• CLASSIFICATION OF CROPS
• CLASSES AND USES OF FARM ANIMALS
• CHARACTERISTICS OF SELECTED FARM ANIMALS
• METHOD OF WEEDS AND PEST CONTROL
• METHODS OF WEEDS AND PEST CONTROL
CLASSIFICATION OF CROPS
Agriculture JSS1 Second Term
Week 1
Topic: CLASSIFICATION OF CROPS BASED ON LIFE CYCLE
Classification of Crops based on Life cycle and Uses
Crops plants are classified based on three criteria which are;
- Botanical classification – Based on generic and specific names
- Agricultural classification – Based on the uses or important of crops to man and animals
- Classification based on life cycle – Based on numbers of year or season from germination to harvesting or death.
General Classification of Plants
1. By Growth habit:
Succulent plants – herbaceous or herbs (succulent seed plants possessing self-supporting stems)
Vine – a climbing or trailing herbaceous plant (Liana – a climbing or trailing woody plant)
Trees – having a single central axis
Shrub – having several more or less upright stems
2. By Leaf drops:
Deciduous – no living leaves during dormant (winter) season (apple)
Evergreen – retaining functional leaves throughout the year (spruce)
3. By Life span:
Annuals – plants that normally complete their life cycle during a single growing season (lettuce, spinach, marigold)
Biennials – plant that normally completes its life cycle during a period of two growing seasons (celery, carrot)
Perennials – plants that grow year after year, often taking many years to mature.
4. By Temperature tolerance:
Tender plant – damaged or killed by low temperature
Hardy plant – withstands winter low temperatures
Wood hardy – a whole plant is winter hardy
Flower-bud hardiness – ability of flower buds to survive low winter temperatures (peach, ginkgo tree)
5. By Temperature requirements:
Cool-season crop – prefers cool temperatures (peas, lettuce)
Warm-season crop – prefers warm temperatures (tomato, pepper)
6. By Habitat or Site preference:
Xerophyte – prefers dry sites
Shade plants – prefers low light intensity
Acid loving – prefers low pH soils
Halophyte – prefers salty soils
Plant crops are grouped into three categories according to their life cycles such as;
I) Annual Crops
From the name it is clear that the plants live for one season or less. They complete their life cycle once in a year or a growing season; during which the vegetative and reproductive stages are completed e.g. maize, rice, cowpea, millet, vegetables, cotton, groundnut, etc. Annual plant is one which completes its life cycle from germination to seed formation within one season and then dies usually as a result of complete exhaustion of its food reserve in the process of reproduction. They comprise of several of most beautiful and easily grown plants, widely varying in from habit of growth and colour. Annuals are very effective, grown neither in pots or in ground. Particular annuals thrive best in particular period of the year. The annuals are conveniently grouped according to season as follows.
1. Rainy Season Annuals: They can stand more in rain than others and therefore grown to flower during rainy season. The time of sowing then would be from April to May in most places e.g. Mary gold, Aster, Zinnia etc.
2. Winter or Cold Season Annuals: The thrive and bloom best during winter. These are sown in September, October e.g. phlox, Antirrithium.
3. Hot weather or Summer season Annuals: They are sown in January – February and blooming period is April, May e.g. Sunflower and Zinnia.
II) Biennial Crops
They complete their life cycle once in two years or two group seasons. In the first year, they undergo the vegetative stages where leaves and roots are produced in abundance, the plant also elongates. But during the second year, the plants undergo reproductive stages where flowers, fruits and seeds are produced e.g carrot, lettuce, cabbage, ginger, cassava, etc. These plants usually requires two years or at least two growing seasons with more or less of a dominant season or lasting season between two completed life cycle. Seed sown in spring or summer, and vegetative growth is completed in first year and in the following spring, flowering and fruiting takes place. Generally the period of growth is 6 to 9 months e.g. Gladioli, Dahlia. No hard and fast line can be drawn between annuals and biennials crops like turnip, carrot, cabbage and onion are classified as biennials.
