COMMON WEEDS FOUND ON FARMS
AGRICULTURAL SCIENCE

COMMON WEEDS FOUND ON FARMS

Common weeds found on farms including their common names and botanical names are shown below:

  • Guinea grass (Panicum maximum).
  • Bahama grass (Cynodon dactylon).
  • Carpet grass (Axonopus compressus).
  • Sensitive plant (Mimosa pundica).
  • Spear grass (Imperiata cylindrica).
  • Wire grass (Aspilia africana).
  • Centro (Centrosema pubescens)
  • Blue feather (Commelina nudiflora)
  • Stubborn grass (Eleucine indica).
  • Stubborn weed (Sida acuta).
  • Goat weed (Ageratum conizoids).
  • Elephant grass (Penisetum purpureum).
  • Giant star grass (Cynodon plactostachyum).
  • Pig weed (Boerhavia diffusa).
  • Bush green (Amaranthus spinosus).
  • Water leaf (Talinum triangulare).
  • Sedge plant (Cyperus rotandus).
  • Tridax (Tridax procumbens).
  • Calopo (Calopogonium mucunoides).
  • Northern gamba (Andropogon gayanus).
  • Sun hemp (Crotalaria juncea).
  • Mucuna (Mucuna utilis).
  • Stylo (Stylosanthes gracilis).
  • Southern gamba (Andropogon tectorum).
  • Kudzu or puero (Pueraria phaseoloides).

 

Identification of Selected Weeds

1) Tridax (Tridax procumbens)

Tridax plant is an annual plant commonly found growing in farm as weed. The leaves are serrated with long flower stalk. On top is the flower. The entire body of the plant is hairy.

Agent of Dispersal

  • The seeds are dispersed by wind.

Characteristics of Seeds which Aid Dispersal by Wind

  • Seeds are very light.
  • They have hairy (pappus) structures attached to the top which help them to suspend their seeds in the air.

Control

  • Tridax can be controlled by any of the following methods: physically by cutlass, mechanically by mower and culturally or chemically by spraying with herbicides.

 

2) Blue feather (Commelina nudiflora)

Commelina is a simple plant commonly found in farms as weed. The stem is more of a stolon or runner which grows horizontally above the surface of the ground. It has adventitious roots at each node. The leaves are simple and at the top of the stem are flowers which are bluish or purple in colour.

Agents of Dispersal

  • Animals are agents of the seed dispersal.

Reason

  • The seeds are sticky with hooks which make them adhere to the coat or body of animals.

Control

  • Physically by the use of cutlass, mechanically by mower and chemically by spraying them with herbicides.

 

3) Goat weed (Ageratum conizoides)

Goat weed is an annual weed plant commonly found in farms. It is a simple plant with slender stem which bear simple leaves. On top of the stem are numerous small flowers and fruits.

Agent of Dispersal

  • The agent of dispersal of seeds/fruits is by wind.

Reason

  • The fruits are light and powdery which are carried or blown easily by wind.

Control

  • Mechanically by the use of mower or plough.
  • Manually by cutlass
  • By the use of chemicals (herbicides).

 

4) Waterleaf plant (Talinum triangulare)

The waterleaf plant is a simple herbaceous plant with tap root system. It has succulent stems and leaves. The leaves are simple while the flowers and seeds are borne at the top of the plant.

Agent of Dispersal of Seeds/Fruit

  • By explosive mechanism.

Reason

  • The fruit/seed splits open by itself when mature or ripe.

Control

  • Physically by the use of cutlass.
  • Mechanically by the use of mower or tractor.
  • Chemically by use of herbicides.

 

5) Pig weed (Boerhavia diffusa)

Pig weed is a simple plant with many branches. It has slender stem and broad leaves. Its seeds / fruits are sticky or have spines which can stick to the body of animals.

Agents of Dispersal

  • The agent of dispersal of the seeds/fruits is by man or animals.

Reasons/characteristics

  • The seeds have sticky external surface which adhere to the body of animal/skin or cloth of man.
  • The seeds/fruits are easily detached from the plant.

Control

  • Use of cutlass, mower, plough and herbicides on the plant.

 

6) Spear grass (Imperata cylindrica)

The plant is a rhizome with underground stem which runs horizontally on the ground. It is usually fleshy with long nodes and internodes. The rhizome is usually covered with a thin scale leaf and a bud at each node. Adventitious roots arise at each node. Food is usually stored in the stem.

Agent of Dispersal

  • The spear grass hardly produces fruits/seeds but it is propagated vegetatively by stem-cutting, especially by man’s activities.

