PhD Theses

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Agriculture development in the coffee-banana zone of Uganda: a linear programming approach.
(University of Dar es Salaam, 1971) Hall, Malcom
Dar es Salaam, Tanzania, University of East Africa, Department of Agriculture, 1971. The thesis is concerned with aspect of the agricultural development problem in the main robusta coffee growing area of Southern Uganda, an area of small holding agriculture which has been termed the coffee banana zone. Part One of the thesis examines the physical parameters of the zone and also the economic social, technical and institutional setting of its agricultural development problems. The second part considers details of data collection and planning methodology as well as presenting the results of the planning exercises and their policy implications for research extension and agricultural development planning. The basis of the zonal development problems (Chapter 3 and 9) is identified as the need to achieve immediate increases in agricultural production in order to facilitate the realization of longer term national aspirations involving the diversification of the general economy. The initially rapid development of the agricultural sector of the zonal economy is described in chapter 4. Cotton was introduced at the beginning of the century and first this crop and later Robusta coffee was integrated into the small holding economy. Coffee prices began to decline in the mid 1950s, but production has continued to increase. Another aspect of the problem concerns the effects of urbanization and rapid population growth, together with the slow growth of non-agricultural employment opportunities. The development of agriculture will almost certainly occur within the existing framework of small holding agriculture (Chapter 7 and 11). Chapter 5 describes the main characteristics of this type of farming illustrating the description of with empirical data gathered during the field survey and from the results of the 1963 national agricultural census. The structure of the government services connected with agriculture and the major improvement approaches which they are pursuing are discussed in Chapter 7 and an evaluation of technical economic research strategy is contained in Chapter 6. Current approaches to agricultural development planning are analysed in chapter 9. These approaches tend to be based on general improvement policies concerning better a husbandry and higher fields derived without any formal reference to relative costs and returns in either private or social terms. By analyzing the differences between the two equilibrium supply positions, policies which can stimulate the desired resources allocation can be evolved (Chapter 10). The phasing of such changes could be aided by utilizing of such changes could be aided by utilizing a multi period planning model of the type described in chapters 11 and 12. While retaining reservations about the details of the planning approach, the models reveal a current misallocation of resources (Chapter 10 and 13). Economically desirable policy adjustments indicated by the planning models and their implications for research and extension orientation are discussed and further investigations suggested.
The status of phosphorus in some Tanzania soils
(University of Dar es Salaam, 1972) Uriyo, Andrew Paul
A detailed study was conducted on the fractionation of inorganic phosphorus from the main soil orders found in Tanzania. The results obtained showed that the extracting time of one hour for Al-P with NH4F solution offered the least dissolution of iron-bound and calcium-bound phosphates in the soil. Ammonium fluoride extracting solution of pH 8 was Shawn to be the most selective extractant for A1-P as it had the least attack on the Fe-P and Ca-P in the soils studied. The inorganic phosphate fractions were determined in 23 soil profiles from eight soil orders commonly occuring in Tanzania. The distribution percentages for Ca-P, AI-P and Fe-P were found to be sensitive indicators of the weathering environment. Where soils were young, calcarious or the parent material rich in phosphorus bearing minerals Ca -P was the dominant fraction of inorganic phosphorus. In areas where the soils were highly weathered, A1-P and Fe-P were the dominant fractions. The distribution of organic phosphorus fractions in soil from three soil orders showed. that organic phosphorus was highest on the clay followed by the silt separates. The clay and silt were also found to contain the highest amount of Al-P and Fe-P, while the Ca-P fraction was highest on the sand. In another study on the distribution of organic P in soil profiles it was found that the` organic phosphorus content decreased with depth, except in a few cases where the accumulation. of organic phosphorus tended to occur in the second horizon. A highly significant correlation was obtained between the organic carbon and organic phosphorus content on the top soils of the profiles. The C:P ratio of the organic matter in the A horizons of the soil orders ranged from 25.7 to 493.3. The majority of the C:P ratios were below 200. The lack of response to applied P on some of the soils in Tanzania is attributed to the large amounts of organic phosphorus and the accompanying low C:P ratios. Decomposition of organic matter in these soils results in mineralization of significant amounts of organic phosphates which are then available for plant use. The activity of the enzyme phosphamonoesterase as measured by the amount of phenol liberated in soils was found to be highly significantly correlated with altitude and organic phosphorus. A highly significant negative correlation was obtained between the enzyme activity and the C:P ratio. The enzyme activity decreased as the C:P ratio increased. The enzyme activity decreased as the C:P increased and would appear to tail off around a C:P value of 200.
The status of phosphorus in some Tanzania soils
(University of Dar es Salaam, 1972) Uriyo, Andrew. P.
A detailed study was conducted on the fractionation of inorganic phosphorus from the main soil orders found in Tanzania. The results obtained showed that the extracting time of one hour for Al-P with NH4F solution offered the least dissolution of iron-bound and calcium-bound phosphates in the soil. Ammonium fluoride extracting solution of pH 8 was Shawn to be the most selective extractant for A1-P as it had the least attack on the Fe-P and Ca-P in the soils studied. The inorganic phosphate fractions were determined in 23 soil profiles from eight soil orders commonly occuring in Tanzania. The distribution percentages for Ca-P, AI-P and Fe-P were found to be sensitive indicators of the weathering environment. Where soils were young, calcarious or the parent material rich in phosphorus bearing minerals Ca -P was the dominant fraction of inorganic phosphorus. In areas where the soils were highly weathered, A1-P and Fe-P were the dominant fractions. The distribution of organic phosphorus fractions in soil from three soil orders showed that organic phosphorus was highest on the clay followed by the silt separates. The clay and silt were also found to contain the highest amount of Al-P and Fe-P, while the Ca-P fraction was highest on the sand. In another study on the distribution of organic P in soil profiles it was found that the` organic phosphorus content decreased with depth, except in a few cases where the accumulation of organic phosphorus tended to occur in the second horizon. A highly significant correlation was obtained between the organic carbon and organic phosphorus content on the top soils of the profiles. The C: P ratio of the organic matter in the A horizons of the soil orders ranged from 25.7 to 493.3. The majority of the C: P ratios were below 200. The lack of response to applied P on some of the soils in Tanzania is attributed to the large amounts of organic phosphorus and the accompanying low C: P ratios. Decomposition of organic matter in these soils results in mineralization of significant amounts of organic phosphates which are then available for plant use. The activity of the enzyme phosphamonoesterase as measured by the amount of phenol liberated in soils was found to be highly significantly correlated with altitude and organic phosphorus. A highly significant negative correlation was obtained between the enzyme activity and the C: P ratio. The enzyme activity decreased as the C:P ratio increased. The enzyme activity decreased as the C:P increased and would appear to tail off around a C:P value of 200.