III) Perennial Crops
Any plant that lives more than two years is a perennial e.g. Mango, Citrus. They complete their life cycle once in three years. In the first two cycles once in three years, they undergo vegetative stages while in the last years, the reproductive stages are completed e.g. rhizome, sugarcane, banana, plantain. A perennial plant that can survive for thirty years and above is called permanent crop e.g. cocoa, kola, mango, oil palm, rubber, coconut, etc.
These crops are classified in to two groups.
i) Herbaceous:
Herbaceous perennials are those with more or less soft succulent stems. In Temperate climates the tips die off after seasons growth but root remains alive and produce new stem and tops on favorable conditions. In other words their tips are annual while ground parts are perennials lie many years and are classified as: a) Trees b) Shrubs c) Vines according to their habit of growth.
a) Trees: Trees are upright in habit and stems take the form of central axis e.g. Mango, guava, Mandarins etc.
b) Shrubs: Shrubs have no main trunk but a number of erect or semi erect stems are seen but do not forms the main frame work e.g. Hibiscus, Rose etc.
c) Vine: Both woody and herbaceous have stems which are flexible and not in position to keep their branches and leaves erect. They either spread on the ground or require some support whether alive or man made e.g. Grape vines, Passion fruit etc.
Agricultural Classification or classification based on the uses of crops:- In this category crops are classified into the following groups, legumes, cereals, spice, latex, beverages, fibre.
IV) Ephemerals: They are crops that complete their life cycle once in three or four months and can undergo two or three life cycles in a year e.g. tomato
Classification Based on Uses
Food Crops – These are crops used by man for food. They are sub-divided into various groups
- Cereal Grains – They are grass crops grown for their seeds or grains which are rich in carbohydrate e.g maize, rice, millet, wheat, sorghum and barley
- Grain Legumes – They supply proteins in the food of man. E.g cowpeas, soyabeans, groundnut, pigeon peas.
- Root Crops – These are crops grown mainly for food stored in the swollen roots. They are the major sources of carbohydrate e.g cassava, carrots
- Tuber Crops – They are underground stems which are enlarged to store food in form of carbohydrtes e.g. cocoyam, yam, irish potatoes
- Vegetable Crops – Crops grown for their leaves of fruits. The leaves or fruits are eaten fresh or cooked. They supply mainly vitamins and minerals.
- Fruits – Crops with succulent fruits which are eaten fresh. They can supply vitamins and minerals and sometimes carbohydrates. e.g are mango, banana, citrus, cashew, pawpaw
- Beverages – they are crops whos products are used for making food drinks (bournvita and mila) or making non-alcoholic drinks. These crops are cocoa, coffee
- Spices – these are crops used to add special taste or flavour to food e.g. castor, ginger, garlic
Oil Crops – These crops produce seeds or fruits from which we extract oil. They are the major source of oil used for cooking e.g groundnut oil, soya oil, shea butter, coconut oil
Fibre Crops – These are crops grown especially for their fibre. Fibres are used for making carpets, sacks, ropes. Fibres may be produced from stem or leaves or fruits and seeds. Examples are cotton, jute, kenaf, hemps, raffia.
Forage crops – These are crops grown mainly for feeding farm animals. Examples are elephant grass, guinea grass, centrosema, and some food crops such as millets, sorghum, cowpea and groundnut.
Latex Crops – These are crops whose stem or leaves produce sap which maybe used as gum or coagulated to form rubber. e.g gum arabica, para rubber
Drug Crops and Stimulants – Crops used for making medicines or for their stimulating effects. Examples are tobacco, cocaine, quinine, kolanut, eucalyptus
Ornamental Crops – Crops grown for purpose of making our environment beautiful e.g. barbados, lily, marigold, hibiscus, zinnia.
