The Need for Collaborative Research on Environment, Soil, and Water Management for Sustainable Agriculture
Mozambique’s economy is heavily dependent on the exploitation of the natural resource base. Richly endowed in terms of land, with a considerable amount of coal and natural gas, some strategic minerals, important fisheries, and substantial hydropower potential, its relatively small economy has a high potential for growth. An enabling environment for foreign private investment further enhances this growth potential.
The primary sector of the country’s economy is agriculture, contributing about 25 percent of GDP and 60 percent of exports in 1996. The high level of absorption of the labor force also indicates the relevance of the agricultural sector to the economy. In 1990 83 percent of the work force was engaged in agricultural activities and only 8 percent in industry (Diogo, 1997). Agriculture is in fact the engine to attain food security, to reduce poverty and, therefore, to build a sound basis for sustainable management of natural resources.
Land degradation as a consequence of agriculture occurs mainly in rural areas (Menete and Mazuze, 1997). In those areas there are two main sectors involved in agriculture production: the family (small-scale farming) and private sectors. The family sector is a heterogeneous group of dispersed farmers practicing subsistence farming on an average of 1.82 hectares (ha) per family household (DEA, 1995). In all there are some 2.5 million family households cultivating approximately 4.5 million ha of land, from a total of 36 million hectares of arable land (DEA, 1995), which represents 95 percent of the total cultivated area. Until 1994, the family sector was responsible for the production of 95 percent of cereals, 98 percent of leguminous, 100 percent of cassava and cashew, 50 percent of copra, and 72 percent of cotton produced in the country. It also contributes considerably to the production of vegetables, citrus, and other tropical fruits. in 1995 75 percent of all livestock belonged to this sector (MAP, 1997). From the above figures, it is obvious that the family sector predominates over the private sector, which is increasingly being given more attention under the economic reform program.
Emphasis on agricultural sustainability arises out of increasing awareness about the finite nature of arable land resources, the widespread problem of land degradation, the rapid deterioration of environmental quality, and the vicious cycle of low crop yields, malnutrition, and famine.
Soil and water conservation practices are needed to prevent or minimize land degradation and to make sustainable agriculture development possible. Sustainable land use is aimed at establishing an ecological approach to resource management. The objective is to balance the inherent soil, water, and crop requirements with innovative management systems that optimize resource use and sustain productivity over a long period of time.
Environment for Agricultural Production
The climate of Mozambique ranges from the very dry arid zone to the very wet humid zone. According to the modified Thornthwaite method, about 80 percent of the country is classified as semi-arid tropics, constituting the dryland agriculture belt. The sub-humid zone covers about 15 percent of the country, and constitutes the wetland agriculture belt. The arid and humid zones make up 2 and 3 percent of the country, respectively, and are primarily suitable for pasture and non-food crops (Reddy, 1984).
There are two distinct seasons, namely, winter and summer. Rainfall is mainly restricted to the warm season, which takes place between October and April, and decreases from North to South and from the coast to inland areas. The average country annual rainfall is 968 mm, but varies between 350 mm in Pafuri to 2,000 mm in Gurué.
The mean annual potential evapotranspiration exceeds significantly the mean annual rainfall for the majority of the country (Reddy, 1984), with values between around 1600 mm in Tete and 1200 mm in Lichinga (Kassam et al., 1981).
In the northwest part of the country, soils are predominantly clay to clay loam with low to moderate fertility and good physical characteristics. The soils of the low-lying coastal plain in the south and along the coastal belt are sandy with low fertility. Their low water-holding capacity, combined with erratic and low rainfall, exacerbates the drought risk. Extensive areas of alluvial soils exist along rivers such as the Zambezi, Limpopo, Incomati, Umbeluzi, etc. These areas have good agriculture potential and are suitable for irrigation.
