemed alright,it was difficult to make it work for all combinations. Although the model worked well with an 0° axis angle and 90° sweep angle, the edge effect and inclination for the other combinations needed greater definition.
Simulation of water productivity for maize under drip irrigation.
(Sokoine University of Agriculture, 2011) Richard,Festo
Water has become increasingly scarce in most of the countries in the world. To use the available water efficiently in crop production, agricultural water productivity (WP) need to be improved. Drip irrigation systems and deficit irrigation practices are the most efficient methods in improving WP. Availability of soil-water-crop simulation and climatic models can also help in the efforts to improve WP. A study was conducted in Morogoro using CROPWAT model to simulate water productivity of maize under drip irrigation by supplying different water deficits. A completely randomized block design was used with three replications and four treatments. The treatments were Tl, T2, T3 and T4 representing 60, 40, 20, 0 percent deficit of ETC (crop evapo-transpiration) respectively. Biomass accumulation (at 45 DAP and 75 DAP), grain yield and harvest index were determined for each treatment and experimental yield reductions were calculated. The CROPWAT simulation was done for each water deficit level and yield reductions were recorded. A comparison was made between experimental and simulated yield reductions. The mean biomass production between the treatments at 45 DAP were not significant different (P<0.05). At 75 DAP mean biomass production (0.684, 0.728, 1.049, 1.378 kg/m2 for Tl, T2, T3 and T4 respectively) were highly significant different (P<0.05). The mean grain yield between treatments, mean water productivity (1.67, 2.2, 1.78, 1.72 kg/m3 for Tl, T2, T3 and T4 respectively) and harvest index values were significant different (PO.Ol). Experimental and CROPWAT simulated yield reductions were not significant different (P<0.01) at all stages for all the treatments. The CROPWAT model adequately simulated the experimental yield response to water for maize (maize water productivity).
Study on tillage systems and their impacts on land degradation for eastern agro-ecological zone in Tanzania
(Sokoine University of Agriculture, 2011) Mohamedi,Saidi Jambuya
Soil tillage had been identified as a major cause of land degradation and soil erosion in Tanzania resulting in soil infertility and low crop yields. A study was conducted at Mkambalani village, in Mkambalani ward, Mikese division in Morogoro Rural District, Morogoro Region, Tanzania. The study aimed to assess tillage systems and their impacts on land degradation for eastern agro-ecological zone. Five (5) tillage systems were selected for the study. The selected systems were No Tillage (NT), Strip Tillage (ST), Basin Tillage (BT), Tied Ridges (TR) and Conventional Tillage (CT). A plot of size 20 m long with width of 1.8 m was established for each tillage system selected and replicated in three times in the slope of 6° farm. The plots planted with maize crop variety TMV1. At the down slope end of each plot the modified Gerlanch troughs were installed to trap water flow and sediment. The study arranged in CRBD design to help in data analysis. Variables measured including, daily sediment for the rainy days, water runoff, daily rainfall, plant growth and yield and soil physical and chemical properties. The results shows that NT treatments produced high amount of runoff on average in most of rainfall events due presence of few cover in the first year of farming while TR treatment were the least. Significant differences were observed between the NT treatments and CT, TR and BT. It means that in first year of practising NT due to bare soil there was no soil protection from rainfall and water flow hence more water runoff. CT was found to be the biggest collector of sediment than other tillage treatments. Significant changes were observed among CT, NT and TR in collection of sediment. CT treatment produced sediment loss of 23.2ton/ha/season, while the TR produced the least amount of 14.4ton/ha/season. This reflects the extent of the productive soils lost in each year due to tillage. There were no significant differences in crop growth and yield were observed and also in soil physical and chemical properties in the first year of the experiment. Under natural rainfall conditions rainfall amount, intensity and distribution differs greatly and all affect soil properties and crop development, hence the one year trial is not enough to draw appropriate conclusion.
Economic valuation of irrigation water in smallholder farming system in rwanda: the case of Kibaya – Cyunuzi scheme
(Sokoine University of Agriculture, 2012) Urujeni Sandrine
Rwanda is in a current shift of management of state controlled irrigation schemes to farmers through the Irrigation Management Transfer (1MT) programme. However, such water management decisions require conceptually correct and empirically accurate estimates of the economic value of water. This study was carried out to determine the economic value of irrigation water in a smallholder irrigation scheme of Kibaya - Cyunuzi. Data was collected from 110 respondents within the scheme. The data was analyzed using descriptive and quantitative methods. The Residual Computation Method was used to compute the economic value of irrigation water for paddy rice - the main crop cultivated in the scheme. The Contingent Valuation Method was employed to elicit the farmers’ willingness to pay for irrigation water and its related infrastructure. Socio-technical analysis helped to capture the process of water control and management through Water Users Associations. Results showed that the average economic value of water in irrigated paddy was low (5.33 Rwf/m3), mainly due to poor management of water. Water productivity was also low (0.08 kg/m3) due to an insufficient supply of water to the scheme. The CVM analysis showed that on average, the respondents were willing to pay 8000 Rwf per ha per annum for irrigation water. IMT impact assessment showed that WUAs are the realms of interaction for different stakeholders involved in water management. The problems farmers were facing in improving water productivity in the scheme were identified but the solutions require joint effort among the stakeholders. Policy decisions related to water sector investments, allocation and management could be better guided if the key dimensions of water i.e. water availability and use, are properly taken into account in valuation.