Classification Based on Food Nutrient
As source of carbohydrates – Yam, maize, Millet, cassava, potatoes
As source of protein – Beans, groundnut, soyabeans, pigeon peas
As source of fats and oil – castor oil, melon, palm tree, groundut
As source of minerals – Calcium. potassium, iodine, managanese, iron, sodium chloride are the examples of nutrients which can be supplied. example of such crops are fresh vegetables, apple, pineapple
As source of vitamins – Vegetables, orange, cabbage, carrot, soya beans
Assessment
Section A – Use the options below to answer the following questions
Latex, Forage, Oil, Biennial, Perennial, Fibre, Spice, Cereal grain, Root, Halophyte, Drug, Ornamental, Ephemeral, Annual, Xerophyte, Tuber
- ____ crops complete their life cycle once in two years or two group seasons
- ____ crops are crops that complete their life cycle once in three or four months and can undergo two or three life cycles in a year
- _____ crops are crops whose stem or leaves produce sap which maybe used as gum or coagulated to form rubber
- _____ crops are underground stems which are enlarged to store food in form of carbohydrtes
- ____ crops are crops that produce seeds or fruits from which we extract oil.
- Any plant that lives more than 2years is a _____ crop
- ____ crops are grown for the purpose of making our environment beautiful
- ____ plant prefers salty soils
- _____ are crops used to add special taste or flavour to food
- ___ crops are used for making medicines or for thir stimulating effects
Section B – Categorise the following crops according to the options given below
Latex crop, Forage crop, Oil crop, Biennial crop, Perennial crop, Fibre crop, Spice , Cereal grain, Root crop, Halophyte, Drug crop, Ornamental crop, Ephemeral crop, Annual crop, Xerophyte, Tuber crop, Beverage,
- Mango
- Yam
- Ginger
- Shea butter
- Cocoa
- Hibiscus
- Quinine
- Carrot
- Maize
- Tomato
Section C
- Give 2 examples each of annual, biennial, perennial crops
- Give 2 examples of classifications of plant crops.
Answers – Section A
- Biennial
- Ephemeral
- Latex
- Tuber
- Oil
- Perennial
- Ornamental
- Halophyte
- Spice
- Drug
Answers – Section B
- Mango – Perennial
- Yam – Tuber crop
- Ginger – Spice
- Shea butter – Oil crop
- Cocoa – Beverage
- Hibiscus – Ornamental crop
- Quinine – Drug crop
- Carrot – Biennial crop
- Maize – Annual crop
- Tomato – Ephemeral crop
Classes and Uses of Farm Animals
Agricultural Science JSS 1 Second Term
Week 2 & 3
Topic: Classification of Farm Animals
Introduction
Animals are those group of living things which depend mainly on plants for their food. They are found in tropics as well as in the temperate regions on the land, in the forest and salt water.
Classification of Farm Animals
Classification is based on the following
- On the basis of size
- According to their Habitat
- According to their mode of reproduction
- According to their type of Stomach
Classification According to Size
On the basis of size, farm animals can be broadly classified into two – large and small animals. Large animals are farm animals which are relatively big in size e.g cattle, sheep, goats, pigs. Small animals are small in size e.g crab, crayfish, mice, periwinkle.
Classification According to Habitat
Farm animals can be classified into two: land (terrestrial animals) e.g cattle, goats, pigs, sheep, horse, fowl, rabbits and donkeys and aquatic animals e.g. fish, crab, oyster, lobster, octopus, periwinkle.
Classification According to Mode of reproduction
This can be classified to animals that give birth to their young ones alive and animals that lay eggs. Animals that give birth to their young ones alive and feed them with milk from their mammary glands. e.g cattle, sheep, goat. Animals that lay eggs ie non-mammals e.g. fish, reptiles and bird.
Classification According to the type of Stomach
Farm animals e.g mammals can also be classified according to the type of stomach they have. Some mammals have a complex stomach and are called ruminants e.g cattle, sheep and goats. Other mammals have a simple stomach and are called non-ruminants e.g pigs, rabbits and guinea pigs. Ruminants have four stomach compartments which are rumen, reticulum, omasum and abomasum. Ruminant animals chew their cud as ingested food comes back to the mouth and the animal begins to chew again.
ASSESSMENT
- Animals can be classified in 4 ways, list them.