Lime, Nitrogen and Phosphorus effects on some chemical characteristics of an oxisol, leaf elemental content and yield in upland rice and maize at Morogoro
(University of Dar es Salaam, 1974) Mongi, Hussein O
The effect of lime, at varied N and P fertility, on some chemical characteristics of a moderately acid Oxisol (initial pH 5.6; average LR 10 tons/ha), leaf nutrient content, some growth, yield and yield components in upland rice cv. “Salama” and maize cv. “Ilonga composite” were evaluated during 1970-73 in a field study to further examine the nature of crop response to lime under tropical conditions at Morogoro, Tanzania. The lime rates were 0, 7.5, 10.0 and 12.5 tons agricultural lime/ha (mean ECCE* 90%); N rates were 0, 100, 200 and 300kg/N/ha as ammonium sulphate; and P rates were 0, 40, 80 and 120kg/ha as triple superphosphate. Lime was applied in November, 1970; the N and P rates were applied annually during 1970-73 except that P was not applied on the rice crop during 1972/73. Lime decreased exchangeable AI, Mn and Fe; this effect was complemented by P but counteracted by applied N. Exchangeable AI was not affected by lime in the absence of added N. Base saturation, electrical conductivity, N mineralization, Ca2+ and Ca-P were increased with liming along with increase in soil pH. Levels of AI-P and Fe-P were generally slightly increased by lime under rice cropping but under maize cropping AI-P increased slightly while, although Fe-P was reduced, there was a significant increase in FE-P at the 10 tons lime rate. Increases, the P effect being more pronounced. Exchangeable K under rice cropping was increased by lime at all applied N rates except in the absence of N where reductions occurred up to the 10 tons lime level but increased at 12.5 tons lime rate. Under maize cropping exchangeable K was increased by lime with the 10 tons lime rate recording the highest K levels at virtually all N and P rates. Exchangeable Mg was reduced considerably by lime only in the absence of added N under rice cropping and only up to the 10 tons lime level, the negative effect of lime being annulled by applied N. However, mean Mg levels were lowest and highest respectively under rice and maize at the 10 tons lime rate. Exchangeable Na under rice cropping was reduced by lime only up to the7.5 tons lime rate, beyond which increases occurred, with a peak at the 10 tons lime level. Grain yield in upland rice and maize increased with liming, with optimum yield obtained around the lime requirement rate (10 tons/ha) except for the second cropping year where optimum maize grain yields were obtained by liming with 7.5 tons/ha. Liming enhanced crop response to applied N and P, the respective optimum N and P rates being 100 and 40kg/kg/ha. Rice straw and grain yields, and maize silage yield were depressed at the 10 tons lime rate due to likely nutrient imbalances resulting from reduced soil N availability and probable increased uptake of N03-N. The optimum lime, N and P rates were also associated with low mean root-lodging indices, optimum plant population, grain/shelled-cob ratio and lower vegetative material production in maize as indicated by the silage data, and with optimum grain straw weight and grain yield ratio in upland rice. Liming beyond the lime requirement level generally reduced yields at low N and P fertility, the reduction being associated with generally decreased leaf concentrations of N, P, K, Ca, Mg, Zn, Cu, B, Fe, Mn, Mo, Na and Al. Reduced upland rice straw and grain yields at 10 tons lime rate were associated with increased leaf concentrations of Al, Fe, Ca and B and reduced leaf K, N and Cu concentrations. Reduced silage yields at the 10.0 lime rate were also somewhat associated with increased leaf content of Ca, B, Mo, P and Zn, and with slight increases in leaf Mn content. Yield decreases were generally associated with decreased N/K and K/(Ca+Mg)½ ratios in the soil and plant. Yield increases, however, were only significantly correlated with leaf contents on N, K and Zn in upland rice, and with increased Mo, P (at 10%), Fe (at 10%) and Ca (at 10%) in maize. Genetic differences in nutrient uptake were apparent as the rice leaves had more than double the Fe and Mn levels and about half the Al levels found in maize; increases in leaf Fe content at the low levels found in maize were generally beneficial, while increases at the high levels found in rice were associated with decreased yields; and increases in leaf Mn content at the low levels found in maize were yield limiting, while leaf Mn increases at the higher levels found in rice were generally not yield limiting. Exchangeable Al and leaf P content in maize were related, leaf Al content was not related to leaf P concentration. Because of confounding effects of soil fertility, soil pH was not strongly related to yield, the correlation being quadratic and significant only at the 10% level. Least squares mean grain yields were obtained at an ultimate pH of about 6.3-6.4 in upland rice and 5.8-6.4 in maize, but optimum mean rice and maize gain yields without applied N were obtained at pH 6.8. High yields at high N and P fertility were, however, generally obtained up to pH 7.0. The data suggest that liming criterion for Oxisols low in exchangeable Al should be based on a lime level required to bring the soil reaction to an eventual pH 6.5 for cropping cycles involving legumes and pH 6.0 for continuous maize cropping.
