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This report was prepared by Dr
Amos Enock Majule last updated: 29 July 2004 |
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News : Directory of Soil Institutions and Experts in Africa is available through [Link 2.2.1].[29/07/04]
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1. Country overview 1.1 Geography and administrative units 1.3 Climate 1. > top |
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1.1 Geography and administrative units Lying between 1° and 12° South of the equator, Tanzania is the land of the biggest mountain in Africa-the Kilimanjaro and of the great Lakes of Victoria, Nyasa and Tanganyika. Tanzania (formally Tanganyika) is found in the coast of eastern Africa with an estimated area of about 832,300 sq.km (De Pauw 1984). The country is bordered by Kenya (Northeast), Uganda (north), Rwanda and Burundi (Northwest), Mozambique (south) and Malawi and Zambia (southwest). A higher proportion of her border to the east is shared with the Indian Ocean as compared to the surrounding countries. The shores of this ocean are characterized by the coral reef that stretches from the north to the south. Administratively, Tanzania is divided into 25 Regions, 20 of them are in the mainland whereby 5 are in Zanzibar islands. Regions are administratively subdivided into Districts, which are further subdivided into divisions and finally divisions are divided into wards. The capital city of Tanzania is Dodoma and this is located in the central part of Tanzania. This is a new capital city to replace Dar es Salaam which is located along the eastern coast of the country. Since most of ministerial offices are still in Dar es Salaam, a number of administrative activities are still done there. There are efforts to move these offices to Dodoma, a new capital city. [Map 1.1.1: Outline Map] 1.1 > 1. The populations of many developing countries have been growing at rapid rates often exceeding 2.0%. An increase in population has always been associated to rapid degradation of the environment particularly deforestation, pollution and soil erosion. Both population growth and environmental degradation have become global problems. Analysis of population growth requires periodic and systematic information on population totals, regular collection of births and death records, and data collection on migratory movements. In order to clearly assess the population growth rates of Tanzania, three sets of data on population census are hereby considered. These are 1988, 1978 and 1967 data. The total population of Tanzania has almost doubled between 1967 and 1988 (Table 1.2.1). During the 1988 census, the population in Tanzania was 23,174,336. This data can be compared with population census for 1967 and 1978 which, were 12,313,469 and 17,512,610 persons respectively. Data indicates that the population grew by 5,199,141 between 1967 and 1978 and by 5,661,726 between 1978 and 1988. These present an increase of 42.2% for 1967/78 and 32.1% for 1978/88 periods (United Republic of Tanzania –URT, 1988). Tanzanian population has been estimated to be 31 million peoples in 1998. Compared to the land area of the country, Tanzania’s population can be described as small. However its growth rate is high and thus there is rapid increase in the size and density of the population. A national population census is planned to be conducted in year 2002. Table 1.2.1 shows the population size (millions), the percent change, and annual rates of growth between 1967 and 1988. It can be observed that the population has been increasing in-terms of absolute members. However, the intercensal population growth declined in the mainland and in the whole of Tanzania from 3.2% in 1967/78 to 2.8% in 1978/88. An increase in the growth rate from 2.7% to 3.0% can be observed in Zanzibar between the two censuses. The past trends in Tanzania shows that the annual growth rates increased from 1.8% to 3.0% in 1948/57 and 1957/67 respectively. The growth rates for Zanzibar in 1948/57 and 1957/67 were 1.3% and 1.8% respectively. Population density (PD) This is a measure of the ratio of a given number of people to a given land area and it has been widely used to determine the population concentrations. It expresses how people within the country are spatially distributed. Generally, PD illustrates the link between population and resource distribution at different levels of analysis. However density as a measure of population concentration is limited in the sense that it masks many considerable disparities and tends to treat all land equal. The population density of Tanzania in 1978 was 19.8 persons per sq.km while in 1988 it was 26.2 persons per sq.km. These figures indicate an increase in population density by 32% between the two censuses. According to international standards, the population density of 26.2 persons per sq. km seems to be very low. In Tanzania, the most populated Regions are the Dar es Salaam and Mjini Magharibi. Although the population density data for Tanzania give the impression that Tanzania is sparsely populated, it is important to note that the population is unevenly distributed. The population density is highly concentrated in Regions with favorable climatic conditions, good soils, adequate and reliable sources of water. Rural/Urban populations The majority