Geography

Topic area: Physical Geography
Sub-topic area: Soils in Rwanda
Key unit competence
By the end of this unit, you should be able to compare different soil types and assess their importance to Rwanda.
Unit objectives
By the end of this unit, you should be able to:
• State the different types of soils in Rwanda.
• Identify the causes and effects of soil erosion in Rwanda.
• Identify the importance of soil to Rwanda.
Soil
Activity 5.1
Work in pairs. Study the following photograph and answer the questions that follow.
1. Name what sample X represents.
 2. Discuss the composition of sample X.
3. Explain why sample X appears in different colours.
4. List the uses of sample X.

In Senior One, you learnt about soils. You studied the soil formation processes, properties of soil, soil profile, soil catena, different types of soils and the importance of soils. In Senior Four, you are going to study the different types of soils in Rwanda, causes and effects of soil erosion and the importance of soil to Rwanda.
Definition of soil
Soil is the upper layer of the Earth in which plants grow. It is made up of a mixture of rock particles, organic matter, minerals, gases, liquids, air and living organisms that support life.

Types of soils and where they are found in Rwanda
Activity 5.2
Work in groups of five.
1. Go outside your classroom.
2. Collect 5 samples of soil from different areas within your school compound.
3. Observe the soils and analyse their characteristics.
4. Using the knowledge on soils that you had learnt earlier, classify the soil samples according to their types.
5. Record your findings and present them in a class discussion.
Generally, there are four different types of soils. Three are basic while the fourth one is a combination of the three.
• Clay
• Silt
• Sand
 • Loam
Rwanda also has these soils in addition to other soil types. The table below shows a summary of their characteristics and places where they are found.


There is a wide range of soils in Rwanda. The soils are classified according to how they are formed and where they occur. Basing on these classifications, the country has the following types of soils listed and described in the table below.



Other soils in Rwanda result from the physical and chemical alteration of schistose, quartzite, gneiss, granite and volcanic rocks which form the surface geology of the country. These soils are classified as follows:
(a) Soils derived from schistose, sandstone and quartzite: These are found in the Congo-Nile crest, parts of the Central plateau and on the highlands of Gicumbi district. They make up about 50% of the national land area.
 (b) Soils derived from granite and gneiss: These are found in most parts of the Central plateau especially Muhanga and in the Eastern plain. They cover about 20% of the national land area.
 (c) Soils derived from intrusive basic rocks: These are found in the Northern Province especially Gicumbi and Burera districts. They cover only about 10% of the national land area.

(d) Alluvial and colluvial soils: These soils comprise of minerals found in the valleys of the Eastern plain and the river valleys of the Akagera, Nyabarongo and Rugezi Rivers. They cover about 6% of the national land area. They are common in the swamps found in the country.
(e) Soils derived from recent volcanic materials: These soils are found in the plateaus of Rusizi and the northwestern parts of the country. They cover about 10% of the national land area.
(f) Soils derived from ancient volcanic materials: They cover about 4% of the national land area.

Activity 5.3
Work in groups of three.
Use the Internet, atlas and other geographical materials to do the following.
1. Find out the different types of soils in Rwanda.
2. Find out where they are located in Rwanda.
3. Draw a sketch map of Rwanda.
 4. Locate the different places on the maps where the different types of soils are found.
5. Write down the names of the places located on the maps and the types of soil found there.
6. Make a class presentation on the locations of the different types of soil.
Activity 5.4
Rwanda is a country that is gifted with different relief features giving rise to different soils.
1. Analyse the importance of the different types of soils in the regions where they are located and to the country as a whole.
 2. Write down your findings and present them in a class discussion.
Task 5.1
1. (a) With the help of a sketch map of Rwanda identify the locations where the different types of soils are found.
 (b) Describe the characteristics of the types of soils mentioned in (a) above.
2. Account for the presence of varying soil types in Rwanda.
3. In relation to Rwandan soils, write short notes on the following.
(a) Loam soils
 (b) Clay soils
(c) Sandy soils
Activity 5.5
Study the photograph shown below and use the findings of your analysis to answer the questions that follow.

