UNIT 2 : CEREALS
Key Unit Competence:
Learners should be able to conduct cultivation of cereals.
2.1 Learning Objectives
(i) Knowledge and understanding
• State the characteristics of cereals.
• Give examples of cereals grown in Rwanda.
• Discuss the importance of cereals.
• Explain the cultural practises done on cereals.
(ii) Skills
• Detect characteristics of cereals.
• Select common cereals cultivated in Rwanda.
• Recognise the importance of cereals.
• Conduct cereals cultivation.
(iii) Attitudes and values
• Agree to the characteristics of cereals.
• Be aware of cereals cultivated in Rwanda.
• Appraise the importance of cereals.
• Show team spirit in research and group discussions.
• Show concern while doing cultivation techniques of cereals.
Introduction
Most farmers in Bugesera District faced a problem of low production of maize because they did not reflect the time of sowing. The main cause was the use of hand hoe on large area and manpower labourers were not available. Help them to find the solution of that problem. Link these solutions to the improvement of maize yield.
2.2 Botanical characteristics of cereals
Activity 1 2.1: A field visit to a field growing cereals to observe the characteristics of cereals
Visit a farm where cereal plants such as maize, sorghum and wheat are grown and carry out the following activities:
(i) Observe the characteristics of the leaves, the stems and the inflorescence of the cereals grown.
(ii) Uproot the plants and observe the characteristics of the roots.
(iii) Discuss and record your findings.
(iv) Present your findings to the class.
(v) Take teacher’s summary notes.
Cereals belong to the grass family graminae and are mainly cultivated for production of seeds. They are the most cultivated crops in the world. Cereals provide carbohydrates. They are mainly used as staple foods.
Cereal plants have the following characteristics:
(i) Leaves – Cereals have narrow, long leaves with parallel veins, a characteristic of all monocots.
(ii) Stems – They have herbaceous stems which grow vertically with nodes and internodes.
(iii) Roots – They have shallow and fibrous roots.
(iv) Inflorescence – The flowers are small and clustered to form an inflorescence. However, in some plants such as maize, the male and female parts of the flowers are separated to form a tassel and a cob respectively.
(v) Buds – These are the growing points of the plants. Cereals have hidden buds.
(vi) Seeds – The grain seed is a fruit known as a caryopsis which is composed of an endosperm, germ and bran.
Exercise 2.1
Study the figure and identify the parts labelled A, B, C and D.
Exercise 2.2
The following pictures show different inflorescence of cereal crops. Study them carefully and identify the types of the cereal crops labelled E, F, G and H.
2.3 Cereals cultivated in Rwanda
Activity 1 2.2: Research or a discussion to find out the types of cereals cultivated in Rwanda.
Using the materials provided, carry out the following activities:
(i) Identify the cereals in the pictures provided.
(ii) Search on the internet or library on the cereals grown in Rwanda.
(iii) Sketch on the map the various areas where different cereals are produced in Rwanda using a suitable key.
(iv) Find out the most and least produced cereals in Rwanda.
(v) Discuss and record your findings.
(vi) Present your findings to the class.
(vii) Take teacher's summary notes.
Some of the cereals cultivated in Rwanda include rice, maize, sorghum and wheat.
(a) Rice
This is a primary cereal cultivated in the tropical region such as the lowlands of Africa and in flood plain regions through flood irrigation. Highland rice can also be cultivated although this type is not irrigated but rainfed.
Rice production is encouraged in Rwanda to supplement importation. Rice is produced by companies such as NAUR Ltd., SODAR, MBI Co. Ltd., Dukorerehamwe, Nyagatare Rice Company, Kihere Gafunzo Rice Mill, Gatsibo and Mayange Rice Mills. In 2009, 44907 farmers grouped into 60 cooperatives were engaged in rice production producing 17,355 metric tonnes.
(b) Maize
This is a staple food in East Africa. It is also used to make livestock feed in form of fodder where the stems are chopped or grains used as ingredients in making various products.
Maize is grown in all regions in Rwanda. Dried grains are grounded to produce maize flour. Surplus maize is exported to neighbouring countries. With the use of modern methods of farming and farm machinery, the yield is about 3 tonnes per hectare. (Source: Rwanda statistical year book 2015)
(c) Sorghum
This is an indigenous cereal crop. It is an important crop since it is drought resistant and requires less fertiliser as compared to maize. Sorghum is used for traditional ceremonies such as “Umuganura” and in marriage celebrations. A lot of sorghum is produced around Kigali.