Control

  • By mechanical means such as ploughing and harrowing,
  • By spraying with chemicals (herbicides).

Reasons Why Spear Grass Is Difficult to Control

  • It has underground stem (rhizome) which produces new shoots from its axillary buds, even after cutting or burning.
  • It has the ability to produce both roots and new shoots from each node.
  • It is buried underground, thereby making it difficult to uproot.
  • It is resistant to burning because of its watery rhizome.
  • It is resistant to drought.

 

7) Stubborn weed (Sida acuta)

Stubborn weed is a perennial shrub plant with tough stem; hence, it is described as stubborn weed. The leaves are narrow, pointed and serrated. Along the stem are buds, flowers and fruits.

Agent of Dispersal

  • The fruits/seeds can be dispersed by (a) Explosive mechanism.

Reason

  • The fruit is a capsule which splits on its own, thus scattering the seeds in the farm.

(b) Animals and man

Reason

  • The sharp edges of seeds can adhere to the clothings and hair which can drop off anywhere.

Control

  • By pulling with hands.
  • Use of cutlass.
  • Use of mower.
  • Use of chemicals or herbicides.

 

8) Spigelia (Spigelia anthelmia)

Spigelia is a herbaceous annual weed commonly found growing in farms, pasture and lawns near streams. The main stem is hollow and bears only one or two branches at the only node. It has broad, simple leaves which taper at the tips. The seeds/fruits are borne on top of the plant.

Agent of Dispersal

  • The fruits are dispersed by explosive mechanism.

Reason

  • When the fruit is matured and ripe, it splits open by itself, thereby scattering the seeds in the farm.

Control

  • Mechanically, by mower or tractor,
  • Physically, by the use of cutlass,
  • Chemically, by the use of herbicides.

 

9) Guinea grass (Panicum maximum)

It is a dominant pasture grass in the rainforest zone. It is a bunchy or erect or tufted grass.

It has a very vigorous growth of about 2m tall. It is perennial and has short underground rootstock. It is drought resistant with high leaf to stem ratio. It is propagated by seeds or stolon. It is palatable to livestock and also good for making of hay.

 

10) Elephant grass (Pennisetum purpureum)

It is a widely distributed pasture grass throughout the rain forest zone. It is erect and of about 3-5m tall. It is a perennial grass with cane-like stems and dull green or purplish leaf blade. It is a highly leafy, palatable and aggressive grass.

It is a high yielding grass, propagated by stolon and it is good for making silage.

 

11) Giant Star Grass (Cynodon plectostachyum)

A spreading, drought-resistant perennial grass with a long and rapidly growing stem. This grass can grow more than one metre high. It is most easily propagated by cuttings and once established, it spreads very quickly, thereby making it difficult to control. It makes a nutritious pasture grass and responds well to fertilizers, especially the phosphate fertilizers.

 

12) Carpet Grass (Axonopus compressus)

It is a perennial and a creeping type of grass. Stems are creeping, short, compressed and two-edged. Stems have the tendency to root at the nodes. The grass does best on soils where the moisture is near to the surface but not on swamps. It is very aggressive and not nutritive, hence, it is not so much recommended for pasture.

 

13) Centro (Centrosema pubescens) Centro is a vigorous and aggressive growing legume. It is a creeping and twining plant with trifoliate leaves that are attached to the stem by a pulvinus. Stem and leaves are hairless. It is leafy, perennial, shade-tolerant and drought-resistant legume. It is self-seeding as the pods split open by explosive mechanism during dry weather and the seeds germinate during the following rainy season. It is palatable and highly nutritious to ruminants. It is highly nodulated and does well in combination with guinea grass.

 

14) Tropical Kudzu (Pueraria phaseoloides)

It is a vigorous climbing and perennial legume. Stem and leaves are densely hairy and spread over the soil to form a good cover crop. Leaves are trifoliate. It is sensitive to soil moisture stress and cannot survive drought condition. It is propagated by seeds and roots are nodulated. It is usually avoided by cattle on range and it can be used as hay and silage.

 

15) Stylo (Stylosanthes gracilis)

It can reach 60 – 89cm in height. When kept short through regular cutting or grazing, it develops into a leafy plant, highly nodulated, the leaves trifoliate and creep along the ground. It is drought-resistant, propagated by seeds and performs better in dry areas.

It takes livestock a little while to get used to the taste.

 

Economic Importance /Uses of Grasses such as:

  • Elephant grass.
  • Guinea grass.
  • Northern Gamba.
  • Southern Gamba.