1. Describe the colour of the water flowing in River Akagera.
2. Why do the waters of the Akagera River and most of the rivers of Rwanda have the colour represented in the photograph above?
3. Identify and explain the main causes of too much silt in the rivers of Rwanda.
4. Using the geographical skills and compentences already acquired, suggest the possible ways of making sure that the environment is conserved and managed suistainably.
5. Write down your findings and discuss them in a class presentation.
Activity 5.6
Work in pairs. The photograph below shows one of the areas in Gicumbi District. Study it and answer the questions that follow.

1. Describe the changes on the land indicated in the photograph.
2. Explain the causes of the changes identified in (1) above.
3. Examine the effects of such changes on the environment.
4. Show how best man can conserve and manage the environment suistainably.
5. Suggest the possible solutions to the main causes of destruction of land and soils that Rwanda can implement to reverse the degradation of land such as the one shown above.
6. Write down your findings and discuss them in a class presentation.
Activity 5.7
Work in groups of three.
1. Collect different samples of soil i.e sandy soils, lateritic soils, loam soils and clay soils.
2. Each group should have a portion of the different soil types.
3. Display the soil samples by spreading them on a flat board.
4. Put water in a watering can and lift it up to about 11 2 metres high.
5. Gently pour water on top of the specimens.
 6. Critically observe what happens and note down the findings.
 7. Use the findings for class presentation and to answer the following questions.
 (a) What happens to the soil particles after water drops are poured on them?
 (b) What name is given to the washing away of the soils?
(c) Explain the various types of the washing away of soils by either running water, moving ice or wind.
(d) Apart from water, name other agents of erosion.
Soil erosion refers to the wearing away of the top soil from a specific place to another by water, wind, ice and gravity.
Soil erosion in Rwanda has caused the loss of large quantities of fertile topsoils. These soils are washed away and end up in rivers within the valleys. This explains why many rivers in Rwanda have coloured water.
The water has too much silt and dissolved particles of soil washed into the streams. Soil erosion in Rwanda is made worse by the steep nature of most parts of the country. This is the reason areas such as Nyabihu, Musanze , Rubavu and Muhanga are affected by soil erosion.
Types of soil erosion in Rwanda
Activity 5.8
Work in pairs.
Use the Internet, Geography textbooks and other materials.
1. Find out the major types of soil erosion in Rwanda.
2. Discuss how the different types of soil erosion identified have affected land use and the environment in Rwanda.
3. Write down your findings and present them in a class discussion.
There are mainly four types of soil erosion experienced in Rwanda. They are described below.
(a) Sheet erosion
Activity 5.9
Work in pairs. Study the following photograph provided. It represents Kabagali area in Ruhango district where a maize garden was affected by the running water. Answer the questions that follow.
1. Explain the process that led to destruction of the above garden.
2. According to your own experience, explain how the process happened.

Sheet erosion is a type of soil erosion where the top soils are washed uniformly by the running water such as surface runoff. This occurs mainly along slopes or on steep pieces of land that have little or no vegetation cover. This means that water flows evenly over an area, wiping off the top soils.
(b) Rill erosion
Activity 5.10
Work in pairs. Use the photograph provided to answer the questions that follow.


Rill erosion occurs when several tiny channels, measuring a few centrimetres deep are created by water on a piece of land. The tiny channels are referred to as rills. The rills in rill erosion usually take a linear pattern. They are formed by water. This type of erosion is common in Gashora area of Bugesera district and in other parts of Eastern Province. It is more pronounced during the rainy season. The absence of vegetation cover speeds up this form of erosion.
(c) Gully erosion
Activity 5.11
Study the photograph provided taken from Rushaki in Gicumbi area and answer the questions that follow. 1. Name the type of soil erosion shown in the photograph.
2. Identify the main agent of erosion shown in the photograph.
3. Explain the causes of this type of erosion.
4. Name other areas in Rwanda where this type of erosion is common.
5. Describe the effect this has had on the environment.

Gulley erosion occurs when big depressions are created by the heavy run-off that occupies narrow rills. This water widens and deepens the rills to form gulleys.
This type of erosion is common in parts of Musanze, Gicumbi , Western and Southern Provinces of Rwanda.
Splash erosion Activity 5.12
Work in pairs.
 Analyse the photograph shown below and use it to answer the questions that follow.