(d) Wheat
This is the fourth most important cereal crop grown in Rwanda. It is cultivated in Congo-Nile crest, volcanic soils and Buberuka highlands which include Burera, Musanze, Nyabihu, Rulindo, Gakenke, Gicumbi, Karongi, Ngororero, Rutsiro, Nyamagabe and Nyaruguru districts.
The average yield is 2–3 tonnes/ha. Wheat production is encouraged to reduce importation which is used to make pasta. Over 600,000 ha are used in its production which is more mechanised and modernised.
Wheat is used to make flour that is used to make bread and other wheat products.
2.4 Importance of cereals
(a) Nutritional importance of cereal crops
Activity 1 2.3: Research and discussion activity for finding out the importance of cereal crops
(i) Find out the importance of cereal crops from library books and internet.
(ii) Discuss and record your findings.
(iii) Present your findings to the class.
(iv) Fill in the table 2.1 on page 83.
(v) Take teacher's summary notes.
Cereals are important in all societies worldwide. They are used as staple foods together with other foods and provide 60% –70% of the diet requirements of a society.
Cereal crops have the following importance:
Nutritional importance:
• Cereals contain 60 % – 70% starch which is a carbohydrate. They are rich in fibre and, therefore, recommended for use in baby foods.
• Cereals are also rich in proteins which is important for growth and repair of body tissues.
• Cereals contain vitamins particularly vitamin E and important minerals such as calcium, zinc, selenium and copper.
• Cereals contain oil which is an important source of energy. Vegetable oils can be extracted and used as cooking oil.
• Cereals are used as fodder when grown at a more close spacing and are harvested at flowering stage or when the kernels are at milk stage. The most commonly used cereals for fodder is maize and sorghum.
(b) Agricultural importance of cereals
Activity 1 2.4: Research activity to find out the agricultural importance of cereals
Use the materials provided to:
(i) Find out the agricultural importance of cereal crops from library books, textbooks and the internet.
(ii) Discuss and record your findings.
(iii) Present your findings to the class.
(iv) Take teacher’s summary notes.
Agricultural importance of cereals include:
• Provision of mulching materials; stalks and straws from cereals harvesting are spread evenly between the crops to provide organic mulch. This mulch smothers weeds, conserves moisture and improves soil structure after decomposition.
• Organic manure production
– Leafy cereals such as maize and sorghum are chopped and filled in a compost pit/heap.
– Straw used as animal bedding may be heaped to form farmyard manure.
– Leafy cereals can be incorporated into the soil at flowering stage using a disc harrow. The plants are left to decompose as green manure.
Other uses of cereals
• Source of employment: Cereal farms employ a large number of people who engage in preparing land, planting, weeding and harvesting.
• Source of government revenue and foreign earnings: Surplus cereals produced in the country are exported to the neighbouring countries which bring in foreign exchange.
• The government taxes the farmers to get income for providing social amenities and constructing structures such as roads, bridges, schools and hospitals.
• Socio-cultural practices: Cereals such as sorghum are important in the society. They are used in the making of traditional brews, presented in marriage ceremonies and exchanged as a sign of goodwill between different families.
• Source of income: Surplus cereal grains are sold to earn farmers income used to buy farm inputs such as machinery, fertilisers and seeds.
2.5 Cultural practices of cereals
2.5.1. Cultural practices of paddy rice
Activity 1 2.5: A field visit to find out the cultural practices in the production of paddy rice
Visit a farm producing paddy rice and carry out the following activities:
(i) Carry out land preparation.
(ii) Carry out planting of rice seeds.
(iii) Carry out transplanting.
(iv) Carry out cultural practices in the production of transplanted rice.
(v) Observe harvesting techniques in rice production.
(vi) Discuss and record your findings.
(vii) Present your findings to the class.
(viii) Take teacher's summary notes.
Rice production in Rwanda is carried out through both rain-fed and irrigation methods. Rain-fed rice growing is carried out in the highland under natural rainfall conditions. It is, therefore, referred to as upland rice.
Irrigated rice growing is carried out in the lowlands. The lowland rice is grown in flooded fields. It is, therefore, referred to as paddy rice. Improved varieties of paddy rice include, Afaa (faya), Kaogo, IR8, IR22 and IR257.
(a) Land preparation for paddy rice
The fields for planting paddy rice are prepared differently from the other cereal crops since flooding is required.
After clearing, the fields are divided into blocks of 0.4 hectares each. Each block is levelled and bunds of about 30 cm – 45 cm are constructed with inlets and outlets to control water. The fields are then flooded with water up to 7 cm – 10 cm high. This water is allowed to remain in the fields for 4 days before rotavation. Rotavators are used to puddle the flooded fields. Where tractor-drawn rotavators are not available, digging implements such as hand hoes can be used to puddle the soil. The puddled fields are then levelled to allow uniform depth of planting as illustrated in figure 2.9.