- On the basis of size, farm animals can be broadly classified into ________
- Farm animals can be classified into two, which are _________
- Mammals that have a complex stomach are called _________
ANSWER
- (i) On the basis of size (ii) According to their Habitat (iii) According to their mode of reproduction (iv) According to their type of Stomach
- Large and Small animals
- Land and Aquatic Animals
- Ruminants
Characteristics of Selected Farm Animals
Agricultural Science JSS 1 Second Term
Week 4 & 5
Topic: Characteristics of Selected Farm Animals
Types, Distribution and Uses of Farm Animals
Cattle
They are kept mainly for beef and milk production. There are different types of cattles and classification is based on their uses.
- Dairy cattle – Cattle kept for milk production. e.g White Fulani
- Beef cattle – Cattle kept for meat production. e.g. Sokoto Gudali
- Dual Purpose Cattle – Cattle kept for both milk and meat production. e.g. White Fulani and Kuri
Dairy Breeds
- Long horned humped Zebu – White Fulani, Red Bororo, Jet Koram
- Short horned humped Zebu – Sokoto Gudali, Yola or Adamawa
Beef Brands
- Long horned humpless cattle – Ndama, Kuri
- Short horned humpless cattle – Muturu, Ghana short horn
Terms used in describing cattle
- Bulls – Adult male cattle
- Cow – Adult female cattle
- Heifer – Female cattle
- Bullock – Castrated male cattle
- Calf – Young cattle
- Bull Calf – Male calf
- Heifer Calf – Female calf
- Calving or Parturition – Giving birth to a calf
- Dairy Cattle – Cattle kept solely for milk production
- Beef Cattle – Cattle kept solely for meat production
- Beef – Meat from cattle
Goats
One of the earliest domesticated animal. They are kept for milk and meat production.
Types of Goats
The Sokoto Red – Well defined breed with uniform red colour in both sexes.
- Kano Brown – Medium sized animal with brown colour
- Sahel Goat – Medium to large sized animal found in scanty vegetation
- Borno White
- West African Dwarf Goat
Terms used in describing Goats
- Billy – Adult male goat
- Nanny – Adult female goat
- Buck – Male goat of breeding age
- Doe – A female goat of breeding age
- Kid – A young goat of either sex
- Kidding – Process of giving birth
- Heat Period – Period in which the female is most likely to accept a male
- Oestrus Cycle – Time interval between heat periods
- Gestation – Period between conception and birth
- Lactation – Act of producing milk
- Udder – The mammary gland which produces milk
- Weaning – Stopping an animal from suckling the mothers milk
- Castrate – Castrated billy
- Herd – Group of adult goat
Sheep
They are hollow-horned , even-toed ruminants which are said to have probably originated from Iran or Iraq area.
Types of Sheep
Three well known breeds
- The Ouda – The commonest breed. Rams have large, wide and spiral horns and ewe are polled (hornless). They have a characteristic long and pendulous ears with a distinct colour. They have long legs and long tiny tails. They are kept for meat production.
- Yankasa – This breed is commonly found in North. The rams have long curved horns while ewes may have short horns or polled. They have moderately floppy ears. They are mainly kept for meat production.
- West African Dwarf Sheep – This is smallest breed of sheep in West Africa. They are found in humid areas of West Africa. They have short horizontal ears with the males horned and females polled.
Terms used in describing Sheep
- Ram – Adult male sheep
- Ewe – Adult female sheep
- Gimmer – Young female
- Lamb – Young sheep of either sex
- Tupping – Act of mating Sheep
- Wether – Castrates male sheep
- Lambing – Process of giving birth to sheep
- Flock – Group of adult sheep
Poultry
Poultry refers to all domesticated bird raised for meat, eggs or feather. These include chicken, geese, ducks, guinea fowl, turkeys.
Types of Fowls
The Exotic Breeds
- The Leghorns – Originated from the Mediterranean region. they are kept for egg production. Two types, the brown and the white leghorn
- Rhode Island Red – Foreign breed from America. A dual purpose for meat and egg production. Eggs are large with brown shells
- Plymouth Rock – Kept for egg production
- New Hampshire – Dual purpose breed for egg and meat production
Local Breeds
Breed that resulted from crosses between two different breed commonly known as cross breed.