of people (nearly 80%) live in the rural area and they mostly depend on land for their subsistence. The availability of arable land and its quality is of considerable importance in explaining the internal distribution of the population. During the same period it was also established that 95.8% among the urban population were living in Tanzania mainland whereby only 4.2% were living in Zanzibar. Generally, although there is a rapid growth of population in urban areas (increases from 6.2% in 1967 to 21.1% in 1988) a large proportion of the population is still living in rural areas. The current rapid urbanization if not planned properly, its consequences may be reflected in the deterioration of the social services available. Agriculture According to URT report of 1997, Tanzania has 43 million hectares of land which are suitable for agriculture. A large population of Tanzanian practices agriculture activities on a small-scale basis in rural areas. Farming activities in the rural areas is their main occupation. The main products of their labor in farming are food and cash crops as well as livestock, which are basically for subsistence. Cash crops are sold to earn the people some money for other family needs. In the medium term and long-term horizon, Agriculture will continue to play a central role in Tanzanian’s economy. A key area of the economy in which the contribution of agriculture is decisive is the country Gross Domestic Product (GDP). The sector contributes to both export earnings and employment, which accounts for 60% and 84% respectively. Crucial components of the agricultural sector are food crops, livestock and traditional export of crops whose contribution currently stands at 55%, 30% and 8% respectively of the total GDP. Traditional Export Crops include coffee, cotton, cashewnut, tobacco, tea, sisal, and pyrethrum. The production of major cash crops shows no clear trend, annual fluctuations are largely influenced by climatic circumstances, incidence of pests and diseases, and short-term price variations. With only a very small share of the international market (except sisal and pyrethrum), increased production of these commodities in the country would not affect export prices. In the medium term, these prices are expected to remain at a production level sufficient to support the financial viability of the production of these crops in Tanzania. The development of new technologies and its delivery systems will be a key area of focus in order to remove identified constraints, and increase productivity and profitability of these crops. According to URT (2000) report, the trend in the production of major cash for 18 years and food crops over the past 17 years are summarized in Tables 1.2.2 and 1.2.3 respectively. Table 1.2.2. Total Annual Production (in ‘000 Tons) and Growth Rates of Cash Crops From 1981/82-1998/99.
*Significant at 5-10% Source: Crop Boards, MDB-MAC Table 1.2.3. Food Crop Production (in ‘000 Tons) and Growth Rates From 1981-1998.
*Significant at 5-10% Source: Statistical Abstract, 1994, Bureau of Statistics, President’s Office, Planning Commision. 1.2 > 1. Climate is defined as the synthesis of weather or day-to-day atmospheric conditions. Climate is affected by several factors including; geographical position or latitude, relief, configuration or alignment, and ocean currents (Griffiths, 1968; Ngana, 1983). From these factors, five major climatic regions are common in Tanzania (Pratty and Gwynne, 1977). These includes the following;
[Map 1.3.1: Eco-climatic zones of Tanzania] [Map 1.3.2: Mean Annual Rainfall] 1.3 > 1. |
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2.1 Physiography 2.2 Soils 2.4 Wetlands, mangroves and inland valley bottoms 2.6 Natural hazards 2.7 Land cover 2.8 Land use 2.9 Land use change 2.10 Land Productivity 2.11 Environmental Impact of land uses 2. > top |
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Main Physiographic Regions in Tanzania and their subdivision units have been indicated in Map 1.1.3. These units includes the Coast, Northern (1a), Coast southern (1b), Coast Islands (1c), Arid lands, Northern (2a), Arid lands, Masai steppe (2b), Semi arid lands, Central (3a), Semi arid lands, South eastern (3b), Plateaux, Western (4a), Plateaux, Southern (4b), Highlands (Southern), Highlands, South western (5b), Highlands, Western (5c), Highlands (Northern), Highlands, Granitic mountains (6b), Alluvial plains, Kilombero (K), Alluvial plains, Rufiji (R), Alluvial plains, Usangu (U), Alluvial plains Wami (W). 2.1 > 2. In Tanzania the distribution of different soil types are going to be presented according to the different agro-ecological zones (see soil map). [Map 2.2.1: Soil map of Tanzania] [Link 2.2.1: Directory of Soil Institutions and Experts in Africa] 2.2 > 2. Agro-ecological Zones (AEZ) are land resource mapping units, defined in terms of climate, landform and soils, and/or land cover, and having a specific range of potentials and constraints for land use (FAO). The present Agro-ecological Zone Map of Tanzania provides data on climate, physiography, soils and vegetation/land use and tsetse occurrence, which are the main physical factors that influence potential and constraints for crop and livestock production. The following are the major Agro-ecological Zones of Tanzania (Currently, AEZ map s not in a digital form).