The level of the water in the field is reduced by draining to about 5 cm to allow transplanting.
(b) Sowing rice
Seeds for the upland rice are sown directly into the field, while for the lowland rice (puddy rice), the seedlings are raised into the nursery before they are transplanted.
(i) Preparation of a nursery bed
A nursery bed for raising rice seedlings is prepared as follows:
• A single nursery bed for raising rice seedlings should measure 18.5 m × 18.5 m.
• The land is cleared and all the trash is removed.
• Bunds are constructed by heaping the soil to a height of 30 cm – 45 cm round the bed to hold water.
• Inlet and outlet channels are then constructed to control water.
• The land is then prepared by a rotary cultivator or deeply dug using a hand hoe.
• The cultivated land is then flooded up to 10 cm high.
• The nursery bed is then puddled to form a smooth paste.
• Levelling is done by dragging a levelling board through the nursery bed.
(ii) Sowing seeds in the nursery
• Selected seeds are pre-germinated by soaking them in water for 24–36 hours. This is done by placing the seeds in a gunny bag which has been dipped in water.
• 25 kg of sulphate of ammonia fertiliser is applied per each nursery bed.
• Water in the nursery bed is drained to leave a level of 1.5 cm before planting.
• Pre-germinated seeds are then broadcasted at a rate of 20 kg per each nursery bed of 18.5 m × 18.5 m.
• Water level is maintained at 1.5 cm and increased gradually to a height of 2.5 cm – 5 cm as the seedlings grow.
(iii) Weed control This should be done through flooding to control non-aquatic weeds and use of selective herbicides against broad leaved weeds such as water hyacinth.
(iv) Pest control Soil borne pests are controlled through flooding while spraying with recommended insecticides is carried out to control foliage pests.
(v) Disease control Resistant varieties are used to control fungal diseases such as rice blast and smuts. Fumigants such as carbafuran are used during land preparation to control soil borne disease organisms.
(vi) Fertiliser application 25 kg of Diammonium phosphate fertilisers should be applied through bund application method 10 days before uprooting the seedlings for transplanting.
(vii) The seedlings are ready for transplanting after 2 – 3 weeks when they reach 15 cm tall. They should have 4–6 true leaves depending on the variety.
Exercise 2.3
Table 2.2 illustrates the processes of establishing rice seedlings in a nursery bed. Study it and then in groups, discuss the illustrations and identify each activity shown in the illustrations.
(c) Transplanting and fertiliser application
Transplanting of rice seedlings is carried when the puddled fields are levelled. At this stage, the water level is about 5 cm deep to allow the seedling roots to hold onto the mud.
Double superphosphate fertiliser is broadcasted in the puddle fields at the rate of 120 kg per hectare. Sulphate of ammonia fertiliser is applied at the rate of 125 kg per hectare just before transplanting and 125 kg per hectare 40 days after transplanting. Seedlings are then transplanted at a spacing of 10 – 20 cm × 10 – 20 cm depending on the variety.
(d) Field maintenance practices
(i) Water control
The level of water in the field is increased from 5 cm at planting time, gradually to a height of 15 cm, by the time the seedlings are fully grown. Water level in the field should be maintained at 1 3 the height of the plant. Water should be allowed to flow slowly through the fields. If the flow of water is not possible, then old water should be drained and fresh water added every 2–3 weeks. Water should be drained completely, the last 2–3 weeks before harvesting to allow the fields and the crop to dry.
(ii) Weed control
Terrestrial weeds are easily controlled by flooding. Water weeds which manage to survive in flood water are controlled using effective herbicides such as propanil and butachlor. These weeds can also be uprooted.
(iii) Pests and their control
Soil borne pests such as cutworms and crickets are controlled by flooding while stem borers are controlled by spraying effective insecticides.
(iv) Diseases and their control
• Rice blast: This is a fungal disease caused by Pericularia oryzae. It attacks rice stalks at the base of the panicle and the leaves.
Symptoms
The stalks bear brown lesions and the panicle is covered with olive brown fungal mass. The panicles break easily at the lesioned parts of the ears, resulting to no grain formation. This condition is known as empty heads, which leads to low yields of grains.
Control
Rice seeds should be treated with fungicides before planting. Disease-free and resistant varieties should be used.
• Rice yellow mottle virus disease: This is a viral disease which attacks rice leaves.