Improvement of the nutritive value of maize cob using Sodium Hydroxide
(University of Dar es Salaam, 1978) Kategile, Jackson Augusto
The factors that influence the extent of in vivo digestibility and voluntary feed intake of NaOH treated maize cobs based diets were examined. The standard procedure of Na0H treatment was to mix the coarsely ground maize cob with Na0H solution and then allow it to react for 24 hours after which the maize cobs were dried in the sun or in the room. The dried maize cob was mixed with other ingredients prior to feeding caged sheep and the maize cob formed 50 to 85% of the rations. Na0H treatment is expressed as % to mean kg Na0H per 100 kg dry matter of maize cob. Na0H treatment rates ranged from 0 to 10% and resulted in significant increases in in vivo digestibility of dry matter (DM), organic matter (OM), cell wall constituents (CWC) and crude fibre (CF). The linear increases were obtained up to 5.0% NaOH treatment beyond which no further responses were obtained. A regression equation y =51 .57 + 2.28 x in which y = in vivo DM digestion of ration and x = % Na0H treatment rate (from 0 to 5%) was calculated with typical results. Similarly the voluntary feed intake followed the same trend and the values for g DM intake per W kg .75 were 60.5, 83.3, 95.7 and 96.0 for the control, 2.5 %, 5.0% and 7.5% in the order of increasing NaOH treatment rates in one experiment. The total digestible DM,OM, and energy was more correlated to voluntary feed intake than digestibility coefficients indicating the significance of improved feed intake by NaOH treatment. The volume of Na0H solution was varied from 25 to 200 1 per 100 kg DM of maize cob and the DM, OM, and CWC digestibilities were not affected by this factor, except the 25 1 volume which resulted in depressed digestion indicating the difficulty of getting effective mixing with small volumes. The incorporation of nitrogen in the form of urea at 0 0.5, 1.0 and 1.5% in the rations was beneficial in improving the digestion of DM, OM, and CWC and regression equations y1= 35•9 + 19.0 x, y2= 39.6 + 16.8 x and y3=24.8 + 21.6 x for y1 =DM digestion %, y2 = OM digestion % and y1= CWC digestion %, and x = urea incorporation in the diet. In one experiment molasses as a source of readily available carbohydrates was incorporated at 20% in maize cob based diet and in three other diets the molasses was completely replaced by cassava flour maize meal or maize bran. The replacement of molasses was detrimental on bath digestibility coefficients and voluntary feed intake, demonstrating the incompatibility of maize cob with high starch containing feedstuffs. The knowledge gained in the digestibility and voluntary feed intake experiments was used in formulating complete rations for a 63 days experiment involving 9 - 15 month old growing dairy heifers. Six animals per treatment group were assigned to a 0% NaOH or a 5% NaOH treated maize cob diet of sorghum silage. The voluntary feed intakes were 103 g and 119 g DM/ W kg .75 for the control and NaOH treated groups respectively. The growth rate was significantly (P < 0. 01) improved from 0. 412 to 0. 585 kg per day and the DM consumed per unit gain was reduced from 13.0 to 11.5 kg with NaOH treatment. In spite of the high concentration of sodium in the diet at 1.40 % on a DM basis in the treated group the animall were healthy. The sorghum silage group lost weight due to low quality characteristics of the silage and subsequent low feed intake. From this study it is evident that it is feasible to improve the nutritive value of maize cob by having the right conditions of NaOH treatment rate, volume of NaOH solution and feeding the treated maize together with molasses and adequate protein
Comparative effectiveness of group extension methods in village farming in the coastal zone of Tanzania
(University of Dar es Salaam, 1979) Kauzeni, Athanas Stephen
This dissertation compares the effectiveness of three group-based agricultural extension methods: (I) demonstrations together with formal scheduled group discussion meeting, (ii) formal scheduled group discussion meetings alone and (iii) informal unscheduled or general meetings or contacts that were applied in 24 villages of the coastal zone in Bigamy, Handiness, Korogwe, and Morogoro Districts, Tanzania. It examines social, economic, political, administrative, educational, and environmental factors that directly or indirectly affect the effectiveness of agricultural extension methods and the extension service in general. The aim of the study is: first, to identify the best or most effective group-based agricultural extension methods which conform to the country’s policy for villagization as related to the prevailing economic and social conditions. Secondly, to identify constraints to agricultural extension methods and the extension service in general that render agricultural extension workers ineffective and consequently inhibit increased agricultural production. Third, the study aims at making recommendations that will help agricultural extension workers in villages to increase their communication effectiveness which will hopefully lead to increased agricultural production. Historically the agricultural extension service has been understaffed, and most seriously under-educated (in basic education), and under-trained (in extension and agriculture). Inadequate training, particularly in the extension approach or methods, is alleged to be one of the main causes for ineffectiveness of agricultural extension workers and the extension service in general. The training given lacks understanding and proper emphasis, therefore does not produce extension workers able to communicate effectively with farmers. Consequently extension workers have apparently had a minor impact in inducing changes in farming. Five operational dependent variables used in measuring the effectiveness of the three group-based agricultural extension methods are: (I) knowledge of recommended farming practices, (ii) Adoption rate of recommended farming practices, (iii) Development increase of the village, (iv) Income per ha and (v) Income per man-day. Results of the study show that differences exist in effectiveness of the three group-based agricultural extension methods as stated in the hypotheses tested. Some of these differences are statistically significant, others are not. Of the three group-based agricultural extension methods studied, demonstrations together with formal scheduled group discussion meetings proved to be the most effective. Formal scheduled group discussion meetings were second in effectiveness, and informal unscheduled general meetings or contacts were last in effectiveness. The analytical methods used in arriving at these results include simple and multiple regression and analysis of variance. There are also differences between Districts in relation to the effectiveness of extension methods in respect of the five operational variables. Some of these differences were statistically significant, other were not. Districts differ in levels of performance in respect to nature of activities (communal versus individual) but none of these differences between Districts are statistically significant. Finally, results show that there are, on average, statistically significant differences between communal and individual types of farming systems in respect of the two income variables under all three types of group-based extension methods. Several obstacles affect agricultural information communication in the coastal zone villages: These include poor basic education and professional training of agricultural extension workers, high illiteracy percentage level among farmers, inadequate structural organisation of the extension service, poor supervision of village level extension workers, and economic and social disparity between villagers and extension workers. In order to improve effectiveness of the agricultural extension approach and the extension service as a whole, it is recommended that evaluation of the agricultural extension service, particularly extension methods, be made more often. Demonstrations and meetings should be the key educational tool of the extension workers in villages. The entire agricultural training programmes should be reviewed to insure that relevant subjects have their due emphasis in the syllabi. The number of trainees should be increased and only form IV and above with high passes in relevant subjects should be recruited in so far as adequate numbers are available. Village-level agriculture extension workers should be employees of villages. Research recommendations for villages should be accompanied by their economic aspects to make them complete and should be written in layman’s language for extension workers and farmers to understand. Farmers should be required to adopt complete packages of recommendations for a maximum increase in agricultural production to the extent that they are economically viable. There is an urgent need for a socialist credit system to be established to serve villages. Refresher or in-service courses for junior and senior agricultural extension workers should be arranged annually or after every two years. Finally, an intensive political education campaign should be launched for villagers, particularly village council members, to enlighten them on the meaning, demands, and relevance of socialism in their own context.