1. Name the type of soil erosion shown.
2. Describe how this type of erosion forms.
3. Describe its effects on the environment.
4. What measures can be taken to avoid such an effect on the environment?
5. Note down your findings and discuss them in a class presentation.
Splash erosion is caused by the force of pounding raindrops that hit the upper layer of soils detaching small soil particles from the unconsolidated soils.
 In the process, the soil particles are splashed away as the raindrops fall on the ground hence the name splash erosion. This type of erosion is very common in the Eastern Province in areas where the vegetation cover is minimal or completely lacks in some places.
Task 5.2
1. Define soil erosion.
2. Describe the agents of soil erosion in Rwanda.
3. Write short notes on the following.
 (a) Sheet erosion
(b) Rill erosion
(c) Gully erosion
(d) Splash erosion
The causes of soil erosion in Rwanda
Case study
Miss Mukabananira Vestine a well-known farmer in Burera district invested a lot of her time and resources in crop growing. In 2014, the crop yield was so low and her funds were wasted. She was so surprised because she had used a lot of organic manure in her farm. Her land was located along a steep slope. She never followed the advice given to her by the agricultural extension worker from her sector. She had been advised to build terraces on the land and to practise countour ploughing. On the day that she ploughed her farm and put the organic manure, it rained heavily. The run-off from the upper parts of the slope washed away the soil carrying the organic manure along with it. All these were deposited down slope into the neighbour’s farm which had a well prepared terracing system and crops planted in strips. During harvest time, her neighbour harvested baskets full of farm produce.
This was a discouraging experience.
(a) Explain what caused Miss Mukabananira’s land to be unproductive despite the generous application of organic manure.
(b) Why was her neighbour’s yield bountiful?
(c) Using the geographical knowledge and skills you have acquired, what would you advise Miss Mukabananira to do?
There are many areas in Rwanda that face severe soil erosion. They include the following.
• Gicumbi district
• Burera district
 • Musanze district
• Rubavu district
• Muhanga district
• Nyabihu district
• Rusizi district
The areas mentioned above experience severe erosion due to a number of factors. These factors are divided into physical and human factors. They are discussed below.
(a) Relief
This influences the occurrence of soil erosion whereby areas with steep gradients cause the run-off to flow at high speeds hence quickly eroding and transporting the soils. Areas with gentle slopes and flat regions, the run-off flows at a lesser speed and the strength to erode is reduced.
(b) Climate
 Climate leads to the formation of agents of erosion such as the run-off, moving glaciers and wind. In Rwanda, rainfall is the most active agent of erosion. In areas where heavy rainfall is received the surface runoff present washes away large quantities of the topsoils. On the other hand, wind erosion is dominant in areas such as parts of Bugesera and the Eastern Province. There is also seasonal glacial erosion on the summit of Mt. Karisimbi especially during the wet season.
(c) Vegetation
Plants growing in a given area provide a binding role to the soils. Plant roots hold the soil particles together enabling them to resist erosion. The presence of vegetation reduces the impact of falling rain droplets. The branches or canopies of forested areas limit the pounding ability of rain drops. Areas with less vegetation or bare soils are subjected to agents of erosion.
(d) Soil erodibility This is an estimate of the ability of soils to resist erosion based on the physical characteristics of each soil. Soils with faster infiltration rates, higher levels of organic matter and improved soil structure have a greater resistance to erosion. Sand, sandy loam and loam textured soils tend to be less erodible than silt, very fine sand and certain clay textured soils.
(e) Poor methods of farming
Farming methods such as monoculture and ploughing of land along slopes speed up erosion. They subject the soils to erosion especially by water.
(f) Mining and quarrying
These activities expose the soils to erosion. They make the soil particles unstable and when agents of erosion come by, much of the soils are carried away. Methods such as open cast mining cause severe erosion.
(g) Overgrazing
In some parts of Rwanda where animals are still communally grazed, much of the soils remain bare due to the clearance of the vegetation by animals. This exposes the land to agents of erosion.
Bush burning
The pastoral communities have a tendency of burning grass or pasture lands during the dry season in preparation for the rainy season. The burning of vegetation leaves a given area bare and totally exposed to agents of erosion.