Symptoms
It is characterised by yellow or orange leaf discolouration, stunted growth and empty spikelets.
Tillering of the plants is also reduced and the plants may die following severe infections.
Control
Use of resistant rice varieties and control of insect vectors with effective insecticides.
(e) Harvesting rice
Rice is harvested by hand using sickles to cut stems of ripe brown rice plants. The rice plants are tied together to form a bale.
Rice may also be harvested using a combined harvester which combines harvesting and threshing. The hand cut rice stalks are then threshed by holding the stem end and hitting against the ground.
Exercise 2.4
Table 2.3 shows various field maintenance practices carried out in rice production. Study them carefully and then fill in the blank spaces.
2.5.2 Cultural practices of maize
Activity 1 2.6: Practical activity to carry out cultural practices in the production of maize
2.5.2 Cultural practices of maize
Activity 1 2.6: Practical activity to carry out cultural practices in the production of maize
Using the materials provided:
(i) Carry out cultural practices in the production of maize.
(ii) Discuss your findings and record your observations.
(iii) Report your findings to class.
(iv) Take teacher’s summary notes.
Maize should be planted early, at the beginning of the rains so that the crop can make maximum use of available moisture. Dry planting can be practised in areas with short rain seasons.
The varieties of maize planted in Rwanda depend on the altitude and other ecological requirements such as rainfall amount and temperature. These varieties include M081, RHM102, M104, M10Z, Z607, KH500-46A, KH50031A and RHM103.
(a) Land preparation
Land should be prepared early during the dry season to allow all the weeds to dry and to give time for other practices to be done on time.
(b) Planting
Planting maize is either done by hand or tractor-operated machinery such as seeders and planters.
(i) Hand planting
When hand planting, a garden line is used to ensure that the planting lines are straight.
Holes are dug at a spacing of 75 cm – 90 cm × 23 cm – 30 cm depending on the variety. Soil fertility and soil moisture conditions and a depth of 10 cm –15 cm. In Rwandan context we commonly use 80cm × 30cm with two seeds and 70cm × 30cm with one seed.
Ridging may be done in poorly drained soils where the ridges are raised 15 cm – 20 cm high. Ridging is done by special cultivation known as ridgers as shown below.
Making ridges for planting
• Apply 100 kg –150 kg of double superphosphate fertiliser/ha or 1–2 teaspoons/hole.
• Apply 7–10 tonnes of well decomposed manure/ha or a handful of manure/ hole.
• Place 2 seeds per hole after mixing thoroughly with soil and cover with 2.5 cm – 5 cm of soil.
Row planting
Straight furrows are made by digging or using ridgers or mouldboard ploughs 90 cm – 100 cm apart. The seeds are placed singly at a spacing of 23 cm – 30 cm. 100–150 kg of double superphosphate is applied within the furrows mixed with 7–10 tonnes of manure.
(ii) Mechanised planting
This involves the use of machinery to plant maize seeds. The seeds and phosphatic fertilisers are placed into seeders known as planters or seed drills.
Planters
The fertiliser holding hopper is larger than the seed hopper and placed right in front of it.
The planter has a furrow opener, a kind of ridger. The seeds are placed below the fertiliser level at a predetermined distance or spacing. The seed rate and fertiliser rate is set using a seed and fertiliser plate. The furrow is then closed with a groove at the centre of the ridger.
(c) Fertiliser application
When planting maize, about 100 kg – 150 kg of double superphosphate fertiliser is used per hectare. However, there are other compound fertilisers which can be applied at the time of planting, for example, 20-20-0 is used at a rate of 200 kg per hectare. Organic manures also give good responses. Planting: 0M:10T/ha, NPK 17-17-17: 125kg/ha, DAP:100kg/ha or alternative of NPK. Weeding: 100kg of Urea. Soil acidity: 2.5 tonnes – 5 tones of lime, 2 weeks before planting.
(d) Maintenance practices
(i) Gapping: Gapping is carried out where the seeds fail to germinate within the first two weeks of germination.
(ii) Thinning: Thinning is done by uprooting overcrowded seedlings to leave one plant per hole depending on the spacing.
(iii) Topdressing: Topdressing is done by applying 200 kg of sulphate of ammonia or calcium ammonium nitrate in two split applications. The first is done when the maize is knee high and the second when the maize is tussling.
(iv) Weed control: Weeding is done by tillage to control annual weeds, uprooting and burning to control noxious weeds and those growing close to the crops. Selective herbicides can be used to control broadleaved weeds. Proper spacing ensures that the weeds are smothered before they get established. Maize tillers are removed during weeding to prevent competition for nutrients.