2.3 > 2. 2.4 Wetlands, mangroves and inland valley bottoms The coastal area of Tanzania is important for mangroves and it harbors a number of biodiversity. For example, the Rufiji basin in Rufiji district of the central coastal in Coast region is one of large site for tidal (mangrove) forest on the eastern coast of Africa. These mangroves support an extensive inter-tidal fishery, provide nursery grounds for nationally important prawn industry, and have considerable importance locally and regionally. Rufiji also harbours many other forest and woodland associations-many of which are influenced by the floods from the Rufiji River which provide surface and sub-surface waters to the riparian forests, swamp forests, fringing woodlands thickets and wetlands on and adjacent to its lower floodplain. Over 150,000 people inhabit the Rufiji delta and floodplain, the majority of whom depends on fishing, cultivation and extraction of forest, woodland and wetland product. There are some very valuable dry coastal forests in Rufiji District in the upland away from the delta and floodplain which certainly contain biodiversity of local, national and probably international importance-such as Kichi hills forest, the Nyamuete-Namakutwa and Mchungu Forest reserve. Over the last decade, however the Rufiji forests, woodland and wetland have come under increasing pressures from a wide variety of factors, including unsustainable harvesting of both timber and fish resources, the conversion of mangrove areas to cultivation and the use of riparian forest and woodlands for fuel. The mangroves, Floodplain, forest and freshwater wetlands are also threatened by developments within the district like improvement of the road network, including a bridge over the Rufiji River, Mining exploration activities as well as by upstream development activities that include the construction of hydroelectric dams and water extraction schemes. Similar problems are affecting other areas. 2.4 > 2. Inundation is a situation whereby land is covered with a variety of things such as salt, discovery and expansion of mining activity on a site, seasonal flooding or excessive livestock numbers per unit land. When this occurred it become difficult to control leading to change in landuse. Example of Inundation land types in Tanzania includes the following: Table 1.2.5 . A summary of Inundation land types in Tanzania.
2.5 > 2. In Tanzania, a section that deals with natural disasters is under the Prime Ministers Office. The following are documented natural hazards occurred in Tanzania. DROUGHT In 1993 drought occurred and affected Arusha, Kilimanjaro, Kagera and Kigoma regions and the total number of people affected was 282,053. The government received an assistance of 26,833 tones of cereals, 2,683 tones of beans and also sugar, dates and milk from UK, Holland, Japan, China and EEC. In 1999, drought occurred in most parts of Tanzania particularly in the 14 regions. About 3.9 million people were affected. The government of Tanzania and donor communities supported the people affected. The government donated 8,800 tones of food whereby the donor community donated 76,746 tones of food with a value of Tshs 23 billions. In 1996, drought occurred in most parts of Tanzania. It was acute particularly in the 14 regions, drought effects were acute, and the effect was carried out to year 1997. About 3.9 million people were affected. The major problem occurred in Monduli (Arusha region). Mitigation measures taken were to construct 48 dams and opening up 115 deep and 54 shallow wells respectively. About 20,000 tones of food were given free to people affected whereas 55,600 tones were offered for sale. In 1999, 17 regions were affected by drought whereby a total of 1,305,336 people faced this problem. Nearly 18,000 tones of food were given to businessmen for sale to shortage areas whereby 142,624 tones was imported by businessmen for sale. FLOODS In 1993, floods occurred in Lushoto and Korongwe in Tanga region. The scale of damage included infrastructure, environment, water system, school, homes, hospital, and roads. The government provided a sum of Tshs 263.3 million to assist the affected communities. EL-NINO In 1998, 14 regions were affected whereby 416 people died, roads, railways, bridges, water system and crop fields (nearly 211,945 ha) were damaged. Additionally, epidemic disease particularly cholera occurred in many areas, airport strips were damaged, schools buildings and nearly 37,615 residential houses were destroyed. Nearly 238,995 ha of agricultural land were affected. Birds and animals (both domesticated and wildlife were affected. In Arusha region, landslide occurred whereby 68 people died. The government received an assistance from World Food Program (WFP) (25,738 tones of food), 69,140 tones of food