Influence of institutional set up on performance of traditional irrigation schemes. a case study of Nyandira wards, Mvomero district, Tanzania.
(Sokoine University of Agriculture, 2016) Sumuni,Philip Mathew
This study was conducted in Nyandira ward, Mvomero District, Tanzania to evaluate the influence of institutional set up on performance of traditional irrigation schemes. The study was envisaged to produce knowledge of institutional framework to guide performance of traditional irrigation schemes on efficient use of water resources. GPS reading to digitise the traditional canal, farmer’s interview, focus group discussion and V- notch weir for canal flow measurements were used for data collection. Out of twelve traditional canals, four canals namely Fuku, Mbakana Kati, Mzinga and Nyamiseta No. I were purposively selected. The data were analysed using descriptive statistics, inferential statistical analysis and content analysis. Results showed that out of 93 interviewed farmers (91.4%) 85 people out of 93 were not aware of the National Water Policy of 2002 whereas only (8.6%) 8 people out 93 were aware of the National Water Policy of 2002. This shows that policies are formed and remain to the management (Decision and Policy makers) while people on the ground who are the actual implemented are not aware of what is going on. The results also showed that the majority of the respondents (93.5%) 87 people out of 93 in the study area were not aware of the Water Resources Management Act of 2009. This implies that the community members do not understand their role in water conservation and management in line with the Water Resources Management Act of 2009. The conveyance efficiency for the four canals, i.e. Fuku, Mbakana Kati, Mzinga and Nyamiseta No. 1 were calculated and found to be 63.05%, 62.74%, 60.89% and 60.5% respectively which is fairly good. But the overall efficiency of 34%, 32%, 33% and 37% for Fuku, Mbakana Kati, Mzinga and Nyamiseta respectively was low due to the fact that canals are unlined.
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.
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.
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
Assessing the effectiveness of locally made clay pot as an irrigation device.
(Sokoine University of Agriculture, 2011) Solo, Mahatsindry Randzato
Among traditional irrigation systems, pitcher irrigation is one of the most efficient. Water seeps out of a buried pitcher due to the pressure head gradient across the wall of the pitcher directly into the root zone of the irrigated crop. The pressure gradient results from a positive pressure head inside the pitcher and negative pressure head at the outer surface of the pitcher which is in contact with soil. Pitcher irrigation is a cost effective traditional technique, which is easy for small scale farmers to comprehend with. This study considered the effectiveness of locally made pitchers as a micro-irrigation device using beans and amaranths crops. The experimental design was 2x3 factorial arrangements of treatments in a split plot design. The main-plots were two different initial soil moisture contents i.e. soil moisture content at field capacity (31 %, vol.) and 26 % (vol.). The sub-plots were three different plant densities i.e. 4 plants/pot, 6 plants/pot and 8 plants/pot and were replicated three times giving a total of 18 combination treatments. A positive relationship was found between seepage rate and actual evapotranspiration for all pitchers (R = 0.37) showing a sign of auto-regulative capabilities. Under beans, the pitchers were not effective in water saving in all the combination treatments because of high water loss through deep percolation because of poor pot characterization. However under amaranths the pitchers were effective in optimizing the water applied. The water applied was not statistically different (P < 0.05) for all the treatments. These results show that clay pots had low application efficiency. However the pots can still be used on amaranths, with a plant density of 16 plants/pot and at initial soil moisture content of 26 % (volume).
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.
Evaluation of centre pivot sprinkler irrigation system performance and its effect on sugar cane yield at Kagera Sugar Estate.
(Sokoine University of Agriculture, 2010) Reuben,Paul
Centre pivot irrigation is a medium to low pressure sprinkler system capable of irrigating large circular areas. It consists of a galvanised steel lateral supported by “A" - shaped frame mounted on powered wheels. It rotates about a fixed point at the centre of the irrigated field. The study evaluated the performance of a centre pivot spray nozzle irrigation system and its effects on sugarcane yield at Kagera Sugar Estate, Tanzania. The specific objectives were to assess: (i) the performance of the centre pivot spray nozzle sprinkler system (ii) soil parameters that influence cane yields and (iii) irrigation water quality. High and low yielding areas were represented by centre pivot GP7 and BP5. The results showed that low yields were contributed by poor performance of centre pivots and soil parameters. Centre pivot GP7 had average coefficient of uniformity (CU) of 96.91% while it was 86.28% for BP5; average distribution uniformity (DU) of 95.1% and 78.23%; average potential application efficiency (PELQ) of 86.83% and 79.14%; average application efficiency (AELQ) of 64.97% and 59.36%, respectively. The minimum recommended values for CU, DU, PELQ, and AELQ were 85%, 75%, 90%, and 85%.The performance parameters for GP7 were within the recommended values except AELQ and PELQ which was lower than the recommended value. The PELQ and ALQ for BP5 were lower than the recommended value. In general, the performance parameter estimated for GP7 were higher than for BP5 as the result of differences in sugarcane yield. For instance, fields under GP7 and BP5 had average yields of 123 and 74 tonnes per hectare respectively. Soil parameters that contributed to low yield were low water holding capacity., low cation exchange capacity; high acidity; poor structure and compaction by farm machinery. Irrigation water quality was high that could not contribute to low yield.
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.
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.
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.
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.
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.

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