According to research, the presence of weed in a crop field accounts for up to 34% of the worldwide annual production tonnage percentage lost.
In some cases, if left untreated, yield loss attributed to weed can be as high as 90%.
This implies that the impact of weeds in crop production and the general income of a farmer can never be overstated.
To a large extent, the presence of weed can single-handedly determine what you make from your crop production.
Also, there are several instances where weeds completely dominated the field and reduce the harvest to 0% especially in developed countries like Africa and some parts of Asia where farmers are still dependent on the use of the manual method of controlling weeds.
Briefly, we will dive into proper definition of weeds and their effects in a broader view. Also, we will examine the various methods of weed control.
What are Weeds?
- To many stakeholders in the various aspect of crop production, there are numerous definitions to what weeds are. Here are some of the most prevalent descriptions of weeds;
- To a layman, weeds are basically unwanted plants growing in unwanted places.
- To an agriculturist, weeds are plants that require to be controlled practically and economically to produce feed and fiber for both human and animal consumption. Other definitions include;
- Weeds are defined as plants that need specific actions in order to limit their effects on the economy, the ecosystem, animal and human health and other infrastructures.
- Plants that interact negatively with human activities displaying persistency, competitiveness, and perniciousness
Irrespective of the definition that resonates best with you, weeds are not desirable, and their adverse effects far outweigh the positives.
Thus, there is a need to tackle the growth of weeds in farmland effectively.
Effects of Weeds on Agriculture Production
Some of the impacts of weed on field crops include;
- Reduced quantity and quality
- Contamination of the farm produces
- Toxic to livestock and humans
- Increased cost of production
- Reduction in the income of farmers
- Harboring of pests, parasites, and pathogens
- Increase in irrigation requirement
Various Methods used in Weed Management
- The physical or mechanical method
This is the use of multiple activities that can physically or manually control weeds.
Some of the means include tilling, mulching, grazing, burning, mowing, hand removal, etc. Also, weeds can be manually removed through the use of various tools such as hoes and cutlasses.
The use of machinery also falls sunder mechanical weed control system.
- Cultural method
Cultural control is associated with the use of a different combination of farming systems that suppress the growth of weeds by restricting their access to sunlight, moisture, and nutrients.
Examples of cultural methods of cultural control are crop rotation, stale seedbed, and buried drip irrigation.
- Biological approach
It involves the use of the weeds’ natural enemies in getting rid of them or limiting their impacts.
Examples of the agents used in biological control are larvae of insects, grazing animals, and small vertebrates.
- Through the use of chemical
Chemical control is the use of manufactured chemicals known as an herbicide in the prevention and elimination of weeds.
In many cases, herbicides provide the only practical method of weed control as they can be selective, cost-effective; prevent soil erosion and loss of water.
Also, herbicide use does not interfere with the land. Thus, they are best for conserving farmland.
Herbicides Defined: What are herbicides?
Having weeds dominating your crop field can be irritating. Sometimes, they frustrate your effort as a farmer.
However, you don’t have to worry; herbicides can effectively control virtually all types of weeds.
An herbicide is the combination of the different chemical in the right proportion that can control or inhibit the growth of undesirable plants – weeds.
Herbicides are essentially known as weed killers, and they exist in various forms.
We have highlighted the different types of herbicides, their mode of action, impacts, and how you can effectively select the one that fit into your crop type and region weather.
Types of Herbicides
Herbicides are classified based on several factors such as application, selectivity, persistence, action, and effect.
Application Form
Herbicides exist in various form, as such, they require different application form according to the form in which they are manufactured.
If you have your herbicide come in liquid, spraying will be your method. Some are in granular form while are available as a powder.
However, liquid herbicides are the most prevalent of them all.
Mode of Selection
When it comes to the selectivity, there are two types. These are;
Selective
These herbicides can distinguish between specific crop.
For instance, herbicides shown selectivity in grasses will only affect broad leaves and vice versa.
Also, some selective herbicides are manufactured for only a particular type of crop.
For instance, a 2, 4 – D selective herbicide for rice will kill grasses such as maize belonging to the same class.
Selective herbicides are mostly systemic.
Non-selective
These herbicides cannot distinguish between grasses and broadleaves, thorn or thistle.
They kill any plants they come in contact with. As such, they are referred to as knockdown. Non-selective herbicides can be contact or systemic.
Good examples of non-selective herbicides are Roundup and Diquat.
Level of Persistency
This has to do with the duration of effectiveness of the herbicide after application.
While some remain active for a short time, some continue to be effective for a more extended period.
Mechanism of Action (MoA)
During herbicide application, you may be interested as to how these herbicide works.
MoA shows the first protein, enzyme or the biochemical steps affected in plants after applying the herbicide. Some of the primary modes of action include;
· ACCases Inhibitors
Acetyl-coenzyme A carboxylases (ACCases) are compounds that destroy grasses and are the first step in the synthesis of lipids.
While the ACCases of grasses is sensitive to the application of these herbicides, however, the ACCases of dicots are unaffected.
Thus, the cell membrane production in grass meristem is affected by ACCases.
· Acids and Bases
They work by burning the plant cells as they are extremely toxic to the plants either as an acid or a base.
· ALS Inhibitors
Also are known as the first step in branched-chain amino acid syntheses such as leucine, valine, and isoleucine.
These herbicides work by gradually depriving the affected plant of amino acid. When this situation occurs for a long time, the DNA synthesis will be inhibited causing the eventual death of plants. With tacetolactate synthase (ALS) enzyme (acetohydroxyacid synthase, or AHAS), both dicots and grasses are affected.