from Denmark, USA and Germany, 892, 800 tones of food from UNDP. The government also received US $ 82, 000 from UK. Sweden and Ireland provided 194 tones of seeds for distribution to farmers. CYCLONE In August 1994, Five children dead in Zanzibar. A ship (MV BUKOBA) sunk in Lake Victoria in 1996 and 865 people dead while 112 people survived the accident. The government received assistance from different international organizations, Non Governmental Organizations (NGO’s) and from various local Institutions within the country. A sum of Tshs 4 80,769 (0.5 million Tshs) was each given to the family of the dead whereas Tshs 100,000 (0.1 million) was each given to survivors. BOMB BLAST In August 1998, a bomb blast occurred at the US Embassy in Dar es Salaam whereby 11 people dead and 85 were injured. In this event, which also occurred in Nairobi, a number of houses and vehicles were affected. There was also a damage on environment and infrastructures. The cost of damage was estimated to be Tshs 721,384,900. Assistance from foreign government was Tshs 233,532,601.50. United State of America (USA) provided US $ 9 millions together with medicine, sugar, oil, date and wheat flour. 2.6 > 2. The estimate of overall landuse is derived from a recent remote sensing mapping exercise using the LandSat images covering parts of the country. However there are efforts to produce a digital Landuse/cover map of the country at IRA. According to National Reconnaissance Level Land Use and Natural Resource Project (1997) estimated landuse/cover ('000 ha) in Tanzania is summarized below in Table2.7.1. Table 2.7.1. Distribution of Major Land Cover/Use Types
Source: National Reconnaissance Level Land Use and Natural Resources Mapping Project (1997). 2.7 > 2. The land under total cultivation is 42%, 29% is under protection (national parks, conservation areas, and game and forest reserves), and other areas are infested by tsetse fly (26% of rangeland) which restricts livestock production and use of animal traction. The following is a summary of cropland in Tanzania ('000 ha). Table 2.7.2. Selected Land Use Systems in Tanzania and Approximate Area.
Source: URT (2000). 2.8 > 2. Not available 2.9 > 2. Not available 2.10 > 2. 2.11 Environmental Impact of land uses Soil acidification process is currently one of the problems in southern coastal areas of Tanzania. This is associated with the dusting of large quantities of elemental sulphur upon cashew trees aimed at controlling powdery mildew disease (Majule et al., 1997; Majule, 1999). Soil acidification has been associated with leaching or removal of basic cation such as Ca, Mg and K. This is common in Mtwara and Lindi regions in the southern coastal areas of Tanzania. This acidification is likely to reduce the productivity of poor and fragile soils. Soil acidification has also been reported to be associated with an excessive use of nitrogenous fertilizers in Songea and Iringa regions particularly in maize fields. Generally, declining in soil fertility in most fields has been reported to accelerate the soil acidification process. There is soil erosion problem in Kondoa (Dodoma region) and Shinyanga where livestock keeping and encroachment of forest has been reported to be major causes. Soil erosion is also very common on steep slopes where there is vegetation clearing, intensive cultivation and poor land management practices (Murray-rust, 1973; Kaihura, 1991; Lat, 1995 and Dejene, 1996). 2.11 > 2. |
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3.1 Hydrography 3. > top |
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Country information on water resources is available at AQUASTAT. In case there is more information available, describe as follows. 3.1 Hydrograph(see Figure 3.1.1) Tanzania shares three major Lakes (Victoria, Tanganyika and Nyasa) with other countries in the eastern and central Africa. Other Lakes in the country includes, Masoko, Rukwa, Eyasi and Magadi. Tanzania also has many permanent and seasonal rivers. Main river includes Rufiji, Ruvuma, Pangani, Ruvu, and many others indicated in Map 3.1.1. Total renewable water resources are estimated at 80 km3/year, of which 30 km3/year are groundwater resources. Water in the country is under-utilized for agriculture because there is generally a poor coincidence between available water resources and suitable land. [Map 3.1.1: Major Lakes and Rivers] Surface water The surface river flow regime and moisture conditions in the country correspond to the general rainfall pattern. The hydrological year starts in October/November in most areas and ends in September/October. About 50% of the surface runoff flows directly into the Indian Ocean from the major river systems. The main internal drainage basins are the Lake Rukwa, the Bubu complex, Lake. Eyasi, and Lake