Terms used in describing chickens
- Cock – Adult male
- Hen – Adult female
- Cockerel – Young male
- Pullet – Young female
- Chick – Young chicken pf either sex
- Capon – Castrated chicken
- Treading – Mating of chickens
- In-lay – Pregnancy
- Parturition – Process of laying eggs
- Clutch – A group of young chickens
- Flock – A group of adult chicken
Factors affecting the Geographical distribution of Farm animal in Nigeria
- Climate – Average weather conditions of a place. It includes factors such as rainfall, temperature, light, atmospheric pressure, relative humidity and wind. Climate to an extent determines the number of farm animals that can be distributed to an area.
- Availability of Natural Pasture
- Religious and Social Factor
Assessment
Use the following options to answer the questions below.
Heifer, Udder, Ewe, Capon, Beef cattle, Wether, Nanny, Buck, Gestation, Bullock, Ram, Parturition, In-lay, Lactation, Heat period, Kidding, Calf, Clutch, Diary cattle, Cow, Bull, Calf, Pullet, Weaning, Cockerel, Doe, Kid, Billy, Gimmer.
- Cattle kept solely for milk production is called ____
- ___ means giving birth to a calf
- The act of mating in sheep is called ____
- The period between conception and birth is called ____
- A group of young chicken is called ___
- Castrated male cattle is called ____
- The mammary gland which produces milk is called ____
- A young female chicken is called ____
- A young female sheep is called ___
- Young cattle is called ____
- A castrated chicken is called ____
- Mating in chicken is referred to as ___
- Period in which the female is most likely to accept a male is called _____
- The process of giving birth is called ____
- Castrated male sheep is called ____
Answers
- Diary Cattle
- Parturition
- Tupping
- Gestation
- Clutch
- Bullock
- Udder
- Pullet
- Gimmer
- Calf
- Capon
- Treading
- Heat period
- Kidding
- Wether
Method of Weeds and Pest Control
Agricultural Science JSS1 Second Term
Week 7 & 8
Topic: Method of Weeds and Pest Control
Weeds
A Weed is any plant that grows in a place where it is not expected to grow or plant which grows out of place. A weed is a plant considered undesirable in a particular situation, “a plant in the wrong place”. Weed is any plant that grows in a place where it is not expected to grow or a plant which grow out of place. Such a plant constitutes nuisance either to man, livestock or plants.
Characteristics of weeds
- Weed has the ability to regenerate itself – They are difficult to eradicate because of their regenerative feature
- Weed produce many seeds which are easily dispersed
- High resistant capacity – They are capable of withstanding very adverse weather conditions because of their tough protective seed coats
- Weed has the ability to establish easy-grow faster than crop plants – weeds possess highly competitive and aggressive growth habit that can easily smother crops if not removed on time
- Weed has ability to survive under adverse climatic and soil conditions – persistent
- Weeds have devices for easy dispersal – These include spines, hooks, parachutes, wings with which they can be easily dispersed. Examples of weeds are – tridax, goat weed
- Weed has long period of viability
Uses of weeds
- They act as cover crop to control soil erosion e.g centrosema, calopogonium, stylosanthes
- Weed can be used as much and compost materials. Much helps to conserve soil moisture while compost is an organic manure which improves soil fertility.
- Weeds are used for food by man e.g. African spinach
- Weed roots help to bind the soil particles to getting thereby preventing erosion.
- They are sources of feeds to livestock e.g guinea grass, elephant grass, sedge
- Some weeds are medicinal in nature e.g lemon grass
- Weeds are major source of ornamental crops e.g pride of barbados, rose, canalily, hibiscus
- Some weeds can control soil erosion.
- Some weeds are used for roofing and mat making.
- Weeds are used for compost making.
- Leguminous weeds harbour bacteria that help fix atmospheric nitrogen in the soil
Effect/Economic Importance of Weeds
- Weeds compete with crops for sunlight – Weeds are capable of producing many large leaves which may grow and cover other plants around it.