Activity 5.13
 Work in pairs.
 Use the Internet, Geography textbooks and journals, personal experience and the local environment.
1. Find out and explain other causes of soil erosion in Rwanda.
2. Suggest soil conservation measures that should be put in place to prevent and reduce the effects of soil erosion in the country.
 3. Note down your findings and present them in a class discussion.
Task 5.3
1. Using specific examples, explain the causes of soil erosion in Rwanda.
2. To what extent is increase in population a direct cause of soil erosion in Rwanda?
Effects of soil
erosion in Rwanda
 Case study
 Miss Dushimimana Sarah conducted a fieldwork study on soil erosion in one of the parts of the Eastern Province. In the process of her fieldwork, she took the photograph shown in fig 5.10. Study it and use it to answer the questions that follow.
(a) Define fieldwork study.
 (b) Why did Sarah conduct the fieldwork?
 (c) Describe what happened to the land represented by photograph in fig 5.10.
(d) With good reasons, describe the geographical name given to the depression shown in the photograph.

There are several effects of soil erosion that are experienced in Rwanda. They include the following:
(a) Low soil productivity
Soils subjected to erosion lose all nutrients. This lowers their economic value. This is because they can hardly support crop production due to their infertility.
(b) Low soil moisture
Areas affected by erosion experience loss of moisture. The removal of the top soils which would allow infiltration of the run-off exposes the sub soils which are associated with soil compaction. This further reduces the permeability, porosity, and biological activity of soils hence rendering them unproductive.
(c) Destruction of crops
 Wind erosion destroys young seedlings. This means that extra costs are incurred by the farmers through replanting. Sometimes, the sediments being transported are deposited in farms where they end up burying germinating seeds to deeper depths preventing them from reaching the surface.
(d) Affects underground water
Soil erosion sometimes involves run-off which percolates and dissolves soluble minerals. Some of the minerals pollute the underground water. The removal of the upper layers of soils provides a smooth surface upon which the run-off flows at high speeds having no chances of infiltrating into the soils. This reduces the chances of increasing the volume of underground water. Hence, the water table is lowered. In some places, springs and other underground water sources dry up.
(e) Affects transport systems
 Many roads in Rwanda especially up country and feeder roads are affected by gullies created by continuous surface run-off. This hinders the movement of goods and services and increases the government’s expenditure due to frequent rehabilitations.
(f) Flooding
Through soil erosion, sediments are deposited into lakes, rivers and streams. When there is too much deposition in a river or lake, its carrying capacity reduces and becomes shallow. As a result, water starts overflowing hence flooding the surrounding areas.
(g) Silting
 Closely related to the flooding, the silting problem comes along with increased expenses of dredging, resettling people and total disruption of the eco-system. For example River Akagera is not suitable for large ships or motor boats because most of the parts are shallow and have too much sediments.
Activity 5.14
Work in pairs.
 Use the Internet, Geography textbooks and journals, personal experience and the local environment.
1. Find out and explain other effects of soil erosion in Rwanda.
2. Note down your findings and present them in a class discussion.
Case study
You have been appointed the minister in charge of agriculture in Rwanda. Some regions of the country suffer from perennial famine. On setting up a task force to investigate the reason for this, you discover that the root cause of this is soil erosion. The soils in the region cannot support plant growth. The residents of the region use traditional planting methods.
They plough along slopes, they do not use fertilisers nor pesticides, they clear vegetation from the fields by burning them and most of them keep a large number of traditional breeds of cattle that feed in a communal grazing field.
 (a) Explain ways in which you will address the causes of erosion in these regions.
 (b) Present your report and recommendations in a class discussion.
 (c) From the findings of your research and recommendations from your study, advise the community around your school and home on the following;
• Causes of soil erosion
• Prevention
 • Management of the effects of soil erosion.
Soil conservation and management measures in Rwanda
 Activity 5.15
Study the photograph below and answer the questions that follow.