Manyara. Lake Nyasa, Lake Victoria and Lake Tanganyika basins drain into international water bodies. A considerable water resource exists in the country’s Lakes namely Victoria, Nyasa, Rukwa, Eyasi and Natron. Effective assessment, planning and management of water resources as well as for effective monitoring instituting preparedness, response and remedial action against adverse effects of environmental degradation such as pollution of water bodies, drought and desertification and floods, meteorological and hydrological information is needed. Ground water Ground water potential varies from one locality to another and so does its development. Over a wide part of the country ground water development has concentrated mainly on shallow wells for domestic purposes. The inland drainage basin is explored and its water tapped mainly for domestic and industrial use. It is only in few localities in Dodoma region where ground water is used for irrigation. The ground water potential zones are classified as high, medium and low or negligible for each basin. High ground water potential areas are;
Major basins
Dams 1. Nyumba ya Mungu
3.1 > 3. Department of Irrigation is currently within the Ministry of Agriculture and Food Security. The major roles of the Irrigation department are; To provide advisory services to smallholders traditional irrigation schemes Identification of potential areas for irrigation in the country To carry out feasibility studies for irrigation Designing of irrigation projects and finally, To undertake the construction of irrigation structures. Agriculture, which is the most important sector in Tanzanian economy is very much affected with the inadequacy, seasonally and unreliability and rainfall as well as periodic droughts. It is for these reasons that Irrigation was considered necessary in providing protection against drought, a means of stabilizing crop production and assurance of house food security. TYPES OF IRRIGATION IN TANZANIA
The importance of water for crop production and the development of mankind in general are obvious. History tells us that the World civilization started along some of the famous Rivers like for instance Euphrates, Tigris and the Nile. In Tanzania irrigation practice history sends us back to the Iron Age whereby traditional irrigation systems have long been of considerable importance in various parts of the country to date. Available information indicates the irrigation potential of fifty-three Districts of Tanzania derived from a survey conducted by the Institute of Resource Assessment (IRA) and the Ministry of Agriculture and Food Security. Appraisal of irrigation up to 1970 revealed about four broad types of irrigation in Tanzania (Mascarenhas et al., 1985). The classification adopted is summarized below. Flood Plains and Valleys. The ground is prepared and planted with crops like sugar cane, oil palms, bananas as well as rice at the beginning of the long rain season in anticipation of flooding which usually occurs. Water normally comes from overflowing or may be gathered from hillsides, sometimes by funneling channels and led into fields previously prepared to hold water. Dikes and drainage channels are part of the water control system. Traditional Irrigated Areas Small holders in mountainous areas and in small river valleys normally do this. Water is normally obtained from low-cost, temporary or semi-permanent river diversion structures. Common examples includes Vinyungu irrigation system in Iringa, Majaluba irrigation system in Shinyanga and Mwanza, and Kilimanjaro and Meru mountain irrigation systems. Irrigation Schemes Constructed by the Government Schemes are designed and constructed by engineering staff. Land irrigated is rather flat topography and is farmed by small holders. Distribution of water and general management of these schemes is under a government agency, although districts or village councils administers some of schemes. Water is obtained from reservoirs well built river diversions or by pumping. A good example of the irrigation scheme under this category is the Kitere irrigation project in southern Tanzania, Mtwara Region. Irrigated Estates This last category includes irrigated estates, managed by individuals, companies, or parastatal government organizations. Hired employees carry out preparation of the fields. Water is obtained from river diversions or boreholes. The sugar estate at Arusha-Chini, and the coffee estates in Kilimanjaro, Kapunga Rice Irrigation Project and Mbarali rice farm in Mbeya region are good examples of these. Roles of the water institution/mandates
Future development of the observed pattern Taxes collection
Water –land legislation Currently, there are three post independence pieces of legislation pertaining to water resources administration in Tanzania (URT, 1995).