- Weed compete with crops for nutrients – The roots of weeds develop rapidly and remove considerable amount of nutrients from the soil
- Weeds harbour crop pest and diseases – Some weeds may harbour crop pests and diseases
- Weed compete with crop for soil moisture – Their roots are capable of developing fast and removing large portion of moisture
- Losses in crop yield
- Weeds compete with crop for soil oxygen
- Some weeds act as parasites of crops and may kill their hosts e.g striga, dodder, mistletoe
- Losses in quality of crops
- Losses in income to farmers – The low yield coupled with the reduction in quality of produce affects the income of farmers.
- Some weeds are toxic to farm animal
- They increase the cost of production
Classification of weeds
- Based on habitat (i) aquatic weed e.g water hyacinth (ii) terrestial weed e.g goat weed, tridax (iii) epiphytic (grow on other plants) e.g striga, dodder.
- Based on life cycle (i) Annual (one year life span) goat weed (ii) Biennial weeds (2 years life span) e.g morning glory wild carrot.
- Perennial (more than 2 year – life span) – elephant grass, sida acuta, spear grass.
- Based on the type of leaves (i) broad leaf grasses
Methods of weed control
Physical (mechanical) method
- Hoeing – use of hoe to remove the weeds from the roots
- Hand pulling – hand is used to pull out the weeds
- Slashing – using cutlass to cut the shoot of weeds
- Use of plough – uproot and bury the weed
- Rogueing
Cultural method
- Mulching – Mulch are spread on flat and to suppress weeds and prevent them from sprouting.
- Flooding- water is led to the farm land to kill the weeds
- Burning – the vegetation crop residue is set on fire to kill the weed seeds
- Cover cropping – Fast growing legumes are planted to another weed
- Crop rotation – It is effective for controlling weeds associated with specific crop – the weed starve to death.
- Close spacing
- Closed season
Biological Method- use of living organisms to control weeds
- Use of parasites and predators to control weeds
- Legume can be used to smoother weeds
- Some animals like cattle, sheep can also feed on weeds
- Insects can be used to kill some weed e.g cactoblastic is used to destroy cactus weed.
Chemical method
This involves the use of herbicides to destroy weed. Herbicides are chemical substances that can kill weeds.
Assessment
- A ____ is any plant that grows in a place where it is not expected to grow or plant which grows out of place.
- Mention 4 cultural methods of weed control and explain 2.
- List three uses of weeds
Answers
- Weed
- Mulching – Mulch are spread on flat and to suppress weeds and prevent them from sprouting
Flooding- water is led to the farm land to kill the weeds
Burning – the vegetation crop residue is set on fire to kill the weed seeds
Cover cropping – Fast growing legumes are planted to another weed
Crop rotation - Weed roots help to bind the soil particles to getting thereby preventing erosion.
They are sources of feeds to livestock e.g guinea grass, elephant grass, sedge
Some weeds are medicinal in nature e.g lemon grass
Weeds are major source of ornamental crops e.g pride of barbados, rose, canalily, hibiscus
Some weeds can control soil erosion.
Some weeds are used for roofing and mat making.
Weeds are used for compost making.
Methods of Weeds and Pest Control
Agricultural Science JSS1 Second Term
Week 9
Topic: Weeds(II)
Methods of dispersal of weeds
- By wind – The fruits and seeds of many weeds are carried by winds and they are spread from one place to another
- By Animals – Animals like rabbits, rats, squirrels and man are involved in the dispersal of weed seeds. Animal dispersed seeds usually have sticky fruits or seeds which may adhere to the coat of the animal and they are carried from one place to another
- By Water – Seeds of weeds may fall into water and are thus transported as the water carries it along as it moves.
Examples of Common Weeds
Common Name: Spear grass
Botanical Name: Heteropogoncontorous
Family: Poaceae
Habitat: They grow on poor soil as well as soil with high acidity.
Description of Characteristics:
- They are cool seasoned tufted perennial grasses
- The foliage grows from 10 -20cm high.
- Most species flowers in spring.