(v) Earthing up: Soil is placed around the base of the maize plants in heaps. This provides support to prevent lodging of the plants. See figure 2.19.
(vi) Pests and their control: Maize is attacked by several pests which include:
• Maize stalk borer There are two types of stalk borers that attack maize in the field.
These are:
– Chilo spp.
– Busseola fusca Adult moths lay their eggs in the funnel of the leaves and the larvae eat holes and bore into the stems where they cause damage. The larvae also attack the maize cobs.
Damage
– They destroy the growing points of maize stem leading to death of the plant.
– They destroy maize grains leading to low yields.
Control
The pests can be controlled by early planting, rogueing, field hygiene and use of effective pesticides such as stalk borer dust. This dust is applied down the funnel of each plant when about 30 cm high.
• Army worms (Spodoptera exempta)
These are migratory pests which move from zone to zone in large numbers. Army worms are larvae of moths. They are greyish-green in colour with characteristic black stripes at the back on both sides.
Damage
They eat large quantities of maize leaves causing heavy defoliation. This leads to total loss of photosynthetic materials hence lack of production.
Control
It is recommended to use effective pesticides in the farm. However, since they are migratory pests and appear in outbreaks, their control involves internal cooperation from neighbouring countries, for example, the East African Army Worm Forecasting Programme involves many East African countries who collaborate their efforts to combat this pest.
• Aphids (Phopalosiphum maidis)
These are pests which pierce and suck sap from young maize leaves.
Damage
They cause distortion of the leaves and transmit viral diseases from one plant to the other.
Control
They are controlled by spraying the crop with effective insecticides.
• Birds
Damage
They eat the grains at milky stage. They remove the husks to reach the grains. This opens up route for the water to get into the grains, causing rotting.
Control
Birds can be scared away using scarecrows, noise or throwing stones at them.
(vii) Maize diseases and their control
• Maize streak virus diseases
This is a viral disease which attacks the leaves and is spread by aphids and leaf hoppers (Cicadulina mbila).
Symptoms
Yellow longitudinal stripes which run parallel to the mid-rib of the leaves. This reduces the photosynthetic area of the leaves. Ears are often small and partially filled leading to low yields.
Control
It is controlled by use of certified seeds, early planting, uprooting and burning affected plants to prevent further spread.
• Maize smuts
This is a fungal disease caused by the fungus Ustilago maydis.
Symptoms
The fungus attacks grains and tassels causing masses of black powder on them.
Control
It is controlled by crop rotation, field hygiene and rogueing.
• White leaf blight
It is caused by a fungus Helminthosporium turcicum which attacks the leaves.
Symptoms
Oval grey and thin lesions on the leaves.
Control
Planting resistant varieties and field hygiene.
• Maize rust
This is a fungal disease caused by Puccinia polysora which attacks leaves.
Symptoms
Circular brown powdery pustules on both surface of the leaf. This reduces the photosynthetic surface of the leaf.
Control
Planting resistant varieties and field hygiene.
(e) Harvesting maize
Maize plants are cut and stocked when the stems and leaves are brown and dry. This is manual harvesting by small-scale farmers. Cobs are then dehusked, dried and shelled.
Shelling can be done by hand or by use of mechanical maize shellers. In large-scale maize production, combined harvesters are used. These harvesters have shelling mechanism to separate the grains from the cobs. Harvested maize is then sun-dried to reduce moisture for storage.
Exercise 2.5
Table 2.4 shows various field maintenance practices carried out in maize production. Study them carefully and then identify the practices being carried out.
2.5.3 Cultural practices of sorghum
Activity 1 2.7: Practical activity to carry out cultural practices in the production of sorghum
Using the materials provided:
(i) Carry out cultural practices in the production of sorghum.
(ii) Discuss your findings and record your observations.
(iii) Report your findings to class.
(iv) Take teacher’s summary notes.
Sorghum is the second most produced cereal crop after maize. Sorghum is grown mainly in the eastern and southern parts of Rwanda. Sorghum is drought resistant and can tolerate waterlogging conditions. It produces good yields in infertile soils.
Sorghum grains are ground into flour which is cooked to form “meal”. The grains are an important ingredient used to make banana wines. Young growing crops are used as fodder where they are wilted or used to make silage. Some sorghum varieties used to make fodder contain prussic and hydrocyanic acid. These should be left to dry for two days before they are utilised.
The varieties of sorghum grown include serena and seredo. Serena matures in about
months and is brown seeded. Other varieties include dobbs, epuripon and sekedo. Exercise 2.6
Table 2.5 below shows different varieties of sorghum cultivated in various parts of the world. Study the diagrams and use internet to identify each variety.