The current status of land degradation in Mozambique is not alarming as compared with other SADC countries, mainly because only 4.5 million hectares out of 36 million hectares of arable land are used annually for agriculture and only 50 thousand hectares out of 3.3 million hectares are used for irrigation of potential land for such purpose (MAP, 1997). However, the situation is expected to deteriorate as a result of the relatively high economic growth, the high annual population growth rate, estimated at 2.65 percent, the favorable climate for investment, and increasing water consumption by industries. Therefore, positive actions are needed in order to prevent and/or minimize the expected increase in land degradation, since as it proceeds and intensifies there will be a consequent decrease in land productivity.
The major forms of land degradation in the country are:
Land productivity symptoms resulting from these factors may include the following (FAO/UNEO, 1983):
Soil fertility decline
The spatial distribution of fertility classes of Mozambique (Geurts, 1997) indicates that, except for alluvial soils, the soils of Mozambique vary from moderate to low fertility. Table 1 shows the average values of NPK (fertilizer) in 50 cm layer of surface soil.
In cultivated areas depletion of nutrients is caused by the imbalance between the output of nutrients (mainly through crop harvest and erosion) and the input of nutrients (in form of organic and inorganic fertilizers), resulting in a negative nutrient balance of the soil and its consequent gradual loss of soil productivity. The areas used for small-scale farming have moderate-to-high nutrient mining due to low levels of inputs used for crop production.
Actual data on erosion do not exist. However, the Erosion Hazard Map (Van Wambeke, 1986) gives an indication of the soil erosion potential of the country. Areas of greatest erosion potential are those with high altitude (between 200 and 1500 meters). The area of greatest risk covers the central provinces of Manica, Tete, and Zambezia and all northern provinces.
A qualitative assessment of the spatial distribution of salinity hazard in Mozambique (Berg & Menete, 1995) indicated, for dominant soil grouping, that 75 percent of the country had no risk, 5 percent showed moderate risk, 17 percent had severe risk, and 3 percent was already saline (see Table 2). Looking at these figures, it seems as if the problem of salinization and sodification is not an important issue, but note that 25 percent of the country shows a certain risk and these areas include the main river basins (Limpopo, Incomati, and Zambezi) and the densely populated coastal areas, which are very important for agriculture production.
Frenkel et al (1994) have produced a Soil Acidity Map based on pH values of major soil groupings of the Soil Map of Mozambique and the available soil profile data of the south of Mozambique. According to that map, the majority of the country is characterized by slightly acidic to neutral soils.
Alkaline soils cover only small areas where sodium accumulation occurs and/or estuarine soils exist. Sandy soils of the coastal belt in southern Mozambique are strongly acid due to the marine influence. These soils consist of Quaternary sediments characterized by lower base saturation and high aluminum content. Other strongly acid soils are made up of strong weathered soils like Ferralsols and poorly drained Fluvisols (INIA, 1995).
Loss of vegetation cover
Accurate information on land cover changes do not exist, since the land use maps in use date from 1985 (Sijnders, 1985), on a 1:2M scale for the whole country and 1:500,000 scale for some parts of the country. But these data will soon be available because digital land use maps for the whole country, at the scale of 1:250,000, are being produced under The Land Cover Mapping Project.
According to Saket (1994), changes in natural vegetation cover in general and in forest cover in particular were very small and were caused by forest clearings for agriculture purpose, uncontrolled forest fires, wood-fuel and building material extractions, timber harvesting, and hand-crafting. Itinerant agriculture and its shifting cultivation system for regeneration of soil productivity were the prime causes of the damages to forests, natural vegetation, and ecosystems. The rates of change in forest cover were calculated per province between 1972 and 1990; the results are shown in Table 3.
The overall rate of deforestation between 1972 and 1990 was approximately 4.27 percent or 0.24 percent per year.
Surface water is the main source of fresh water in the country. The majority of the rivers flow in a west-east direction, draining the central high plateau into the Indian ocean. In many rivers, flows are intermittent with high water flow for three to four months during summer season and low flows for the remaining part of the year. Droughts are common especially in the south of the country, and they are related to the erratic distribution of the rainfall during wet season. Heavy storms and high floods are common in the south and center of the country and usually follow months and/or years of drought.