Various sectors uses land and their interactions affect fresh water ecology and its management. These include irrigated agriculture, livestock, fisheries, and forestry. There should be a close linkage between water and land resources management. Respective legislation should be reviewed and harmonized in relation to environmentally sound management and use of water resources. Shared international waters In the current Tanzania Water Legislation, as contained in the Water Utilization and Pollution control Act. No. 1974, the country is divided into nine (9) drainage basins (URT, 1995). Six (6) of these are international drainage basins and includes:
The only existing cooperative mechanisms in which Tanzania is involved are concentrated in the Lake Victoria basin. There is an organization for the management and development of the Kagera Basin Organization (KBO). This organization was established in 1977 with members being Burundi, Rwanda, Tanzania and Uganda focusing on hydropower, agriculture, transportation and telecommunication as priority areas. The agreements have either grounded to a halt or very small activities are going on. Partly this situation can be attributed to the problems of internal financing, which include cost sharing criteria. The members must participate in conservation and proper use of water and in the determination of the equitable entitlement of each riparian state to the use of water. 3.2 > 3. |
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4.1 Plant nutrient use and nutrient balance 4.2 Fertilizer production and costs 4. > top |
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4.1 Plant nutrient use and nutrient balance There is a growing concern over the decline in the productivity of most agricultural soils in Tanzania. This is a result of unsustainable landuse practices that have lead to soil erosion and adverse change in hydrological, biological, chemical and physical properties of the soil. A study, which assessed the extent of nutrient mining, concluded in 1993 that there was an overall negative nutrient balance for N, P, and K of -27, -4 and -18 kg/ha/year respectively (URT, 2000). In many parts of the country, soil moisture availability is considered to be the primary limiting factor on crop yields. In order to minimize the negative balance in terms of nutrients, primary nutrients (nitrogen, phosphorus and potassium) are added to the soil. Other secondary nutrients added include calcium, sulphur and magnesium whereby micronutrients used are iron, copper and zinc. The effectiveness of organic residues in ameliorating soil fertility is now being tested in many parts of the country through Zonal Research and Development Institutions and other Research Institutions at Universities. A trend in nutrient use is summarized in Table 4.1 below. Table 4.1. Trend in plant nutrient use per metric tons
Source: National Bureau of Statistics, Tanzania. 4.1 > 4. 4.2 Fertilizer production and costs Between 1970s and 1980s fertilizers were produced, imported, and distributed by the Tanzania Fertilizer Company (TFC). State owned TFC sold fertilizers at subsidized and pan-territorial prices. From 1991, import and distribution were liberalized and subsidies gradually removed and this caused TFC to cease its production activities but continue to import and distribute fertilizers. This resulted to a drop in fertilizer consumption from nearly 140,000 tones to some 60,000 tones for the 1998/99 season. Tanzania receives particularly from Japan a little donation of fertilizer. Fertilizer prices are high by international standards and it is around US$ 250 per ton on average (URT, 2000). In Tanzania, there are deposits of Rock Phosphate at Minjingu in Arusha (Minjingu Rock Phosphate-MRP), Panda, Nguala and Sangu Ikolla in Mbeya. MRP ore are estimated at 8 million tones while only 1,000 tones/year are used in the country. Field research has indicated that there is a good response to P from MRP particularly in acid soils low in available P particularly in the second season of application. Table 4.2.1 presents results obtained after the application of two different sources of P (MRP and TSP) on acidic soils at Mlingano. MRP was superior than TSP in the second year of application. Table 4.2.1. Effects of N and P applications on maize grain yield (kg/ha) at Mlingano, Tanga.