1. Name the type farming being practised in the area where this photograph was taken.
2. Why do you think the farmer decided to plant crops and trees at the same time?
3. Write down your findings and present them in a class discussion.
Activity 5.16
Work in groups of three.
1. Go outside your school compound.
2. Observe the surrounding environment in the area.
3. Identify ways in which the people in that community have prevented and managed the effects of soil erosion.
4. Write down your findings and present them in a class discussion.
Soil conservation refers to the prevention of soils from erosion, degradation or loss of fertility. Soil management refers to all the measures put in place to ensure proper use of soils in a sustainable manner. In Rwanda, there are several measures taken to conserve and manage soils so that they can be used by humans sustainably. Some of the soil conservation and management measures include the following.
(a) Afforestation
Afforestation is the establishment of forests in an area where there was no forest. Planting trees where they have never existed before especially along the steep slopes of Rwanda checks the rate and occurrence of soil erosion. Trees bind the soils together and reduce the impact of the falling and pounding raindrops. The speed of surface run-off is also reduced, hence providing soils with a protecting cover against agents of erosion.
(b) Reforestation
This is the re-establishment of forest cover, either naturally or artificially in an area. There are many areas in Rwanda that have been deforested and reforested by planting of new trees. The steep areas of Gicumbi have been reforested by planting of quick maturing trees. This was done to protect the soils from erosion and at the same time to conserve and protect the environment.
(c) Agroforestry
 This is a land use management system in which trees are grown around or among crops or pastureland. Farmers in Rwanda are encouraged to plant crops and trees on the same piece of land. This is practiced in places like Bugesera, Musanze and Rubavu districts.
(d) Terracing
This is the making of sloping land into a number of level flat areas resembling a series of steps. This was advocated for by the government of Rwanda. Almost, all the steep slopes demarcated for agriculture were terraced so as to prevent soil erosion by surface run-off. Terracing helps in reducing continuous and lengthy slopes. It also helps to reduce the speed and impact of the run-off on the topsoil.

(e) Contour ploughing
This is a form of cultivation where land is cultivated across the slope instead of along the slope. In this method, crops are planted according to the contours of the slope.

(f) Mulching
Mulches are loose coverings of material placed on the surface of cultivated soil. They can be applied to bare soil or to cover the surface of compost. There are many benefits of mulching. They include; retaining moisture in dry and hot weather and to suppress weeds.
Mulching also prevents the topsoils from being washed away by the surface run–off. At the same time, the mulching materials decay with time adding more organic matter into the soil hence maintaining its fertility.
(g) Strip cultivation
Strip cultivation is a method of farming used when a slope is too steep or too long. This method alternates strips of closely sown crops such as wheat with strips of row crops, such as maize and beans. The growing of cultivated crops in alternating strips is arranged to follow the contour of the land and to minimise erosion.
                                    