Optimizing returns from forest estates and from wood processing industries in Tanzania using linear programming
(University of Dar es Salaam, 1983) Kowero, Godwin Sifueli
The forest policy of Tanzania provides far two optimization objectives: (a) to manage the forest estate in such a manner as to make it as productive as possible; and (b} to utilize forest produce from public lands to the best advantage of the community. This study was undertaken in an effort to develop a comprehensive methodology to assist both managers of forest projects and managers of wood processing facilities to manage their operations so that these objectives can be satisfied. In order to determine the degree to which the objectives are being fulfilled at present, case studies were made of the Meru Forest Project (MFP) and a wood processing complex, Fibreboard Africa Ltd. (FAL). Both are located in Arusha Region in northern Tanzania. The methodology developed in this study to improve decisions relating to forest operations and wood processing operations makes use of linear programming. Two independent linear progamming (LP) models were developed: the general processing model (GPM), based on the wood processing facility, and the plantation model (PM), and based on the forest project. Since Fibreboard Africa Ltd. is the major customer of the Meru F Forest ' Project, and the forest project is the major supplier of wood raw materials to this processing complex, it was also possible to .link the two models into a limited model of the forestry sector in that region. This is called the miniforestry sector medal (MF5M). The results of the GPM revealed superiority, in various ways, of this LP model over current planning techniques at FAL. For example, in addition to providing very valuable economic information in the process of its formulation, the GPM solutions identify different wood raw material combinations which FAL can use to manufacture specified product combinations. As an example, one of the most suitable alternative solutions for implementation, alternative one, indicates that 17% of FAL's hardboard mill wood raw material should be obtained from FA sawmill residues, with the remaining 83% being supplied by MFP.On implementing the production programme identified for alternative one, FAL would earn estimated annual net revenue of shs 24.6 million. This would make FAL a profitable enterprise for the first time since it became operational ten years ago. These revenue earnings are, however, based on two basic assumptions. First, FAL would have to be fully operational without major disruptions resulting from technical constraints. In addition, FAL would require an annual recurrent expenditure of shs.16.4 million, a level of funding which is not very different: from that ob erved from the previous .years. The results from the PM indicated that MFP could, if it implements these results, earn a net revenue of she. 25.61 million in the first five year period, assuming that MFP level of funding would continue at levels not significantly different from those observed during the past three years: In addition, such revenues would be earned by harvesting only 57.6% of the harvest volume scheduled in the managemeet plan for the same period. Current projections by MFP indicate forecasted earnings of shs.25.15 million during this period, or 2% less than that achievable by the PM solution on a much lower harvest volume. This is because of the superiority of PM in selecting the mix of species and age classes to harvest on the basis of a financial optimality criterion, as compared to intuitive guidelines pursued by the management of MFP. The results from the MFSM indicated that net earnings to MFP would decline to shs.`15.87 million in the first five year plan period as compared to the PM solution. Net revenues to the industries remained at the levels in the GPM solution, implying that wood raw material supply to these industries is not a binding constraint at their current levels of capacity utilization. This indicates that MFP cannot sell all its produce to FAL. It can only sell up to the level of demand, which is limited not only by the installed capacity but more by the low level of actual capacity utilization, which was less than 30% for all FAL units except the sawm ll which operated at 60% capacity utilization. As a result, the decline in revenues to MFP should be interpreted as resulting from the inability of the mills to consume more wood from the forest either due to technical or financial constraints. Therefore MFP will operate according to the MFSM results and not according to the PM results. It can be concluded that MFP's revenue projections are overly optimistic because of limitations imposed by installed capacity and the level of capacity utilization presently attained at the mills. This indicates rather conclusively that investments in the immediate future should concentrate on the expansion of the wood processing capacity in this region rather than on the expansion of the forest estate. Also, the study indicates that LP can be used successfully to improve decisions relating to the management of both forest operations and wood processing operations. In doing so, LP fulfills the two optimizing objectives stated in Tanzania's forest policy directive. However, these decisions cannot be taken independently but must be connected through the wood raw material link that exists in common between them.