Most river basins are shared with other countries. As Mozambique is located at the downstream end of those basins, it is in a very vulnerable position from being extremely dependent on the imported flows in terms of their quantity and quality. Groundwater is the main source of water for the rural water supply as well as for villages and small towns.
Rainfed agriculture is by definition dependent on the rainfall regime and is practiced during rainy season. Given the agro-climatic conditions of the country, crop failure in the north is usually less than 5 percent while in the south the value reaches 60 to 75 percent. Thus the lack of rainfall in the south represents a severe constraint to rainfed crop production.
Recent estimates indicate that irrigated agriculture is the largest water consumer, accounting for about 510 million cubic meters per year, representing 80 percent of the country's total water consumption (Consultec, 1998). High water losses, low efficiencies, highly subsidized water rates, and low yields per unit of applied water characterize irrigated agriculture.
The following considerations should be taken into account when identifying further research needs:
Berg, M., and Menete, M.Z.L., 1995. Salinity Hazard in Mozambique. Paper presented at 21st meeting of the SARCCUS standing committee for soil science. Inhaca, Mozambique.
Consultec, 1998. Country Situation Report: Water Resources (Final draft) Vol I, II and III. DNA. Maputo, Mozambique.
DEA, 1997. Inquéritos Agrícolas ao Sector Familiar 1993 e 1994. Resultados definitivos. Ministério da Agricultura e Pescas. Maputo, Mozambique.
Diogo, D., 1997. Caracterização da Agricultura Moçambicana. Resultados dos levantamentos agrícolas. DEA, Ministério da Agricultura e Pescas. Maputo, Mozambique.
Frenkel, J., Menete, M.Z.L., and Vilanculos, M., 1994. Soil Acidity Map. Paper presented at 20th meeting of SARCCUS standing committee for soil science.
Folmer, E., and Francisco, J., 1997. Soil Fertility Decline Caused by Agriculture Land Use. INIA, comunicação n.89. Maputo, Mozambique.
Geurts, P.M.H., 1997. Recomendações de Adubação Azotada e Fosfórica para Culturas Alimentares e Algodão em Moçambique. INIA, comunicação n.89. Maputo, Mozambique.
INIA, 1995. Carta Nacional de Solos, 1:1M. Maputo, Mozambique.
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Mafalacuseser, J.M., 1995. The Use of Indigenous Knowledge For Land Use Planning in a Part of Xai-Xai District, Gaza Province, Mozambique. Institute For Aerospace Survey and Earth Sciences. Enschede, the Netherlands.
Menete, M.Z.L, and Berg, M., 1996. Management of Saline and Sodic Soils in Mozambique: Uses and Constraints. Paper presented at 22nd meeting of the SARCCUS standing committee for soil science. Gaborone, Botswana.
Menete, M.Z.L., and Mazuze, F.M., 1997. Situação Ambiental em Moçambique: Solos e Uso da Terra. Ministério Para a Coordenação da Acção Ambiental. Maputo, Mozambique.
Reddy, S.J., 1984. General Climate of Mozambique. Serie Terra e Agua. INIA, Comunicação n. 19-1. Maputo, Mozambique,
Snijders, F.L., 1985. Land Use Inventory of Mozambique. Instituto Nacional de Investigação Agronómica. Série Terra e Água, Comunicação n. 43. Maputo, Mozambique.
Saket, M., 1994. Report on the Updating of the Exploratory National Forest Inventory. Department of Forestry Inventory, Forest Inventory Unit. Ministério da Agricultura e Pescas. Maputo, Mozambique.
Van Wambeke, J., and Marques, M.R., 1986. Erosion Hazard Mapping in Mozambique. Instituto Nacional de Investigação Agronómica. Série Terra e Água, Comunicação n. 20. Maputo, Mozambique.
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