Examples of ALS inhibitors are imidazolinones (IMIs), sulfonylamino carbonyl triazolinones (SCTs), triazolopyrimidines (TPs), sulfonylureas (SUs), and the others.
· Desiccators
Their mode of action is through the removal of moisture from plants which automatically lead to the death of plants.
· EPSPS Inhibitor
Affecting grasses and legumes, the enolpyruvylshikimate 3-phosphate synthase enzyme EPSPS synthesizes tyrosine, tryptophan, and phenylalanine.
A notable example is Glysophate which also doubles as a systemic herbicide.
· Nutritional Control
The working mode of this type of herbicide is through the disruption of nutrient balance in targeted plants.
Such herbicides supply an excess of specific nutrients or totally restrict its presence in killing weeds.
· Photosystem II Inhibitors
They reduce the flow of electron from water to NADPH2+ during photosynthesis.
They work by activating excess oxidation reaction resulting in the death of plant cells.
A typical example is triazine herbicide of which atrazine is an important member.
· Synthetic Auxin
Synthetic auxins are often classified as organic herbicides.
The pattern of their work is by mimicking plants hormone with multiple points of action on the cell membrane.
They are effective in the elimination of broad leaves. A notable example is 2, 4 –D herbicides.
Effects on Plants
Pre-emergent
They are used as a preventive measure against the growth of weeds. Their best time of application is before the growth of plants.
Post-emergent
Post-emergent work by killing the vegetative parts of weeds but they exert no effect whatever on the buried seeds of these weeds.
Contact
Just like the name implies, contact herbicides kill or inhibit the growth of weeds, but they have to come in touch with that particular weeds before they can be effective.
Contact herbicide works faster than systemic. However, they need to be re-applied every time to before you can fully enjoy their benefits. An excellent example is Paraquat.
Residual
Residual herbicides will continue to be effective after you have applied it for a very long time.
They are the best type to use when you notice that some specific weeds are offering resistance. Residual herbicides usually possess different modes of action.
Drench
They are applied directly to the soil rather than to the plants. This type of herbicide is best used where you are not planning to cultivate crop as they will affect both crops and weeds.
Systemic
Of all the types of herbicides we have discussed, systemic herbicides have proven to be the most desirable for crop production.
What are systemic herbicides?
Systemic herbicides, also known as translocated herbicide are combinations of chemicals that are applied to the vegetative parts of a weed and are absorbed to the phloem and xylem tissue where they act in destroying weeds.
Systemic herbicides are different from contact in that they follow a slow process of action.
Contact herbicides work immediately, but systemic herbicides offer a more lasting solution to weed control.
This is because systemic herbicides are absorbed by the root of crops during photosynthesis which leads to the total death of the plant.
Apart from the facts that contact herbicides work instantly and are often cheaper, systemic herbicides have a wide range of benefits over contact herbicides.
Below are the advantages of using a systemic herbicide.
How do systemic herbicides work?
You may be wondering how systemic herbicide work, this is how they actually carry out their destructive acts on weeds.
Most systemic herbicides work by disrupting the biochemical balance in weeds.
Prevalent phenoxy herbicides like 2,4 – D that are both systemic and selective mimic natural occurring plant chemical called Indole Acetic Acid (IAA).
This cause an imbalance in IAA which in turn cause inhibited growth, elongation, twisting, and starvation, then eventual death of the weed.
Also, when absorbed by plants, systemic herbicides are capable of interrupting photosynthesis.
They also release of hydroxyl compound that is toxic to the weeds. This process deprives weeds of essential nutrients and leads to their gradual destruction.
Systemic herbicides that target the enzyme plants in weeds will disrupt the sequence of a complex chemical reaction.
Thus, toxic substances are released to the weed system which kills the plant.
Benefits of Systemic Herbicides
- Thorough and complete weed killer
Unlike contact herbicide which only burns the leave of plants parts they get touch with, with a systemic herbicide, you can expect to kill all the parts of plants, from the leave to the root.
- Effectively tackle resistant weeds
Many weeds have developed resistance to the use of contact herbicides.
When you apply a contact herbicide repeatedly, they tend to outsmart the chemicals by initiating a defensive mechanism.
However, with the application of systemic herbicide, you will destroy these weeds seamlessly.
Some of these annual hard-to-remove weeds are blank bindweed, Sida acuta, Eleucine indica, lesser trefoil, annual mercury, wild radish, and many more
- Works for an extended period
Because systemic herbicides are absorbed into the system of plants, they destroy both the shoot and root which implies that you can be confident of not tackling weeds when you apply systemic herbicides.
- More cost-effective in the long run
Although contact herbicides are usually cheaper, since you will have to keep reapplying them, you will find it more beneficial when you go for systemic herbicides.
Systemic herbicides can effectively control weeds in a single production cycle when applied correctly.
- Better suited as a selective herbicide
Most selective herbicides are systemic.
This implies that they are more suitable for commercial production compared to contact herbicide.
Best ways to import systemic herbicides from China
China is the leading manufacturer of herbicide globally. However, herbicide importation like every other product can be challenging even to the most experienced importer.
Thus, Awiner was created solely to assist importers to enjoy a seamless process on importation. We have a vast chain of networks across the biggest cities in the world.
We have successfully handled a countless number of importations to countries such as Ireland, Mauritius, Kenya, Afghanistan, Nepal and many more.
Leave a message and tell us how do you think it.
References
https://extension.psu.edu/introduction-to-weeds-what-are-weeds-and-why-do-we-care
http://www.environment.gov.au/biodiversity/invasive/weeds/index.html