Source: (NSS, 1989) Fertilizer price structure in Tanzania for the past 5 years hasn't changed significantly. In 1996/97, a tone of UREA had the following prices, FOB US $ 200, CIF US $ 252, Landed cost US $ 263.5, ex-go down US $ 356.9, price at regional center US $ 382.2, price to stockiest US $382.2 and farmer's price US $ 415.1. This suggests that a farmer pays almost twice the actual price of fertilizer and this is a burden to him/her. 4.2 > 4. |
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5.0 Overview: constraints to sustainable agriculture 5.3 Plant Nutrition-related constraints 5. > top |
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5.0 > 5. 5.1 Land-related constraints to sustainable agriculture Soil fertility refers to the availability of plant nutrients particularly nitrogen, phosphorus, and potassium and organic matters in the soil. Soil fertility decline occurs when the mining of soil nutrients exceeds their replenishment resulting to a negative balance of nutrients. In Tanzania, agricultural development is supported by the application of two types of fertilizers, organic and inorganic. Some of fertilizer materials are acidic in nature particularly UREA and Sulphate of Ammonium (SA). These compounds are acidic in nature and if applied continuously they may cause soil acidity. Areas affected much through application of nitrogenous fertilizers include Rukwa, Iringa and Ruvuma. The soil acidification process has also been observed in Mtwara and Lindi regions and it has been linked to the dusting of elemental sulphur in cashew field intended to control powdery mildew disease (Majule et al., 1997). The effects of these acidic compounds after being applied continuously are:
Compaction and crusting Soil compaction is a process whereby the particles of soil are mechanically constrained to pack more closely together. It is achieved by expulsion of air from the soil and reduction of voids by a force which is sufficient to overcome the friction and cohesive resistance but which is no great enough to cause bearing capacity failure (Lukas, 1986). Overgrazing and stock routes are the main causes of sheet and gully erosion. Overstocking was crucial in the lake and central regions and was overall a major problem in the whole country among erosion factors. Compaction can be improved by reducing the resistance to grain movement. Added water reduces the resisting forces of the absorbed layers and capillary tension, by increasing the degree of saturation. If there is so much water that the voids are filled with water, compaction is resisted by water itself. Wind erosion Erosion by wind is common in arid and semi-arid areas where the vegetative cover is naturally sparse and where overgrazing worsens the situation, often leaving the soil completely bare and exposed to the energy of the winds. Effects of this wind erosion on sites are:
Converting the vegetative cover on steep slopes. Example, from forests to crops, accelerates the risk of landslides as both the stabilizing and the hydrological effects of the trees are lost. Off sites effects are: -Burying of cultivated fields by sediments in valley bottoms -Pollution of water sources -Siltation of dams -Destruction of beaches -Killing of coral reefs Tanzania is a country that depends on agriculture for its economic and social development. Typical of tropical soils, the majority of Tanzanian soils are marginally suitable for agriculture. Climate and human activity are the main factors affecting erosion. Among human factors accelerating erosion are cultivation on steep slopes without any conservation measures, mono-cropping practices, overgrazing, burning of forests, trees down cutting, high rate of population growth leading to over utilization of land and limited potential agriculture land collectively accelerate soil erosion. The most important types of erosion are rain splash and sheet wash. Gully erosion appears in distinct zones of the upper pediment slopes near the foot of the inselbergs. Overgrazing and livestock routes are the main causes of sheet and gully erosion. 5.1 > 5. 5.2 Water-related constraints to sustainable agriculture Water erosion
Water erosion off site effects are:
5.2 > 5. 5.3 Plant Nutrition-related constraints to sustainable agriculture The majority of soils lack major nutrients such as nitrogen, phosphorus and potassium (NPK) and thus leading to a negative nutrient balance (URT, 2000). There is minimal use of artificial fertilizers (both nitrogenous and phosphate fertilizers). Poor agronomic practices such a frequent fire has tended to reduce soil organic matter and thus reducing the amount of soil organic matter vital in conserving nutrients. Another problem is poor recycling of nutrients from various sources of residues. 5.3 > 5. 5.4 Other constraints to sustainable agriculture There are two categories of constrains, natural and manmade constrains. These constrains are technological development and transfer, extension services, food security, agricultural research, infrastructure, gender aspects, marketing pricing policy and macroeconomic policy (Msambichaka et al., 1995). Technological development and transfer includes these elements: poor crop and animal husbandry practices, continue use of hand tools 80-85%, tractors 5%, plough 10-15%, continued dependence on rainfall agriculture, high cost of modern on packages as contributed by high production cost and unreliable supply of inputs caused by infrastructure bottlenecks Food security: food crisis management is poor and there is insufficient marketing system. Agricultural research is not well organized and poorly financed. It includes weak linkages between agents of research and development and potential users. However there are efforts to work very close with farmers. The sake of national research priority is weak. Infrastructure includes transportation, storage, etc. Transportation systems are poor and storage system is also poor. So the marketability of crops is low. The gender aspects involve inequality of labor supply. Woman does most of agricultural activities in rural areas. Marketing pricing policy is very poor leading to non-or very little profit to farmers; there is also weak market infrastructure (marketing information, prices, inputs, availability of transport and storage facilities). Macroeconomic policy related with taxes to agricultural sector is said to be excessive and budgets are unrealistic. Rural credits are not readily available to people. Finally, there is lack of information on available resources and lack of intensive inventive plan. 5.4 > 5. |
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6. Bright spots 6.0 Overview: society's response to ameliorate the situation 6.1 Land-related response indicators 6.2 Water-related response indicators 6.3 Plant Nutrition-related response indicators 6. > top |
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6.0 Overview: society's response to ameliorate the situation Main issues and summary of bright spots. 6.0 > 6. 6.1 Land-related response indicators
6.1 > 6. 6.2 Water-related response indicators
6.2 > 6. 6.3 Plant Nutrition-related response indicators Restoration of Soil Fertility in Sub-Saharan region is so crucial (Sharma et al., 1995).