Pollution, adsorption,, and mobility of mercury in Tanzania Soils, its uptake by plants, and effects on microbial activity in soils
(University of Dar es Salaam, 1985) Semu, Ernest
Studies were conducted to evaluate mercury (Hg) pollution of effluent, air, and soil near a battery factory in Dar es Salaam, to study adsorption and mobility of Hg, its uptake by wheat and beans, and its effects on micro-organisms in Morogoro, Arusha, and Dar es Salaam soils. Effects of sample pretreatment on Hg losses from plant materials were also studied to establish optimal conditions. In adsorption, pollution and part of plant uptake studies Hg measurements were made using flameless atomic absorption spectrophotometry. In mobility and plant uptake studies Hg was determined by gamma scintillation counting. Total microbial populations were determined using the plate count method. Nitrogen fixation (nitrogenase activity) was assayed using the acetylene reduction technique. Nitrification was assessed by monitoring nitrate produced. Effluent, air, and soil near the battery factory were found to contain Hg levels of up to 5.2 mg/L, 4.0 *g/cubic metre, and 472 mg/kg, respectively. Soil Hg content decreased to 1.0 mg/kg two km away in the direction of winds, indicating the influence of winds on Hg dispersal. The soils studied displayed large capacity to adsorb applied Hg, but varied in their adsorption capacities. Mercury adsorption depended both on soil: solution ratio and on the initial Hg concentration in solution, indicating that results obtained using different ratios and concentrations should not be compared. Removal of organic matter from soil resulted in large reductions in Hg adsorption, as much as 95% from mercuric chloride and 31% from 2-methoxyethylmercury chloride (Aretan), suggesting that organic matter played a major role in the adsorption of inorganic Hg while soils' mineral matter was involved more in the adsorption of the organic Hg compound. For all soils, adsorption of mercuric chloride increased with increasing pH, between pH 5 and 8, when it was artificially manipulated. Adsorption of Aretan showed little or no change with this pH increase. In all soils, there were wide differences in the adsorption of both compounds among profile horizons. In the Morogoro soil, Aretan adsorption was correlated well (r=0.821*) with the natural horizonwise variation in pH. Similar correlations were obtained with organic matter and CEC distribution for both Hg compounds. No such correlations were observed with the Arusha and Dar es Salaam soils. All soils showed greater capacity for Aretan than for mercuric chloride adsorption, but the bonding energy was larger for the latter. The Freundlich isotherm described the adsorption of mercuric chloride better than that of Aretan. There was little mobility of Hg from mercuric chloride when leached with water or dilute salt solution, and it moved to only 8 cm depth even when leached with 0.5m calcium chloride or 0.1 M EDTA, indicating that these soils' ability to adsorb Hg may preclude any groundwater pollution by Hg. Crop plants generally absorbed very little Hg from soil up to 5 mg Hg/kg soil, although the absorption increased with iincreasign soil Hg levels. But at 50 mg Hg/kg soil, wheat straw and grain absorbed 261 and 236 µg Hg/kg, respectively, from mercuric chloride, but much less from Aretan. Bean straw from 5 mg Hg/kg soil contained 45 and 23 µg Hg/kg from mercuric chloride and Aretan, respectively, but only 1 µg/kg was translocated to grain fromboth compounds. This confirms that generally translocation to grain is very little and, suggests that such grain may not pose health risks under the conditions of these studies. But lettuce grown on peat with 50 mg Hg/L (as mercuric chloride) contained 370 *g Hg/kg of dry matter and this could be hazardous. Total microbial populations of the Morogoro and Arusha soils were not affected much by up to 100 mg Hg/kg in soil relative to the control, showing 10 7/g up to this Hg level. Non-symbiotic nitrogen fixation, and nitrification, wete very sensitive at less than 50 and 5 mg Hg/kg soil, respectively. This shows that availability of specific plant nutrients may be impaired by Hg pollution
Effect of sulphur and other protein metabolism influencing factors on cyanogenesis in cassava
(University of Dar es Salaam, 1988) Bangu, Nicholas T. A
The effect of sulphur and other environmental factors on cyanogenic glucosides (CNG) and protein concentrations in different parts of cassava plants grown in pots or in field was studied. At low N level, increasing S level decreased CNG concentration but increased that of protein. The decrease in CNG concentration as a result of increasing the level of S was also observed in tubers of cassava plants grown under field conditions and in another cyanophoric plant Linum usitatissimum. The reduction in CNG concentration in tubers was > 50%. Inhibition of protein synthesis in Linum usitatissimum by cycloheximide resulted in increased CNG concentration. At medium and higher N levels, increasing S level increased both CNG and protein concentrations. Reduction of light intensity from 16 to 4 MJ m-2 day-1 had little or no effect on the pattern of changes in CNG and protein concentrations as influenced by increasing levels of S but decreased the overall mean CNG concentrations in the aerial parts and increased that in roots. The overall mean CNG concentration in the aerial parts was significantly increased by drought. Exogenous application of cysteine and/or methionine to cassava seedlings resulted in large increases in CNG concentrations. Feeding roots of cassava seedlings with L-valine-U-14C gave rise to a labelled compound with characteristics other than those reported in similar feeding investigations. The observed changes in CNG and protein concentrations are discussed in terms of events at molecular level and agronomic implications. The results are suggestive that there exists a competition for the precursor amino acids between CNG and protein synthesis, that in the course of competition protein synthesis excels over CNG synthesis, that as long as the availability of the precursor amino acids is nonlimiting the concentrations of CNG and proteins are independent of each other, that application of sulphur at low N can be used as an agronomic technique to minimize accumulation of cyanogenic glucosides in tubers of cassava.
Soil resource survey and evaluation for agricultural land use planning in part of Mbeya region, Tanzania
(University of Dar es Salaam, 1988) Rugumamu, William
In Tanzania there is a great and urgent need for land resource assessment as a basis for a rational land use planning. This study attempts to apply a soil resource survey to meet this need. A detailed examination of the philosophies and principles underlying most existing studies on soil survey and land evaluation in the tropics in general and Tanzania in particular has revealed that they are based on environmental conditions prevailing in Europe and North America. Landsat satellite images and aerial photo interpretation as well as field work and soil laboratory analysis of physical, mineralogical and chemical properties as a technique of analysing the physical and human environment against which soil survey and land evaluation for agricultural activities are conducted is employed. The environmental conditions of the study area also inventoried. The study of porous soils derived from volcanic parent materials has shown that pedogenetic processes such as leaching, gleying, salinization and erosion which tend to lower the agricultural potential of part of Mbeya region are operative and their severity varies over the study area whilst processes such as formation of structure, humification and mineralization of organic matter, formation of clay minerals and lessivage which maintain or improve soil productivity do also occcur. The rate of loss of plant nutrients and soil productivity do also occur. The rate of loss of plant nutrients and soil degradation is greater on the windward side than on the leeward side of the Poroto and Rungwe mountains due mainly to differences in climate. It is therefore predicted that the future soils behaviour is more inclined to degradation unless scientific management practices are applied. The studied soils are also correlated to the FAO-UNESCO Legend and the Soil Taxonomy. Evaluation of these soils has revealed that specific land utilization types are suited only to particular ecological and management conditions and topographic and climatic conditions influence the selection of land use types. Current potential suitability offers some development strategy including farmers' education, training of extension staff as well as research support in order to offer better opportunities for a sustainable agricultural production.