The varieties of sorghum are categorised into three types based on the following criteria:
(a) Panicle type
This is the type of flowering panicle. There are three types of which include:
• Open panicle
• Compact panicle
• Goose neck panicle – This type is resistant to bird pests at milk stage.
(b) Seed colour type
The sorghum varieties are grouped into:
• Brown seeded type
• White seeded type
The white seeded type is low in tannin and, therefore, sweeter. This type is preferred for brewing. It is more susceptible to birds attack.
The brown seeded type is higher in tannin and, therefore, bitter. It is mixed with cassava and other plants to prepare flour. Is more resistant to bird pests attack.
(c) Level of tannin
Sorghum varieties are grouped into those with high tannin and those with low tannin. Those with high tannin are bitter and those with low tannin are sweeter.
(a) Land preparation
(i) Land clearing
Land should be prepared early during the dry season by slashing, tree felling, destumping, bush clearing to remove perennial, annual and biennial weeds. Raking is done to remove the crop residue and slashed weeds.
(ii) Primary cultivation
Primary cultivation is done by digging in small farm holdings or ploughing in medium to large farms. The ploughing should be done deeply to open the soil for aeration and infiltration of water. The surface trash and weeds should be buried completely. Ploughing should be done during the dry season to allow enough time for other farming operations to be carried out.
(iii) Secondary cultivation Secondary cultivation after primary cultivation through harrowing and digging to achieve medium tilth. Harrowing is done by use of hand hoes and tractor or ox-drawn harrows.
(b) Planting Sorghum is planted using the following methods:
(i) Broadcasting
(ii) Row planting
(iii) Intercropping
Broadcasting
The seedbed is prepared from medium to fine tilth. The seeds are then evenly broadcasted. Phosphatic fertilisers can be added to improve root development.
Row planting
The holes are dug at a spacing of 60 cm – 75 cm by 15 cm – 20 cm. The seeds are sown singly or two per hole. When one seed is planted, it encourages a lot of tillering. Manure is applied at a rate of 7 tonnes /ha.
Intercropping
Sorghum can be sown together with other crops such as beans, soya beans and other pulses. This is done by planting sorghum seeds with beans in the same hole or furrow.
(c) Field management practices
(i) Gapping
Gapping is done by replanting seeds where they failed to germinate two weeks after planting.
(i) Thinning
Thinning is done when broadcasting type of planting has been used. The shoots are left at a spacing of 45 cm – 60 cm × 15 cm – 20 cm. The uprooted shoots can be fed to livestock where more thinning is done. Sorghum produces more tillers.
(iii) Weeding
Annual weeds are controlled through tillage and use of selective herbicides 2–3 weeks after planting. The striga weed (purple witchweed) Striga hermonthica is a noxious and notorious parasitic weed to sorghum plants.
Striga is controlled by the following methods:
(a) Crop rotation.
(b) Vigorous uprooting.
(c) Intercropping with desmodium (push and pull system)
(d) Proper seedbed preparation.
(e) Use of selective herbicides against the witchweed.
(iv) Pest Control
Pests that affect sorghum include:
• Birds
These affect sorghum during the milte stage of maturity. The most notorious bird pests include Sudan dioch, waver birds and mouse bird.
• Sorghum shoot fly
The larva of the sorghum shoot fly affects the stems of young plants which damages the stem leading to wilting of the plants and severe tillering.
(v) Disease control
Diseases which affect sorghum include:
• Leaf blight (Helminthosporum turcicum)
Control is carried out through:
(a) Planting resistant varieties.
(b) Using certified disease free seeds.
• Anthracnose (Colletotrichum gruminicola)
This is a fungal disease which affects sorghum. The symptoms include dark, water soaked lesions on stems, leaves or fruit.
It is controlled by the following methods:
• Use of resistant varieties.
• Crop rotation with non-cereal crops such as beans.
• Proper disposal of crop residue.
• Sooty stripe (Ramulispora sorghi)
This is a fungal disease which affects sorghum. The symptoms include:
• Reddish brown lesions on the leaves.
• The centre of these lesions form black sooty bodies which appear as soot.
Sooty stripe is controlled by:
• Use of resistant varieties.
• Crop rotation.
• Destruction of crop residues and ratoons which are infected.
Other diseases include loose smut and head smut which affect the panicle.
(vi) Control of tillers
Tillers in sorghum plants can affect their production. It is recommended to remove excess tillers so that each plant has 2–3 tillers. The uprooted tillers are fed to livestock.