Common Name: Day flower
Botanical Name: Commelina communis
Family: Commelinaceae
Habitat: It strives in edges of garden and yards, fence row; vacant lots and waste areas.
Description of Characteristics:
- It is about 1-3m long
- It can be erect or spraw across the ground like vine .
- The round stems are smooth and hairless.
- Their margins are smooth and veins runs parallel to each other .
- Upper edge of the sheath is usually hairless.
- Each flower blooms during the morning for a single day.
Common Name: Elephant grass
Botanical Name: Pennistrum purpureum
Family: Poaceae
Habitat: It is found on wide range of soils.
Description of Characteristics:
- It is a tall grass.
- It grows in dense clumps of up to 10 feet tall.
- In the savannah of Africa, it grows along lake beds and rivers where the soil is rich.
- They are yellowish or purple in colour .
- The stems are coarse and hairy
- The leaves are 2-3 feet long
- The edges of the leaves are razor sharp.
Common Name: Turbina
Botanical Name: Turbina corymbosa
Family: Convolvulaceae
Habitat: It grows along rainforest margins and water ways
Description of Characteristics:
- It is a scrambling vine growing to at least 8 meters in height.
- Its leaves are heart shaped.
- It produces many branched flowers.
Classification of herbicides
- Based on mode of action (i) selective herbicide – kill a particular type of weed e.g 2,4-D used in grassy/monocot plants (maize farm. Fusillade super used in cowpea farm.
- Non-selective herbicide – kill both broad leaf and narrow leaf weeds e.g paraquad, gramoxone, round up.
- System – active ingredient goes from the root into the weed system and kills it. e.g Primextra, alachor, fusillade super.
- Contact herbicides – has immediate effect on the weeds upon contact with thin e.g paraquat, diquat, gramoxone.
Time of application of herbicides
- Pre-plant herbicides – applied before seed are planted.
- Pre-emergence herbicides – applied before planted seeds emerge e.g Galex for maize, Diurron for cassava.
- Post emergence herbicides- applied after the emergence of both crops and weeds. Post – emergence herbicides are context in action.
Benefits of herbicides
– Easy to apply
– Fast in action
– Cover large area of land
– Saves labour
Disadvantages of using herbicides
– Some beneficial organisms may be killed
– They are poisonous to man and animals
– Air, water and soil are polluted
– Requires technical knowledge
Integrated Control Method: Combination of two or more of the methods discussed.
Effects of cultural control method
– Fire may kill beneficial organisms
– Burning may be difficult to control
– Fire destroys organic matter
– Tillage operations destroy soil structure that may lead to erosion
Effects to biological control
– Predators may later feed on the crops
– Introduced plant may be difficult to be controlled
Wind dispersal methods
- By wind
– Seeds are very small and light
– Possession of pappus hours e.g Emilic
– Possession of parachute – e.g Tridax
– Some seeds are fluffy outgrowth – e.g Cotton
- By Man/Animal
– Some are edible, pass through the alimentary canal and deposited in soil
– Some posses adhesive hook e.g desmodium, Boerharia diffusa
- By water
– Water proof epicarp and light e.g cocoanut from seeds of some legumes and grasses.
- Explosive Mechanism
– Dry pod of weed Sph+ open and throw the seeds to some distance e.g water leaf para
rubber, calopogonium, puerana, centrose sida acuta
– Farm tools – Tools and equipment such as cutlass, plough may have seed of weed
stuck on them. If not cleaned properly before use may transfer seeds of weeds to new
areas.
Assessment
- When should herbicides be applied to control weed?
- Name 3 methods by which weeds can be dispersed?
- List 2 disadvantages of using herbicides
- List 2 effects of cultural control of weeds
Answers
- Before seeds are planted
Before seeds emerge
After crops and weeds emerge - By Winds, Animal and Water
- Some beneficial organisms may be killed
They are poisonous to man and animals
Air, water and soil are polluted
Requires technical knowledge - Fire may kill beneficial organisms
Burning may be difficult to control
Fire destroys organic matter
Tillage operations destroy soil structure that may lead to erosion