Microbiological analysis of the waters of lake Victoria in relation to the invasion of the water hyacinth, Eichhornia crassipes (Mart.) solms: a case study of the lake Shores of Mwanza Municipality.
(University of Dar es Salaam, 2000) Muyodi, Fredrick Jones
Physico-chemical properties of sediment and water were analyzed from six stations in Mwanza municipality along the shores of Lake Victoria. Parameters which were analyzed included pH, dissolved oxygen, temperature, surface light intensity, conductivity and Secchi depths. All samples were analyzed for phosphate-phosphorus (P04 P), nitrate-nitrogen (N03-N), dissolved trace metals and ions. The mouth of Mirongo River and water hyacinth-infested stations were observed to be the most polluted, as indicated by higher concentrations of phosphate-phosphorus (P04-P), nitrate-nitrogen (N03-N) and trace metals as compared to offshore open water areas. The least polluted station was the control station. Major sources of pollution included municipal sewage, floodwater containing agro-chemicals especially fertilizers, agroindustrial wastewaters and manure from intensive livestock farming contributed significantly to the pollution load in Lake Victoria. Low dissolved oxygen (DO) levels were observed in the water column under the water hyacinth plants which caused precipitation of metals which then settled in the sediments. The recorded values of the physico-chemical parameters and limits set for surface waters for domestic and recreational purposes by international water quality bodies suggest that the shores of Lake Victoria along the study area are polluted. It should be noted that the study was carried out in an extremely complex ecosystem, where indeed there could be many factors affecting the parameters studied. The presence or absence of the water hyacinth may be one of the variables in addition to others which could have varied as well. The biotic characteristics of the nearshore waters of Lake Victoria are also described. The objective was to evaluate biomass of aerobic and anaerobic bacteria, phytoplankton (algae), moulds and yeasts in the water column of Lake Victoria in Mwanza as biological indicators of water quality. High algal biomass (Chl. a), dissolved oxygen (DO) content and aerobic bacteria counts were observed in clear and open waters. These sampling stations were also characterized with less numbers of moulds, yeasts and lower values of total suspended solids (TSS) and volatile solids (VS).Stations infested by the water hyacinth weed were characterized with less DO and phytoplankton biomass (Chl. a), high content of TSS and VS, high anaerobic bacteria, moulds and yeasts counts. The mouth of Mirongo River station had the highest content of TSS and TSS and VS, Chl. a and counts of r moulds and yeasts. Water hyacinth-infested shores and the mouth of Mirongo River were observed to be more eutrophic than the offshore open waters. The water hyacinth root swab (HY) was observed to have the highest density of pathogenic bacteria indicators and pathogens (total coliforms, faecal coliforms, faecal streptococci, Clostridium perfringens, Salmonella species, and Vibrio species) and the lowest MPNs wete observed in the water column at the control station (NY). Identification of isolates indicated that the water hycinth root swabs contained more bacterial species than the other samples tested, followed by water column from the mouth of Mirongo River station. These results suggested that there is an input of bacteriologically contaminated wastewater into the lake especially through riverine and municipal discharge. Faecal coliforms/ faecal streptococci ration (FC/FS) showed that there was faecal contamination of human origin as indicated by high values of the tested samples. The results also showed that the water hyacinth weed has a negative effect on the bacteriological quality of water as it immobilises pathogenic bacteria around its roots, which then live longer on the roots than in water, and therefore acts as a reservoir for pathogenic bacteria. These observations have health implications to those whose livelihood depends directly upon the lake's waters. The distribution of populations of sulphate-reducing bacteria (SRB) in sediments from various stations in Lake Victoria shores of Mwanza municipality was studied. Lactate-utilizing SRB were observed to be the dominant species in sediments covered by the water hyacinth weed (S2) and at mouth of Mirongo River station (S3) while acetate-utilizing SRB dominated the offshore open water sediments. Sediments from the offshore and open water station (SI) were observed to have the lowest most probable numbers (MPNs) for all the SRB species investigated. Lactate-utilizing SRB were almost absent in sediments from the offshore and open water. A positive correlation between the total populations of SRB and sulphate (SO) in sediments was observed. The cause of the foul smell at the lake shores resulted from gaseous form of HS produced by SRB activity. Most probable numbers (MPNs) of methanogens in various freshwater sediments were also determined using an anaerobic culture medium supplemented with either acetate or formate. Average MPNs for acetate-utilizing methanogens dominated at all the stations studied. Sediments from the mouth of Mirongo River station (S3) were recorded to have the highest average MPN of (7.2 ± 4.0) x 106 g-1of dry weight sediment for acetate-utilizing methanogens while those from the offshore and open water station (S1) had the lowest average acetate-utilizing methanogenic population of (1.2 0.4) x g' of dry weight sediment. A maximum population of (4.4± 1.7) x 105 MPN g-1 dry weight sediment of formate-utilizing methanogens was recorded at the mouth of Mirongo River station (S3) while sediments from the water hyacinthinfested station (S2) and the offshore and open water station (S 1) had average populations of (5.1 ± 8.7) x 105 and (3.9 ± 2.0) x 104 g-1 dry weight sediment, respectively. A new methanogen, strain TM, was isolated from sediments of Lake Victoria in Mwanza in a minimal medium containing trimethylamine as the sole carbon and energy source. The goal of the study was to isolate and identify the methanogenic archaea from eutrophic freshwater sediments of Lake Victoria, which up to now had not been investigated. Strain TM consisted of coccoid-like irregular cells occurring in clusters and were non-motile. The clusters consisted of cells mostly in twos and fours. The cells fluoresced weakly under ultraviolet light. The diameter of the individual cells ranged from 0.5 to 1.2 um. In agar, strain TM formed white ovallike colonies which reached a diameter of 1.0 to 1.5 mm in 6 weeks. Strain TM was analyzed phylogenetically and a phylogenetic tree was constructed. On basis of its high level of homology with the most closely related methanogen, Methanomethylovorans hollandica(97.0%), its position on the phylogenetic tree, its morphology (which is different from that of members of the genera Methanomethylovorans hollandica), it was proposed that strain TM is a member of the novel genus Methanomethylovorans, This isolate was named Methanomethylovorans victoriae since its origin is Lake Victoria. The GenBank/EMBL nucleotide accession number for the sequence of the 16S rRNA gene of strain TM is AJ276437.