(d) Harvesting
Sorghum is ready for harvesting at 3–4 months of age after planting depending on the variety and ecological conditions.
The panicles which are ripe and oftenly large kennels with slightly dark colour are cut off using a sharp knife. The panicles are sun dried and stored unthreshed in granaries. Dried sorghum heads are threshed mechanically using a threshing machine or by hand through hitting with a light stick.
The yield ranges from 500–1500 kg/ha. Sorghum can be left to grow as a ratoon for the second and third crop although the yields of the ratoon are much lower.
Exercise 2.7
The photographs below show activities carried out during sorghum harvesting. Study them carefully and then identify each activity.
2.5.4 Cultural practices of wheat
Activity 1 2.8: A field visit to find out the cultural practices in the production of wheat
Visit a farm producing wheat and carry out the following activities:
(i) Observe and record the methods of land preparation.
(ii) Observe the planting of wheat manually and by use of a seed drill dragged by a tractor.
(iii) Carry out cultural practices after germination in the field containing wheat.
(iv) Observe the harvesting methods in wheat production.
(v) Discuss and record your observations.
(vi) Present your findings to the class.
(vii) Take teacher’s summary notes.
Wheat has become an increasingly important crop in Rwanda. It is grown to reduce the need for import of wheat from neighbouring countries. Wheat is grown in the highlands where rainfall is reliable and the level of humidity is low, which minimises diseases. Wheat is grown to supply the baking industry and making of macaroni, spaghetti and in the confectionary industry. The straws got after harvesting wheat is used as livestock feed and as bedding for livestock. It can also be used as mulch.
The varieties of wheat grown in Rwanda include Musama, Uganda 6, Morroco, KS- Mwamba, among others.
(a) Land preparation
(i) Land clearing
Land for growing wheat should be prepared early during the dry season by slashing, bush clearing and removal of trash and previous crop residue.
(ii) Primary cultivation
Primary cultivation is done through ploughing since wheat requires a fairly larger farm. A mould-board plough is recommended. Cultivation should be done early to allow enough time for other subsequent activities to take place.
(iii) Secondary cultivation
Harrowing of land is done two or three times until a fine tilth is achieved. The wheat seeds are smaller and, therefore, require a fine tilth. Levelling of land is done by use of a tine harrow.
(b) Planting
Wheat is commonly planted using tractor-drawn planters called wheat drillers where the seeds and fertiliser are placed in the soil simultaneously.
Wheat seed can also be broadcasted after spreading phosphatic fertiliser over the prepared land. When planting using the wheat drill, the seed rate is between 44 –132 kg/ha.
Under the optimum soil condition, 88 kg/ha of seed is planted.
(c) Fertiliser application
During planting, 95 kg – 120 kg of phosphate is applied per hectare. Nitrogen is also important at the production of wheat. 67 kg of nitrogen is applied per hectare in two splits. 45 kg of nitrogen/ha at planting through drilling and the other split during maximum growth.
Fertiliser can also be mixed with fungicides and insecticides and applied as foliar feed.
(d) Field maintenance practices
(i) Weed control
• This is done by proper seedbed preparation to control annual weeds at planting time.
• An appropriate spacing is also important in controlling weeds. When the crops grow, they form a canopy which smothers the weeds.
• Use of selective herbicides to control broad leaved weeds such as black jack, pigweed, cleavers and bindweed.
(ii) Pests control
Birds
Birds are the most serious pests in wheat farming. The most notorious being the Sudan dioch (Quelea aethiopica) and the mouse bird (Collius spp.).
Damage
They eat large quantities of wheat grains leading to low yields.
Control
The birds are controlled using chemicals, scaring and destroying their breeding places by burning or using explosives.
Wheat stem borers
Damage
The larvae which are caterpillars bore into the stem and feed on the central shoot. The infected plant produces ‘dead hert’ or ‘white ear heads’.
Control
Spraying using effective insecticides.
(iii) Disease control
Wheat rust
This is a fungal disease caused by Puccinia graminis which attack the leaves.
Symptoms
• Brown rusty powdery.
• Mass on the leaves.
Damage
The rusty coloured dust reduce the photosynthetic area of the leaves resulting to low yields.
Control
Spraying with copper fungicides such as bordeaux mixture.
Loose smuts
A fungal disease caused by Ustilago nuda which attacks the head.
Symptoms
Black powder on the panicle of wheat.
Control
Hot water treatment of wheat seeds before planting, use of certified seeds, crop rotation and field hygiene.