Crop rotation
This is a farming practice where a given type of a crop is grown on a piece of land, after a different type of crop is harvested from the same piece of land in the following season. This rotation balances the soil nutrients.
(i) Application of artificial and organic fertilisers
It is necessary for farmers to apply both artificial and organic fertilisers where possible. This improves the nature and quality of the soils. The fertilisers and manure enable the soils to support vegetation. The vegetation plays a great role in protecting soils against erosion.
(j) Land rotation
 This method involves the use of land at different times. The land is divided into several pieces. Not all pieces are cultivated at the same time. Some parts of the land are left fallow while other parts are cultivated. This practice allows land to rest and regain its fertility.
(k) Reducing the number of livestock
Reducing the number of livestock that a farmer keeps prevents overgrazing which causes soil erosion.
Activity 5.17
Work in groups.
Use the Internet, knowledge gained in Geography and other geographical sources. 1. Show how the following soil conservation measures can be adopted in Rwanda. (a) Research and training (b) Establishing specific water points (c) Planting of cover crops (d) Row planting (e) Shelter belts 2. Explain their importance to the soils of Rwanda. 3. Explain the importance of soil conservation to Rwanda as a country
Importance of soil in Rwanda
Case study
Use the case study given below to answer the questions that follow: Karisa Francis is a resident in the Northern Province. He has become a renowned farmer in the region. His harvests are so encouraging and many families find their livelihood from the products of his efforts. He sells his Irish potatoes to his neighbours and also provides employment to people in his farm. In the recent past, he decided to use soil from his farm to make bricks to extend his house. Soil is an important to the life of Karisa.
(a) Identify and explain the importance of soil that are mentioned in Karisa’s story.
(b) Examine other importance of soils to the socio-economic development of Rwanda.
(c) Come up with sustainable land use measures that you can teach farmers like Karisa to enable them to use soils sustainably in Rwanda.
 (d) Write down your findings for a class discussion and presentation.
In Rwanda land and by extension soil is a valuable resource that must be protected and well managed. Some of its benefits include the following:
(a) Source of food
The increasing population of Rwanda depends directly on the agricultural produce from the farms. Available land and fertile soils can enable farmers to plant a variety of crops. The Northern Province is the national food basket that supports and ensures food security for the masses in Rwanda. This because the region has fertile volcanic soils.
(b) Modification of climate
 Fertile soils support the growth of dense forests which play a great role in modifying the climate of Rwanda. In some parts of Western and Northern Provinces, the fertile soils have led to the occurrence of dense vegetation. This has contributed to the formation of a favourable climate.
(c) Source of raw materials
Soil in form of clay and sand are used in the construction sector in the making of materials like bricks and roof tiles. In Rwanda, the Ruliba Clays Limited Company is in existence because of the availability of good quality clay. The bricks used in building houses are also made from soils.
(d) Research and study
Students who study soil science in the higher institutions of learning in Rwanda use soils to understand concepts of their course.
(e) Art and craft
 Soils such as clay are used in crafts like pottery. The items made out of clay include, candle stands and kitchen utensils, flower vases and other decorative items. These items assist humans by making their living better.
(f) Habitat for living organisms
Soils are homelands for living organisms such as bacteria, algae, fungi and protozoa to more complex organisms like earthworms, insects, small vertebrates and plants. These organisms have a positive contribution to the ecosystem and to the well being of the soils.
(g) Ground water
Soils allow the infiltration of surface runoff which percolates forming a water table which is a natural water reservoir underground.
Formation of rocks Soils assist in the formation of rocks. The rocks formed have their contribution to the development of a country. Rocks such as sedimentary rocks are formed when the sediments of soil are deposited and hardened.
(i) Mineral formation
Soils especially those that are highly saline lead to the formation of salt and soda ash which are utilised by humans in various ways. Peat coal is mined in form of soils that are found in marshy areas. An example of such an area in Rwanda is the Rusizi area. Peat coal is a cheaper source of energy that is more environmentally friendly. It is used in many homes as fuel.
(j) Soil supports wildlife and the builtup environment.
 It also stores carbon and preserves records of the ecological and cultural past.
Activity 5.18
Work in pairs. Use the Internet, Geography textbooks, journals and different soil maps of Rwanda. 1. Examine the variations of soils in different parts of Rwanda.
2. Give reasons that account for the variations of the soil types in the different areas.
3. Draw a table that shows a summary of the soil types, where they are located and reasons why they are located in the places identified.
4. Find out the impact of the soil types on the distribution of population in the country.
5. Write up a report on your findings in the form of a short essay.
Did you know?
• The best soils in Rwanda are formed from volcanic lavas and alluvium. They are found in the northwest part of the country and along the lower portions of the larger river valleys. (Environmental profile of Rwanda report)
 • Steep slopes, abundant rainfall, deforestation and intensive farming contribute to extreme soil erosion in Rwanda.
• Soil losses from erosion per year average close to 14 million tonnes of soil, according to the Ministry of Agriculture in Rwanda.
 • Infiltration benches, terraces, reforestation and afforestation are the most widely used soil erosion control methods in Rwanda.
 • Planting of grass and hedge rows is practiced as part of the biological soil conservation measures.
End of unit revision task
1. To what extent are humans responsible for soil erosion in Rwanda?
2.  (a) Define soil conservation.
      (b) Describe the soil conservation measures that the government of Rwanda advocates for.
 3. Account for the severe soil erosion in Northern part of Rwanda.
 4. With the help of a sketch map of Rwanda, describe the soil types of Rwanda.
5. (a) Define soil erosion.
    (b) Name and describe the types of soil erosion.
    (c) Examine the effects of the types of soil erosion that you have discussed on the environment.
6. Assess the effects of soil erosion on the socio-economic development of Rwanda.
7.  (a) Distinguish between splash erosion and rill erosion in the context of Rwanda.
     (b) Name the various causes of soil erosion in various parts of Rwanda.