6.3 > 6.
6.4 > 6. |
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7.0 > top |
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8. References and related internet links 8.1 References 8. > top |
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Dejene, A, Shishira E.K,. Yanda P.Z. and Johnsen F.H. (1996). Land Degradation in Tanzania. Perception from the Village. World Bank Technical Paper no. 370, World Bank, Washington DC. Griffiths, J.F. (1968). Climate of East Africa. L E.W. Russell (editor), Natural Resources of E.A, Hawkins, Nairobi. Pp 77-87. Kaihura F.B.S. (1991). Soil Erosion and Conservation Studies in Tanzania, Opportunities and Strategies for research. Soil Fertility and Management Report f 8, 1991. Lukas R.O. (1986). The Influence of Compaction on the Stability of Lateric Earth Fill Dams. Thesis for the Ph.D of Technology. University of Dar es Salaam. Majule, A.E., Toper, C.P. and Nortcliff, S. (1997). The environmental effect of dusting cashew (Anarcadium occidentale L) trees with sulphur in southern Tanzania. Tropical Agriculture Journal (Trinidad) 74:25-33. Majule, A.E. (1999). The effects of organic residue and elemental sulphur additions in soils of southern Tanzania. Ph.D Thesis, Reading University, UK. Mascarenhas, A., Ngana, J and Yoshida, M. (1985). Opportunities for Irrigation Development in Tanzania. JRP Series 52. Murray-rust, D.H. (1973). Soil erosion and reservoir sedimentation in grazing areas west of Arusha, Northern Tanzania, Research Monograph no.1. BRALUP, University of Dar es salaam, Msambichaka L.A., Kilindo A.A.L and Mjema G.D. (1995). Beyond Structural Adjustment Programs in Tanzania. Economic Research Bureau, University of Dar es Salaam. Ngana, J. O. (1983). Rainfall and Agriculture, Drought and Famine in Dodoma District, Tanzania. IRA Publication. National Soil Service (NSS). (1990). A Progress Report Presented to Annual Soils and Fertilizers Use Co-ordinating Committee Meeting Held in Arusha on 27-28/11/1990. Lat, R. (1995). Erosion-Crop Productivity Relationship for Soils in Africa. American Journal of Social Science Society 59:661-667. Sharma, N. S. Denning and K. Cleaver. (1995). Restoration of Soil Fertility in Sub-Saharan Africa, Concept Paper and Action plan. Africa region, World Bank, Washington DC. United Republic of Tanzania. (1988). The Population of Tanzania. The analytical report. Bureau of Statistics, Presidents Office, Planning Commission, Dar es Salaam. United Republic of Tanzania. (1995). Ministry of Water, Energy and Minerals, Water and Sanitation Sector Review, Final Report. pp. 45,46 United Republic of Tanzania. (1997). Agricultural and Livestock Policy. Ministry of Agricultural and Co-operative. United Republic of Tanzania. (2000). Soil Fertility Initiative. Ministry of Agriculture and Cooperative. Report No 00/081 CP-URT. 8.1 > 8. 1. Tanzania Facts/Figures/Flag - www.graphicmaps.com 2. SEACAM history:
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