Other diseases of wheat include bacterial leaf blight downy mildew powdery milded and anthracnose. They are controlled by spraying with copper based fungicides, planting resistant varieties and use of certified seeds.
(e) Harvesting
Wheat is ready for harvesting after 4–5 months when the straw is yellow to brown in colour. Harvesting is done by machine using a combined harvester or by use of hand where a sickle is used to cut off the stems. The combined harvester combines both harvesting and threshing of the wheat.
Group activity
Video on production of rice.
Use the references provided to carry out the following activities:
(i) Watch a video on the steps of growing paddy rice.
(ii) Discuss and record your findings on growing of paddy rice.
(iii) Present your findings to the class.
(iv) Take teacher’s summary notes.
Unit Summary
Cereals are grain crops which belong to the grass Family graminae. The seed is also a fruit known as kernel or a caryopsis. Cereals provide man with carbohydrates and are widely produced and consumed as staple crops. Cereal plants have herbaceous stems, narrow and parallel veined leaves hidden buds with flowers on inflorescence and fibrous roots.
Cereal crops cultivated in Rwanda include rice, maize, sorghum and wheat. Rice is mainly produced under irrigation in the swampy lowlands. Wheat is produced in the cooler highlands while maize is produced in the medium altitude areas.
Cereals are mainly grown for food, bedding for livestock, income, source of employment, source of government revenue, provision of grains for sociocultural practices, preparation of manure and mulch. Cereal production practices include land preparation, planting, weeding, gapping, thinning, pest and disease control and harvesting.
Key terms
1. Bran – Hard outer layer of a cereal grain consisting of the pericarp.
2. Bread – Staple food prepared from dough of flour from cereal grains, mixed with water and yeast then baked.
3. Bund – A raised soil embankment with plants grown on them.
4. Caryopsis –Is a fruit of a grain crop which resembles a seed. It contains an endosperm and embryo enclosed in a pericarp.
5. Cereals – These are grain crops commonly produced to produce carbohydrates and used as staple food in some regions.
6. Combined harvester – A machine which combines the practice of harvesting and threshing mature cereal crops.
7. Destumping – Removal of stumps from a field after falling trees.
8. Endosperm – Part of a grain which stores food for the developing embryo during germination.
9. Fibre – A substance that contains a large amount of cellulose and lignin that is not easily digestible.
10. Fibrous roots – Thin and highly branched root system originating from the stem. Usually feed in grasses.
11. Fodder – Plants that are harvested and chopped for use by livestock.
12. Fungicide – A chemical used to kill fungal organisms and diseases.
13. Gapping – Replanting seeds where they failed to germinate or were destroyed by pests.
14. Germ – Part of a grain that develops to a plant (also the embryo).
15. Green manure – Manure made from incorporating green leafy plant materials into the soil through cultivation.
16. Herbaceous – Succulent plants with no persistent woody stem above the ground.
17. Herbicide – A chemical which kills plants.
18. Hidden buds – A bud which is covered or enclosed with other leaves usually seeds in grasses.
19. Inflorescence – A group or a cluster of flowers arranged on a stem.
20. Mould-board plough – A plough with a part fixed at its end called a mould-board that inverts cut furrow slices during ploughing.
21. Mulch – Materials which are placed over the soil surface and between crops to smother weeds and conserve soil moisture.
22. Narrow leaved – Grass type of leaf with narrow leaf blade and parallel veins.
23. Prussic acid – An organic substance that is metabolised by animals to form cyanide which is poisonous.
24. Rice mill – A machine which is used to separate bran from the seeds by polishing them.
25. Ridger – An implement which is used to open furrows.
26. Rotary cultivator – A ploughing implement which combines the practices of primary slices during ploughing.
27. Silage – Fodder converted into succulent feed for livestock through processes of anaerobic bacterial fermentation.
28. Soil fumigation – Application of chemicals in the soil to kill or sterilise the soil by suffocating the organisms.
29. Staple –Basic food.
30. Subsoiling – A method of cultivation where ploughs dig deep to bring up soil from lower levels to upper levels.
31. Surplus – Excess.
32. Thinning – Removing excess seedlings from a planting hole or bed by uprooting.
End of Unit 2 Assessment
1. Study the diagram below and on it label parts A, B, and C.
2. Carry out preparation of land to suitable tilth for planting maize.
3. Carry out fertiliser application in wheat production.
4. Describe water control in the production of rice.
5. State two ways of controlling yellow mottle virus in rice.
6. Give two reasons for removing tillers in maize and sorghum.
7. Identify the disease in the illustration provided below that affect maize.
8. Draw the three categories of sorghum based on their panicle type.