Organic matter sources and trophic interactions among fish species in Pangani estuary – Tanzania
(University of Dar es Salaam, 2009) Mwijage, Alistidia Paul
Estuaries are primary habitat that serves as feeding and nursery grounds for most juvenile marine fish. However, estuaries in Tanzania have been affected by anthropogenic activities in the upstream of the river catchments including the use of these areas as fishing grounds by the artisanal fishers. These human activities contribute to determine the abundance and diversity of OM sources that support the nutrition of fish; and also to define the complexity of the estuarine food webs. The four complementary methods: stomach contents, stable isotopes (Ֆ13C and Ֆ15N) fatty acid (FA) biomarkers and trophic flow modeling approach were used to describe the OM Nutritional sources and trophic interactions among the dominant marine fish in the Pangani estuary. Among the Fish species investigated (Hilsa Kelee, Valamugil buchanani, Arius africanus, Carangoides chrysophrys and Epinephelus malabaricus), PERMANOVA, Pseudo – F = 125.27: P = 0.001), stable isotopes (PERMANOVA, pseudo –F 300.29: p = 0.001), and FA composition (PERMANOVA, pseudo-F = 74.75; p = 0.001). Moreover, the stable isotopes results revealed slight differences in the most important OM sources relied by individual species from depleted in Ֆ13C values to relatively enriched in Ֆ13C OM Sources among the estuarine zones. Yet, the combined methods – stable isotopes, FA biomarkers and Eco path modeling emphasized that terrestrially – derived OM Supplement the main benthic micro-algae basal food sources is an indication resources to sustain the overall estuarine food web. The reliance on benthic diatom – dominated estuarine and marine basal food sources in an indication of low estuarine food connectivity to the fresh water related food web. This situation is most likely threatening the resilience and stability of the estuarine food web structure. This was also highlighted by Ecopath trophic flow model which indicated that the Pangani estuarine food web structure is less resilient to any perpetuation when compared with the other tropical estuarine systems
Traditional knowledge in the management of coastal and marine resources in Tanzania: with emphasis on fisheries resources
(University of Dar es Salaam, 2011) Shalli, Mwanahija Salehe
Monitoring of fisheries resources and contemporary rules for coastal and marine resource management in Tanzania has been challenged for their inadequacy. While searching for management models that work, it is worthwhile to consider the knowledge that enabled traditional communities to sustainably live with their environment for centuries. This study investigated the role of traditional knowledge in the management of coastal and marine resources in rural and urban coastal communities of Tanzania. Interview schedules. field observations, focused group discussions. and a review of literature were used to gather data. Descriptive statistics, Chi square and Contingency Coefficient tests were used to analyze data. The study found that fish catch assessments can be inferred from Fishers' knowledge. Local fishers reveal that at the present time common fish catches have been significantly over-exploited in urban areas compared to many areas based on their sizes and quantities. Some common fish catches such as Caranx spp. are most vulnerable to fishing pressure while others such as Chanos chanos were consistently reported to miss in the catch. Moreover. traditional management practices in the study areas are dominated by taboos and customs, but compliance ta many of these practices were found to decrease with time, especially in urban areas due to rapid socio-economic changes: This tends to contribute to more degradation of coastal and marine resources, including tabooed fish species such as manta rays that are globally recognized as threatened. Also, knowledge of some traditional fishing methods are at a risk of disappearing in urban areas albeit the mode of knowledge transmission is the same for both areas (p= 0.078). Since trasmission of traditional fishing knowledge occurs at average ages of 12- 17 years for rural and 12 -22 years for urban communities, there is potential for the incorporation of this knowledge at least into primary school education where majority of coastal people ended. This study suggests actions to protect traditional knowledge to ensure sustainable conservation of coastal and marine resources in Tanzania. Local communities, scientists and managers need to work together to amalgamate the best practices of traditional knowledge and scientific facts to reduce both the cost of monitoring and management and achieve public acceptance.
Epizootiology of microbial diseases of wild and cultured fish in the Mtera dam catchment area, Tanzania
(University of Dar es Salaam, 2015) Shayo, Salome Daniel
Bacterial diseases are responsible for heavy mortalities of fish in wild environment and cultured systems worldwide, thus causing significant economic losses threatening livelihood of people. In the present study, causes of outbreak of ulcerative infections and mortalities in Nile tilapia (Oreochromis niloticus) at Mtera dam and in fish farms around the Mtera catchment were investigated. Collections of fish samples for examination and measurement of environmental parameters were done for a period of eighteen months to cover seasonal variation in epizootic occurrence. Conventional and molecular techniques were employed in the confirmation of the causative agents. Furthermore, virulence of the recovered bacteria was studied in vitro using similar fish species to confirm the causative agent of ulcerative infections in Nile tilapia at the Mtera dam. 50 bacterial isolates belonging to 13 genera were obtained. Virulence experiment confirmed that the causative agents of ulcerative infections in the dam were Aeromonas, and Pseudomonas species. Temperature, DO, Turbidity, and conductivity showed significant effects on the observed infections pattern in the dam. Occurrence of fish mortality and clinical symptoms were profound during the dry period. The presence of infectious bacteria in the fish samples indicate a potential health risks for consumers as bacteria such as Aeromonas hydrophila are associated with human infections. Fishers/consumers are advised to avoid ulcerative fish from the dam particularly during the dry season. The high number of the isolated opportunistic bacteria from the dam is an alert for proper fish health management to evade great losses in case of stress oriented disease outbreaks.