 

  1. These grasses are grazed or fed to livestock as feed as they provide carbohydrates for farm animals.
  2. They are used as mulching materials.
  3. They help to check soil erosion.
  4. They supply material for fencing and door mats when woven.
  5. They provide straw for bedding material.
  6. They can be used as compost material.
  7. They can be used for roofing purposes.
  8. Their stem when dried can serve as fuelwood or firewood.

 

Economic importance of legumes such as:

  • Centrosema pubescens.
  • Stylosanthes gracilis.
  • Pueraria phaseolodies.
  • Calopogonium mucunoides.

 

  1. Legumes are grazed or fed to livestock as feed as they provide protein for farm animals.
  2. They serve as cover crops.
  3. They supply nitrogen to the soil.
  4. They can be used as green manure.
  5. They help to check soil erosion.
  6. They can be used as compost material.

 

Advantages of Growing Grasses and Legumes Together

  1. The combination of grasses and legumes serve as source of balanced ration to ruminants.
  2. Calopogonium/pueraria/ centrosema spp. will supply nitrogen to the soil, thus enriching the soil to aid the growth of the grasses.
  3. Their growth will help in the smothering of weeds.
  4. It will help to improve the taste of forage.
  5. Their combination will make more effective ground cover which prevents erosion and destruction of soil structure.

 

GENERAL CONTROL OF WEEDS, GRASSES AND LEGUMES

Weeds can be controlled through a number of methods. These include:

1) Mechanical / Physical Control: The mechanical methods of controlling weeds are:

  • Hand pulling/hand picking: This involves uprooting weeds from the soil by hand. It is mostly used by peasant farmers and it is most effective for the control of annual and biennial weeds of raw crops.
  • Hoeing: This involves uprooting weeds with hoes before or after planting. Roots of uprooted weeds are exposed to sunlight and killed. Hoes may be used to bury the weeds.
  • Slashing: Through this method, the aerial part of the weeds are removed with cutlasses, leaving behind the roots in the soil. This can also be done using mowers mounted on tractor.
  • Rotary Cultivation: This involves using hand-drawn implements to undertake the ploughing and burying of weeds.

 

2) Biological Control: This involves the introduction of some insects and herbivorous animals to farmlands to eat up the leaves of these weeds. The major problem with this method is that the insect introduced may start to eat crop leaves when the weeds have been removed.

 

3) Cultural Control: This involves the practice of crop rotation and the growth of cover crops to suppress the growth of weeds on the farm.

 

THE CULTURAL METHODS OF WEED CONTROL

  • Flooding: Flooding is one of the best ways of cultural weed control. Under this method, the farmland is surrounded by dikes and water is led into it, up to a height of 15 – 30cm for about 6 weeks. The method is effective for controlling weeds with underground perennial organs.
  • Burning: Burning as a cultural method of weed control involves setting the vegetation on fire, usually when preparing the land for planting. This method is effective for controlling weeds propagated by seeds and aerial portions.
  • Mulching: Mulching involves the placement of dead inactive materials e.g. grass or straw around planted crops. It also prevents weeds from sprouting and smothers those that have sprung up.
  • Cover Cropping: This involves the planting of fast-growing crops, especially legumes such as mucuna and calopogonium on land to act as cover and to smother weeds. This method is effective in controlling weeds on plantation farms.
  • Crop Rotation: Crop rotation is an effective way of controlling weeds associated with specific crop. The crops grown on the land are rotated to exclude the preferred crops and the weed is starved to death.

 

4) Chemical Control: This involves the use of chemical solutions called herbicides to control the growth of weeds. Some of the chemicals are selective, that is, they kill specific types of weeds. Some herbicides kill the parts of the plant on which they fall and are referred to as contact herbicides. Common examples of herbicides include grammoxone, paraquat, simazine, linuron, 2, 4 – dichloroacetic acid (2, 4 – D), and 2, 4, 5 – trichloroacetic acid (2,4,5-T).

 

REASONS WHY WEEDS ARE DIFFICULT TO CONTROL

  1. Weeds are aggressive and persistent in their growth. They have vigorous growth.
  2. Weeds have high reproductive capacity.
  3. Most weed seeds have long periods of viability.
  4. Weeds have efficient dispersal methods.
  5. Weeds have efficient means of propagation.
  6. Weed seeds have long period of dormancy.
  7. Some weed seeds mature at the same time as the crops and are harvested and stored along with the crops, waiting for the next cropping season.
  8. Weeds have modified parts, leaves, stems, roots and seeds that help them survive very adverse environmental conditions. They have wide adaptation.
  9. Most weeds produce many seeds. They are prolific.
  10. They have short life cycle.
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