Processes driving carbon, nitrogen and phosphorus balance in mangrove creeks with varying anthropogenic influence.
(University of Dar es Salaam, 2018) Ulomi, Shadrack Joseph
The main objective of this study was to investigate the processes driving dissolved gases (carbon and oxygen) and nutrients (nitrogen and phosphorus) balance in Mtoni and Ras Dege mangrove forests. This was achieved by comparing: i) creek waters physicochemical characteristics between the two sites (Mtoni and Ras Dege) within wet and dry seasons, ii) forests benthic sediment characteristics, anaerobic organic matter mineralization and fluxes of dissolved gasses (CO2 and O2) between Mtoni and Ras Dege mangrove forests, iii) water column processes governing concentration of dissolved gases (O2 and CO2), nutrients (N and P) and organic carbon (particulate and dissolved) and iv) the processes happening in the natural forest (Mtoni and Ras Dege) and those happening in the experimental mesocosms planted with Avicennia marina and Rhizophora mucronata seedlings and experimentally exposed to domestic sewage of varying strength. DIC studied in the water column was higher in Mtoni than Ras Dege creeks ANOVA test: p=0.0138 and generally higher in wet season than in dry season while turbidity was generally higher in Mtoni than in Ras Dege (student’s- t-test, p < 0.05). Generally Ras Dege creek water had higher pH than Mtoni water (one way ANOVA: Fs=5.585, df=1, p=0.039). Wet season samples from Mtoni creek waters, had significantly higher particulate organic carbon (POC) and nitrogen (PON) than the waters from Ras Dege creek(one-way ANOVA: df= 1, Fs= 4.43, p= 0.04 and one-way ANOVA: df= 1, Fs= 10.25, p= 0.012)respectively. On general account, sediment samples from Ras Dege had higher SRR’s than those from Mtoni regardless of the season ( one-way ANOVA: df =7, Fs = 13.77, p= 0.00001)and outer boundary sites(R1 and M1)had higher FeR than inner sites t-test: t = -3.596, df=3, p= 0.036 and sample t-test: t= -5.109, df=3 , p= 0.015) respectively. CO2 fluxes during the wet season for both stations were significantly higher (one-way ANOVA: df =7, Fs =37.999, p =0.002 ) than that of the dry in Ras Dege indicating that Mtoni is more polluted than Ras Dege. There was also higher CO2 fluxes in wet season than in dry season for both sites indicating the effect of the wet season in controlling the benthic metabolism. Anaerobic carbon oxidation was dominated by FeR irrespective of anthropogenic influence in sediments in natural mangrove forests. In the Mesocosm study the microbial mineralization in the water column reduced organic pollutants by > 90% while anaerobic carbon mineralization in the sediment was dominated by SRR and increased with sewage dose. The study proved the resilience nature of mangrove forest by sinking most of organic pollutants which could cause eutrophication in adjacent coastal waters. Anaerobic mineralization higher GPP in Mtoni (4.5-5.2 μM O2 h−1 ) than RasDege(3.4-3.9 μM O2 h−1 as evidenced by Mesocosm study: (cells receiving higher sewage dose (60%) revealed higher GPP than the cells receiving low dose) indicate that anthropogenic activities in Mtoni are main drivers of the balance in nutrients and dissolved gases in mangrove forests. Higher DOC and NH4+ production in both stations in neap waters indicate the influence of tidal waves and season in general water column metabolism.
Assessment of the effects of aspilia mossambicensis and azadirachta indica in controlling prolific breeding in farmed Nile Tilapia (oreochromis niloticus linnaeus, 1758)
(University of Dar es Salaam, 2019) Kapinga, Imani
There is growing demand of fish for food as the world population is expected to reach more than nine billion people by 2050 yet fish production from capture fishery has stagnated at 90 million tonnes since the late 1980s (UN 2017,FAO 2018). Therefore, further increase in global fish production is expected from aquaculture which is currently the fastest growing animal protein production system. Nile Tilapia, Oreochromis niliticusis the second (next to carp) most important finfish species cultured worldwide in terms of production. This is due to its hardiness, tolerance to varying degrees of environmental factors, high resistance to diseases and wide consumer acceptability. Despite these attributes, smallholder tilapia farming in Tanzania is constrained by pond over-crowding due to early maturation and prolific breeding often leading to poor water quality, increased competition for food, oxygen and space, as well as diversion of energy from somatic growth. Use of synthetic hormones to produce all-monosex is the most widely used technique to control the prolific breeding. Nevertheless, hormonal sex reversal in Tanzania is limited by its high costs, lack of skills and hormone unavailability. Therefore, this study assessed suitability of two medicinal plants Aspilia mossambicensis and Azadirachta indica in controlling breeding of Nile tilapia. Phtytochemical screening of Aspilia mossambicensis and Azadirachta indica leaf powders showed presence of two phytocompunds namely alkaloids and flavonoids which are known for their antifertility properties. The phytocompunds are are structurally or functionally similar to sex hormones capable of interfering reproduction in fish. Dietary inclusion of leaf powder from the two plants reduced prolific breeding by inducing histological alterations fish gonads. There was also a shift of sex ratio in favour of males. The reduction was higher content of antifertility phytocompounds in the former. Furthermore, growth and feed utilization was reduced at high doses whereas survival and haematogical parameters were improved. Therefore, dietary inclusion of 2.0g kg-1 and 4.0 g kg-1 of Azadirachta indica and Aspilia mossambicensis leaf powders. Respectively can be used by smallholder farmers to reduce prolific breeding of Nile Tilapia.

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